Publications archive

Due to copyright restrictions, only abstracts are listed here. For further information on any of the listed topics, please contact us at info@kleindiek.com.

Electrical characterization

S. Kleindiek, K. Schock, A. Rummel, M. Zschornack, P. Limbecker, A. Meyer, M. Kemmler, Current imaging, EBIC/EBAC, and electrical probing combined for fast and reliable in situ electrical fault isolation, Microelectronics Reliability, 2016/09/18

S. Kleindiek, K. Schock, A. Rummel, M. Zschornack, P. Limbecker, A. Meyer, M. Kemmler, Current imaging, EBIC/EBAC, and electrical probing combined for fast and reliable in situ electrical fault isolation, Microelectronics Reliability, 2016/09/18

Using a compact nanoprobing setup comprising eight probe tips attached to piezo-driven micromanipulators, various techniques for fault isolation are performed on 28 nm samples inside an SEM. The employed techniques include nanoprobing as well as EBAC. The recently implemented Current Imaging technique is used to quickly image large arrays of contacts providing a means of locating faults. In this case, Current Imaging provides insight into the sample's behaviour yielding qualitatively comparable results to the more cumbersome cAFM technique. While the results of the TEM investigations including EDX mappings were inconclusive, the Current Imaging technique clearly shows that the root cause is located below the SiGe layer. By combining these techniques inside a FIB/SEM microscope, it is possible to locate and characterize a failure as well as prepare a TEM lamella for further investigation without the necessity to switch to a different tool.

J. Ledig, X. Wang, S. Fündling, H. Schuhmann, M. Seibt, U. Jahn, H.-H. Wehmann, A. Waag, Characterization of the internal properties of InGaN/GaN core–shell LEDs, Phys. Stat. Sol (213) p.11-18, 2016

J. Ledig, X. Wang, S. Fündling, H. Schuhmann, M. Seibt, U. Jahn, H.-H. Wehmann, A. Waag, Characterization of the internal properties of InGaN/GaN core–shell LEDs, Phys. Stat. Sol (213) p.11-18, 2016

In this paper, we present the structural, optical, and electrical characterization of InGaN/GaN core-shell micro-LED structures selectively grown by metal organic vapor phase epitaxy (MOVPE) in arranged arrays. In particular we analyze the core-shell geometry of the pillars, consisting of a fivefold InGaN/GaN multiple quantum well and a p-type layer on all sidewall and top facets. Additionally we analyze the optical properties of the structure and the active region with high spatial resolution by cathodoluminescence. Electron beam induced current measurements (EBIC) are performed using an SEM based manipulator setup, giving proof of the presence of a depletion region as well as the intended doping polarity of the n-type core and a p-type shell wrapped around the whole structure. Using a p–n–p configuration also current crowding is discussed by EBIC and electroluminescence is demonstrated by measuring emission patterns from single core–shell structures.

M. Kemmler, A. Rummel, K. Schock, S. Kleindiek, 2015. Correlating SEM and SPM for Nanoprobing in Failure Analysis

M. Kemmler, A. Rummel, K. Schock, S. Kleindiek, 2015. <i> Correlating SEM and SPM for Nanoprobing in Failure Analysis </i>

A compact nanoprober suitable for SEM/FIB is presented. Each of the eight probes can be biased and scanned over the sample surface, allowing for the acquisition of current flow images (CI) with sub-pA resolution. The correlation of SEM and CI is used to locate leakages in 22 nm SRAM devices.

A. Schulze, T. Hantschel, P. Eyben, A.S. Verhulst, R. Rooyackers, A. Vandooren, W. Vandervorst, 2013. Quantitative three-dimensional carrier mapping in nanowire-based transistors using scanning spreading resistance microscopy

A. Schulze, T. Hantschel, P. Eyben, A.S. Verhulst, R. Rooyackers, A. Vandooren, W. Vandervorst, 2013. <i> Quantitative three-dimensional carrier mapping in nanowire-based transistors using scanning spreading resistance microscopy </i>

The performance of nanoelectronic devices critically depends on the distribution of charge carriers inside such structures. High-vacuum scanning spreading resistance microscopy (HV-SSRM) has established as the method of choice for quantitative 2D-carrier mapping in nanoscale devices during the last decade. However, due to the 3D-nature of these nanoscale device architectures, dopant incorporation and dopant diffusion mechanisms can vary for any of the three dimensions, depending on the particular processes used. Therefore, mapping of carriers in three dimensions with high spatial resolution is inevitable to study and understand the distribution of active dopants in confined 3D-volumes and ultimately to support the process development of next generation devices. In this work, we present for the first time an approach to extend the capabilities of SSRM from an inherent 2D- carrier profiling technique towards a quantitative 3D-characterization technique based on the example of a nanowire (NW)-based heterojunction (SiGe–Si) tunneling transistor. In order to implement a 3D-methodology with a 2D-imaging technique, we acquired 2D-carrier concentration maps on successive cross-section planes through the device of interest. This was facilitated by arranging several devices in a staggered array, allowing to produce a series of cross-sections with incremental offset by a single cleave. A dedicated interpolation algorithm especially suited for structures with rotational symmetry like NWs was developed in order to reconstruct a 3D-carrier distribution map. The validity of the method was assessed by proving the absence of variations in carrier distribution in the third dimension, as expected for NWs etched into a blanket stack.

K. Arstila, T. Hantschel, A. Schulze, A. Vandooren, A.S. Verhulst, R. Rooyackers, P. Eyben, W. Vande, 2012. Nanoprober-based EBIC measurements for nanowire transistor structures

K. Arstila, T. Hantschel, A. Schulze, A. Vandooren, A.S. Verhulst, R. Rooyackers, P. Eyben, W. Vande, 2012. <i>Nanoprober-based EBIC measurements for nanowire transistor structures</i>

Electron beam induced current (EBIC) measurements can be used to visualize depletion region in semi-conductor junction structures. In this work we use a nanoprober setup to create local contacts to nano-wire (NW) based tunnel-field-effect-transistors (TFET), which are gated p–i–n diodes, and perform EBIC measurements to investigate dopant diffusion effects in the junction region of TFET structures fabricated with high and low thermal budget. For contacting we use commercial tungsten probes and in-house fabricated conductive diamond tips. The results show that nanoprober based EBIC measurements are a straight forward way to study the functionality of a large number of NWs simultaneously while also allowing to make an in-depth investigation of the junction position as a result of different processing conditions of the nanowire transistors.

Yong Lin, Qiming Li, Andrew Armstrong, George T. Wang, 2009. In situ scanning electron microscope electrical characterization of GaN nanowire nanodiodes using tungsten and tungsten/gallium nanoprobes

Yong Lin, Qiming Li, Andrew Armstrong, George T. Wang, 2009. In situ scanning electron microscope electrical characterization of GaN nanowire nanodiodes using tungsten and tungsten/gallium nanoprobes

A lithography-free technique for measuring the electrical properties of n-type GaN nanowires has been investigated using nanoprobes mounted in a scanning electron microscope (SEM). Schottky contacts were made to the nanowires using tungsten nanoprobes, while gallium droplets placed in situ at the end of tungsten nanoprobes were found to be capable of providing Ohmic contacts to GaN nanowires. Schottky nanodiodes were fabricated based on single n-type nanowires, and measured current–voltage (I–V) results suggest that the Schottky nanodiodes deviate from ideal diodes mainly due to their nanoscopic contact area. Additionally, the effect of the SEM electron beam on the I–V characteristics was investigated and was found to impact the transport properties of the Schottky nanodiodes, possibly due to an increase in carrier density in the nanodiodes.

Peng, Y., Cullis, T. and Inkson, B., 2008. Accurate electrical testing of individual gold nanowires by in situ scanning electron microscope nanomanipulators.

Peng, Y., Cullis, T. and Inkson, B., 2008. <i>Accurate electrical testing of individual gold nanowires by in situ scanning electron microscope nanomanipulators.</i>

This work presents an accurate measurement of electrical properties of individual gold nanowires, directly measured by nanomanipulators in situ in a scanning electron microscope. The electrical testing of 55 nm width gold nanowires, with a bamboo-type polycrystalline micorstructure, shows that individual gold nanowires have an ideal resistivity of about 2.26 Ohm cm and remarkably high failure current density of 4.94 10^-8 A cmˆ2.

There is no evidence that the polycrystalline grain structure, 55 nm width and 500 - 2800 nm length, generates any size-induced electrical effects. The accurate electrical testing of gold nanowires should be significant for nanodevices and nanoelectronics using them as building blocks or interconnects. © 2008 American Institute of Physics.

Suriano, F., Veronese, G.P., Impronta, M., Rummel, A. and Kleindiek, S., 2008. Tips for Low Level Electrical Measurements by SEM Equipped with Micromanipulators.

Suriano, F., Veronese, G.P., Impronta, M., Rummel, A. and Kleindiek, S., 2008. <i>Tips for Low Level Electrical Measurements by SEM Equipped with Micromanipulators.</i>

In this paper, an extensive experimental analysis was conducted to identify the main sources of measurement errors, when low-level electrical measurements are performed on micro- to nano-scaled devices as carbon nanotubes in a scanning electron microscope, equipped with in-chamber micromanipulators. We applied our expertise on wafer-level microelectronic-device characterization to reduce noise and leakage problems that can affect the electrical characterization, when the proper cabling and guarding techniques are not used. In conclusion, guidelines are given to obtain an accurate and reliable measurement setup.

Chen, Q., Wang, S. and Peng, L.-M., 2006. Establishing Ohmic contacts for in situ current-voltage characteristic measurements on a carbon nanotube inside the scanning electron microscope.

Chen, Q., Wang, S. and Peng, L.-M., 2006. <i>Establishing Ohmic contacts for in situ current-voltage characteristic measurements on a carbon nanotube inside the scanning electron microscope.</i>

Multi-walled carbon nanotubes (CNTs), either on an SiO2 substrate or suspended above the substrate, were contacted to W, Au and Pt tips using a nanoprobe system, and current / voltage (I / V) characteristics were measured inside a scanning electron microscope. Linear I / V curves were obtained when Ohmic contacts were established to metallic CNTs. Methods for establishing Ohmic contacts on a CNT have been developed using the Joule heating effect when the tips are clean and e-beam exposing the contacting area of the tip when the tips are covered by a very thin contamination layer. When the contact is not good, non-linear I / V curves are obtained even though the CNTs that have been contacted are metallic. The resistance measured from the metal tip-CNT-metal tip system ranges from 14 to 200 kOhm. When the CNT was contacted via with Ohmic contacts the total resistance of the CNT was found to change roughly linearly with the length of the CNTs between the two tips. Field effect measurements were also carried out using a third probe as the gate, and field effects were found on certain CNTs with non-linear I / V characteristics.

Mulders, J.J.L., 2005. An in-situ four-point probe method for the electrical characterization of beam induced depositions.

Mulders, J.J.L., 2005. <i>An in-situ four-point probe method for the electrical characterization of beam induced depositions.</i>

Electron and ion beam systems can be applied for the local deposition of material. This is realized by the local decomposition of organo-metallic precursor gas, released close to the surface of interest. The excellent control of the beam position and dwell time, allow the creation of welldefined structures at the micro and nano scale. In application of these depositions for semiconductor and nanD technology it is important to understand the electrical, optical, mechanical, magnetic or chemical properties of such a deposition. Especially metallic depositions are often used for the direct creation of a very local conductivity path and hence the local resistance of a structure is an important parameter. For this reason the electrical characterization of metallic deposits of thin metal lines (Ohm·m) or of thin films (Ohm/sq) is necessary.

Guise, O., Marbach, H., Yates, J.T. Jr., Jung, M.-C., Levy, J. and Ahner, J., 2005. Development and performance of the nanoworkbench: A four tip STM for conductivity measurements down to submicrometer scales.

Guise, O., Marbach, H., Yates, J.T. Jr., Jung, M.-C., Levy, J. and Ahner, J., 2005. <i>Development and performance of the nanoworkbench: A four tip STM for conductivity measurements down to submicrometer scales.</i>

A multiple-tip ultrahigh vacuum (UHV) scanning tunneling microscope (MTSTM) with a scanning electron microscope (SEM) for imaging and molecular-beam epitaxy growth capabilities has been developed. This instrument (nanoworkbench) is used to perform four-point probe conductivity measurements at µm spatial dimension. The system is composed of four chambers, the multiple-tip STM/SEM chamber, a surface analysis and preparation chamber, a molecular-beam epitaxy chamber, and a load–lock chamber for fast transfer of samples and probes. The four chambers are interconnected by a unique transfer system based on a sample box with integrated heating and temperature-measuring capabilities. We demonstrate the operation and the performance of the nanoworkbench with STM imaging on graphite and with four-point-probe conductivity measurements on a silicon-on-insulator (SOI) crystal. The creation of a local FET, whose dimension and localization are, respectively, determined by the spacing between the probes and their position on the SOI surface, is demonstrated.

Peng, L.-M., Chen, Q., Liang, X.L., Goa, S., Wang, J.Y., Kleindiek, S. and Tai, S.W., 2004. Performing probe experiments in the SEM.

Peng, L.-M., Chen, Q., Liang, X.L., Goa, S., Wang, J.Y., Kleindiek, S. and Tai, S.W., 2004. <i>Performing probe experiments in the SEM.</i>

A four nanoprobe system has been installed inside a FEI XL30 F scanning electron microscope (SEM), and shown to be fully compatible with the normal functions of the SEM and also a Gatan cold stage (model C1003, 2185-400 8C). With some selected examples of applications, we have shown that this nanoprobe system may be used effectively for gripping, moving and manipulating nanoobjects, e.g. carbon nanotubes, setting up electric contacts for electronic measurements, tailoring the structure of the nanoobject by cutting, etc. and even for making unexpected nanostructures, e.g. a nanohook. Applications in other areas have also been speculated, limitations or disadvantages of the current design of the probe system were discussed, and methods for possible improvement were suggested.

S. Hasegawa, N. Sato, I. Shiraki, C. L. Petersen, P. Boggild, T.M. Hansen, T. Nagao, F. Grey , 2000. Surface-state bands on silicon - Si(111)-sqrt(3)—sqrt(3)-Ag surface superstructure.

S. Hasegawa, N. Sato, I. Shiraki, C. L. Petersen, P. Boggild, T.M. Hansen, T. Nagao, F. Grey , 2000. <i>Surface-state bands on silicon - Si(111)-sqrt(3)—sqrt(3)-Ag surface superstructure.</i>

After reviewing the atomic and electronic structures of the Si(III)-sqrt(3) x sqrt(3)-Ag surface, which have recently been clarified after much research, we describe the experimental confirmations of electrical conduction through its surface-state band. A newborn method, micro-four-point probe, is introduced for conductivity measurements with high surface sensitivity.

In-situ lift-out

Lee, J.C. and Lee, B.H., 2005. The versatile application for in-situ lift-out TEM sample preparation by micromanipulator and nanomotor.

Lee, J.C. and Lee, B.H., 2005. <i>The versatile application for in-situ lift-out TEM sample preparation by micromanipulator and nanomotor.</i>

The device features have shrunk to sub-micron/nano-meter range, and the process technology has been getting more complicated, so TEM has become a necessary tool for PFA imaging and element analysis. Conventional FIB ex-situ lift- out is the most common technique for precise sample preparation. But this method has some limitations: samples cannot be reprocessed for further analysis; the carbon film supported grid affects the EDS analysis for carbon elements. A new installation will be introduced in this article, which is set up in FIB chamber for in-situ lift-out application. It not only overcomes the above problems, but also covers a wide application of TEM sample preparation.

Burkhardt, C., Kleindiek, S., Gnauck, P., Bihr, J. and Nisch, W., 2002. In-situ lift-out of TEM-lamellae using a compact and precise micromanipulator.

Burkhardt, C., Kleindiek, S., Gnauck, P., Bihr, J. and Nisch, W., 2002. <i>In-situ lift-out of TEM-lamellae using a compact and precise micromanipulator.</i>

Almost all sensory neurones in the dorsal root ganglia have a mechanosensory function. The transduction of mechanical stimuli in vivo takes place exclusively at the sensory ending. For cutaneous sensory receptors it has so far proved impossible to directly record the mechanically gated receptor potential because of the small size and inaccessibility of the sensory ending. Here we investigate whether mechanosensitive currents are present in the neurites of freshly isolated adult mouse sensory neurones in culture. Amost all sensory neurone neurites possess currents gated by submicrometre displacement stimuli (92%). Three types of mechanically activated conductance were characterized based on different inactivation kinetics. A rapidly adapting conductance was found in larger sensory neurones with narrow action potentials characteristic of mechanoreceptors. Slowly and intermediate adapting conductances were found exclusively in putative nociceptive neurones. Mechanically activated currents with similar kinetics were found also after stimulating the cell soma. However, soma currents were only observed in around 60% of cells tested and the displacement threshold was several times larger than for the neurite. The reversal potential of the rapidly adapting current indicated that this current is largely selective for sodium ions whereas the slowly adapting current is non-selective. It is likely that distinct ion channel entities underlie these two currents. In summary, our data suggest that the high sensitivity and robustness of mechanically gated currents in the sensory neurite make this a useful in vitro model for the mechanosensitive sensory endings in vivo.

Life science

Stephanie Venteo, Gary R. Lewin, et al., 2016. Fxyd2 regulates A?- and C- ber mechanosensitivity and is required for the maintenance of neuropathic pain

Stephanie Venteo, Gary R. Lewin, et al., 2016. <i>Fxyd2 regulates A?- and C- ber mechanosensitivity and is required for the maintenance of neuropathic pain</i>

Identi cation of the molecular mechanisms governing sensory neuron subtype excitability is a key requisite for the development of treatments for somatic sensory disorders. Here, we show that the Na,K-ATPase modulator Fxyd2 is speci cally required for setting the mechanosensitivity of A?- ber low-threshold mechanoreceptors and sub-populations of C- ber nociceptors, a role consistent with its restricted expression pro le in the spinal somatosensory system. We also establish using the spared nerve injury model of neuropathic pain, that loss of Fxyd2 function, either constitutively in Fxyd2?/? mice or acutely in neuropathic rats, e ciently alleviates mechanical hypersensitivity induced by peripheral nerve lesions. The role of Fxyd2 in modulating A?- and C- bers mechanosensitivity likely accounts for the anti-allodynic e ect of Fxyd2 knockdown. Finally, we uncover the evolutionarily conserved restricted expression pattern of FXYD2 in human dorsal root ganglia, thus identifying this molecule as a potentially promising therapeutic target for peripheral neuropathic pain management.

Qiusong Tang, Michael Brecht, Andrea Burgalossi, 2014 Juxtacellular recording and morphological identification of single neurons in freely moving rats

Qiusong Tang, Michael Brecht, Andrea Burgalossi, 2014 <i>Juxtacellular recording and morphological identification of single neurons in freely moving rats</i>

It is well established that neural circuits consist of a great diversity of cell types, but very little is known about how neuronal diversity contributes to cognition and behavior. One approach to addressing this problem is to directly link cellular diversity to neuronal activity recorded in vivo in behaving animals. Here we describe the technical procedures for obtaining juxtacellular recordings from single neurons in trained rats engaged in exploratory behavior. The recorded neurons can be labeled to allow subsequent anatomical identification. In its current format, the protocol can be used for resolving the cellular identity of spatially modulated neurons (i.e., head-direction cells and grid cells), which form the basis of the animal's internal representation of space, but this approach can easily be extended to other unrestrained behaviors. The procedures described here, from the beginning of animal training to the histological processing of brain sections, can be completed in ~3–4 weeks.

Henrik Alle, Hisahiko Kubota, and Jörg R. P. Geiger, 2011. Sparse But Highly Efficient Kv3 Outpace BKCa Channels in Action Potential Repolarization at Hippocampal Mossy Fiber Boutons

Henrik Alle, Hisahiko Kubota, and Jörg R. P. Geiger, 2011. <i>Sparse But Highly Efficient Kv3 Outpace BKCa Channels in Action Potential Repolarization at Hippocampal Mossy Fiber Boutons</i>

Presynaptic elements of axons, in which action potentials (APs) cause release of neurotransmitter, are sites of high densities and complex interactions of proteins. We report that the presence of Kv3 channels in addition to Kv1 at glutamatergic mossy fiber boutons (MFBs) in rat hippocampal slices considerably limits the number of fast, voltage-activated potassium channels necessary to achieve basal presyn- aptic AP repolarization. The 10-fold higher repolarization efficacy per Kv3 channel compared with presynaptic Kv1 results from a higher steady-state availability at rest, a better recruitment by the presynaptic AP as a result of faster activation kinetics, and a larger single-channel conductance. Large-conductance calcium- and voltage-activated potassium channels (BKCa ) at MFBs give rise to a fast activating/fast inactivating and a slowly activating/sustained K current component during long depolarizations. However, BKCa contribute to MFB–AP repolarization only after presynaptic Kv3 have been disabled. The calcium chelators EGTA and BAPTA are equally effective in preventing BKCa activation, suggesting that BKCa are not organized in nanodomain complexes with presynaptic voltage-gated calcium channels. Thus, the functional properties of Kv3 channels at MFBs are tuned to both promote brevity of presynaptic APs limiting glutamate release and at the same time keep surface protein density of potassium channels low. Presynaptic BKCa channels are restricted to limit additional increases of the AP half-duration in case of Kv3 hypofunction, because rapid membrane repolarization by Kv3 combined with distant calcium sources prevent BKCa activation during basal APs.

Daniel Vilceanu and Cheryl L. Stucky, 2010 TRPA1 Mediates Mechanical Currents in the Plasma Membrane of Mouse Sensory Neurons

Daniel Vilceanu and Cheryl L. Stucky, 2010 <i>TRPA1 Mediates Mechanical Currents in the Plasma Membrane of Mouse Sensory Neurons</i>

Mechanosensitive channels serve as essential sensors for cells to interact with their environment. The identity of mechanosensitive channels that underlie somatosensory touch transduction is still a mystery. One promising mechanotransduction candidate is the Transient Receptor Potential Ankyrin 1 (TRPA1) ion channel. To determine the role of TRPA1 in the generation of mechanically-sensitive currents, we used dorsal root ganglion (DRG) neuron cultures from adult mice and applied rapid focal mechanical stimulation (indentation) to the soma membrane. Small neurons (diameter under 27 µm) were studied because TRPA1 is functionally present in these neurons which largely give rise to C-fiber afferents in vivo. Small neurons were classified by isolectin B4 binding.

 

Mechanically-activated inward currents were classified into two subtypes: Slowly Adapting and Transient. First, significantly more IB4 negative neurons (84%) responded to mechanical stimulation than IB4 positive neurons (54%). Second, 89% of Slowly Adapting currents were present in IB4 negative neurons whereas only 11% were found in IB4 positive neurons. Third, Slowly Adapting currents were completely absent in IB4 negative neurons from TRPA1?/? mice. Consistent with this, Slowly Adapting currents were abolished in wild type IB4 negative neurons stimulated in the presence of a TRPA1 antagonist, HC-030031. In addition, the amplitude of Transient mechanically-activated currents in IB4 positive neurons from TRPA1?/? mice was reduced by over 60% compared to TRPA1+/+ controls; however, a similar reduction did not occur in wild-type neurons treated with HC-030031. Transfection of TRPA1 in HEK293 cells did not significantly alter the proportion or magnitude of mechanically-activated currents in HEK293 cells, indicating that TRPA1 alone is not sufficient to confer mechanical sensitivity.

 

These parallel genetic and pharmacological data demonstrate that TRPA1 mediates the Slowly Adapting mechanically-activated currents in small-diameter IB4 negative neurons from adult mice. The TRPA1 protein may also contribute to a complex that mediates Transient mechanically-activated currents in small IB4 positive C fiber type neurons.

Henrik Alle, Arnd Roth, Jörg R. P. Geiger, 2009. Energy-Efficient Action Potentials in Hippocampal Mossy Fibers

Henrik Alle, Arnd Roth, Jörg R. P. Geiger, 2009. <i>Energy-Efficient Action Potentials in Hippocampal Mossy Fibers</i>

Action potentials in nonmyelinated axons are considered to contribute substantially to activity- dependent brain metabolism. Here we show that fast Na+ current decay and delayed K+ current onset during action potentials in nonmyelinated mossy fibers of the rat hippocampus minimize the overlap of their respective ion fluxes. This results in total Na+ influx and associated energy demand per action potential of only 1.3 times the theoretical minimum, in contrast to the factor of 4 used in previous energy budget calculations for neural activity. Analysis of ionic conductance parameters revealed that the properties of Na+ and K+ channels are matched to make axonal action potentials energy-efficient, minimizing their contribution to activity-dependent metabolism.

Felder, E., Appelt, D., Zheng, X. and Dietl, P., 2008. Lamellar body secretion in cyclically stretched rat alveolar type II cells depends on the geometry of cell-cell interaction.

Felder, E., Appelt, D., Zheng, X. and Dietl, P., 2008. <i>Lamellar body secretion in cyclically stretched rat alveolar type II cells depends on the geometry of cell-cell interaction.</i>

Alveolar type II cells respond to mechanical stimulation with a fusion of surfactant containing lamellar bodies (LBs) with the cell membrane. Single fusion events of LBs can be detected with the fluorescent dye FM1-43 in vitro and we determined this parameter to investigate the effect of cyclic stretch on primary rat type II cells. After cultivating the cells on an elastic growth support we used a micro-robotic arm (kleindiek nanotechnik) that allowed us to locally stretch the underlying growth substrate and hence to apply unidirectional stretch to individual clusters of cells. Stretch of different frequencies (1, 2 and 4hz) and varying amplitude showed that the average stretch frequency of cells that responded with LB fusion was only slightly lower (1.84Hz) compared to cells with no LB fusion (2.0Hz) and also the stretch amplitude did barely correlate with the number of LB fusions. Cells that responded with fusions were generally attached to more cells than the ones without response indicating cell-cell interaction of some kind to account for the process. In cases were the position of the adjacent cells with respect to the stretch axis could precisely be defined we found that an unsymmetric deformation rather than simple elongation of a cell cluster lead to an increased number of fusions. Latter shows that the mechanosensitive machinery of the ATII cell is able to distinguish between force patterns and we suggest cytoskeletal elements to be a key player in mediating this process. To investigate whether focal adhesion - the classic intracellular sensors for mechanotransduction - account for the effect, we labelled several focal adhesion proteins in vivo and compared their response to stretch in different sectors of the inhomogeneous stretch field.

Henrik Alle and Jörg R. P. Geiger, 2007. GABAergic Spill-Over Transmission onto Hippocampal Mossy Fiber Boutons

Henrik Alle and Jörg R. P. Geiger, 2007. <i>GABAergic Spill-Over Transmission onto Hippocampal Mossy Fiber Boutons</i>

Presynaptic ionotropic GABAA receptors have been suggested to contribute to the regulation of cortical glutamatergic synaptic trans- mission. Here, we analyzed presynaptic GABAA receptor-mediated currents (34°C) recorded from mossy fiber boutons (MFBs) in rat hippocampal slices. In MFBs from young and adult animals, GABA puff application activated currents that were blocked by GABAA receptor antagonists. The conductance density of 0.65 mS cm 2 was comparable to that of other presynaptic terminals. The single- channel conductance was 36 pS (symmetrical chloride), yielding an estimated GABAA receptor density of 20 –200 receptors per MFB. Presynaptic GABAA receptors likely contain 2-subunits as indicated by their zolpidem sensitivity. In accordance with the low apparent GABA affinity (EC50 60 M) of the receptors and a tight control of ambient GABA concentration by GABA transporters, no tonic background activation of presynaptic GABAA receptors was observed. Instead, extracellular high-frequency stimulation led to transient presynaptic currents, which were blocked by GABAA receptor antagonists but were enhanced by block of GAT 1 (GABA transporter 1), indicating that these currents were generated by GABA spill-over and subsequent presynaptic GABAA receptor activation. Presynaptic spill-over currents were depressed by pharmacological cannabinoid 1 (CB1) receptor activation, suggesting that GABA was released predominantly by a CB1 receptor-expressing interneuron subpopulation. Because GABAA receptors in axons are considered to act depolarizing, high activity of CB1 receptor-expressing interneurons will exert substantial impact on presynaptic membrane potential, thus modulating action potential-evoked transmitter release at the mossy fiber–CA3 synapse.

Wetzel, C., Hu, J., Riethmacher, D., Benckendorff, A., Harder, L., Eilers, A., Moshourab, R., Kozlenkov, A., Labuz, D., Caspani, O., Erdmann, B., Machelska, H., Heppenstall, P.A. and Lewin, G.R., 2007. A stomatin-domain protein essential for touch

Wetzel, C., Hu, J., Riethmacher, D., Benckendorff, A., Harder, L., Eilers, A., Moshourab, R., Kozlenkov, A., Labuz, D., Caspani, O., Erdmann, B., Machelska, H., Heppenstall, P.A. and Lewin, G.R., 2007. <i>A stomatin-domain protein essential for touch </i>

Touch and mechanical pain are first detected at our largest sensory surface, the skin. The cell bodies of sensory neurons that detect such stimuli are located in the dorsal root ganglia, and subtypes of these neurons are specialized to detect specific modalities of mech- anical stimuli. Molecules have been identified that are necessary for mechanosensation in invertebrates but so far not in mammals. In Caenorhabditis elegans, mec-2 is one of several genes identified in a screen for touch insensitivity and encodes an integral mem- brane protein with a stomatin homology domain1. Here we show that about 35% of skin mechanoreceptors do not respond to mech- anical stimuli in mice with a mutation in stomatin-like protein 3 (SLP3, also called Stoml3), a mammalian mec-2 homologue that is expressed in sensory neurons. In addition, mechanosensitive ion channels found in many sensory neurons do not function without SLP3. Tactile-driven behaviours are also impaired in SLP3 mutant mice, including touch-evoked pain caused by neuropathic injury. SLP3 is therefore indispensable for the function of a subset of cuta- neous mechanoreceptors, and our data support the idea that this protein is an essential subunit of a mammalian mechanotransducer.

Henrik Alle and Jörg R. P. Geiger, 2006. Combined Analog and Action Potential Coding in Hippocampal Mossy Fibers

Henrik Alle and Jörg R. P. Geiger, 2006. <i>Combined Analog and Action Potential Coding in Hippocampal Mossy Fibers</i>

In the mammalian cortex, it is generally assumed that the output information of neurons is encoded in the number and the timing of action potentials. Here, we show, by using direct patch- clamp recordings from presynaptic hippocampal mossy fiber boutons, that axons transmit analog signals in addition to action potentials. Excitatory presynaptic potentials result from subthreshold dendritic synaptic inputs, which propagate several hundreds of micrometers along the axon and modulate action potential–evoked transmitter release at the mossy fiber–CA3 synapse. This combined analog and action potential coding represents an additional mechanism for information transmission in a major hippocampal pathway.

Hu, J. and Lewin, G.R., 2006. Mechanosensitive currents in the neurites of cultured mouse sensory neurones.

Hu, J. and Lewin, G.R., 2006. <i>Mechanosensitive currents in the neurites of cultured mouse sensory neurones.</i>

Almost all sensory neurones in the dorsal root ganglia have a mechanosensory function. The transduction of mechanical stimuli in vivo takes place exclusively at the sensory ending. For cutaneous sensory receptors it has so far proved impossible to directly record the mechanically gated receptor potential because of the small size and inaccessibility of the sensory ending. Here we investigate whether mechanosensitive currents are present in the neurites of freshly isolated adult mouse sensory neurones in culture. Amost all sensory neurone neurites possess currents gated by submicrometre displacement stimuli (92%). Three types of mechanically activated conductance were characterized based on different inactivation kinetics. A rapidly adapting conductance was found in larger sensory neurones with narrow action potentials characteristic of mechanoreceptors. Slowly and intermediate adapting conductances were found exclusively in putative nociceptive neurones. Mechanically activated currents with similar kinetics were found also after stimulating the cell soma. However, soma currents were only observed in around 60% of cells tested and the displacement threshold was several times larger than for the neurite. The reversal potential of the rapidly adapting current indicated that this current is largely selective for sodium ions whereas the slowly adapting current is non-selective. It is likely that distinct ion channel entities underlie these two currents. In summary, our data suggest that the high sensitivity and robustness of mechanically gated currents in the sensory neurite make this a useful in vitro model for the mechanosensitive sensory endings in vivo.

Marten, H., Konrad, K., Dietrich, P., Roelfsema, M.R.G. and Hedrich, R., 2006. ABA activation of anion channels in tobacco guard cells.

Marten, H., Konrad, K., Dietrich, P., Roelfsema, M.R.G. and Hedrich, R., 2006. <i>ABA activation of anion channels in tobacco guard cells.</i>

Drought induces stomatal closure, a response that is associated with the activation of plasma membrane anion channels in guard cells, by the phytohormone ABA. In several species, this response is associated with changes in the cytoplasmic free Ca2+ concentration. In Vicia faba, however, guard cell anion channels activate in a Ca2+-independent manner (Levchenko et al., 2005, PNAS 102; 4203-4208). Because of potential differences between species, Nicotiana tabacum guard cells were studied in intact plants, with simultaneous recordings of the plasma membrane conductance and the cytoplasmic free Ca2+ concentration. ABA triggered transient rises in cytoplasmic Ca2+ in the majority of the guard cells (14 out of 19). In 7 out of 14 guard cells the change in cytoplasmic free Ca2+ closely matched the activation of anion channels, while the Ca2+ rise was delayed in 7 other cells. In the remaining 5 cells, ABA stimulated anion channels without a change in the cytoplasmic Ca2+ level. Even though ABA could activate anion channels in N. tabacum guard cells independent of a rise in the cytoplasmic Ca2+ concentration, patch clamp experiments showed that anion channels in these cells are stimulated by elevated Ca2+, in an ATP-dependent manner. Guard cells thus seem to have evolved both Ca2+- independent and -dependent ABA signalling pathways. Guard cells of N. tabacum apparently utilize both pathways, while ABA signalling in V. faba seems to be restricted to the Ca2+- independent pathway.

Lee, A.K., Manns, I.D., Sakmann, B. and Brecht, M., 2006. Whole-cell recordings in freely moving rats.

Lee, A.K., Manns, I.D., Sakmann, B. and Brecht, M., 2006. <i>Whole-cell recordings in freely moving rats.</i>

Intracellular recording, which allows direct measure- ment of the membrane potential and currents of indi- vidual neurons, requires a very mechanically stable preparation and has thus been limited to in vitro and head-immobilized in vivo experiments. This restriction constitutes a major obstacle for linking cellular and synaptic physiology with animal behavior. To over- come this limitation we have developed a method for performing whole-cell recordings in freely moving rats. We constructed a miniature head-mountable re- cording device, with mechanical stabilization achieved by anchoring the recording pipette rigidly in place after the whole-cell configuration is established. We obtain long-duration recordings (mean of w20 min, maximum 60 min) in freely moving animals that are remarkably insensitive to mechanical disturbances, then recon- struct the anatomy of the recorded cells. This head-an- chored whole-cell recording technique will enable a wide range of new studies involving detailed measure- ment and manipulation of the physiological properties of identified cells during natural behaviors.

Roelfsema, M.R.G., Konrad, K.R., Marten, H., George, K.P., Wolfram, H. and Rainer, H., 2005. Guard cells in albino leaf patches do not respond to photosynthetically active radiation, but are sensitive to blue light, CO2 and abscisic acid.

Roelfsema, M.R.G., Konrad, K.R., Marten, H., George, K.P., Wolfram, H. and Rainer, H., 2005. <i>Guard cells in albino leaf patches do not respond to photosynthetically active radiation, but are sensitive to blue light, CO2 and abscisic acid.</i>

Stomatal openings can be stimulated by light through two signalling pathways. The first pathway is blue light specific and involves phototropins, while the second pathway medi- ates a response to photosynthetically active radiation (PAR). This second pathway was studied with the use of albino Vicia faba plants and variegated leaves of Chloro- phytum comosum. Treatment of V. faba with norflurazon (Nf) inhibits the synthesis of carotenoids and leads to albino leaves with guard cells that lack functional green chloro- plasts. Guard cells in albino leaf patches of C. comosum, however, do contain photosynthetically active chloroplasts. Stomata in albino leaf patches of both plants did not respond to red light, although blue light could still induce stomatal opening. This shows that the response to PAR is not func- tioning in albino leaf patches, even though guard cells of C. comosum harbour chloroplasts. Stomata of Nf-treated plants still responded to CO2 and abscisic acid (ABA). The size of Nf-treated guard cells was increased, but impalement studies with double-barrelled microelectrodes revealed no changes in ion-transport properties at the plasma membrane of guard cells. Blue light could hyperpolarize albino guard cells by triggering outward currents with peak values of 37 pA in albino plants and 51 pA in green control cells. Because of the inhibition of carotenoid biosynthesis, Nf-treated V. faba plants contained only 4% of the ABA content found in green control plants. The ABA dose dependence of anion channel activation in guard cells was shifted in these plants, causing a reduced response to 10 mM ABA. These data show that despite the dramatic changes in physiology caused by Nf, the gross responsiveness of guard cells to blue light, CO2 and ABA remains unaltered. Stomata in albino leaf patches, however, do not respond to PAR, but require photosynthet- ically active mesophyll cells for this response.

Hess, D. and Richter, D.W., 2004. Function of a differential expression of serotonin receptors: a methodical approach.

Hess, D. and Richter, D.W., 2004. <i>Function of a differential expression of serotonin receptors: a methodical approach.</i>

Serotonin (5-HT) plays an important role in the modulation of neuronal excitability and synaptic interaction. Several receptor subtypes and isoforms, mostly linked to a G-protein coupled process, have been described. Here we focus on those receptors, i.e. the 5-HT1A, the 5HT4 and the 5-HT7 receptor isoform, modulating the adenylate-cyclase and thereby varying the cAMP concentration.

Recently, we have demonstrated that selective activation of serotonin receptor-isoforms modulate the efficacy of synaptic transmission from CA3 to CA1 neurons in hippocampal slice. EPSP amplitudes in CA1 neurons evoked by stimulation of the Schaffer collaterals were monitored while 5-HT agonists were applied. Activation of 5-HT1A receptors at distal dendrites reduced EPSP amplitudes, while activation of somatic 5-HT4 receptors increased EPSP amplitudes. These findings provide evidence for a heterogeneous expression profile of serotonin receptors in hippocampal CA1 neurons.

In order to verify such differential modulation in different cellular subdomains, we developed an appropriate model system. Here we present the arrangement of recording and applications electrodes in primary hippocampal cell cultures allowing direct access to identified synapses. To perform long-term recordings and to avoid wash out of cytosolic components, we use loose patch or focal extracellular recordings of the synaptic field potential to study individual synaptic processes. Synaptic activity is evoked by local electrical stimulation of presynaptic axons or local ionophoretic glutamate application. Using a push-pull application system, drugs are applied at circumscribed loci at different locations close to the synapse selected. This approach allows us to investigate the local microdomains of the modulatory processes of selective 5-HT receptors.

Shin, J., Martinez-Salgado, C., Heppenstall, P.A. and Lewin, G.R., 2003. A T-type calcium channel required for normal function of a mammalian mechanoreceptor.

Shin, J., Martinez-Salgado, C., Heppenstall, P.A. and Lewin, G.R., 2003. <i>A T-type calcium channel required for normal function of a mammalian mechanoreceptor.</i>

The dorsal root ganglia (DRG) contain a variety of mechanoreceptors, but no molecular markers uniquely identify specific mechanoreceptor subtypes. We have used DNA microarrays and subtracted cDNA libraries to isolate genes that are specifically expressed by one type of mouse mechanoreceptor. The T-type calcium channel C3y3.2 was exclusively expressed in the DRG by D-hair receptors, a very sensitive mechanoreceptor. Pharmacological blockade of T-type calcium channels indicated that this channel may be essential for normal D-hair receptor excitability including mechanosensitivity. This is the first evidence that a calcium channel is required for normal function of a vertebrate mechanoreceptor.

Materials science

P. G. Martin, T. ?. Scott, Electron microscopy at the nano-scale to investigate the Fukushima Daiichi nuclear power plant radiation releases, Microscopy & Analysis, September/October 2016, 29-33

P. G. Martin, T. ?. Scott, Electron microscopy at the nano-scale to investigate the Fukushima Daiichi nuclear power plant radiation releases, Microscopy & Analysis, September/October 2016, 29-33

Nudear power is never far from the spotlight, with ?arch 2016 having marked the fifth anniversary o fthe magnitude 9.0 earthquake and ensuing tsunami that crippled the Fukushi?a Daiichi Nuclear Power Plant (FDNPP) on Japan's eastern coast...

R. Erdélyi, V. Halász, Z. Szabó, I.E. Lukács, J. Volk, Mechanical characterization of epitaxially grown zinc oxide nanorods, Physica E 44 (2012) 1050–1053

R. Erdélyi, V. Halász, Z. Szabó, I.E. Lukács, J. Volk, Mechanical characterization of epitaxially grown zinc oxide nanorods, Physica E 44 (2012) 1050–1053

We performed a well controlled in situ bending test in a scanning electron microscope on individual ZnO nanorods to determine the bending modulus. The crystallographically aligned vertical nanocrystals were grown by wet epitaxial growth method through an electron beam generated pattern. They show good homogeneity, their length and top facet diameter vary in the range of 1.3–1.5 mm and 97–113 nm, respectively. The nanorods, which are fixed at their roots by the substrate, were bent at their free end along /11–20S and /10–10S crystallographic directions by a calibrated atomic force microscopy cantilever. The typical deflections, caused by 40–60 nN lateral loads, fall in the range of 50–100 nm. In order to take into the account the non-uniform cross section along the vertical axis, we propose a two-part mechanical model, which is built up from a lower truncated circular, and an upper truncated hexagonal cone. The obtained bending modulus is 36.078.3 GPa, which is significantly lower than that of the bulk ZnO (140 GPa).

S. Zaefferer, S. Kleindiek , K. Schock, B. Volbert, Combined Application of EBSD and ECCI Using a Versatile 5-Axes Goniometer in an SEM, 2013

S. Zaefferer, S. Kleindiek , K. Schock, B. Volbert, Combined Application of EBSD and ECCI Using a Versatile 5-Axes Goniometer in an SEM, 2013

Electron backscatter diffraction (EBSD) and electron channelling contrast imaging (ECCI) are two complementary diffraction techniques used to characterize microstructures of crystalline materials in a scanning electron microscope (SEM). EBSD allows the accurate measurement and mapping of crystal orientations and crystallographic phases. ECCI in contrast, is applied to observe individual lattice defects like dislocations, stacking faults and nano twins in the same manner as in TEM dark field images. Furthermore, ECCI can be used to image elastic strain fields with high accuracy. As in TEM optimum lattice defect contrast is obtained only if the sample is oriented in so-called two-beam conditions, when only one set of crystal lattice planes is in Bragg position with respect to the primary electron beam. We call the resulting technique ‘ECCI under controlled diffraction conditions’, cECCI. To obtain proper diffraction conditions one can either use electron channeling patterns (ECP) or one has to calculate the position from the orientation determined by EBSD.

Lixin Dong, Arunkumar Subramanian, Daniel Hugentobler, Bradley J. Nelson, Yu Sun, Nano encoders based on vertical arrays of individual carbon nanotubes, Advanced Robotics, Vol. 20, No. 11, 2006

Lixin Dong, Arunkumar Subramanian, Daniel Hugentobler, Bradley J. Nelson, Yu Sun, Nano encoders based on vertical arrays of individual carbon nanotubes, Advanced Robotics, Vol. 20, No. 11, 2006

Electron backscatter diffraction (EBSD) and electron channelling contrast imaging (ECCI) are two complementary diffraction techniques used to characterize microstructures of crystalline materials in a scanning electron microscope (SEM). EBSD allows the accurate measurement and mapping of crystal orientations and crystallographic phases. ECCI in contrast, is applied to observe individual lattice defects like dislocations, stacking faults and nano twins in the same manner as in TEM dark field images. Furthermore, ECCI can be used to image elastic strain fields with high accuracy. As in TEM optimum lattice defect contrast is obtained only if the sample is oriented in so-called two-beam conditions, when only one set of crystal lattice planes is in Bragg position with respect to the primary electron beam. We call the resulting technique ‘ECCI under controlled diffraction conditions’, cECCI. To obtain proper diffraction conditions one can either use electron channeling patterns (ECP) or one has to calculate the position from the orientation determined by EBSD.

P.G. Martin, I. Griffiths, C.P. Jones, et. al., In-situ removal and characterisation of uranium-containing particles from sediments surrounding the Fukushima Daiichi Nuclear Power Plant, Spectrochimica Acta Part B 117 (2016) 1–7

P.G. Martin, I. Griffiths, C.P. Jones, et. al., In-situ removal and characterisation of uranium-containing particles from sediments surrounding the Fukushima Daiichi Nuclear Power Plant, Spectrochimica Acta Part B 117 (2016) 1–7

Due to their high specific strength at high temperatures, TiAl-alloys are attractive candidates for high temperature applications. However, the low ductility of this material class at room temperature is a concern and therefore, a deeper understanding of crack nucleation and propagation in these alloys is desirable.

In this work, the crack nucleation and propagation mechanisms of TiAl alloys with fully lamellar microstructures were investigated and explained with the help of in-situ fracture experiments on the specimens of different length scale. The first part of this study is focused on crack propagation mechanisms in lamellar microstructures of a polycrystalline Ti-45Al-1Cr and polysynthetically twinned (PST) Ti-48Al crystals. For in- situ investigation on tensile and 3-point bend specimens, atomic force microscopy (AFM) was primarily used, which is the first attempt of in-situ investigations using AFM on TiAl-alloys. AFM has the advantage that small elastic strain fields and local plastic deformation in the crack tip vicinity can be mapped. SEM supplements the in-situ observations and was used to get a basic understanding of the crack propagation path over larger distances. The complex results on crack nucleation and deformation confinement drawn through in-situ AFM investigation were qualitatively explained with the help of finite element modeling. Focused ion beam (FIB) cross-sections, electron backscattered diffraction (EBSD) and transmission electron microscope (TEM) investigations of crack tip region were carried out for post mortem characterization. In addition to these fundamental understanding, fracture properties and cracking behavior of technologically important TiAl-alloys, namely a two phase TNB-V5 and a three phase TNMTM alloy containing ?0 phase were also investigated for their different microstructural variants.

The second major focus of this work was the development and exploitation of new small scale in-situ fracture tests on FIB prepared geometries, which can ease up the understanding of the complex crack nucleation and propagation mechanisms of lamellar TiAl-alloys. Therefore, the validation of micro-cantilever method was first exploited on stoichiometric intermetallic B2-NiAl single crystals due to its brittle nature and limited plasticity. Notched micro-cantilever experiments were optimized for getting consistent values of fracture toughness in comparison with the available literature according to ASTM-399. This method was optimized and used further to unveil the fracture

properties of constituent phases and interfaces existing in the complex lamellar microstructure of TiAl-alloys. Micro-cantilevers from ?2 and ? phases as well as from ?2/? interfaces were prepared from lamellar Ti-48Al PST crystals and tested in-situ with a cantilever-based nanoindenter in the SEM. The calculated fracture toughness of ?2, ?- phase and ?2/? interfaces were found to be closer to ab-initio literature values but 8-10 times lower than the bulk fracture toughness of TiAl compound. This shows that the extrinsic toughening mechanisms (micro-crack formation in stress concentrated regions, localized plasticity, crack branching and shear ligament bridging) contribute towards the higher bulk fracture toughness of TiAl alloys.

Farasat Iqbal, Dissertation, Erlangen, 2012. Fracture Mechanisms of gamma–TiAl Alloys Investigated by In-situ Experiments in a Scanning Electron and Atomic Force Microscope

Farasat Iqbal, Dissertation, Erlangen, 2012. Fracture Mechanisms of gamma–TiAl Alloys Investigated by In-situ Experiments in a Scanning Electron and Atomic Force Microscope

Due to their high specific strength at high temperatures, TiAl-alloys are attractive candidates for high temperature applications. However, the low ductility of this material class at room temperature is a concern and therefore, a deeper understanding of crack nucleation and propagation in these alloys is desirable.

In this work, the crack nucleation and propagation mechanisms of TiAl alloys with fully lamellar microstructures were investigated and explained with the help of in-situ fracture experiments on the specimens of different length scale. The first part of this study is focused on crack propagation mechanisms in lamellar microstructures of a polycrystalline Ti-45Al-1Cr and polysynthetically twinned (PST) Ti-48Al crystals. For in- situ investigation on tensile and 3-point bend specimens, atomic force microscopy (AFM) was primarily used, which is the first attempt of in-situ investigations using AFM on TiAl-alloys. AFM has the advantage that small elastic strain fields and local plastic deformation in the crack tip vicinity can be mapped. SEM supplements the in-situ observations and was used to get a basic understanding of the crack propagation path over larger distances. The complex results on crack nucleation and deformation confinement drawn through in-situ AFM investigation were qualitatively explained with the help of finite element modeling. Focused ion beam (FIB) cross-sections, electron backscattered diffraction (EBSD) and transmission electron microscope (TEM) investigations of crack tip region were carried out for post mortem characterization. In addition to these fundamental understanding, fracture properties and cracking behavior of technologically important TiAl-alloys, namely a two phase TNB-V5 and a three phase TNMTM alloy containing ?0 phase were also investigated for their different microstructural variants.

The second major focus of this work was the development and exploitation of new small scale in-situ fracture tests on FIB prepared geometries, which can ease up the understanding of the complex crack nucleation and propagation mechanisms of lamellar TiAl-alloys. Therefore, the validation of micro-cantilever method was first exploited on stoichiometric intermetallic B2-NiAl single crystals due to its brittle nature and limited plasticity. Notched micro-cantilever experiments were optimized for getting consistent values of fracture toughness in comparison with the available literature according to ASTM-399. This method was optimized and used further to unveil the fracture

properties of constituent phases and interfaces existing in the complex lamellar microstructure of TiAl-alloys. Micro-cantilevers from ?2 and ? phases as well as from ?2/? interfaces were prepared from lamellar Ti-48Al PST crystals and tested in-situ with a cantilever-based nanoindenter in the SEM. The calculated fracture toughness of ?2, ?- phase and ?2/? interfaces were found to be closer to ab-initio literature values but 8-10 times lower than the bulk fracture toughness of TiAl compound. This shows that the extrinsic toughening mechanisms (micro-crack formation in stress concentrated regions, localized plasticity, crack branching and shear ligament bridging) contribute towards the higher bulk fracture toughness of TiAl alloys.

Rufan Zhang, Zhiyuan Ning, Yingying Zhang, Quanshui Zheng, Qing Chen, Huanhuan Xie, Qiang Zhang, Weizhong Qian, Fei Wei, Superlubricity in centimetres-long double-walled carbon nanotubes under ambient conditions

Rufan Zhang, Zhiyuan Ning, Yingying Zhang, Quanshui Zheng, Qing Chen, Huanhuan Xie, Qiang Zhang, Weizhong Qian, Fei Wei, Superlubricity in centimetres-long double-walled carbon nanotubes under ambient conditions

Friction and wear are two main causes of mechanical energy dissipation and component failure, especially in micro/nano- mechanical systems with large surface-to-volume ratios. In the past decade there has been an increasing level of research interest regarding superlubricity, a phenomenon, also called structural superlubricity, in which friction almost vanishes between two incommensurate solid surfaces. However, all experimental structural superlubricity has been obtained on the microscale or nanoscale, and predominantly under high vacuum. Here, we show that superlubricity can be realized in centimetres-long double-walled carbon nanotubes (DWCNTs) under ambient conditions. Centimetres-long inner shells can be pulled out continuously from such nanotubes, with an inter- shell friction lower than 1 nN that is independent of nanotube length. The shear strength of the DWCNTs is only several pascals, four orders of magnitude lower than the lowest reported value in CNTs and graphite. The perfect structure of the ultralong DWCNTs used in our experiments is essential for macroscale superlubricity.

Gilgueng Hwang, Juan Camilo Acosta, Emir Vela, Sinan Haliyo, Stéphane Régnier, Graphene as Thin Film Infrared Optoelectronic Sensor

Gilgueng Hwang, Juan Camilo Acosta, Emir Vela, Sinan Haliyo, Stéphane Régnier, Graphene as Thin Film Infrared Optoelectronic Sensor

We present the conductometric behavior of a single atomic carbon nanostructure (graphene) that could be promising to infrared optoelectronic applications. A graphene nanomanipulation system with focused infrared laser source for optoelectronic property characterizations is implemented. The feasibility of mechanical and electrical probing manipulations on two-dimensional thin film nanostructures is studied. Using this system, we revealed the infrared optoelectronic properties of mono- and multilayer graphene. The obtained optoelectronic parameters are compared to the single- and multi-walled nanotubes. A graphene infrared sensor is prototyped by direct writing of electrodes using gold nanoink fountain-pen method and is analyzed by electrical probing. Results show that graphene could be a promising building block for thin film optoelectronic devices.

Ofer Teveta, Palle Von-Huthb, Ronit Popovitz-Birob, Rita Rosentsveiga. Daniel Wagnera, Reshef Tennea, 2011. Friction mechanism of individual multilayered nanoparticles.

Ofer Teveta, Palle Von-Huthb, Ronit Popovitz-Birob, Rita Rosentsveiga. Daniel Wagnera, Reshef Tennea, 2011. <i>Friction mechanism of individual multilayered nanoparticles.</i>

Inorganic nanoparticles of layered [two-dimensional (2D)] com- pounds with hollow polyhedral structure, known as fullerene- like nanoparticles (IF), were found to have excellent lubricating properties. This behavior can be explained by superposition of three main mechanisms: rolling, sliding, and exfoliation-material transfer (third body). In order to elucidate the tribological mechan- ism of individual nanoparticles in different regimes, in situ axial nanocompression and shearing forces were applied to individual nanoparticles using a high resolution scanning electron micro- scope. Gold nanoparticles deposited onto the IF nanoparticles surface served as markers, delineating the motion of individual IF nanoparticle. It can be concluded from these experiments that rolling is an important lubrication mechanism for IF-WS2 in the re- latively low range of normal stress (0.96±0.38 GPa). Sliding is shown to be relevant under slightly higher normal stress, where the spacing between the two mating surfaces does not permit free rolling of the nanoparticles. Exfoliation of the IF nanoparticles becomes the dominant mechanism at the high end of normal stress; above 1.2 GPa and (slow) shear; i.e., boundary lubrication conditions. It is argued that the modus operandi of the nanoparti- cles depends on their degree of crystallinity (defects); sizes; shape, and their mechanical characteristics. This study suggests that the rolling mechanism, which leads to low friction and wear, could be attained by improving the sphericity of the IF nanoparticle, the dispersion (deagglomeration) of the nanoparticles, and the smoothness of the mating surfaces.

Moriz Mayer, Wolfgang Augustin, Stephan Scholl, 2012. Adhesion of single crystals on modified surfaces in crystallization fouling.

Moriz Mayer, Wolfgang Augustin, Stephan Scholl, 2012. <i>Adhesion of single crystals on modified surfaces in crystallization fouling.</i>

In crystallization fouling it has been observed that during a certain initial phase the fouling is formed by a non-uniform layer consisting of a population of single crystals. These single crystals are frequently formed by inverse soluble salts such as CaCO3. During heterogeneous nucleation and heterogeneous growth an interfacial area between the crystal and the heat transfer surface occurs. The development of this interfacial area is the reason for the adhesion of each single crystal and of all individual crystals, once a uniform layer has been built up. The emerging interfacial area is intrinsic to the heterogeneous nucleation of crystals and can be explained by the thermodynamic principle of the minimum of the Gibbs free energy. In this study CaCO3 crystals were grown heterogeneously on untreated and on modi?ed surfaces inside a ?ow channel. An untreated stainless steel (AISI 304) surface was used as a reference. Following surface modi?cations were investigated: enameled and electropolished stainless steel as well as diamond-like-carbon based coatings on stainless steel substrate. The adhesion was measured through a novel measurement technique using a micromanipulator to shear off single crystals from the substrate which was ?xed to a spring table inside a SEM.

A Schulze, T Hantschel, A Dathe, P Eyben, X Ke, W Vandervorst, 2012. Electrical tomography using atomic force microscopy and its application towards carbon nanotube-based interconnects.

A Schulze, T Hantschel, A Dathe, P Eyben, X Ke, W Vandervorst, 2012. <i>Electrical tomography using atomic force microscopy and its application towards carbon nanotube-based interconnects.</i>

The fabrication and integration of low-resistance carbon nanotubes (CNTs) for interconnects in future integrated circuits requires characterization techniques providing structural and electrical information at the nanometer scale. In this paper we present a slice-and-view approach based on electrical atomic force microscopy. Material removal achieved by successive scanning using doped ultra-sharp full-diamond probes, manufactured in-house, enables us to acquire two-dimensional (2D) resistance maps originating from different depths (equivalently different CNT lengths) on CNT-based interconnects. Stacking and interpolating these 2D resistance maps results in a three-dimensional (3D) representation (tomogram). This allows insight from a structural (e.g. size, density, distribution, straightness) and electrical point of view simultaneously. By extracting the resistance evolution over the length of an individual CNT we derive quantitative information about the resistivity and the contact resistance between the CNT and bottom electrode.

Chaoying Zhang, Zhiyuan Ning, Yang Liu, Tingting Xu, Yao Guo et al., 2012. Electrical transport properties of individual WS2 nanotubes and their dependence on water and oxygen absorption.

Chaoying Zhang, Zhiyuan Ning, Yang Liu, Tingting Xu, Yao Guo et al., 2012. <i>Electrical transport properties of individual WS2 nanotubes and their dependence on water and oxygen absorption.</i>

The electrical properties of WS2 nanotubes (NTs) were studied through measuring 59 devices. Important electrical parameters, such as the carrier concentration, mobility, and effective barrier height at the contacts, were obtained through fitting experimental non-linear I-V curves using a metal-semiconductor-metal model. The carrier mobility was found to be several orders of magnitude higher than that have been reported previously for WS2 NTs. Water absorption was found to decrease the conductivity and carrier mobility of the NTs, and could be removed when the sample was dried. Oxygen absorption also slightly decreased the conductivity of WS2 NTs.

Xiaodong He, Chao Wang, Liyong Tong, Rongguo Wang, Anyuan Cao, Qingyu Peng, Steven Moody, Yibin Li, 2012. Direct measurement of grafting strength between an individual carbon nanotube and a carbon fiber.

Xiaodong He, Chao Wang, Liyong Tong, Rongguo Wang, Anyuan Cao, Qingyu Peng, Steven Moody, Yibin Li, 2012. <i>Direct measurement of grafting strength between an individual carbon nanotube and a carbon fiber.</i>

Hierarchical structures consisting of carbon nanotubes (CNTs) grafted onto a carbon fiber (CF) have the potential to improve the performance of fiber/polymer composites. The strength between a CNT and a CF is a key factor that influences the load-transfer behavior and inter-laminar properties. Here, we directly measured the grafting strength of a chem- ically bonded CNT–CF hierarchical structure by detaching individual CNT from the CF sub- strate and simultaneously recording the force–displacement characteristics in a scanning electron microscopy equipped with a nano-manipulator. We observed a relatively wide dis- tribution of the maximum forces at complete detachment for different grafted CNTs, which ranges from below the van der Waals (vdW) force existing at the CNT–CF interface up to 7 times higher than that. For a typical configuration where a CNT is partially anchored on a CF, we obtained grafting strengths in the range of 5–90 MPa, which are dominated by the vdW force as well as other factors such as chemical bonding. Our results, based on the measurements at individual nanostructure level, might be useful for designing and fabrica- tion of high performance hierarchical composites.

M. Mayer, W. Augustin and S. Scholl, 2011. Experimental Study on the Adhesion of Single Crystals on Modified Surfaces in Crystallization Fouling.

M. Mayer, W. Augustin and S. Scholl, 2011. <i>Experimental Study on the Adhesion of Single Crystals on Modified Surfaces in Crystallization Fouling.</i>

Since a long time it was tried to describe fouling on heat transfer surfaces by mathematical models. Most studies about fouling concentrate on the description of the thermal effects by the developing fouling resistance Rf. In general it is assumed that a homogeneous fouling layer builds up. Some fouling models include the adhesion of the uniform fouling layer. In crystallization fouling it has been observed that during a certain initial phase the fouling is formed by a non-uniform layer consisting of a population of single crystals. These single crystals are formed by inverse soluble salts such as CaCO3. During heterogeneous nucleation and heterogeneous growth an interface between the crystal and the heat exchanger surface occurs. The development of this interface is the reason for the adhesion of each single crystal and in total, once a uniform layer has been built up. The emerging interface is intrinsic to the heterogeneous nucleation of crystals and can be explained the thermodynamic principle of the minimum of the Gibbs free energy. In this study CaCO3 crystals were grown heterogeneously on untreated and on modified surfaces inside a flow channel. The adhesion was measured through a micro manipulator that sheared off single crystals from the substrate that was fixed to a spring table inside a SEM.

Kobs, A., Spahr, H., Stickler, D., Hankemeier, S., Frömter, R. and Oepen, H.P., 2009. Magnetic energies of single submicron permalloy rectangles determined via magnetotransport.

Kobs, A., Spahr, H., Stickler, D., Hankemeier, S., Frömter, R. and Oepen, H.P., 2009. <i>Magnetic energies of single submicron permalloy rectangles determined via magnetotransport.</i>

We have investigated the magnetic properties of single submicron permalloy rectangles with a thickness of 20 nm and an aspect ratio of 2:1 via anisotropic magnetoresistance. Preparation and investigation via magnetotransport are performed in situ in ultrahigh vacuum. The field-dependent magnetization behavior of the two generic cases with the magnetic field applied perpendicular and parallel to the long axis of the rectangles is studied. Due to the high sensitivity of our setup, single field sweeps are sufficient to obtain magnetoresis- tance curves of structures with dimensions as small as 600ô-300 nm2. To link features of the AMR to changes in the micromagnetic states, the remanent state has been investigated via scanning electron microscopy with polarization analysis. Our main result is that the energy density of micromagnetic states can be obtained from the hard-axis magnetization behavior. It is demonstrated that a C/S state can be distinguished from a Landau state and the energy difference between both states is determined.

Peng, Y., Cullis, T. and Inkson, B., 2008. Bottom-up Nanoconstruction by the Welding of Individual Nanoobjects Using Nanoscale Solder.

Peng, Y., Cullis, T. and Inkson, B., 2008. <i>Bottom-up Nanoconstruction by the Welding of Individual Nanoobjects Using Nanoscale Solder.</i>

We report that individual metallic nanowires and nanoobjects can be assembled and welded together into complex nanostructures and conductive circuits by a new nanoscale electrical welding technique using nanovolumes of metal solder. At the weld sites, nanoscale volumes of a chosen metal are deposited using a sacrificial nanowire, which ensures that the nanoobjects to be bonded retain their structural integrity. We demonstrate by welding both similar and dissimilar materials that the use of nanoscale solder is clean, controllable, and reliable and ensures both mechanically strong and electrically conductive contacts. Nanoscale weld resistances of just 20Ω are achieved by using Sn solder. Precise engineering of nanowelds by this technique, including the chemical flexibility of the nanowire solder, and high spatial resolution of the nanowelding method, should result in research applications including fabrication of nanosensors and nanoelectronics constructed from a small number of nanoobjects, and repair of interconnects and failed nanoscale electronics.

Shinonaga, T., Donohue, D., Ciurapinski, A. and Klose, D., 2008. Age determination of single plutonium particles after chemical separation.

Shinonaga, T., Donohue, D., Ciurapinski, A. and Klose, D., 2008. <i>Age determination of single plutonium particles after chemical separation.</i>

Age determination of single plutonium particles was demonstrated using five particles of the standard reference material, NBS 947 (Plutonium Isotopic Standard. National Bureau of Standards, Washington, D.C. 20234, August 19, 1982, currently distributed as NBL CRM-137) and the radioactive decay of 241Pu into 241Am. The elemental ratio of Am/Pu in Pu particles found on a carbon planchet was measured by wavelength dispersive X-ray spectrometry (WDX) coupled to a scanning electron microscope (SEM). After the WDX measurement, each plutonium particle, with an average size of a few μm, was picked up and relocated to a silicon wafer inside the SEM chamber using a micromanipulator. The silicon wafer was then transferred to a quartz tube for dissolution in an acid solution prior to chemical separation. After the Pu was chemically separated from Am and U, the isotopic ratios of Pu (240Pu/239Pu, 241Pu/239Pu and 242Pu/239Pu) were measured with a thermal ionization mass spectrometer (TIMS) for the calculation of Pu age. The age of particles determined in this study was in good agreement with the expected age (35.9 a) of NBS 947 within the measurement uncertainty.

Jiang, A.N., Gao, S., Wei, X.L., Liang, X.L. and Chen, Q., 2008. Amplitude Response of Multiwalled Carbon Nanotube Probe with Controlled Length during Tapping Mode Atomic Force Microscopy.

Jiang, A.N., Gao, S., Wei, X.L., Liang, X.L. and Chen, Q., 2008. <i>Amplitude Response of Multiwalled Carbon Nanotube Probe with Controlled Length during Tapping Mode Atomic Force Microscopy.</i>

Multiwalled carbon nanotube (MWCNT) atomic force microscope (AFM) probes were fabricated with controlled length using nanomanipulators inside scanning electron microscope. The amplitude-distance responses of MWCNT AFM probes were systematically studied experimentally. Several special characteristics of CNT AFM probes were observed, such as amplitude jump-into-zero, rebounds after the probe already touched the surface and large hysteresis during retraction. Transition from attractive to repulsive regions was also observed when the CNT is long and the amplitude is large. Tapping mode amplitude-distance curves were found to change regularly with the length of the carbon nanotubes and their tilting angle relative to the substrate surface normal. The results were comparable with previous theoretical predictions. Through direct observations by electron microscopes, MWCNT AFM probes were found to bend homogenously even when they were pushed toward the SiO2 wafer for several hundred nanometers after they had touched the surface of the substrate. By analyzing the results obtained from several probes it was found that the MWCNT AFM probes in tapping mode should be suitable for stable operation with proper length and working condition.

Stickler, D. Frömter, R., Li, W., Kobs, A. and Oepen, H.P., 2008. Integrated setup for the fabrication and measurement of magnetoresistive nanoconstrictions in ultrahigh vacuum.

Stickler, D. Frömter, R., Li, W., Kobs, A. and Oepen, H.P., 2008. <i>Integrated setup for the fabrication and measurement of magnetoresistive nanoconstrictions in ultrahigh vacuum.</i>

A UHV instrument is presented for in situ fabrication of nanostructures and in situ investigation of their magnetoresistance. Nanostructures of diverse shape and size are created from thin films utilizing a focused ion beam. The magnetic nanostructures are contacted via a micromanipulator, which makes it possible to address the individual structures. The system is additionally equipped with a scanning electron microscope column, which is used for damage-free navigation and control of the structuring and contacting. First magnetoresistance measurements of structures carved into a Permalloy film demonstrate the high sensitivity and the flexibility of the new setup.

Fernández-Pacheco, A., De Teresa, J.M., Córdoba, R. and Ibarra, M.R., 2008. Exploring the conduction in atomic-sized metallic constrictions created by controlled ion etching.

Fernández-Pacheco, A., De Teresa, J.M., Córdoba, R. and Ibarra, M.R., 2008. <i>Exploring the conduction in atomic-sized metallic constrictions created by controlled ion etching.</i>

A novel technique to establish atomic-sized contacts in metallic materials is shown. It is based on etching a (sub)micrometric electrode via a low-energy focused ion beam. The in situ measurements of the nanoconstriction resistance during the etching process permit control of the formation of atomic-sized constrictions with milling time, observing steps in the conductance in the range of the conductance quantum (G0 = 2e2/h), just before entering the tunnelling regime. These constrictions are highly stable with time due to the adherence to a substrate, which allows further studies such as the detailed current–voltage transport investigation reported here. Scanning electron microscopy images are used to correlate the etching process and the constriction microstructure. The high control achieved in the process makes us suggest this technique as a promising route to study physical phenomena in the verge of the metal–tunnel conduction crossover.

Cimalla, V., Röhlig, C., Pezoldt, J., Niebelschütz, M., Ambacher, O., Brückner, K., Hein, M., Weber, J., Milenkovic, S., Smith, A.J. and Hassel, A.W., 2008. Nanomechanics of Single Crystalline Tungsten Nanowires.

Cimalla, V., Röhlig, C., Pezoldt, J., Niebelschütz, M., Ambacher, O., Brückner, K., Hein, M., Weber, J., Milenkovic, S., Smith, A.J. and Hassel, A.W., 2008. <i>Nanomechanics of Single Crystalline Tungsten Nanowires.</i>

Single crystalline tungsten nanowires were prepared from directionally solidified NiAl-W alloys by a chemical release from the resulting binary phase material. Electron back scatter diffraction (EBSD) proves that they are single crystals having identical crys- tallographic orientation. Mechanical investigations such as bending tests, lateral force measurements, and mechanical resonance measurements were performed on 100–300 nm diameter wires. The wires could be either directly employed using micro tweezers, as a singly clamped nanowire or in a doubly clamped nanobridge. The mechanical tests exhibit a surprisingly high flexibility for such a brittle material resulting from the small dimensions. Force displacement measurements on singly clamped W nanowires by an AFM measurement allowed the determination of a Young's modulus of 332 GPa very close to the bulk value of 355 GPa. Doubly clamped W nanowires were employed as resonant oscillating nanowires in a magnetomotively driven resonator running at 117 kHz. The Young's modulus determined from this setup was found to be higher 450 GPa which is likely to be an artefact resulting from the shift of the resonance frequency by an additional mass loading.

Wei, X.-L., Liu, Y., Chen, Q., Wang, M.-S. and Peng L.-M., 2007. The Very Low Shear Modulus of Multi-Walled Carbon Nanotubes Determined Simultaneously with the Axial Young's Modulus via in situ Experiments.

Wei, X.-L., Liu, Y., Chen, Q., Wang, M.-S. and Peng L.-M., 2007. <i>The Very Low Shear Modulus of Multi-Walled Carbon Nanotubes Determined Simultaneously with the Axial Young's Modulus via in situ Experiments.</i>

The dorsal root ganglia (DRG) contain a variety of mechanoreceptors, but no molecular markers uniquely identify specific mechanoreceptor subtypes. We have used DNA microarrays and subtracted cDNA libraries to isolate genes that are specifically expressed by one type of mouse mechanoreceptor. The T-type calcium channel C3y3.2 was exclusively expressed in the DRG by D-hair receptors, a very sensitive mechanoreceptor. Pharmacological blockade of T-type calcium channels indicated that this channel may be essential for normal D-hair receptor excitability including mechanosensitivity. This is the first evidence that a calcium channel is required for normal function of a vertebrate mechanoreceptor.

Volkringer, C., Popov, D., Loiseau, T., Guillou, N., Ferey, G., Haouas, M., Taulelle, F., Mellot-Draznieks, C., Burghammer, M. and Riekel, C., 2007. A microdiffraction set-up for nanoporous metal-organic-framework-type solids.

Volkringer, C., Popov, D., Loiseau, T., Guillou, N., Ferey, G., Haouas, M., Taulelle, F., Mellot-Draznieks, C., Burghammer, M. and Riekel, C., 2007. <i>A microdiffraction set-up for nanoporous metal-organic-framework-type solids.</i>

For the past decade, the emerging class of porous metal-organic frameworks has been becoming one of the most promising materials for the construction of extralarge pore networks in view of potential applications in catalysis, separation and gas storage. The knowledge of the atomic arrangements in these crystalline compounds is a key point for the understanding of the chemical and physical properties. Their crystal size limits the use of single-crystal diffraction analysis, and synchrotron radiation facilities4 may allow for the analysis of tiny crystals. We present here a microdiffraction set-up for the collection of Bragg intensities, which pushes down the limit to the micrometre scale by using a microfocused X-ray beam of 1 μm. We report the structure determination of a new porous metal– organic-framework-type aluminium trimesate (MIL-110) from a single crystal of a few micrometres length, showing very weak scattering factors owing to the composition of the framework (light elements) and very low density. Its structure is built up from a honeycomb-like network with hexagonal 16 A channels, involving the connection of octahedrally coordinated aluminium octameric motifs with the trimesate ligands. Solid-state NMR (27Al,13C,1H) and molecular modelling are finally considered for the structural characterization.

Rösler, J,, Mukherji, D., Schock, K. and Kleindiek, S., 2007. Forging of metallic nano-objects for the fabrication of submicron-size components.

Rösler, J,, Mukherji, D., Schock, K. and Kleindiek, S., 2007. <i>Forging of metallic nano-objects for the fabrication of submicron-size components.</i>

In recent years, nanoscale fabrication has developed considerably, but the fabrication of free-standing nanosize components is still a great challenge. The fabrication of metallic nanocomponents utilizing three basic steps is demonstrated here. First, metallic alloys are used as factories to produce a metallic raw stock of nano-objects/nanoparticles in large numbers. These objects are then isolated from the powder containing thousands of such objects inside a scanning electron microscope using manipulators, and placed on a micro-anvil or a die. Finally, the shape of the individual nano-object is changed by nanoforging using a microhammer. In this way free-standing, high-strength, metallic nano-objects may be shaped into components with dimensions in the 100 nm range. By assembling such nanocomponents, high-performance microsystems can be fabricated, which are truly in the micrometre scale (the size ratio of a system to its component is typically 10:1).

van Apeldoorn, A.A., Aksenov, Y., Stigter, M., Hofland, I., de Bruijn, J.D., Koerten, H.K., Otto, C., Greve, J. and van Blitterswijk, C.A., 2005. Parallel high-resolution confocal Raman SEM analysis of inorganic and organic bone matrix constituents

van Apeldoorn, A.A., Aksenov, Y., Stigter, M., Hofland, I., de Bruijn, J.D., Koerten, H.K., Otto, C., Greve, J. and van Blitterswijk, C.A., 2005. <i>Parallel high-resolution confocal Raman SEM analysis of inorganic and organic bone matrix constituents</i>

In many multi-disciplinary fields of science, such as tissue engineering, where material and biological sciences are combined, there is a need for a tool that combines ultrastructural and chemical data analysis in a non-destructive manner at high resolution. We show that a combination of confocal Raman spectroscopy (CRS) and scanning electron microscopy (SEM) can be used for such analysis. Studies of atomic composition can be done by X-ray microanalysis in SEM, but this is only possible for atomic numbers greater than five and does not reveal molecular identity. Raman spectroscopy, however, can provide information on molecular composition and identity by detection of wavelength shifts caused by molecular vibrations. In this study, CRS–SEM revealed that early in vitro-formed bone extracellular matrix (ECM) produced by rat osteoprogenitor cells resembles mature bone chemically. We gained insight into the structure and chemical composition of the ECM, which was composed of mainly mineralized collagen type I fibres and areas of dense carbonated calcium phosphate related to the collagen fibre density, as revealed by Raman imaging of SEM samples. We found that CRS–SEM allows the study of specimens in a non-destructive manner and provides high-resolution structural and chemical information about inorganic and organic constituents by parallel measurements on the same sample.

Tay, A.B.H. and Thong, J.T.L., 2004. High-resolution nanowire atomic force microscope probe grown by a field-emission induced process.

Tay, A.B.H. and Thong, J.T.L., 2004. <i>High-resolution nanowire atomic force microscope probe grown by a field-emission induced process.</i>

A technique to grow a nanowire probe on an atomic force microscope tip using a field-emission induced growth process has been developed. The simple and highly reproducible technique produces vertically aligned nanowire probes whose length is controlled by the growth duration. Using a cantilever clamping arrangement, nanowire probes can be grown on low-stiffness cantilevers. Experiments using the robust nanowire AFM probe demonstrate its ability to produce high-resolution tapping mode AFM images and improved profiling of structures with steep sidewalls due to its very sharp tip and high aspect ratio. No degradation in imaging performance was observed after a period of continuous scanning and storage.

Burkhardt, C., Bauerdick, S., Rudorf, R., Nisch, W., Bucher, V., Barth, W., Ehrmann, A., Lutz, T. and Rau, J., 2002. Investigation of low damage mask repair by combination of electron beam and scanning force technology.

Burkhardt, C., Bauerdick, S., Rudorf, R., Nisch, W., Bucher, V., Barth, W., Ehrmann, A., Lutz, T. and Rau, J., 2002. <i>Investigation of low damage mask repair by combination of electron beam and scanning force technology.</i>

To investigate low damage mask repair, we have built a system, which combines electron beam induced deposition (EBID), electron beam induced etching and scratching by an atomic force microscope (AFM). Therefore a three channel gas injection system was built and adapted to a FESEM. The guidance of the precursor gas inside the SEM is done by compact micro manipulators which allow a precise and stable positioning in three dimensions with a resolution below one micrometer. For a first test of the performance of the system we used a mask with defined clear and dark defects with dimensions down to 40 nm nominal size.

Using electrons instead of ions (which are usually used in repair tools) for deposition of material on the mask, clear defects could be completely repaired and show no damage. Defect sizes down to 20 nm can be repaired with a position accuracy below 15 nm. A compact AFM was integrated on the stage of the SEM, thus allowing AFM imaging of the defects under SEM control.

Bauerdick, S., Barth, W., Bucher, V., Burkhardt, C., Rudorf, R. and Nisch, W., 2002. In-situ monitoring of electron beam induced deposition by atomic force microscopy in a scanning electron microscope.

Bauerdick, S., Barth, W., Bucher, V., Burkhardt, C., Rudorf, R. and Nisch, W., 2002. <i>In-situ monitoring of electron beam induced deposition by atomic force microscopy in a scanning electron microscope.</i>

Scanning Electron Microscopes (SEM) are widely used for analytics in the micro- and nanometer range. For further specific inspection an Atomic Force Microscope (AFM) is useful provided that positioning of sample and tip can be obtained quickly. A new type of AFM is proposed, whose compact and guidable setup allows the tip to be positioned inside and under observation of a SEM. Thus information on lateral dimensions and material from the SEM inspection could be completed by precise topography and friction measurements in-situ.

Electron Beam Induced Deposition (EBID) of tungstenhexacarbonyle has been carried out. Thus we are able to investigate the application of various techniques to analytics,

Electron Beam Induced Depositon

Tungstenhexacarbonyle W(CO)6 shows a vapour pressure of 2 Torr @ 35°C and serves as precursor for deposition of tungsten with carbon content (EDX). The external reservoir was heated to 35°C but a dosing valve was used to keep the global chamber

-6 -5 pressure in the range 6 10 to 3 10 mbar at a base pressure

-6 below 2 10 mbar. Deposition has been performed at electron

energies of 1keV to 30 keV, doses of 0.01 to 1.8 nC per spot and a stepsize of 100 to 30 nm on p-type silicon.

The glass drain tubes were 10 to 50 um in diameter and arranged to the point of deposition at a lateral distance of about 50 um

Nanomanipulation

Zheng, Q., Jiang, B., Liu, S., Weng, Y., Lu, L., Xue, Q., Zhu, J., Jiang, Q., Wang, S. and Peng, L., 2008. Self-Retracting Motion of Graphite Microflakes.

Zheng, Q., Jiang, B., Liu, S., Weng, Y., Lu, L., Xue, Q., Zhu, J., Jiang, Q., Wang, S. and Peng, L., 2008. <i>Self-Retracting Motion of Graphite Microflakes.</i>

We report the observation of a novel phenomenon, the self-retracting motion of graphite, in which tiny flakes of graphite, after being displaced to various suspended positions from islands of highly orientated pyrolytic graphite, retract back onto the islands under no external influences. Reports of this phenomenon have not been found in the literature for single crystals of any kind. Models that include the van der Waals force, electrostatic force, and shear strengths were considered to explain the observed phenomenon. These findings may conduce to create nanoelectromechanical systems with a wide range of mechanical frequency from megahertz to gigahertz.

Wei, X.-L., Chen, Q., Liu, Y. and Peng, L.-M., 2007. Cutting and sharpening carbon nanotubes using a carbon nanotube "nanoknife".

Wei, X.-L., Chen, Q., Liu, Y. and Peng, L.-M., 2007. <i>Cutting and sharpening carbon nanotubes using a carbon nanotube "nanoknife".</i>

A new method has been developed to precisely cut and to sharpen carbon nanotubes using a "nanoknife", which is a short carbon nanotube adhered to a metal tip. The mechanism for the cutting and the sharpening was proposed to be local vaporization of carbon caused by Joule heating. The "nanoknife" was also found useful to cut other nanotubes and nanowires. The cutting process was also found useful to construct complex carbon nanotube structures.

Hützendorfer, H., Giouroudi, I., Bou, S. and Ferros, M., 2006. Evaluation of different control algorithms for a micromanipulation system.

Hützendorfer, H., Giouroudi, I., Bou, S. and Ferros, M., 2006. <i>Evaluation of different control algorithms for a micromanipulation system.</i>

In this paper the development of a micromanipulation system with stereoscopic imaging and different control algorithms is reported. The system consists of a commercially available micromanipulator (Kleindiek MM3A), an electromagnetically actuated microgripper, 2 external CCD cameras performing stereovision, a stereoscopic lightmicroscope and a control PC. As the micromanipulator does not possess positional encoders the microgripper's position has to be provided by the implemented visual feedback system. Once this position is known, inverse kinematics is applied to calculate the position of the micromanipulator's axes. The implemented adaptive discrete P-control is evaluated and compared to an artificial neural network model. To get a better understanding of the dynamic model of the micromanipulator, a characterization of its axes is performed. The derived data also assisted the control improvement of the micromanipulator.

Giouroudi, I., Hützendorfer, H., Andrijasevic, D., Ferros, M. and Brenner, W., 2006. Design of a microgripping system with visual and force feedback for MEMS applications.

Giouroudi, I., Hützendorfer, H., Andrijasevic, D., Ferros, M. and Brenner, W., 2006. <i>Design of a microgripping system with visual and force feedback for MEMS applications.</i>

This paper reports the design of a microgripping system with visual and force feedback for handling and assembly in microtechnology. The system consists of a microgripper, an electromagnetic microactuator, the Kleindiek Micromanipulator MM3A, a light microscope, a CCD camera and a computer. The microgripper is mounted on the Kleindiek Micromanipulator MM3A which has 3 degrees of freedom (two rotational axes, one linear axis), wide working range (240° in the rotational axes, 12 mm in the linear axis) and subnanometer resolution. An external CCD camera provides images for obtaining the actual axis positions and by applying inverse kinematics the actual position of the manipulators end-effector is calculated so as to perform coarse positioning. A second CCD camera in combination with a light microscope provides sufficiently precise data to perform the actual manipulation tasks. Since the gripper is electromagnetically driven, the movement of the gripper tips is a continuous mapping of the applied current. The applied current can be correlated to the actual distance between the tips by calibration. In case of gripping an object, the tips are hindered to close to the full extent. The resulting gripping force depends on the actual distance changes.

Nelson, B.J., Dong, L.X., Subramanian, A. and Bell, D.J., 2005. Hybrid nanorobotic approaches to NEMS.

Nelson, B.J., Dong, L.X., Subramanian, A. and Bell, D.J., 2005. <i>Hybrid nanorobotic approaches to NEMS.</i>

Robotic manipulation at the nanometer scale is a promising technology for structuring, characterizing and assembling nano building blocks into nanoelectromechanical systems (NEMS). Combined with recently developed nanofabrication processes, a hybrid approach to building NEMS from individual carbon nanotubes (CNTs) and SiGe/Si nanocoils is described. Nanosensors and nanoactuators are investigated from experimental, theoretical, and design perspectives.

Clévy, C., Hubert, A., Agnus, J. and Chaillet, N., 2005. A micromanipulation cell including a tool changer.

Clévy, C., Hubert, A., Agnus, J. and Chaillet, N., 2005. <i>A micromanipulation cell including a tool changer.</i>

This paper deals with the design, fabrication and characterization of a tool changer for micromanipulation cells. This tool changer is part of a manipulation cell including a three linear axes robot and a piezoelectric microgripper. All these parts are designed to perform micromanipulation tasks in confined spaces such as a microfactory or in the chamber of a scanning electron microscope (SEM). The tool changer principle is to fix a pair of tools (i.e. the gripper tips) either on the tips of the microgripper actuator (piezoceramic bulk) or on a tool magazine. The temperature control of a thermal glue enables one to fix or release this pair of tools. Liquefaction and solidification are generated by surface mounted device (SMD) resistances fixed on the surface of the actuator or magazine. Based on this principle, the tool changer can be adapted to other kinds of micromanipulation cells. Hundreds of automatic tool exchanges were performed with a maximum positioning error between two consecutive tool exchanges of 3.2 um, 2.3 um and 2.8 μm on the X, Y and Z axes respectively (Z refers to the vertical axis). Finally, temperature measurements achieved under atmospheric pressure and in a vacuum environment and pressure measurements confirm the possibility of using this device in the air as well as in a SEM.

Chen, Q. and Peng, L.-M., 2004. Controlled cleavage of single semiconducting nanowires and study on the suitability of their use as nanocavities for nanolasers.

Chen, Q. and Peng, L.-M., 2004. <i>Controlled cleavage of single semiconducting nanowires and study on the suitability of their use as nanocavities for nanolasers.</i>

Single semiconducting nanowires have been cleaved to desired length at desired locations inside the scanning electron microscope (SEM) using a nanoprobe system. SEM and transmission electron microscope examinations of the cleaved nanowires revealed that the cleaved ends of the nanowires are in general atomic flat, but not without atomic steps. Possible use of the cleaved nanowire as nanocavity for nanolaser was considered, and several key parameters were estimated. In particular, our result shows that, for a semiconducting CdS nanowire, the effect of the atomic steps at the cleaved ends of the nanowire is negligible if the nanowire cavity is longer than several micrometers.

Tay, A.B.H. and Thong, J.T.L., 2004. Fabrication of super-sharp nanowire atomic force microscope probes using a field emission induced growth technique.

Tay, A.B.H. and Thong, J.T.L., 2004. <i>Fabrication of super-sharp nanowire atomic force microscope probes using a field emission induced growth technique.</i>

A relatively simple and consistent technique based on field emission induced growth has been developed to grow a single metallic nanowire on an atomic force microscope (AFM) tip. A clamping setup with two micromanipulators ensures that the fabrication of a vertically aligned nanowire probe, which is sharp, robust, and with high aspect ratio, can be achieved on different types of AFM cantilevers with different force constants. The controlled growth technique has been used to produce tungsten nanowire AFM probes with great consistency and high reproducibility. The tungsten nanowires were grown to lengths between 100 nm to 1.5 􏰎m with radius of curvature at the tip end typically between 1–2 nm. Experiments using the fabricated tungsten nanowire AFM probe demonstrate its ability to produce high-resolution AFM images and improved profiling of structures with steep sidewalls due to its very sharp tip and high aspect ratio. The technique can be extended to fabricating other types of metallic nanowire AFM probes or even composite nanowire AFM probes by using different precursor gases. Experiments have been successful in fabricating cobalt nanowire AFM probes which are able to produce good high-resolution AFM images as well.

Kaegi, R. and Holzer, L., 2003. Transfer of a single particle for combined ESEM and TEM analyses.

Kaegi, R. and Holzer, L., 2003. <i>Transfer of a single particle for combined ESEM and TEM analyses.</i>

A new approach for transferring micrometer-sized particles between different sample holders has been developed using manipulators within an environmental scanning electron microscope (ESEM) sample chamber. Particles are transported from one sample holder to another using glass needles attached to manipulators, which allows a combination of microanalytical techniques for detailed analysis of specific particles. The technique was applied to airborne particles sampled in downtown Zurich, Switzerland. Initial, qualitative analysis of morphology and chemistry using the ESEM, led to the distinction of five particle classes. In order to investigate the structure of selected particles further, a specific particle was transferred to a transmission electron microscope (TEM) grid. The combination of analytical methods (ESEM-EDX and TEM) allowed us to characterize this particle in more detail and to identify its source. Thus, the approach presented here can be used to resolve the complex structure of single particles and to refine source apportionment based on single particle analysis.

Kaegi, R., Holzer, L. and Kleindiek, S., 2003. Separation of small particles using nanomanipulators in the ESEM.

Kaegi, R., Holzer, L. and Kleindiek, S., 2003. <i>Separation of small particles using nanomanipulators in the ESEM.</i>

Numerous articles demonstrate that atmospheric aerosols act as major contributors to global climate change and are responsible for adverse health effects on humans. Thus, there is a need to characterize environmental particles in detail. Most established methods are designed to obtain information about chemistry, morphology, structure or surface of single particles. However, to date, no method combines different analytical techniques to obtain information

from a specific particle. We present an approach, which allows us to combine ESEM (Environmental Scanning Electron Microscope) and TEM (Transmission Electron Microscope) to enhance information about selected environmental particles.

Sinram, O., Ritter, M., Kleindiek, S., Schertel A., Hohenberg, H. and Albertz, J., 2002. Calibration of an SEM using a nano positioning tilting table and a microscopic calibration pyramid.

Sinram, O., Ritter, M., Kleindiek, S., Schertel A., Hohenberg, H. and Albertz, J., 2002. <i>Calibration of an SEM using a nano positioning tilting table and a microscopic calibration pyramid.</i>

In this paper we present the calibration of a scanning electron microscope, using a high precision tilting sample stage and a new microscopic calibration pyramid. Difficulties when using extremely high magnifications will be stated and means of solutions are presented and evaluated. Since the scanning electron microscope cannot be moved around the object, the object has to be tilted instead. By this movement, the object can be seen in several virtual points of view, which is a necessity for any three dimensional reconstruction. As for generating the virtual views, the first difficulty encountered is to position the sample into the eucentric axis. Only when positioned in the rotation axis, the sample remains within the field of view, instead of being moved outside. Therefore, a special tilting table was required, which provided maximum precision and accuracy. Furthermore, an object had to be found, which met the requirements of a calibration object. Here, a new microscopic cascade pyramid was developed, supplied with 38 spatially distributed control points. Finally, for each tilting series, all desired images were oriented using a bundle block adjustment following the rules of parallel projection. In this paper, the mathematics of parallel projection will be an important chapter, pointing out the differences to central projection. As a result, the accuracy of the tilting table and the imaging properties of the microscope are presented. These properties are used as the basic essential parameters for further evaluation of microscopic images.

Tensile Measurement

Brand, U., Nesterov, V., Doering, L., Bütefisch, S., Peiner, E. and Büttgenbach, S., 2009. New Tactile Sensors for Micro- and Nanotechnology.

Brand, U., Nesterov, V., Doering, L., Bütefisch, S., Peiner, E. and Büttgenbach, S., 2009. <i>New Tactile Sensors for Micro- and Nanotechnology.</i>

Due to the lack of size-adapted probing elements, it has for a long time not been possible to conduct dimensional measurements on components of microsystem technology. Two new microprobing systems on the basis of piezoresistive silicon sensors are now available and can be used for precision measurements. Due to the diversity of materials to be tested (quite a few of them have a low hardness), the elastic and plastic deformation during the measurement is of great importance. These systematic deviations and the scratches can be avoided only by the use of small probing forces. The paper describes the microforce measuring techniques developed and gives the prospects for nanoforce metrology which is at present under development and which is required for scanning force microscopic precision measurements. A focal point of the research activities concerns the modelling of the deformations during tactile scanning measurements.

Orso, S., 2006. Structural and mechanical investigations of biological materials using a Focussed Ion Beam microscope. Strukturelle und mechanische Untersuchungen von biologischen Materialien unter Verwendung eines Focussed Ion Beam Mikroskops.

Orso, S., 2006. <i>Structural and mechanical investigations of biological materials using a Focussed Ion Beam microscope. Strukturelle und mechanische Untersuchungen von biologischen Materialien unter Verwendung eines Focussed Ion Beam Mikroskops.</i>

In situ mechanical testing procedures for small scale samples in the μm range are rare. For many biological materials sizes in the um range are typical, such as airflow sensors on crickets and individual components of the hairy attachment systems in insects and geckos (Kiel, 1998; Gorb, 2000). A variety of methods and devices exist for the mechanical testing and analysis of conventional bulk samples in the cm and mm range. Downscaling such standard mechanical testing methods (tensile tests, compression tests and bending tests) for specimens in the um and sub-um range provides a number of challenges. The major problem in building suitable mechanical testing devices is the lack of appropriate load cells. These load cells must have a high force resolution in the uN or even nN range. At the same time, they must provide a maximum force in the order of several mN. The second problem is the necessary resolution in strain or displacement. Already the handling of um-sized samples is very difficult and their correct mounting is not trivial. Handling and clamping the samples into a holder can mechanically damage them: cracks can be introduced or, if the clamping is too weak, they can be pulled out of the sample holder on loading.

 

Source: elib.uni-stuttgart.de/opus/volltexte/2006/2717/

Orso, S., Wegst, U.G.K., Arzt, E., 2006. The elastic modulus of spruce wood cell wall material measured by an in situ bending technique.

Orso, S., Wegst, U.G.K., Arzt, E., 2006. <i>The elastic modulus of spruce wood cell wall material measured by an in situ bending technique.</i>

Using a novel in situ testing technique, the elas- tic modulus of wood cell wall material can be de- termined with great accuracy. The method relies on a focussed ion beam system (FIB) to prepare samples from individual structural components at a length scale which otherwise is hardly, if at all, accessible for testing.