Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    Experimental and computational studies on the role of surface functional groups in the mechanical behavior of interfaces between single-walled carbon nanotubes and metals
    ( 2016)
    Hartmann, S.
    ;
    Sturm, H.
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    Blaudeck, T.
    ;
    Hölck, O.
    ;
    Hermann, S.
    ;
    Schulz, S.E.
    ;
    Gessner, T.
    ;
    Wunderle, B.
    To study the mechanical interface behavior of single-walled carbon nanotubes (CNTs) embedded in a noble metal, we performed CNTmetal pull-out tests with in situ scanning electron microscope experiments. Molecular dynamics (MD) simulations were conducted to predict forcedisplacement data during pull-out, providing critical forces for failure of the system. In MD simulations, we focused on the influence of carboxylic surface functional groups (SFGs) covalently linked to the CNT. Experimentally obtained maximum forces between 10 and 102 nN in palladium and gold matrices and simulated achievable pulling forces agree very well. The dominant failure mode in the experiment is CNT rupture, although several pull-out failures were also observed. We explain the huge scatter of experimental values with varying embedding length and SFG surface density. From simulation, we found that SFGs act as small anchors in the metal matrix and significantly enhance the maximum forces. This interface reinforcement can lead to tensile stresses sufficiently high to initiate CNT rupture. To qualify the existence of carboxylic SFGs on our CNT material, we performed analytical investigation by means of fluorescence labeling of surface species and discuss the results. With this contribution, we focus on a synergy between computational and experimental approaches involving MD simulations, nano scale testing, and analytics (1) to predict to a good degree of accuracy maximum pull-out forces of single-walled CNTs embedded in a noble metal matrix and (2) to provide valuable input to understand the underlying mechanisms of failure with focus on SFGs. This is of fundamental interest for the design of future mechanical sensors incorporating piezoresistive single-walled CNTs as the sensing element.
  • Publication
    An in situ tensile test device for thermo-mechanical characterisation of interfaces between carbon nanotubes and metals
    ( 2016)
    Hartmann, S.
    ;
    Bonitz, J.
    ;
    Heggen, M.
    ;
    Hermann, S.
    ;
    Hölck, O.
    ;
    Schulz, S.E.
    ;
    Gessner, T.
    ;
    Wunderle, B.
    In this paper we present our recent efforts to develop an in situ tensile test device for thermo-mechanical characterization of interfaces between single-walled carbon nanotubes (SWCNTs) and metals. For the mechanical tests, the chosen loading condition is a pull-out test. After summarizing results of maximum stresses calculated from molecular dynamics simulations and obtained from in situ scanning electron microscope experiments we outline the requirement for an in situ experimental method with atomic resolution to study the mechanics of SWCNT-metal interfaces in further detail. To this purpose, we designed, fabricated and characterized a silicon-based micromechanical test stage with a thermal actuator for pull-out tests inside a transmission electron microscope. The objective is to obtain in situ images of SWCNT-metal interfaces under mechanical loads at the atomic scale for fundamental structure investigation. The design of this MEMS test stage permits also the integration of SWCNTs by wafer level technologies. First experiments with this MEMS test stage confirmed the presence of suspended thin metal electrodes to embed SWCNTs. These suspended thin metal electrodes are electron transparent at the designated SWCNT locations. Actuator movements were evaluated by digital image correlation and we observed systematic actuator movements that allow for a defined load application of SWCNTS. Although significant image drifts occured during actuation, we achieved atomic resolution of the metal electrode and stable movement in the focal plane of the electron microscope. The presented system may be also used and further developed for in situ characterization of other materials.
  • Publication
    Towards nanoreliability of sensors incorporating interfaces between single-walled carbon nanotubes and metals: Molecular dynamics simulations and in situ experiments using electron microscopy
    ( 2016)
    Hartmann, S.
    ;
    Hermann, S.
    ;
    Bonitz, J.
    ;
    Heggen, M.
    ;
    Hölck, O.
    ;
    Shaporin, A.
    ;
    Mehner, J.
    ;
    Schulz, S.E.
    ;
    Gessner, T.
    ;
    Wunderle, B.
    In this paper we present results of our recent efforts to understand the mechanical interface behaviour of single-walled carbon nanotubes (SWCNTs) embedded in metal matrices. We conducted experimental pull-out tests of SWCNTs embedded in Pd and found maximum forces in the range F ≈ (10 to 65) nN. These values are in good agreement with forces obtained from molecular dynamics simulations taking into account surface functional groups (SFGs) covalently linked to the SWCNT material. The dominant failure mode in experiment is a SWCNT rupture, which can be explained with the presence of SFGs. For further in depth investigations, we present a tensile actuation test system based on a thermal actuator to perform pull-out tests inside a transmission electron microscope with the objective to obtain in situ images of SWCNT-metal interfaces under mechanical loads at the atomic scale. First experiments confirmed the presence of suspended thin metal electrodes to embed SWCNTs. These suspended thin metal electrodes are electron transparent at the designated SWCNT locations. Actuator movements were evaluated by digital image correlation and we observed systematic actuator movements. Although significant image drifts occured during actuation, we achieved atomic resolution of the metal electrode and stable movement in the focal plane of the electron microscope.
  • Publication
    Towards nanoreliability of CNT-based sensor applications: Investigations of CNT-metal interfaces combining molecular dynamics simulations, advanced in situ experiments and analytics
    ( 2015)
    Hartmann, S.
    ;
    Shaporin, A.
    ;
    Hermann, S.
    ;
    Bonitz, J.
    ;
    Heggen, M.
    ;
    Meszmer, P.
    ;
    Sturm, H.
    ;
    Hölck, O.
    ;
    Blaudeck, T.
    ;
    Schulz, S.E.
    ;
    Mehner, J.
    ;
    Gessner, T.
    ;
    Wunderle, B.
    In this paper we present results of our recent efforts to understand the mechanical interface behaviour of single-walled carbon nanotubes (CNTs) embedded in metal matrices. We conducted experimental pull-out tests of CNTs embedded in Pd or Au and found maximum forces in the range 10-102 nN. These values are in good agreement with forces obtained from molecular dynamics simulations taking into account surface functional groups (SFGs) covalently linked to the CNT material. The dominant failure mode in experiment is a CNT rupture, which can be explained with the presence of SFGs. To qualify the existence of SFGs on our used CNT material, we pursue investigations by means of fluorescence labeling of surface species in combination with Raman imaging. We also report of a tensile test system to perform pull-out tests inside a transmission electron microscope to obtain in situ images of CNT-metal interfaces under mechanical loads at the atomic scale.
  • Publication
    Quantitative in-situ scanning electron microscope pull-out experiments and molecular dynamics simulations of carbon nanotubes embedded in palladium
    ( 2014)
    Hartmann, S.
    ;
    Blaudeck, T.
    ;
    Hölck, O.
    ;
    Hermann, S.
    ;
    Schulz, S.E.
    ;
    Gessner, T.
    ;
    Wunderle, B.
    In this paper, we present our results of experimental and numerical pull-out tests on carbon nanotubes (CNTs) embedded in palladium. We prepared simple specimens by employing standard silicon wafers, physical vapor deposition of palladium and deposition of CNTs with a simple drop coating technique. An AFM cantilever with known stiffness connected to a nanomanipulation system was utilized inside a scanning electron microscope (SEM) as a force sensor to determine forces acting on a CNT during the pull-out process. SEM-images of the cantilever attached to a CNT have been evaluated for subsequent displacement steps with greyscale correlation to determine the cantilever deflection. We compare the experimentally obtained pull-out forces with values of numerical investigations by means of molecular dynamics and give interpretations for deviations according to material impurities or defects and their influence on the pull-out data. We find a very good agreement of force data from simulation and experiment, which is 17 nN and in the range of 10-61 nN, respectively. Our findings contribute to the ongoing research of the mechanical characterization of CNT-metal interfaces. This is of significant interest for the design of future mechanical sensors utilizing the intrinsic piezoresistive effect of CNTs or other future devices incorporating CNT-metal interfaces.
  • Publication
    Molecular dynamic simulations of maximum pull-out forces of embedded CNTs for sensor applications and validating nano scale experiments
    ( 2014)
    Hartmann, S.
    ;
    Hölck, O.
    ;
    Blaudeck, T.
    ;
    Hermann, S.
    ;
    Schulz, S.E.
    ;
    Gessner, T.
    ;
    Wunderle, B.
    We present investigations of pull-out tests on CNTs embedded in palladium by means of molecular dynamics (MD) and compare our results of maximum pull-out forces with values of nano scale in situ pull-out tests inside a scanning electron microscope (SEM). Our MD model allows the investigation of crucial influencing parameters on the interface behaviour, like CNT diameter, intrinsic CNT defects and functional groups. For the experiments we prepared simple specimens using silicon substrates and wafer level compliant technologies. We realised the nano scale experiment with a nanomanipulation system supporting an AFM cantilever with known stiffness as a force sensing element inside a SEM. Greyscale correlation has been used to evaluate the cantilever deflection. From simulations derived maximum pull-out forces are approximately 17 nN and depend on the existence of intrinsic defects or functional groups and weakly on temperature. Experimentally obtained maximum pull-out force s with values between 16-29 nN are in good agreement with the computational predictions. Our results are of significant interest for the design and a failure-mechanistic treatment of future mechanical sensors with integrated single-walled CNTs showing high piezoresistive gauge factor or other nano scale systems incorporating CNT-metal interfaces.
  • Publication
    Development of transfer Electrostatic Carriers (T-ESC®) for thin 300mm wafer handling using seal glass bonding technology
    ( 2012)
    Balaj, I.
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    Raschke, R.
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    Baum, M.
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    Uhlig, S.
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    Wiemer, M.
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    Gessner, T.
    ;
    Grafe, J.
  • Publication
    Sensornetzwerk zum Monitoring von Hochspannungsleitungen
    ( 2012)
    Voigt, S.
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    Wolfrum, J.
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    Pfeiffer, M.
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    Keutel, T.
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    Brockmann, C.
    ;
    Grosser, V.
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    Lissek, S.
    ;
    During, H.
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    Rusek, B.
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    Braunschweig, M.
    ;
    Kurth, S.
    ;
    Gessner, T.
    In diesem Beitrag wird ein autarkes Sensornetzwerk zur Überwachung und Optimierung der Auslastung von Hochspannungsleitungen vorgestellt sowie Ergebnisse aus Tests im Hochspannungslabor und auf 110-kV-Hochspannungsleitungen diskutiert. Das Sensornetzwerk besteht aus zahlreichen Sensorknoten, die direkt am Leiterseil der Freileitung montiert sind. Zusätzliche Komponenten am Mast werden nicht benötigt. Das System arbeitet autark. Die Energieversorgung der Sensorknoten erfolgt aus dem elektrischen Streufeld der Hochspannungsleitung. Die Knoten nehmen die Temperatur, die Neigung des Leiterseils sowie den Strom, der durch die Leitung fließt, auf. Diese Messdaten werden anschließend von Sensorknoten zu Sensorknoten bis zur Basisstation per Funk im 2,4 GHz-ISM-Band übertragen. In der Basisstation, welche sich im Umspannwerk befindet, werden die Daten aufbereitet und in Form eines Webservers mit Datenbanksystem der Leittechnik zur Verfügung gestellt.
  • Patent
    Method for characterizing movable micro-mirror for projector used in e.g. digital camera, involves determining function parameters of micro-mirror by evaluating device, based on detected portions of test image of micro-mirror
    ( 2011)
    Specht, H.
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    Kurth, S.
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    Gessner, T.
    ;
    Fiess, R.
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    Krayl, O.
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    Krueger, M.
    ;
    Wiest, G.
    ;
    Hilberath, T.
    The method involves generating the steerable and modulatable light beams (220) by a light beam generating unit (200). The test images (240) of a movable micro-mirror (210) are generated by deflecting the movable micro-mirror and by modulating the light beams directed towards the micro-mirror. The upper edge, lower edge, right edge and left edge of test image are detected by a surface sensor (250). The function parameters such as mechanical parameters and image quality parameters of micro-mirror are determined by an evaluating device (260), based on detected portions of test image. Independent claims are included for the following: (1) device for characterizing movable micro-mirror; and (2) computer program for characterizing movable micro-mirror.
  • Publication
    Thin film encapsulation technology for harms using sacrificial CF-polymer
    ( 2008)
    Reuter, D.
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    Bertz, A.
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    Nowack, A.
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    Gessner, T.