Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    An in situ tensile test device for thermo-mechanical characterisation of interfaces between carbon nanotubes and metals
    ( 2016)
    Hartmann, S.
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    Bonitz, J.
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    Heggen, M.
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    Hermann, S.
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    Hölck, O.
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    Schulz, S.E.
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    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 CNT-based sensor applications: Investigations of CNT-metal interfaces combining molecular dynamics simulations, advanced in situ experiments and analytics
    ( 2015)
    Hartmann, S.
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    Shaporin, A.
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    Hermann, S.
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    Bonitz, J.
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    Heggen, M.
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    Meszmer, P.
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    Sturm, H.
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    Hölck, O.
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    Blaudeck, T.
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    Schulz, S.E.
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    Mehner, J.
    ;
    Gessner, T.
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    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
    Molecular dynamic simulations of maximum pull-out forces of embedded CNTs for sensor applications and validating nano scale experiments
    ( 2014)
    Hartmann, S.
    ;
    Hölck, O.
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    Blaudeck, T.
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    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.
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    Grosser, V.
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    Lissek, S.
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    During, H.
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    Rusek, B.
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    Braunschweig, M.
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    Kurth, S.
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    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.
  • Publication
    A MEMS friction vacuum gauge suitable for high temperature environment
    ( 2008)
    Tenholte, D.
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    Kurth, S.
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    Gessner, T.
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    Dötzel, W.
  • Publication
    Fabrication of magnetic polymer membranes with microfluidic functionality
    ( 2008)
    Morschhauser, A.
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    Nestler, J.
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    Baum, M.
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    Schüller, M.
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    Jänig, O.
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    Otto, T.
    ;
    Gessner, T.
  • Publication
    Waferbond technologies and quality assesment
    ( 2008)
    Wiemer, M.
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    Frömel, J.
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    Chenping J.
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    Haubold, M.
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    Gessner, T.
    Several wafer bond technologies like direct and anodic bonding without intermediate layer or thermo-compression wafer bonding with intermediate layers like low melting frit glasses, eutectic materials or polymers were developed during the last years and are nowadays extensively used in industrial applications. The paper will describe some important aspects of new Ti-Si and Laser assisted transmission Si to Si bonding techniques and their application for the fabrication of an ultrasonic transducer array. Main aspects for the reliability of wafer bonded devices are the yield after bonding, the bond strength and the hermeticity as well as the suitability for the packaging processes (e.g. moulding) and the influence of electrical and mechanical properties of the bonded elements by the bond process. The paper will focus on methods to characterize the bond strength and the hermeticity of bonded compounds. The main method to evaluate the bond strength is the micro chevron test. This test requires special designed test samples and is destructive, but also standard chips with bonded caps can be used for strength measurements. For anodic bonding between transparent glass and silicon a non destructive bond strength test structure can be used. This non-destructive test structure based on structure fabricated on one surface of the bond partners and has dimensions of several 10 to 100 mum. After the anodic bonding the length of the not bonded gap around this structure can be used to calculate the bond strength. The hermeticity can be tested by helium leakage test or by using resonant structure inside of the cavities which change the frequency depending on the pressure inside of the cavity.
  • Publication
    Continuously tunable RF-MEMS varactor for high power applications
    ( 2008)
    Leidich, S.
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    Kurth, S.
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    Gessner, T.
    A high power continuously tunable RF-MEMS capacitor (varactor) for frequencies from DC-4.0 GHz is presented. The device is specified for 0.8-1.6 pF analog tuning range and provides a Q factor of ?100 for frequencies below 2.0 GHz. Using silicon bulk technology and wafer bonding techniques, RF and electrostatic actuation electrodes are arranged vertically. It enables controlled counteracting the attractive electrostatic forces generated by high RF signal amplitudes (self actuation). Using a time domain reflectometer based measurement setup and a resonating test circuit, stability against CW signals of up to 55 V rms has been shown. Due to the highly damped mechanical response, the capacitance setup is intrinsically insensitive to RF bursts (tp=20 ?s) of more than 120 V rms.
  • Publication
    Reliability of MEMS devices in shock and vibration overload situations
    ( 2008)
    Kurth, S.
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    Shaporin, A.
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    Hiller, K.
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    Kaufmann, C.
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    Gessner, T.
    This contribution describes the investigation of the reasons for overload failure and overload reaction based on linear vibration theory by decomposition of the complex reaction into resonant mode reactions and on observation of the reaction. An impulse specific peak deflection (ISPD) is derived as a general characteristic property of a certain shock. It is applicable to predict the mechanical deflection of a certain resonant mode of an arbitrary resonant frequency due to a shock. This is further analyzed and proofed by scanning Laser Doppler interferometer (SLDI) measurement on the example of a Fabry Perot interferometer based tunable infrared filter. The results from ISPD prediction are compared to SLDI measurements and to finite element analysis results.