Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

Filters

1
153
Reset filters

Settings
Now showing 1 - 10 of 153
  • 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 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
    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
    Sensornetzwerk zum Monitoring von Hochspannungsleitungen
    ( 2012)
    Voigt, S.
    ;
    Wolfrum, J.
    ;
    Pfeiffer, M.
    ;
    Keutel, T.
    ;
    Brockmann, C.
    ;
    Grosser, V.
    ;
    Lissek, S.
    ;
    During, H.
    ;
    Rusek, B.
    ;
    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.
  • Publication
    Development of transfer Electrostatic Carriers (T-ESC®) for thin 300mm wafer handling using seal glass bonding technology
    ( 2012)
    Balaj, I.
    ;
    Raschke, R.
    ;
    Baum, M.
    ;
    Uhlig, S.
    ;
    Wiemer, M.
    ;
    Gessner, T.
    ;
    Grafe, J.
  • Publication
  • Publication
    Fabrication of magnetic polymer membranes with microfluidic functionality
    ( 2008)
    Morschhauser, A.
    ;
    Nestler, J.
    ;
    Baum, M.
    ;
    Schüller, M.
    ;
    Jänig, O.
    ;
    Otto, T.
    ;
    Gessner, T.
  • Publication
    A MEMS friction vacuum gauge suitable for high temperature environment
    ( 2008)
    Tenholte, D.
    ;
    Kurth, S.
    ;
    Gessner, T.
    ;
    Dötzel, W.
  • Publication
    Low cost valveless magnetic micropumps suitable for array applications
    ( 2008)
    Schüller, M.
    ;
    Nestler, J.
    ;
    Morschhauser, A.
    ;
    Otto, T.
    ;
    Gessner, T.
    Low cost valveless micropumps based on electromagnetic actuation have been developed. The pumping performance of the electromagnetic micropump for water and gas was investigated. For water, a fluid velocity up to 40 mu l/min without backpressure was measured at a pump frequency of 26 Hz and a Current of 320 mA. For gas, fluid velocity up to 270 mu l/min without backpressure and a maximal backpressure of 900 Pa could be determined at 860 Hz and 350 mA. The planar design of the micropump for pumping water and gas allows the integration of an array of pumps on a single microfluidic chip.
  • Publication
    Continuously tunable RF-MEMS varactor for high power applications
    ( 2008)
    Leidich, S.
    ;
    Kurth, S.
    ;
    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.