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Lecture

Strain distribution in piezotronic ZnO microstructures visualised by X-ray nanodiffraction techniques

Wednesday (19.06.2019)
11:30 - 11:45

Combining piezoelectric/piezotronic and magnetostrictive materials is one promising approach to design bio magnetic field sensors. Such sensors have the ability to generate a signal in response to a magnetic field from the human body. To achieve the extreme sensitivity of less than 100 pT required for medical applications, is a challenge. By using piezotronic readout from magnetoelectric sensors, it is possible to increase the limit of detection. The piezotronic effect occurs in semiconductors with a non-centrosymmetric crystal structure. An induced piezoelectric potential causes additional piezoelectric charges at the metal-semiconductor interface, resulting in a change of height and width of the Schottky barrier. The charge carrier transport across the metal-semiconductor contact is therefore dependent on the piezoelectric charges, which can be controlled by the magnitude and sign of the applied strain or vice versa. For this experiment we used ZnO micro wires with diameters between one and 100 µm. An Ohmic contact was implemented on one end and a Schottky contact on the other end by sputtering of Al and Au, respectively. During the experiment we collected the current voltage curves of the sample and simultaneous apply a mechanical stress with an actuator while observing key Bragg reflections. This nanofocus diffraction experiment provided a unique possibility to determine the spatially resolved lattice deformation in the device during piezotronic measurements. Our results shows that the strain decreases in the pure ZnO near the Schottky barrier and increases in the Schottky Barrier. This may be related to changes in the depletion region with increasing mechanical strain.

Speaker:
Philipp Jordt
Kiel University
Additional Authors:
  • Dr. Stjepan Hrkac
    University of California San Diego
  • Niklas Wolff
    Kiel University
  • Mona St√∂lting
    Kiel University
  • Dr. Christina Krywka
    Deutsches Elektronen-Synchrotron DESY
  • Prof. Dr. Rainer Adelung
    Kiel University
  • Prof. Dr. Lorenz Kienle
    Kiel University
  • Dr. Bridget Murphy
    Kiel University