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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 3: Dielectric, Elastic and Electromechanical Properties

KFM 3.1: Vortrag

Montag, 1. April 2019, 09:30–09:50, PHY 5.0.21

Piezotronic material based on ZnO-ZnO interfaces — •Maximilian Gehringer — Technische Universität Darmstadt, Darmstadt, Deutschland

In recent years, the research field piezotronics gained a lot of attention. It has been shown to have huge potential for applications like nanogenerators, gated field effect transistors and sensors. Zinc oxide nanowires that allow extensive deformation were the focus of many investigations of metal-semiconductor Schottky-barriers. However, ZnO is also well known for polycrystalline ceramics with grain boundary potential barrier. In this case, the barriers at grain boundaries inhibit electrical transport until breakdown at high voltages. Therefore, ZnO is often used for surge protection or for voltage regulation.

In this work, the possibility of using bicrystals or polycrystalline materials with high grain boundary potential barrier for piezotronic applications will be discussed. Our investigations show a large impact of mechanical stress on the linear leakage current in polycrystalline ZnO samples and bicrystals. Extensive conductivity changes could be induced in this low voltage region via application of uniaxial pressure. Hence, very high possible gauge factors (figure of merit for the use in strain/stress sensors) around 1000 can be obtained. Commercial sensors can reach only a factor of 200 so far. A physical model will be introduced to explain the observed behavior and the results are compared with single crystal metal-ZnO Schottky barrier investigations. Evidence will be provided for varistor boundaries showing enhanced piezotronic properties compared to metal-ZnO Schottky barriers.