Berlin 2018 – scientific programme
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DS: Fachverband Dünne Schichten
DS 13: Oxide Semiconductors for Novel Devices (Focussed Session): Session III
DS 13.3: Invited Talk
Tuesday, March 13, 2018, 10:30–11:00, E 020
Indium Oxide and its surface electrons – a model system to study gas interaction and metal/semiconductor junctions — •Marcel Himmerlich, Theresa Berthold, Jonas Michel, Simeon Katzer, and Stefan Krischok — Institut für Physik & IMN Macro Nano, Technische Universität Ilmenau, Germany
The electron accumulation at Indium Oxide surfaces is beneficial for electronic devices that rely on adsorption processes such as gas sensors. However, it is a drawback for electron transport devices since it hinders the fabrication of rectifying metal contacts. In both cases, the manipulation of the electron density by surface reactions is one approach to optimize performance. We analyze the underlying mechanisms of adsorption processes and the formation of metal/semiconductor contacts using model in-situ experiments. For the interaction with O2, O3, H2O, CO and NOx, a clear correlation exists between adsorbate-semiconductor charge transfer, density of surface charge carriers, and the conductivity of the material. If In2O3 is treated by a reactive oxygen plasma, the surface electron layer is fully depleted generating a barrier for interface transport. Photoelectron spectroscopy measurements reveal that adsorption of Pt on these modified surfaces results in sufficient Schottky barriers for rectifying contacts, but fabricated devices fail. It will be demonstrated that the oxygen-rich Pt/In2O3 interface is critical in stability and that oxidation of Pt-based contacts is beneficial to enhance electronic barriers and to exploit the effect of electron depletion via oxygen plasma modification. Combining both processes enables performance improvement of In2O3 Schottky diodes.