Ab initio study of epitaxial oxide/semiconductor interfacesMehmet Dogan Abstract: Thin films of crystalline metal oxides grown on semiconductors have been of great research interest because of their use in electronic devices. A multitude of physical phenomena observed in these films open up the possibility of novel technological applications. An example of such an application is non-volatile transistors and it is caused by ferroelectricity in the oxide film. In this system, the state of the device is encoded in the polarization of the oxide which controls the transport properties of the semiconductor. A system we have been studying is BaTiO$_{3}$ films epitaxially grown on Ge (001). We have analyzed the atomic configurations, interface chemistry and electronic properties of this interface. We have concluded that a modification of the interface chemistry is needed in order to induce ferroelectricity in this type of systems. For that purpose we have began studying monolayers of ZrO$_{2}$ epitaxially grown on Si (001). We have shown that these monolayers are stable in many different configurations with varying out-of-plane polarizations. We present an analysis of these configurations and energy barriers between them. We consider the likely experimental situation where different configurations coexist to form a multi-domain system, and investigate domain dynamics. Furthermore, we demonstrate that the ZrO$_{2}$ monolayers can be used as a buffer layer to induce ferroelectricity in perovskite oxides such as SrTiO$_{3}$ on Si. We also show that these monolayers modify the transport properties of Si which would allow for the desired device applications. |
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