Epitaxial Oxides on Silicon by Pulsed Laser Deposition

Within the perovskite oxides a wide range of physical properties can be found, making this class of materials interesting for use in new types of microelectronic devices. The microelectronic industry is silicon based, which requires integration of these oxides on silicon. This integration should be epitaxial, because the functional properties depend on the crystalline quality of the perovskite oxide and because of the ability to make use of anisotropy in these properties. Epitaxial growth on silicon is not straightforward. Most of the perovskite oxides are chemically unstable on silicon, while the amorphous silicon native oxide prevents the silicon lattice from influencing the perovskite orientation. Therefore, a buffer layer should be incorporated between silicon and most of the perovskites.

In this thesis, several strategies were investigated to obtain such a buffer. Pulsed Laser Deposition (PLD) was used, since this technique is very suitable to grow oxides and can be used to deposit on industrial size silicon wafers. First, the growth mechanism of the buffer material yttria stabilized zirconia (YSZ) was studied in detail, to find the necessary conditions to obtain reproducible growth of high quality YSZ. Thereafter, the growth of (001) oriented perovskites on the fluorite surface of YSZ was investigated. In order to avoid this difficult fluorite to perovskite transition, the growth of perovskite SrZrO3 directly on silicon with native oxide was studied next. Finally, the formation of an epitaxial Sr silicate via reaction between SrO and the silicon native oxide was investigated, which proved to be a suitable buffer layer for crystallization of (001) oriented perovskites.