Keywords: MOCVD, MBE, epitaxy, functional oxides, silicon wafers, thin films, heterostructures, nanostructures, perovskite, interface engineering, nanoelectronics, nanotechnology, film thickness, strain, nanowires
Oxides heterostructures for nanoelectronics
We summarise in this paper the work of two groups focusing on the synthesis and characterisation of functional oxide for nanoelectronic applications. In the first section, we discuss the growth by liquid-injection MOCVD of oxides heterostructures. Interface engineering for the minimisation of silicate formation during the growth of polycrystalline SrTiO3 on Si is first presented. It is realised via the change of reactant flow or chemical nature at the Si surface. We then report on the epitaxy on oxide substrates of manganites films and superlattices and on their magnetic and electrical properties. La0.7Sr0.3MnO3 and La0.8MnO3-δ as well as multiferroic hexagonal ReMnO3 manganites are considered. We show that the film thickness and related strain may be used to tune the properties. Finally, we demonstrate the growth of MgO nanowires by CVD at a moderate temperature of 600°C, using gold as a catalyst. In the second section, we discuss the growth of epitaxial oxide heterostructures by MBE. First, the direct epitaxy of SrTiO3 on Si is considered. Issues and control of the SrTiO3/Si interface are discussed. An abrupt interface is achieved. We show that SrTiO3 on Si can be used as a buffer layer for the epitaxy of various perovskite oxides such as LaAlO3 or La0.7Sr0.3MnO3. La0.7Sr0.3MnO3 films are ferromagnetic and metallic at room temperature. The epitaxial growth of complex oxides on Si wafers opens up the route to the integration of a wide variety of functionalities in nanoelectronics. Finally, we discuss the monolithic integration of III-V compounds such as InP on Si using epitaxial SrTiO3 buffer layers for the future integration of optics on Si.