Silicon in functional epitaxial oxides: A new group of nanostructures

The ability to integrate low-dimensional crystalline silicon into crystalline insulators with high dielectric constant (high-k) can open the way for a variety of novel applications ranging from high-k replacement in future nonvolatile memory devices to insulator/Si/insulator structures for nanoelectronic applications. We will present an approach for nanostructure fabrication by incorporation of crystalline silicon into epitaxial oxide that is based on a solid-phase epitaxy of Si. In dependence on the preparation conditions we obtained nanostructures containing an either ultra-thin single-crystalline Si quantum-well buried in single-crystalline oxide matrix with sharp interfaces or Si-nanocrystals (ncs) embedded into single-crystalline oxide layer. As an example, we demonstrate the growth of Si buried in Gd₂O₃ and the incorporation of epitaxial Si clusters into single-crystalline Gd₂O₃ on silicon as well as silicon carbide substrates using molecular beam epitaxy. The leakage current of the obtained nanostructures exhibited negative differential resistance at lower temperatures. For structures containing Si-ncs a large hysteresis in capacitance–voltage measurements due to charging and discharging of the Si-ncs was obtained.