Hybrid Molecular Beam Epitaxy of Ge-based Oxides

Germanium-containing oxides such as rutile GeO₂ are earning attention owing to their ultra-wide band gap for high power device application. Here, we present the use of germanium tetraisopropoxide (GTIP) as a precursor for hybrid MBE of Ge-containing compounds. We use Ge_xSn_1-xO₂ as a model system for this new synthesis method. Using a combination of high-resolution X-ray diffraction and X-ray photoelectron spectroscopy to characterize these films, we successfully grow epitaxial rutile Ge_xSn_1-xO₂ on TiO₂ (001) substrates up to x = 0.5, above which the films become amorphous at low substrate temperatures. No Ge-rich films grow at higher temperatures likely due to desorption of Ge-based suboxides. These results confirm the viability of the GTIP precursor in the growth of germanium containing oxides by hybrid MBE, and may thus pave the road to achieving high-quality perovskite germanates thin films.