Heteroepitaxy of (1 0 0)-oriented rutile GeO₂ film on c-plane sapphire by pulsed laser deposition

Rutile germanium oxide (r-GeO₂) film has been directly grown heteroepitaxially on c-plane sapphire by pulsed laser deposition. The chemical composition, structural, surface morphology, optical properties, and crystal quality of the film have been systematically investigated. Raman spectroscopy and X-ray diffraction results show that the GeO₂ film is the rutile structure with a good (1 0 0) orientation. The X-ray rocking curve measurement shows that the full width at half maximum of r-GeO₂ (2 0 0) peak is 24 arc min. Atomic force microscope and transmittance measurements indicate that the transparent r-GeO₂ film has a surface roughness of 12.2 nm and a wide bandgap of 5.12 eV. We believed that these results will greatly facilitate the development of wide-bandgap r-GeO₂ film for application in electronic devices.