Layer transfer technique of epitaxial rutile TiO2 thin films for photonic applications

Layer transfer technique of epitaxial (001) oriented rutile TiO2 films sputtered on sapphire substrates using epitaxial ZnO sacrificial layer was developed. It was demonstrated that obtaining an epitaxial structure for rutile layer transfer can be challenging, due to required control of variety of parameters - surface roughness, growth rate, deposition temperature, interface stresses and lattice matching. It was shown that ZnO, directly grown on M-sapphire substrates, promotes polycrystalline rutile growth. Therefore, 50 nm thick (001) rutile seed layer with controlled surface roughness grown on M-sapphire substrate was needed to promote the epitaxial (10 (1) over bar3) ZnO growth, which then allowed to obtain epitaxial (001) rutile layer suitable for the layer transfer process. The examined structural quality, evaluated by means of X-ray diffraction and Raman spectroscopy, showed that the transferred rutile films exhibit promising properties for photonic applications.