Ge incorporated epitaxy of (110) rutile TiO2 on (100) Ge single crystal at low temperature by pulsed laser deposition

• We grew (110) rutile TiO2 film on (100) Ge substrate.
• Rutile TiO2 crystallizes at the crystallization temperature of anatase phase.
• Ge diffusion enhances the crystallization of rutile TiO2.
• Band alignment between rutile TiO2 and p-type Ge is type II band alignment.

The thin film growth of (110) rutile TiO2 on a (100) Ge substrate at a substrate temperature of 450 °C, which is generally the growth temperature of anatase TiO2, was demonstrated by using pulsed laser deposition. X-ray diffraction and X-ray photoelectron spectroscopy revealed that the incorporation of Ge into TiO2 enhances the rutile phase formation, and the ambient oxygen condition enhances the Ge oxide diffusion. Photoelectron spectroscopy also revealed that the valence band offset of rutile TiO2 and p-type Ge is approximately 2.5 ± 0.1 eV with a type II band alignment.