Stoichiometry optimization of homoepitaxiai oxide thin films using x-ray diffraction

摘要

Homoepitaxiai SrTiO_3 thin films grown by molecular beam epitaxy are analyzed using high-resolution x-ray diffraction and transmission electron microscopy. Measured 00L x-ray scans from stoichiometric and nonstoichiometric films are compared with calculations that account for the effects of film thickness, lattice parameter, fractional site occupancy, and an offset between film and substrate at the interface. It is found that thickness fringes, commonly observed around Bragg reflections even in stoichiometric homoepitaxiai SrTiO_3 films, arise from a film/substrate interface offset. Transmission electron microscopy studies confirm the presence of strain at those homoepitaxiai interfaces that show an offset in x-ray diffraction. The consequences for stoichiometry optimization of homoepitaxiai films using high-resolution x-ray diffraction and the quality of regrown oxide interfaces are discussed.