Homoepitaxial SrTiO3 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 homoepitaxial SrTiO3 films, arise from a film/substrate interface offset. Transmission electron microscopy studies confirm the presence of strain at those homoepitaxial interfaces that show an offset in x-ray diffraction. The consequences for stoichiometry optimization of homoepitaxial films using high-resolution x-ray diffraction and the quality of regrown oxide interfaces are discussed.
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The authors thank Jim Speck for many helpful discussions and ideas. The research at UCSB was supported by the Department of Energy (Grant No. DE-FG02-06ER45994). J.M.L. also thanks the U.S. Department of Education for a fellowship under the GAANN program (Grant No. P200A07044). G.B.S. is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357. The work made use of the UCSB MRL Central facilities supported by the MRSEC Program of the National Science Foundation under Award No. DMR 0520415.