Atomic Layer-by-Layer Growth of Homoepitaxial SrTiO$_{3}$ Films by Laser MBE

Two most effective techniques for oxides film growth are reactive MBE and laser MBE. With alternating monolayer growth, reactive MBE has shown the capacity of stoichiometry control and crystalline perfection in SrTiO$_{3}$ films on SrTiO$_{3}$, while most works of laser MBE, using compound targets, often shows non-stoichiometry and lattice defects. In order to control layer-by-layer growth to atomic level, we carried out laser MBE from separate oxide targets, for example, growing SrTiO$_{3}$ from SrO and TiO$_{2}$ targets, such that the SrO and TiO$_{2}$ layers were deposited alternatively one atomic layer at a time. X-ray diffraction spectra showed that the stoichiometric SrTiO$_{3}$ film peak overlapped with and was indistinguishable from the SrTiO$_{3 }$substrate peak, while the off stoichiometric SrTiO$_{3}$ films, either Sr rich or poor, showed lattice expansion. We conclude that laser MBE from separate oxide targets can achieve the same stoichiometry control as reactive MBE.