Atomic Layer-by-layer Growth of Oxide Thin Films by Laser MBE

We have established a laser MBE-based atomic layer-by-layer thin film growth technique. By in-situ monitoring the reflection high-energy electron diffraction (RHEED) intensity, oxide binary compound targets, such as SrO, TiO$_{2}$, were ablated sequentially to assemble SrTiO$_{3}$ in an atomic layer-by-layer manner. Stoichiometry and crystal structures of the films are confirmed ex-situ by Rutherford backscattering spectrometry and x-ray diffraction. UV Raman spectroscopy was used to probe the symmetry breaking due to the cation off-stoichiometry. Highly accurate stoichiometry control as shown by reactive MBE has been demonstrated. Similarly, CaMnO$_{3}$ films were deposited by ablating CaO and MnO$_{2}$ targets separately. The strain states and electronic structure of the CaMnO$_{3}$ films on various substrates were studied via x-ray diffraction and polarization-dependent x-ray absorption spectroscopy. This atomic layer-by-layer growth technique has applications on the growth of a wide range of perovskite thin films and superlattices.