Surface structural reconstruction of SrVO$_{\mathrm{3}}$ thin films on SrTiO$_{\mathrm{3\thinspace }}$(001)*

Paramagnetic metallic oxide SrVO$_{\mathrm{3\thinspace }}$(SVO) is an itinerant system known to undergo thickness-induced metal-insulator-transition (MIT) in ultrathin film form, which makes it a prototype system for the study of the mechanism behind metal-insulator-transition like structure distortion, electron correlations and disorder-induced localization. We have grown SrVO$_{\mathrm{3}}$ thin film with atomically flat surface through the layer-by-layer deposition by laser Molecular Beam Epitaxy (laser-MBE) on SrTiO$_{\mathrm{3}}$ (001) surface. Low Energy Electron Diffraction (LEED) measurements reveal that there is a ($\surd $2X$\surd $2) R45\textdegree surface reconstruction independent of film thickness. By using LEED-I(V) structure refinement, we determine the surface structure. In combination with X-ray Photoelectron Spectroscopy (XPS) and Scanning Tunneling Microscopy (STM), we discuss the implication on the MIT in ultrathin films below 2-3 unit cell thickness.