Time-resolved \textit{in-situ} X-ray Study of Homoepitaxial SrTiO$_3$ Growth Using Reactive Molecular-Beam Epitaxy

Functional materials based on complex oxides in thin film form offer new and exciting strategies for meeting many energy challenges. Unfortunately, synthesis of such oxide films can be a major challenge even when utilizing reactive molecular-beam epitaxy (MBE). To understand the fundamental physics of complex oxide thin film growth, we have developed the world's first reactive MBE system with {\it in-situ} synchrotron x-ray scattering capability at the Advanced Photon Source (APS). Here we present the results of {\it in-situ} surface x-ray scattering measurements taken during homoepitaxial growth of SrTiO$_3$ on (001) SrTiO$_3$ substrates. We compare the shuttered growth technique with codeposition to understand the nature of the distinctly different approaches. Work at the APS, Argonne is supported by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.