Novel Mode of Nucleation and Growth of Complex Oxide Heterostructures at the Extreme of High Supersaturation. Effects of Orbital Reconstruction

摘要

In this document we report a detailed investigation of the kinetics of condensation and switching scaling behavior upon large lattice mismatch and extremely high supersaturation (SS), which is exemplified by the novel class of complex oxide heterostructures composed of a correlated metal RENiO3 (RENO, RE=La,Nd,Pr) and wide-gap dielectric LaAlO3 (LAO). The n(RENO/m LAO)xN superlattices (SL), where n and m are the numbers of unit cells and N denotes the number of periods, were grown by PLD on atomically flat TiO2 terminated (001) SrTiO3 (STO) single crystals, which were prepared by our recently developed wet-etch procedure to minimize electronic surface and near surface defects. In the following, we focus on a representative RE=La subclass of these SLs. For the project our PLD system was substantially redesigned and equipped with a newly developed high pressure RHEED, which is capable of operating in the background oxygen pressure of up to 400 mTorr, with an advanced feedback control of the current and a custom developed 12-bit high-speed imaging system. We employ a real-time 3D imaging mode to monitor both specular and diffuse intensities within a large portion of the momentum space and per laser pulse. By recording the temporal evolution of the diffracted intensity during the growth, we can obtain details on the development of surface morphology and atomic structure including changes in surface disorder, defects formation, agglomeration of islands, and step bunching.