Direct Nanoscale Analysis of Temperature-Resolved Growth Behaviors of Ultrathin Perovskites on SrTiO₃

Revealing growth mechanism of a thin film and properties of its film-substrate interface necessarily require microscopic investigations on the initial growth stages in temperature- and thickness-resolved manners. Here we applied in situ scanning tunneling microscopy and atomic force microscopy to investigate the growth dynamics in homo- (SrTiO₃) and hetero- (SrRuO₃) epitaxies on SrTiO₃(001). A comparison of temperature-dependent surface structures of SrRuO₃ and SrTiO₃ films suggests that the peculiar growth mode switching from a "layer-by-layer" to "step-flow" type in a SrRuO₃ films arises from a reduction of surface migration barrier, caused by the change in the chemical configuration of the interface between the topmost and underlying layers. Island densities in perovskite epitaxies exhibited a clear linear inverse-temperature dependence. A prototypical study on island nucleation stage of SrTiO₃ homoepitaxy revealed that classical diffusion model is valid for the perovskite growths.