Growth mode transition from layer by layer to step flow during the growth of heteroepitaxial SrRuO3 on (001) SrTiO3

We have observed the growth mode transition from two-dimensional (2D) layer-by-layer to step-flow in the earliest stage growth of heteroepitaxial ${\mathrm{SrRuO}}_3$ thin films on ${\mathrm{TiO}}_2$ -terminated (001) ${\mathrm{SrTiO}}_3$ substrates by in situ high pressure reflective high energy electron diffraction (RHEED) and atomic-force microscopy. There is no RHEED intensity recovery after each laser pulse in the first oscillation when the growth mode is 2D layer-by-layer. On the other hand, it is getting more pronounced in the second oscillation, and finally reaches a dynamic steady state in which the growth mode is completely changed into the step-flow mode. The origin of the growth mode transition can be attributed to a change in the mobility of adatoms and switching the surface termination layer from the substrate to the film. ${\mathrm{SrRuO}}_3$ thin films with an atomically smooth surface grown by atomic layer control can be used in oxide multilayered heterostructure devices.