STM Studies of Sub-monolayer SrO and LaAlO$_{3}$ Film Growth on SrTiO$_{3}$(001) Substrate Surfaces

We report atomic-scale observations of initial growth of sub-monolayer SrO and LaAlO$_{3}$ (LAO) films on the atomically-ordered ($\sqrt{13}$$\times$$\sqrt{13}$)-$\textit{R}$33.7$^{\circ}$ SrTiO$_{3}$ (STO) (001) substrate surfaces using scanning tunneling microscopy/spectroscopy (STM/STS). We found that the growth processes depend strongly on the film compositions and the investigations unveil complex chemistry of thin-film oxides. These findings will provide microscopic insights into the understanding of transport properties at the LAO/STO interface, which is known to exhibit conducting and insulating behavior depending on the termination structures of STO substrates, namely, whether ``TiO$_{2}$-" or ``SrO-terminated" surfaces, respectively. Controlling the interface structure genuinely with atomic precision will eventually lead to the creation of exotic electronic phenomena and functionalities at the complex oxide interfaces.