Growth kinetic of perovskite oxide monolayers on SrTiO$_{3}$(100) studied with reflection high energy electron diffraction (RHEED) and oblique-incidence optical reflectivity difference measurements.

Using a combination of RHEED and an oblique-incidence optical reflectivity difference technique (OI-RD, a form of polarization modulated ellipsometry), we studied the growth of 5{\%} doped Nb:SrTiO$_{3}$ monolayers on SrTiO$_{3}$(100) under pulsed laser deposition condition (PLD) in a molecular oxygen ambient. By interrupting the deposition at the completion of one monolayer and continuing the RHEED and OI-RD measurement during post-deposition annealing, we can separate contributions to the optical reflectivity difference signal from kinetics of growth and oxidation. Based on a mean-field theory of optical reflectivity difference off an atomically rough and yet optically smooth film, we find that a growth-dependent part of the reflectivity difference signal is proportional to the step edge density or equivalently the root-mean-square (rms) of the roughness of a growth surface. We show that the surface roughness during the interrupted deposition of Nb:SrTiO$_{3}$ monolayers on SrTiO$_{3}$(100) can be analyzed with a 8-level growth model with two adjustable parameters. The parameters obtained by fitting the model to the OI-RD signal during the \textit{interrupted} deposition can be used subsequently to predict the growth behaviour of Nb:SrTiO$_{3}$ on SrTiO$_{3}$(100) in a \textit{continuous} pulsed laser deposition as reported earlier by Fei and co-workers.