Monolayer Oscillation Observed by an Oblique-Incidence Reflectance Difference Technique for the Epitaxial Growth of Oxides

We report the optical oscillations with monolayer periodicity observed by an oblique-incidence reflectance difference (OIRD) technique on the epitaxial growth of Nb-doped SrTiO₃ on SrTiO₃ substrate. The periodicity was verified by the simultaneously measured reflection high-energy electron diffraction intensity oscillations. The OIRD oscillation damps during deposition, but can recover after the growth is interrupted for some time. We interpret the optical oscillations as a result of the periodic changes of the surface morphologies due to the two-dimensional layer-by-layer growth of thin films.