Epitaxial growth of SrTiO3 on SrTiO3(001) using an oblique-incidence reflectance-difference technique

In a measurement of pulsed laser deposition of ${\mathrm{SrTiO}}_{3}$ on ${\mathrm{SrTiO}}_{3}(001),$ we demonstrate that the difference in relative reflectivity change $\ensuremath{\Delta}R/R$ between $s$- and $p$-polarized light can be used in a real-time monitor of thin film growth at the level of a single atomic layer. This reflectance difference has the same sensitivity (0.01 monolayer), the real-time monitoring capability, and the spectral resolution as the conventional reflectance-difference spectroscopy developed by Aspnes and co-workers. The present reflectance-difference technique does not rely on the existence of optical anisotropy within the surface plane and therefore is applicable to investigation and control of thin film growth on all surfaces. Compared to the surface photoabsorption technique developed by Kobayashi and Horikoshi, our technique improves the signal-to-noise ratio by at least one order of magnitude through reducing the background to a level equivalent to $\ensuremath{\Delta}R/R=1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ or below.