Stoichiometry-driven switching between surface reconstructions on SrTiO_3(001)

摘要

Controlling the surface structure on the atomic scale is a major difficulty for most transition metal oxides; this is especially true for the ternary perovskites. The influence of surface stoichiometry on the atomic structure of the SrTiO_3(001) surface was examined with scanning tunneling microscopy, low-energy electron diffraction, low-energy He~+ ion scattering (LEIS), and X-ray photoelectron spectroscopy (XPS). Vapor deposition of 0.8 monolay-er (ML) strontium and 0.3 ML titanium, with subsequent annealing to 850 ℃ in 4 × 10~(-6) mbar O_2, reversibly switches the surface between c(4 × 2) and (2×2) reconstructions, respectively. The combination of LEIS and XPS shows a different stoichiometry that is confined to the top layer. Geometric models for these reconstructions need to take into account these different surface compositions.