The structure of SrTiO3(001)-2 × 1 surface analyzed by high-resolution medium energy ion scattering coupled with ab initio calculations

Abstract

High-resolution medium energy ion scattering (MEIS) spectrometry coupled with photoelectron spectroscopy revealed unambiguously that the initial SrTiO3(001) surface chemically etched in a buffered NH4F-HF solution was perfectly terminated with a single-layer (SL) of TiO2(001) and annealing the surface at 600-800 [ordinal indicator, masculine]C in ultrahigh vacuum (UHV) led to a (2 × 1)-reconstructed surface terminated with a double-layer (DL) of TiO2(001). After annealing in UHV, rock-salt SrO(001) clusters with two atomic layer height grew epitaxially on the DL-TiO2(001)-2 × 1 surface with a coverage of 20%-30%. High-resolution MEIS in connection with ab initio calculations demonstrated the structure of the DL-TiO2(001)-2 × 1 surface close to that proposed by Erdman et al. [Nature (London) 419, 55 (2002)] rather than that predicted by Herger et al. [Phys. Rev. Lett. 98, 076102 (2007)]. Based on the MEIS analysis combined with the ab initio calculations, we propose the most probable (2 × 1) surface structure.