Surface relaxation and rumpling of TiO 2-terminated SrTiO 3(001) determined by medium energy ion scattering

Abstract

The surface relaxation and rumpling of TiO 2-terminated SrTiO 3(001) were determined by medium energy ion scattering (MEIS). A new toroidal electrostatic analyzer with high energy resolution (Δ E/ E=1×10 −3) allows direct determination of the displacements of surface atoms by a simple triangulation method using the ion shadowing effect. The TiO 2-terminated surface was prepared by the chemical treatment with a buffered NH 4F–HF solution (pH=3.5–3.8). Annealing at 600°C for 1 h in an ultrahigh vacuum under O 2 gas flow (5×10 −6 Torr) led to a clean surface without carbon contamination and oxygen vacancies, which was confirmed by Auger electron and ultraviolet photoelectron spectroscopy. The present MEIS analysis revealed that the occupation fraction of the TiO 2 face ranged from 85 to 95% and the surface relaxation and rumpling were +2.7±0.2% and +3.1±0.4% respectively. The present results were compared with other experimental and theoretical ones.