Surface relaxation and rumpling of TiO2-terminated SrTiO3(001) determined by medium energy ion scattering

The surface relaxation and rumpling of TiO2-terminated SrTiO3(001) were determined by medium energy ion scattering (MEIS). A new toroidal electrostatic analyzer with high energy resolution (Delta E/E=1 x 10(-3)) allows direct determination of the displacements of surface atoms by a simple triangulation method using the ion shadowing effect. The TiO2-terminated surface was prepared by the chemical treatment with a buffered NH4F-HF solution (pH=3.5-3.8). Annealing at 600 degrees C for 1 h in an ultrahigh vacuum under O-2 gas flow (5 x 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 TiO2 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. (C) 1999 Elsevier Science B.V. All rights reserved.