Nanoscale structural variation observed on the vicinal SrTiO3(001) surface

The vicinal (001) surface of a Nb-doped SrTiO3 single crystal has been investigated by scanning tunneling microscopy and low energy electron diffraction. The stepped surface prepared by annealing in ultrahigh vacuum at 250 C exhibits a complex atomic structure composed of four types of reconstructions, which shows short-range variation within nanoscale regions. SrO layers show a c(6x2) structure being stable up to 1000 degrees C, while root 13 x root 13-R33.7 degrees, c(root 13 x root 13)-R33.7 degrees, and c(root 2 x root 18)-R45 degrees structures are formed on TiO2 layers, which disappear at 450-750 degrees C followed by the formation of 2 x 2 and root 5 x root 5-R26.6 degrees structures. These results indicate instability of the reconstructions on the TiO2 terminated surface due to the variation in Sr adatom density caused by multikinetic processes, in contrast to the thermodynamically stable SrO terminated surface. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3447796]