Nanoscale structural variation observed on the vicinal SrTiO 3 ( 001 ) surface

The vicinal (001) surface of a Nb-doped SrTiO 3 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 ( 6 × 2 ) structure being stable up to 1000 ° C , while √ 13 × √ 13 -R 33.7 ° , c ( √ 13 × √ 13 ) -R 33.7 ° , and c ( √ 2 × √ 18 ) -R 45 ° structures are formed on TiO 2 layers, which disappear at 450 - 750 ° C followed by the formation of 2 × 2 and √ 5 × √ 5 -R 26.6 ° structures. These results indicate instability of the reconstructions on the TiO 2 terminated surface due to the variation in Sr adatom density caused by multikinetic processes, in contrast to the thermodynamically stable SrO terminated surface.