Scanning tunneling microscopy, ion-scattering spectroscopy and low-energy electron diffraction were used to investigate the surface morphology of SnO2(110) for various preparation conditions. Annealing in 10-3mbar O resulted in a 1 x 1 diffraction pattern. Such surfaces exhibited terraces separated mainly by straight step edges along low-index crystallographic directions. The terraces exhibited a high density of defects. Annealing to 810K resulted in the loss of surface O but the surface retained a 1 x 1 periodicity. Steps of less than monolayer-height, however, indicated that a significant re-ordering of the surface atoms already occurred at this temperature. Annealing to higher temperatures, or preparation of the surface by sputtering and vacuum annealing, always resulted in a superstructure in the diffraction pattern and a low [O]/[Sn] ratio in ion-scattering spectroscopy. For annealing temperatures of between 920 and 1050K, the co-existence of c(2 x 2) and 4 x 1 reconstructed domains was observed. In this regime, small ad-islands were always present at the surface. Extended terraces were imaged, by scanning tunnelling microscopy, with a 4 x 1 periodicity. This implied that the c(2 x 2)-structure was associated with ad-islands at the surface. Annealing to 1100K resulted only in the formation of a 4 x 1 surface. This surface exhibited terraces with meandering step edges and antiphase domain boundaries of the 4 x 1 surface structure. A new model for this reconstruction was proposed which included Sn atoms that occupied interstitial surface sites. Annealing to 1180K resulted in the fragmentation of the 4 x 1 structure, and the surface lost its long-range order. This caused a 1 x 1 low-energy electron diffraction pattern which originated from the underlying substrate. Surface undulations with sub-interlayer step heights were explained by the frequent presence of stacking faults and other bulk defects that were also accompanied by variations in the electronic structure due to a locally altered Sn/O stoichiometry.

Surface Morphologies of SnO2(110). M.Batzill, K.Katsiev, U.Diebold: Surface Science, 2003, 529[3], 295-311