STM study of ultra-thin (<2 nm) silicon oxide

The morphology of ultra-thin (0.6–2 nm) oxides prepared by chemical ozone-based process and rapid thermal oxidation (RTO) is studied by scanning tunneling microscopy. With a statistical analysis of the height distribution we compare the different methods used to prepare the surfaces. A roughness anisotropy is observed for the thinner oxides samples. An atomically flat surface with a thin conformal oxide is obtained by annealing the sample at temperatures >1100 °C under an hydrogen flux before RTO. In this case, the oxide morphology may be correlated to the crystalline structure underneath.