Direct observation of two-dimensional growth at SiO₂/Si(111) interface

The residue of the two-dimensional (2D) oxide-island growth was directly investigated by observing the morphology change of the SiO₂/Si(111) interface with atomic force microscopy, after removing SiO₂. It was found that oxidation progressed by the bilayers in the (111) orientation instead of by the monolayers. Oxidation created the oxide-islands in an atomic layer, while the Si-islands were found to exist in the previous atomic layer. This result indicates that thermal oxidation progresses not by a strict layer-by-layer process. Furthermore, the deviation from the layer-by-layer process was increased as the oxidation temperature was decreased. This morphology degradation at low-oxidation temperatures (< 1050 °C) is due to the constraint of the 2D expansion rate of the oxide-island.