Crystalline anodic silicon dioxide on silicon

Multi-layer oxide film grows in anodic oxidation of silicon p-type in 0.1 N water diluted hydrofluoric acid. The inner layer of the oxide film on the silicon monocrystal substrate is of α-quartz, while the outer layer of the oxide film to the electrolyte interface is amorphous. By electron diffraction in transmission a orientation, [00.1], of α-quartz layer on the silicon [111] surface is identified. It is supposed that such structure of the oxide film is a result of existing high electric fields on the silicon anode surface in suitable electrolyte and that strong nonequilibrium condition of oxidation are possible.