Structure and electronic property of Si(100)/SiO2 interface

Stable structures and electronic states of Si(100)/SiO2 interface have been investigated with the first-principles molecular dynamics method. Quartz, tridymite, and pseudo beta-cristobalite are employed as the initial structures of SiO2 at the interface to find the stable ones by structural optimization. It is found that the optimized tridymite-type SiO2 on Si is most stable for a thin ( about 7 Angstrom) SiO2 layer. For a thicker (about 15 Angstrom) layer, however, this structure becomes less stable than the others, and the optimized quartz-type SiO2 structure becomes most stable. Variation of the band gap perpendicular to the interface has also been investigated. In the SiO2 region from the structural interface to a point about 1 Angstrom away from it, the band gap remains as narrow as that of silicon. The dramatic change of the band gap takes place in the SiO2 region from about 1 to 4 Angstrom away from the interface.