The interface structures of SiO2/Si(001) samples were studied by using first-principles molecular dynamics methods. Three crystalline phases of the SiO2 (cristobalite, quartz, tridymite) were stacked on the Si(001) substrate and were fully relaxed. When the SiO2 layer was very thin (about 0.7nm), the lowest-energy structure was tridymite; followed by quartz. As the SiO2 layer became thicker (about 1.5nm), the quartz phase had a lower energy than did the tridymite phase. The cristobalite phase on Si(001) was unstable, due to a large lattice mismatch, and transformed into a different crystal structure. No defects appeared at the interface after successive bond breaking and re-bonding, but the energy of the resultant structure was the highest; regardless of the thickness.

Geometrical and Electronic Structures of SiO2/Si(001) Interfaces. T.Yamasaki, C.Kaneta, T.Uchiyama, T.Uda, K.Terakura: Physical Review B, 2001, 63[11], 115314 (5pp)