Valence band edge of ultra-thin silicon oxide near the interface

The changes in X-ray excited valence band of silicon oxide during progressive oxidation of Si(100) surface in 1 Torr dry oxygen at 600–880°C were studied. The following results are obtained: (1) the energy of top of valence band within the critical distance of 0.9 nm from the SiO2/Si interface is different from that of bulk silicon oxide by about 0.2 eV, (2) this critical distance for Si(100) and the amount of change in valence band edge near this critical distance are nearly equal to those for Si(111).