Native oxidation of the Si(001) surface: Evidence for an interfacial phase

We have used grazing incidence x-ray scattering techniques to investigate the structure of the Si-SiO2 interface, obtained by native oxidation of a Si(001) surface. The x-ray diffraction patterns reveal a twofold symmetric interfacial phase, of 2×1 periodicity. This interfacial phase, which is coherent with the silicon substrate, extends over very large lateral distances (up to 5000 Å) and is less than 5 Å thick. This phase is very disordered at the atomic scale. Its extent and perfection strongly depend on the flatness of the initial silicon substrate.