High-Resolution X-Ray Photoelectron Spectroscopy as a Probe of Local Atomic Structure: Application to Amorphous SiO2and the Si-SiO2Interface

The chemical structure of thin Si${\mathrm{O}}_2$ films and Si${\mathrm{O}}_2$-Si interfaces has been investigated using high-resolution x-ray photoelectron spectroscopy. The data are consistent with a continuous random network of four-, six-, seven-, and eight-member rings of Si${\mathrm{O}}_4$ tetrahedra joined together by bridging oxygens. This distribution changes substantially within 30 Å of the Si${\mathrm{O}}_2$-Si interface. The near-interface region is comprised of ${\mathrm{Si}}_2$ ${\mathrm{O}}_3$, SiO, and ${\mathrm{Si}}_2$O. This structure is interpreted by means of a structure-induced-charge-transfer model.