Photoemission assignments of H_xSiO_4-x fragments at the Si/SiO_x interface

Hydrogenation of the silicon/silicon oxide interface is shown to cause changes in every feature spectroscopically discernible by soft x-ray photoemission in addition to depinning the Fermi level. A new feature is observed to grow in at 3.6 eV with respect to bulk Si upon exposure to atomic hydrogen at the expense of interface states intermediate between 3.6 and 0 eV. Assignments of photoemission features are discussed in the context of previous model studies of the interface and issues of electronic versus chemical reversibility are discussed.