The complete valence band in amorphous Si${\mathrm{O}}_2$ has been examined by photoelectron spectroscopy at photon energies of 21.2, 26.9, 40.8, and 1486.6 eV. The spectra show emission from an 11.2-eV-wide $p$-derived valence band and from the oxygen $2s$ level at 20.2 eV below the valence-band edge. Four pieces of structure in the $p$ bands are related to the single bonding and the two nonbonding orbitals of the ${\mathrm{O}}^{--}$ ion. A narrow, nonbonding level found at the valence-band edge may cause lattice trapping of valence-band holes.

• Received 29 September 1971

DOI:https://doi.org/10.1103/PhysRevLett.27.1560