Photoelectric Emission from Silicon for Photon Energies of 6 to 9.6 eV

Energy distributions of photoemitted electrons from cleaved (111) silicon surfaces are given for photon energies from 6 to 9.6 eV. Distributions from clean surfaces and from such surfaces covered with up to a monolayer of cesium are given. A full monolayer deposition of cesium is found to move the surface Fermi level {≤}0.4 eV above its clean surface position 0.33 eV above the valence-band edge (Eᵥ). Structure in the distributions at energy positions Eᵥ+4.3 eV is nearly stationary in energy with changing photon energy. The contribution of secondaries to a peak at Eᵥ+2.8 eV is clearly evident. A dip is found in the distributions at ~Eᵥ+3.1 eV which lends strong support to the proposal that transport effects can strongly modify the initially excited internal energy distribution. Structure appearing at energies Eᵥ+4.5 eV is found to move in energy position more slowly than the change in photon energy. This behavior indicates that the structure is associated with direct optical transitions.