Surface Phonons in Spectral Oscillations in the Photoconductivity on Silicon (111) Surfaces

At clean cleaved silicon (111) surfaces an “oscillatory” photo conductance with excitation of holes out of surface states has been reported [1]. The period of the oscillations is (58 ± 3) meV. A surface phonon (hω s = (56 ± 1) meV) has been found on the same type of surfaces in low energy electron spectroscopy [7]. It is shown that the oscillations in the photoconductivity are caused by the interaction of photoexcited hot holes with the surface phonon.