Band Structure and Surface Effects in Cadmium Sulfide Photoemission Studies

摘要

Photoemission measurements have been made on single crystals of cadmium sulfide which were cleaved and tested in high vacuum at photon energies between 7.2 and 11.6 eV. The electron affinity is found to be 4.8 eV. Additional measurements have been made in an extended range from 6 to 21.2 eV using surfaces cleaved in air or in low vacuum and tested in low vacuum. The apparatus for cleaving and measuring photoemission is described. Important features of the band structure are deduced from the energy distribution and quantum yield measurements. Two conduction band maxima are located about 6.7 and 8.2 eV above the top of the valence band. Two valence band maxima are located about 1.2 and 9.4 eV below the top of the valence band. The effects of surface conditions on photoemission from cadmium sulfide have been studied by comparing measurements made on samples cleaved in high vacuum with the corresponding results from surfaces prepared by other techniques.