The Effect of Ion Bombardment on the Photoelectric Threshold of Single Crystal Cuprous Oxide

Abstract

Samples of single crystal cuprous oxide prepared by quenching after equilibration at various oxygen pressures at high temperature were subjected to bombardment by argon ions and hydrogen ions, and the photoelectric emission was then measured. The curves for the photoelectric quantum yield Y vs. the photon energy E were characterized by the presence of a double shoulder indicating the presence of two thresholds. The data could be fitted to the equation with n usually having the value of 2, and this was used to evaluate the threshold energy Eo. The high energy threshold was relatively constant at 5.1 ev regardless of the amount of ion bombardment, but the low energy threshold was much more variable, often starting at ∼4.0 ev and increasing to 4.6 ev with bombardment. It is proposed that the high energy threshold represents the process of direct excitation with scattering from the valence band. The lower values of the low energy threshold are presumed to represent excitation from surface impurities which are gradually removed by bombardment. The limiting value of the low energy threshold is assigned to excitation from states similar to the bulk acceptor states usually found in at 0.4 ev above the valence band.