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

Samples of single crystal cuprous oxide prepared by quench ing after equi-libration at various oxygen pressures at h igh temperature were subjected to bombardment by argon ions and hydrogen ions, and the photoelectric emiss ion 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 equat ion y1/n ~ k (E--Eo) with n usually hav ing the value of 2, and this was used to evaluate the threshold energy Eo. The h igh 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 wi th bombardment. It is p roposed that the high energy threshold represents the process of direct excitation w i th scattering f rom the valence band. The lower values of the low energy threshold are presumed to represent excitation f rom surface impurities wh ic