Xerographic effects of small chlorine additions to amorphous selenium

Abstract

A study has been made of the xerographic properties of amorphous selenium doped with chlorine at concentrations below 100 parts per million (ppm) by weight. The sample consisted, in each case, of an aluminum plate with a thin deposited rf sputtered aluminum oxide film, on which a 50 μm layer of amorphous selenium was deposited by evaporation, at a substrate temperature of 50 °C. It was found that the chlorine decreased the acceptance voltage following corona charging, increased the dark decay rate, and decreased the residual voltage after illumination discharge. The changes were such as to be beneficial xerographically for small additions of chlorine to the selenium in the ppm range. Analysis of the time derivative of the dark decay voltage indicated that depletion discharge was the dominant process in the decrease of dark decay voltage with time and a modified relation was introduced to describe the increase of bulk space-charge density with time, arising from thermal excitation of holes from deep discrete centers in the photoreceptor. This analysis indicated a decrease of the release time of the holes with increase of chlorine content, whereas an observed decrease of single cycle and cycled-up residual voltages with increased chlorine indicated an increase of hole capture time from their relevant trapping centers.