Sub-bandgap photoenhancement of electron emission and discharging of hydrogenated and hydrogen-free diamond surfaces

Abstract

In this paper we report on the photoinduced enhancement of secondary electron emission and discharging of hydrogenated and hydrogen-free diamond surfaces subjected to continuous low energy electron irradiation. Diamon surfaces subjected to electron irradiation trap charges resulting in upwards surface band bending and consequent decrease of secondary electron emission. It is demonstrated that simultaneous electron irradiation and illumination of the diamond surfaces with sub-bandgap photons in the visible range enhances the secondary electron emission yield of diamond. For the hydrogenated diamond surfaces it is suggested that these effects are associated to a surface photovoltage effect which results in unpinning of the surface bands by photoexcitation of carriers and compensation of trapped surface charges. For the hydrogen-free diamond, discharging is most likely associated with photoexcitation of the trapped charges in midgap electronic states associated with surface reconstruction.