FIELD ELECTRON-EMISSION FROM HYDROGENATED AMORPHOUS-SILICON FILMS ON TUNGSTEN - LIGHT-INDUCED EFFECTS

Field electron emission from a hydrogenated amorphous silicon deposite d tungsten tip has been studied. The effect of prolonged (hourly) expo sure to light on the field electron emission current has been investig ated. The current-voltage characteristics of the as-deposited, light e xposed, and annealed states of the emitter showed semiconducting behav ior in accordance with the Fowler-Nordheim law. In case of an initiall y annealed emitter tip, the field emission current was found to increa se monotonically with the light exposure, reversibly for shorter durat ions of a few minutes. The effect of long term (hourly) exposure of li ght resulted in the increase in the field emission current level nonli nearly with the exposure time. The current level did not come down to the original level even after switching off the light in contrast to t he effect of short duration light exposure. The enhancement in the fie ld emission current has been attributed to tunneling though the dangli ng bond states created by light exposure. The results have been discus sed in light of the Staebler-Wronski effect.