Photon-enhanced field emission from CdS single crystals

In a previous experiment, field emission was observed from sharply pointed CdS single crystals. The experiments have now been extended, illuminating the tip with light from a pulsed argon-ion laser. It was found that (a) the voltage threshold at which emission can be observed is reduced, typically from 500 to 400 V, (b) under some conditions, the emission is increased by a factor of 103, (c) this emission persists for more than 2×10?2s after the laser pulse and appears to have two characteristic decay times, (d) the emission is approximately proportional to the light intensity and (e) the greatest photo-enhanced field emission was obtained with the laser light shining axially on the emitting area of the tip.