Temperature-dependent emptying of grain-boundary charge traps in chemical vapor deposited diamond

We have used the technique of ion beam induced charge with a 2 MeV He+ microprobe to image particle detectors fabricated from polycrystalline chemical vapor deposited diamond as a function of temperature. We find that detectors which display a thermally stimulated current peak at 190 degreesC display increased charge collection efficiency when heated above that temperature. The probability of detecting the impact of a single ion at room temperature was less than 2%, but this probability rises to over 80% at 170 degreesC. We model this effect by showing that charge trapped at grain boundaries is liberated at elevated temperatures and this results in an increased electric field within the detector volume and hence a raised charge collection efficiency. (C) 2004 American Institute of Physics.