Spectroscopic response of coplanar diamond alpha particle detectors

The performance of a chemical-vapor deposited (CVD) diamond radiation detector with an interdigitated coplanar electrode geometry is reported. The coplanar structure produces a shallow lateral electric field distribution. Consequently, charge transport occurs in a region close to the growth surface of the CVD diamond film, where the drift lengths are maximized. The spectroscopic performance of the coplanar diamond detector was investigated using alpha particles from a /sup 241/Am source, and also using a scanning 2-MeV proton microprobe. A broad full energy peak was observed using 5.49-MeV alpha particles, with an overall charge-collection efficiency of approximately 16% at a bias voltage of 300 V. The performance of this device is discussed with reference to Monte Carlo simulations of charge transport in coplanar electrode geometries.