Spectroscopic response of coplanar diamond alpha particle detectors

The performance of a CVD diamond radiation detector with an inter-digitated coplanar electrode geometry is reported. The coplanar structure produces a shallow lateral electric field distribution and consequently charge transport occurs in a region close to the growth surface of the CVD diamond film, where the drift lengths are maximised. The spectroscopic performance of the coplanar diamond detector was investigated using alpha particles from a ²⁴¹Am 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. Images obtained from the proton microprobe demonstrate the inhomogeneous pulse height response across the active surface of the detectors, caused by a combination of the polycrystalline diamond material and also non-uniform electric field profile