Alpha spectroscopy and X-ray induced photocurrent studies of a SC CVD diamond detector fabricated with PLD contacts

Abstract

Using amorphous Carbon blended with Nickel (C/Ni) as electrodes for a polycrystalline diamond radiation detector (PC-C/Ni) was demonstrated previously as a novel technique to produce near-tissue equivalent X-ray dosimeters. In this project, we introduce the first characterisation of a (Chemical Vapour Deposited) single crystal diamond sandwich detector (with thickness of 0.4 mm) fabricated with this technique, labelled SC-C/Ni. To examine the performance of pulsed laser deposition (PLD) C/Ni as an electrode, alpha spectroscopy measurements and X-ray induced photocurrent measurements were studied as a function of the applied bias at room temperature and compared with those of the aforementioned PC-C/Ni.The alpha particle spectroscopy measurement data allows us to differentiate between electron and hole contributions to the charge transport signal, whilst the X-ray data was investigated in terms of dose rate-linearity, sensitivity, signal to noise ratio (SNR) and photoconductive gain.In the case of electron sensitive alpha induced signals, a Charge Collection Efficiency (CCE) higher than 90% has been observed at a bias of −40 V and 100% CCE at −300 V, with energy resolution of ∼3% for 5.48 MeV alpha particles. The sample showed very poor spectroscopy performance for hole sensitive signals up to 200 V.The X-ray induced photocurrents show a high SNR of ∼7.3 × 103, an approximately linear relationship between the photocurrent versus dose rate and a sensitivity of 4.87 μC/Gy.mm3. The photoconductive gain of SC-C/Ni is calculated to be ∼20, this gain calculation might be explained by trapping effects as investigated in the alpha spectroscopy measurements.