CVD diamond photoconductive devices for detection of x-rays

Abstract

Diamond is a very attractive material to realize radiation detectors due to its exceptional properties (thermal, mechanical, optical, electronic, etc). But, the detector performances are highly dependent on the film quality. In this work, two chemical vapour deposition (CVD) diamond films, differing in film quality, obtained by a hot-filament CVD technique were used to fabricate radiation detectors. The measurements of photocurrents and pulse height distributions (PHDs) of the two detectors were carried out using 5.9 keV x-rays from a 55Fe source. For the detector with a better film quality, the electrical contact is fine Ohmic for bias voltages up to 150 V, and a dark current of 23.3 nA and the photocurrent of 16.8 nA are obtained at an electrical field of 50 kV cm−1. The peak of the PHD is well separated from the noise, indicating a high counting efficiency and a high signal-to-noise ratio. After several minutes' stabilization, the time-dependent photocurrent reveals that the photocurrent increases and then levels off due to the polarization effect.