Effects of microstructure of films on CVD diamond X-ray detectors

Although the unique properties of chemical vapor deposition (CVD) diamond films have made it a candidate material for radiation detectors, the polycrystalline nature of the films has severely limited the development of CVD diamond detectors. In this work, three CVD diamond films with different microstructure were grown by using a hot-filament chemical vapor deposition (HFCVD) technique and were fabricated as CVD diamond detectors. The electric contact is good ohmic for bias voltage up to 150 V. 5.9 keV 55Fe X-ray was used to measure the photocurrent and the pulse height distribution (PHD). For the detector based on the best quality film, the dark-current of 16.0 nA and the net photocurrent of 15.9 nA are obtained at an electric field of 50 kV cm−1. The PHD peak is well separated from the noise pedestal, indicating a high counting efficiency and a low detection limit.