The effect of annealing on the X-ray induced photocurrent characteristics of CVD diamond radiation detectors with different electrical contacts

An investigation on the influence of metal-diamond interfaces on the X-ray induced photocurrent characteristics of diamond based solid state radiation detectors has been performed before and after annealing in order to identify the parameters of metal contact formation which maximise the performance. For this purpose, two different samples with different metal contacts were fabricated by sputtering Pt (labelled HPS-Pt) and Al/Pt (labelled HPS-Al/Pt) on to high quality CVD diamond. To examine the performance of the two samples, a set of measurements was performed before and after annealing the devices: I-V characteristics, time response such as rise and fall-off times, sensitivity and specific sensitivity, signal to noise ratio (SNR), photoconductive gain, dose rate dependence and reproducibility were studied. The effect of the changes in bias voltage on the performance of the samples was also investigated. The response of annealing the devices is strongly dependent on the metal contact. HPS-Al/Pt showed a strong increase in the current amplitude (∝240 times the value before annealing) and the stability is improved as a high overshoot is totally removed after annealing. Annealing HPS-Pt showed a slight increase in the current amplitude and the small overshoot existing at low dose rate is also removed, however the stability of the currents is reduced which affected the reproducibility of the signal. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)