Influence of temperature on the response of high-quality polycrystalline diamond detectors

We investigated the charge collection properties of a polycrystalline CVD diamond detector in a temperature range from -10 to 80 C, by means of a 90Sr minimum ionizing β radiation source. The sample is a state-of-the-art diamond sensor yielding a maximum charge collection distance of 260 um at room temperature and 1 V/um applied field, when set in the so called pumped state, i.e., after passivating the deep traps with a pre-irradiation with β particles. We observed a decreasing charge collection distance with increasing temperature, which is a trend opposite to that reported recently by other research groups. We ascribe this discrepancy to the higher quality of our detector, in terms of a lower concentration of defects and grain boundaries. Conversely, we observe a less dramatic temperature dependence which we tentatively explain assuming a combined effect of variation with temperature of the thermal velocity and of the capture cross-section, according to a well known model of multi-phonon non-radiative processes.