Diamond radiation sensors for medical applications

Applicability of commercial CVD diamond films for radiation detector application was studied. The CVD diamonds obtained from different sources were characterised by different optical techniques such as Raman and photoluminescence spectroscopy, cathodoluminescence (CL) and optical absorption. The samples were used for fabrication of MIM sandwich type radiation detectors. The detectors were exposed to γ-exposure (⁶⁰Co source) of a low dose-rate. The output signal of the CVD diamond was compared to that of a high quality natural type IIa single crystal diamond. The comparison of the radiation response signal to the results of the optical studies revealed that the Si related defects inside the single crystallites of the films strongly reduce the sensitivity of the sensors and cause large ionisation currents. It was shown that the free exciton recombination intensity in CL can serve as a direct measure of the radiation sensitivity of diamond. Also it was demonstrated that optical absorption can only be used for initial selection of the diamond substrates