Thin Polycrystalline Diamond for Low Energy X-Ray Detection

The response of polycrystalline diamond detectors to low-energy x-ray beams is presented. Diamond metal/semiconductor/metal vertical structures have been realized to investigate the influence of the electric field in the dark and under x-ray irradiation. Nonlinear contributions to the current, compatible with field-assisted thermal ionization of trapped charges, have been evidenced, as well as the presence of defect-related electronic states acting as traps has been confirmed by subband-gap photoconductivity measurements. Moreover, correlations have been evidenced among irradiation time, variation of the current in the dark, and photoconductive response of the devices to the x-ray beam. An evaluation of the minority-carrier mobility-lifetime product, at the end of the activation process, has led to a value of 9.210−7 cm2 /V. Two orders of magnitude linear response to the beam intensity variations have been evaluated after removal of the bremsstrahlung radiation contribution on a 43-um-thick device.