Effect of nitrogen impurity on x-ray detector based on single-crystal diamond after radiation and boron compensation

Single-crystal diamond, as a substrate material of radiation detector for radiotherapy, has attracted growing attention because of its tissue equivalence and high radiation resistance. X-ray detectors were fabricated from single-crystal diamond with high nitrogen impurity content (N∼1017 atoms/cm−3) and low nitrogen impurity content (N∼1016 atoms/cm−3). Raman spectroscopy, photoluminescence spectroscopy (PL), and electron paramagnetic resonance spectra were used to characterize the change in defects of the three states, such as substrate, after metallization and after x-ray irradiation. The results indicate that the defects containing nitrogen change after x-ray irradiated diamond with high N content. Hence, detectors based on diamond with low N content exhibit less than 0.5% both the uncertainty of repeatability and nonlinearity, while detectors based on diamond with high N content exhibit more than 1% because of the change in NV− and NV0 centers. Boron doping was employed to compensate the defects as a secondary treatment. The results indicate that detectors based on boron-compensated diamond exhibit both the uncertainty in the repeatability and nonlinearity between 0.5% and 1%. This provides a new approach for low-cost fabrication of x-ray detectors.