This work aims to characterize the electrically and optically active defects in commercially available synthetic intrinsic diamond-based radiation detectors intended for alpha spectral response. Different types of commercially available single-crystal diamond (SCD) with varying nitrogen and boron concentrations are employed for detector fabrication in a sandwich configuration. All the detectors exhibited nearly linear \(\mathbf{I}-\mathbf{V}\) characteristics with dark current less than \(50\mathbf{p}\mathbf{A}\) up to \(\pm 600\mathbf{V}\) and constant capacitance of less than \(0.5\mathbf{p}\mathbf{F}\) . Defect characterization is carried out for all diamond samples through optical and electrical spectroscopic techniques including photoluminescence (PL), thermally stimulated current (TSC), and its variant, zero-bias TSC (ZB-TSC). The acquired PL spectra of all the diamond samples reveal the presence of dislocations and nitrogen-related defects, whereas TSC and ZB-TSC measurements confirm the dominance of electron traps in the majority of the SCD samples. It is generally believed that electrically active defects within the diamond bulk are responsible for variation in the charge collection properties and hence the energy resolution. To investigate this, alpha-particle spectroscopy of the diamond detectors is carried out. Only one of the three diamond samples exhibits an alpha spectrum with energy resolution of 1.8% for a239Pu source and with 100% charge collection efficiency. The other samples fail to produce any alpha pulse height spectrum, revealing that the charge collection distance is well within the bulk thickness, which suggests a possible direct correlation of electrically active defects with the charged particle spectroscopic properties of the diamond detectors.
