Device performance of chemical vapor deposition monocrystal diamond radiation detectors correlated with the bulk diamond properties

Diamond radiation detectors (DRDs) based on type-IIa chemical vapor deposition (CVD) monocrystal diamond are more suitable for engineering applications with high consistency requirements due to the lower cost and property controllability. However, their saturated charge collection efficiencies (CCEs) have huge differences. Six type-IIa CVD monocrystal diamond plates were analyzed by the Fourier transform infrared spectrometer, high resolution x-ray diffraction, Raman spectroscopy, photoluminescence and secondary ion mass spectroscopy. Then DRDs were fabricated by them and the CCEs were measured under the irradiation of ²⁴¹Am source. The results show that the most important factor restricting CCEs are the impurities in the diamond plates, while dislocations with a density <1 × 10⁷ cm⁻² for all samples have weaker impact in our case. The reason is that the carrier mobility-lifetime (µτ) product of diamond is more strongly influenced by impurities in this dislocation density range. Thinning diamond plate, if the thickness is kept above 100 µm, is not a good means to obtain high performance DRDs. Therefore, to further improve the detector performance, ultra-high purity diamond growth is most important. Moreover, a diamond test and selection scheme for high performance DRDs is also demonstrated.