Thin CVD diamond detectors with high charge collection efficiency

We report the measurement of charge collection efficiency for nuclear particle detectors made from electronic-grade chemical vapor deposition (CVD) diamond samples with thicknesses of 20 and 150 μm fabricated at CEA/LETI. Although it is well established that the transport properties of CVD diamond, and more specifically the μτ product, tend to improve with the sample thickness, it was observed that excellent collection efficiencies can be achieved on the 20-μm-thick detector owing to the reduced interelectrode distance. Due to the polycrystalline nature of CVD diamond, the charge collection efficiency is inhomogeneous throughout the detector surface. However, a mean collection efficiency of 50% was measured over the whole detector surface, with regions close to 100%, corresponding to the highest values reported in the literature for CVD diamond. This excellent performance enables the detection of very low-energy heavy charged particles with a detection limit well below 200 keV for protons.