Thin CVD diamond detectors with high charge collection efficiency

We report the measurements of charge collection efficiency for nuclear particle detectors made from electronic-grade chemical vapor deposition (CVD) diamond samples with thicknesses of 20 and 150 /spl mu/m fabricated at CEA/LETI. Although it is well established that the transport properties of CVD diamond, and more specifically the /spl mu//spl tau/ product, tend to improve with the sample thickness, it was observed that excellent collection efficiencies can be achieved on the 20-/spl mu/m-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.