HIGH COLLECTION EFFICIENCY CVD DIAMOND ALPHA-DETECTORS

Advances in Chemical Vapour Deposited (CVD) diamond have enabled the r outine use of this material for sensor device fabrication, allowing ex ploitation of its unique combination of physical properties (low tempe rature susceptibility (>500 degrees C), high resistance to radiation d amage (>100Mrad) and to corrosive media). A consequence of CVD diamond growth on silicon is the formation of polycrystalline films which has a profound influence on the physical and electronic properties with r espect to those measured on monocrystalline diamond. We report the opt imisation of physical and geometrical device parameters for radiation detection in the counting mode. Sandwich and co-planar electrode geome tries are tested and their performances evaluated with regard to the n ature of the field profile and drift distances inherent in such device s. The carrier drift length before trapping was measured under alpha p articles and values as high as 40% of the overall film thickness are r eported. Further, by optimising the device geometry, we show that a ga in in collection efficiency, defined as the induced charge divided by the deposited charge within the material, can be achieved even though lower bias values are used.