Thin film diamond alpha detectors for dosimetry applications

Diamond is a resilient material with rather extreme electronic properties. As such it is an interesting candidate for the fabrication of high performance solid state particle detectors. However, the commercially accessible form of diamond, grown by chemical vapour deposition (CVD) methods, is polycrystalline in nature and often displays rather poor electrical characteristics. This paper considers the way that this material may be used to form alpha particle dosimeters with useful performance levels. One approach adopted has been to reduce the impurity levels within the feed-stock gases that are used to grow the diamond films. This has enabled significant improvements to be achieved in the mean carrier drift distance within the films leading alpha detectors with up to 40% collection efficiencies. An alternative approach explored is the use of planar device geometry whereby charge collection is limited to the top surface of the diamond which comprises higher quality material than the bulk of the film. This has lead to collection efficiencies of greater than 70%, the highest yet reported for polycrystalline CVD material based detectors. Techniques for improving the characteristics of these devices further are discussed. (C) 1999 Elsevier Science S.A. All rights reserved.