Radiation detector performances of nitrogen doped HPHT diamond films

The remarkable physical properties of diamond such as tissue equivalence (atomic number Z = 6, close to that of human tissue), radiation and mechanical hardness and a wide band gap (5.5 eV) make it an ideal material for the fabrication of detectors for radiotherapy applications. However, the response to the radiation of such a kind of detector strongly depends on the bulk structure and in particular on the different impurities concentration inside the material. In the present paper we investigated the detector performances of two nitrogen doped HPHT synthetic diamonds grown at the IGM using a split-sphere type high-pressure apparatus. The samples were characterized using two different types of contacts: Au and Ti/Pt/Au configuration. The fabricated devices, studied as active detectors, presented totally different current response when they were exposed to the Co-60 gamma irradiation. One sample in particular showed under irradiation strong value of current for which the photoconductive gain was found to be as high as 10(5). A model of trap-induced sensitizing is suggested in order to explain the very high photoconductive gain obtained. (C) 2008 WILFY-VCH Verlag GmbH & Co. KGaA, Weinheim.