Influence of the growth parameters on the electrical properties of thin polycrystalline CVD diamond films

We report here results concerning significant improvement achieved in the g rowth of electronic grade chemically vapour deposited diamond films used fo r the fabrication of radiation detectors. We especially focused on the opti misation of the carrier mobility and lifetime in thin (20 mu M) undoped pol ycrystalline diamond films. Deposition temperature, methane concentration a nd microwave power density were systematically varied in order to establish deposition processes that provide adequate materials for alpha particle de tection. Raman spectroscopy and scanning electron microscopy were used to p robe the intrinsic quality of the films in term of solid state structure an d purity. The electrical properties of the films were deduced from current- voltage characteristics and from the measurements of diamond detectors sens itivity to alpha particle irradiation (E = 5.5 MeV). Significant correlatio n was observed between the physico-chemical characteristics (crystallograph y quality by Raman line width, and purity by the qualitative ratio I-sp2/I- sp3, nitrogen content) and electrical properties (resistivity, carrier mobi lity lifetime product) of sets of 20 mu m thick films. In addition, at give n growth parameters, the effect of diamond film thickness on their electric al properties was studied. (C) 2000 Elsevier Science S.A. All rights reserv ed.