CORRELATION BETWEEN MATERIAL PROPERTIES AND LEAKAGE CURRENTS IN CVD-DIAMOND-FILMS DEPOSITED BY DC-PLASMA-GLOW-DISCHARGE

A set of chemical vapor deposited (CVD) undoped diamond samples have b een prepared by means of a DC glow discharge CVD apparatus, using the mixture of methane and hydrogen as a source gas at different methane c oncentrations and substrate temperature, keeping constant the power de nsity and the gas flow. A study of the leakage current level of the sa mples has been carried out in order to assess the potential of the app aratus in synthesizing high quality diamonds for application in high e nergy physics. A particular shape of the Mo electrodes has been design ed in order to achieve uniform continuous growth onto the anode. The p resence of non-diamond phases has been related to the electric behavio r of the samples by means of micro-Raman scattering measurements and s canning electron microscopy (SEM) analysis. At the highest growth rate s, depending on methane concentration and substrate temperature, the g raphite-like domains extend all over the substrate side of the samples and at the grain boundaries increasing, in the presence of an applied electric held, the leakage current values of various orders of magnit ude. At lower growth rates the purity of the diamond is highly improve d, resulting in a resistivity of the older of 10(12)-10(13) Omega cm. A theoretical model has been used to estimate the order of magnitude f or the sp(3) to sp(2) ratio in the films. (C) 1997 Elsevier Science S. A.