THICKNESS DEPENDENCE OF THE ELECTRICAL CHARACTERISTICS OF CHEMICAL-VAPOR-DEPOSITED DIAMOND FILMS

The electrical characteristics of chemically vapor deposited (CVD) diamond films were measured as a function of film thickness. The samples studied were polycrystalline with the average grain size increasing from approximately 1 mu m on the substrate side to approximately 30 mu m on the growth surface for the thickest sample. Using time-resolved transient photoconductivity and charged-particle induced conductivity, the collection distance (d) that a free carrier drifts under the influence of an applied electric field was measured. Our data indicate that there is a gradient in the collection distance through the material. This gradient in electrical properties has implications for electronic uses of CVD diamond.