Changes in electrical properties of thin diamond films under heat treatment

The authors present results on both temperature-dependent resistivity (/spl rho/(T)) measurements and current-voltage (I(V)) characteristics of polycrystalline diamond thin films chemically vapour deposited by hot filament (HF-CVD) method from propane-butane gas mixture diluted in hydrogen. The films were deposited on single crystal silicon substrates. In-plane and out-of-plane I-V characteristics of the same sample are shown and observed differences are discussed, which clearly attest to concurrent transport mechanisms in the films. Then, changes in the samples resistivity under heat treatment in vacuum are presented. The authors show that a simple exponential /spl rho/(T) model is inadequate to explain the results, since distinctive peaks are found in the characteristics. Further, observed changes are analysed in terms of gradual dehydrogenation of the samples. The results indicate that electrical properties of CVD diamond films may be to some extent controlled by their proper dehydrogenation either in vacuum or in an inert gas atmosphere.