Electrical properties and Mott parameters of polycrystalline diamond films synthesized by HF CVD method from hydrogen/methanol gas mixture

The influence of diamond crystallinity and preferred orientation on electronic conductivity of synthetic diamond films grown by hot filament chemical vapor deposition (HFCVD) was investigated. The CVD diamond films of different morphologies and crystallite sizes varying from 36 nm to 67 nm, measured in h2 2 0i direction were considered. The charge transport mechanism in the diamond samples was studied using temperature dependent DC conductivity measurements. The obtained results showed that in the temperature range of 90 K to 300 K charge transport is realized via Variable Range Hopping (VRH, m = 1/4) mechanism. Using VRH model, the Mott parameters were evaluated i.e. density of states at Fermi level N(E_F) (0.22 × 10¹⁵ eV^-1·cm^-3 to 1.7 × 10¹⁵ eV^-1·cm^-3), hopping energy W (43.5 meV to 142.3 meV) and average hopping distance R (1.49 × 10^-5cm to 2.56 × 10^-5cm). It was shown that above mentioned parameters strongly depend on diamond film preferential orientation.