Electronic transport mechanism in intrinsic and doped nanocrystalline silicon films deposited by RF-magnetron sputtering at low temperature

The dependence on the temperature range, T, of the electronic transport mechanism in intrinsic and doped hydrogenated nanocrystalline silicon films, deposited by radiofrequency-magnetron sputtering at low substrate temperature, has been studied. Electrical conductivity measurements σ(T) have been conducted on these films, as a function of temperature, in the 93-450 K range. The analysis of these results clearly shows a thermally activated conduction process in the 273-450 K range which allows us to estimate the associated activation energy as well as the preexponential conductivity factor. While, in the lower temperature range (T < 273 K), a non-ohmic behavior is observed for the conductivity changes. The conductivity σ(T) presents a linear dependence on (T−14), and a hopping mechanism is suggested to explain these results. By using the Percolation theory, further information can be gained about the density of states near the Fermi level as well as the range and the hopping energy.