Temperature dependence of the barrier at the tetrahedral amorphous carbon-silicon interface

Tetrahedral amorphous carbon film (ta-C, rich in sp(3) bonds), 50 nm thick, was deposited by magnetron sputtering on n-type Si substrate at room tempe rature. Ohmic contact to the ta-C film was formed by depositing stoichiomet ric titanium nitride (TiN) by magnetron sputtering or aluminum (Al) by elec tron-gun evaporation at room temperature. The capacitance-voltage character istics at different temperatures show negligible hysteresis, indicating low concentration of mobile charges. Electrical conduction in the TiN (Al)/ta- C/n-Si structure, with the TiN or Al biased positively with respect to Si. was investigated in the temperature range 80-300 K. Under high-field condit ions, the electrical conduction is consistent with thermally assisted Fowle r-Nordheim tunnelling of electrons from the Si substrate into the ta-C film for temperatures for 80-260 K and trap-assisted band-to-band indirect tunn elling for higher temperatures. Under low-field conditions, Poole-Frenkel e mission dominates over tunnelling for temperatures even well below room tem perature. The temperature dependence of the tunnelling current was explaine d in terms of the change in the effective barrier height at the ta-C/n-Si i nterface.