Electrical conductivity studies of chemical vapor deposited sulfur-incorporated nanocomposite carbon thin films

The room-temperature electrical conductivity of sulfur-incorporated nanocomposite carbon (n-C:S) thin films synthesized by hot-filament chemical vapor deposition was investigated as a function of the sulfur concentration. The films were prepared using a 2% CH4/H-2 gas mixture and H2S as the dopant source. The n-C:S films exhibited an increase in conductivity by four orders of magnitude (up to 160 S cm(-1)) with an increase in sulfur content compared with those grown without sulfur (n-C). The films grown at the highest [H2S] possess the highest carrier concentration (similar to5x10(19)/cm(3)) and the lowest carrier mobility (0.005 cm(2) V-1 s(-1)). These findings are discussed in terms of the multiple roles of sulfur atoms in the films: (i) induction of structural defects and their corresponding midgap states, (ii) enhancement of the spatial connectivity of the sp(2)-bonded carbon network, and (iii) electrical activity of only a small fraction of the sulfur atoms. (C) 2002 American Institute of Physics.