Electrical and optical properties of CNx(0 <= x <= 0.25) films deposited by reactive magnetron sputtering

The electrical and optical properties of carbon-nitride CNx films (0 less t han or equal tox less than or equal to0.25) deposited by unbalanced reactiv e magnetron sputtering from a graphite target in mixed Ar/N-2 discharges at a substrate temperature of 350 degreesC have been investigated. Pure C fil ms exhibit a dark conductivity at room temperature of 25 Omega (-1) cm(-1), which grows up to 250 Omega (-1) cm(-1) for CNx films with N content of 20 %. For CNx films, temperature-dependent conductivity measurements suggest t hat two electron conduction processes exist in the investigated temperature range 130 <T < 300 K. Under white-light illumination, photoconductivity is observed. The film optical properties obtained from spectroscopic ellipsom etry measurements between 1.24 and 5 eV indicate a semimetallic behavior wi th a large amount of sp(2) bonds in the material. The measured electrical a nd optical properties of the films are related to the apparent film microst ructure and bonding nature. Electron microscopy show that the addition of N -2 in an Ar discharge leads to a transformation from amorphous to a fullere ne-like microstructure consisting of curved, frequently intersecting, and h ighly in-plane oriented basal lattice planes. (C) 2001 American Institute o f Physics.