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 than or equal tox less than or equal to0.25) deposited by unbalanced reactive magnetron sputtering from a graphite target in mixed Ar/N-2 discharges at a substrate temperature of 350 degreesC have been investigated. Pure C films 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 that 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 ellipsometry measurements between 1.24 and 5 eV indicate a semimetallic behavior with a large amount of sp(2) bonds in the material. The measured electrical and optical properties of the films are related to the apparent film microstructure and bonding nature. Electron microscopy show that the addition of N-2 in an Ar discharge leads to a transformation from amorphous to a fullerene-like microstructure consisting of curved, frequently intersecting, and highly in-plane oriented basal lattice planes. (C) 2001 American Institute of Physics.