Carbon nitride CNx thin films were grown by unbalanced dc magnetron sputtering from a graphite target in a pure N-2 discharge, and with the substrate temperature T-s kept between 100 and 550 degrees C. A solenoid coil positioned in the vicinity of the substrate was used to support the magnetic field of the magnetron, so that the plasma could be increased near the substrate. By varying the coil current and gas pressure, the energy distribution and fluxes of N-2(+) ions and C neutrals could be varied independently of each other over a wide range. An array of Langmuir probes in the substrate position was used to monitor the radial ion flux distribution over the 75-mm-diam substrate, while the flux and energy distribution of neutrals was estimated through Monte Carlo simulations. The structure, surface roughness, and mechanical response of the films are found to be strongly dependent on the substrate temperature, and the fluxes and energies of the deposited particles. By controlling the process parameters, the film structure can thus be selected to be amorphous, graphite-like or fullerene-like. When depositing at 3 mTorr N-2 pressure, with T-s> 200 degrees C, a transition from a disordered graphite-like to a hard and elastic fullerene-like structure occurred when the ion flux was increased above similar to 0.5-1.0 mA/cm(2). The nitrogen-to-carbon concentration ratio in the films ranged from similar to 0.1 to 0.65, depending on substrate temperature and gas pressure. The nitrogen film concentration did, however, not change when varying the nitrogen ion-to-carbon atom flux ratios from similar to 1 to 20. (C) 2000 American Institute of Physics. [S0021-8979(00)00413-8].

The growth and microstructure evolution of carbon nitride CNx (0=x=0.35) films, deposited by reactive d.c. magnetron sputtering in Ar/N2 discharges has been studied. The substrate temperature TS varied between 100 and 550 °C, and the N2 fraction in the discharge gas varied from 0 to 100%. It is found that the deposition rate and film morphology show strong dependence on TS and nitrogen fraction. For growth temperature of 100 °C, the films are amorphous, and essentially unaffected by the nitrogen fraction. For TS>200 °C, however, the nitrogen fraction has more significant effect on the growth and structural evolution of the films. The pure carbon films appear porous and have a high surface roughness. For increasing nitrogen fraction the films become denser and the roughness decreases by one order of magnitude. It is suggested that a chemical sputtering process, during which desorption of volatile N2 and CN-species, predominantly C2N2, is important not only for the deposition rate and the nitrogen incorporation, but also for the resulting film structure. The chemical sputtering process becomes more pronounced at elevated temperatures with higher nitrogen fractions.

Carbon and carbon nitride films, grown in argon or nitrogen discharges by reactive Jc magnetron sputtering of a graphite target, were characterized by in situ scanning tunneling microscopy. When the growth temperature increased from ambient to 800 degrees C, we observed a topographic evolution of the carbon films from an amorphous to a graphitelike structure, and further to a distorted-graphitic phase with curved and intersecting basal planes, and finally to a surface containing nanotubes and nanodomes. When nitrogen was incorporated into the films, distortion of the graphitic basal planes occurred at a lower temperature compared to the pure carbon case. At temperatures of similar to 200 degrees C and above, regions of a nongraphitic phase, containing a high degree of carbon sp(3) bonds were observed. Spatially resolved tunneling spectroscopic measurements indicated that the band gaps were 0, similar to 0-0.6 eV, and similar to 0.4-2.0 eV for graphitelike structures, the distorted-graphitic phase, and the nongraphitic phase, respectively. Together with ex sial x-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy measurements, the results suggest that the incorporation of nitrogen promotes bending of the graphitic basal planes and thereby facilitates the formation of three-dimensional covalently bonded networks with a high degree of sp(3)-coordinated carbon atoms.

Reactive direct current magnetron sputtering was used to deposit the hydrogenated carbon nitride films in mixed nitrogen (N2)/argon (Ar)/ hydrogen (H2) discharges. Growth and structure evolution of films was found to be affected by chemical sputtering effects. The hydrogen were found to be bonded to nitrogen and hydrogen incorporation decreases the elasticity and hardness.