Growth, structure, and mechanical properties of CNxHy films deposited by dc magnetron sputtering in N2/Ar/H2 discharges

Abstract

The evolution of the structure and mechanical properties of fullerenelike hydrogenated amorphous carbon films upon annealing J. Appl. Phys.Hydrogenated carbon nitride films were deposited by reactive dc magnetron sputtering in mixed Ar/N 2 /H 2 discharges at temperatures of 100 and 350°C. The total pressure was kept constant at 0.33 Pa and the gas mixtures were varied in order to study the effect of the hydrogen on the resulting film structure and properties. Chemical sputtering effects taking place during deposition were found to be an important factor for the growth and structural evolution. When H 2 is mixed into the discharge gas, the growth rate decreases considerably and the films become denser due to desorption of volatile species, like hydrocarbons, NH 3 and HCN. For a H 2 fraction above 15%, no net film growth takes place. The hydrogen concentration incorporated into the films was highest ͑up to ϳ33 at. %͒ for low growth temperatures and low nitrogen concentrations. Furthermore, the results indicate that substantial amount of hydrogen are bonded to nitrogen. The incorporation of hydrogen in the structure interrupts the relatively long basal planes in graphite-like structures, and some regions transform into an amorphous structure. Nanoindentation measurements of the film showed decreased elasticity, as well as decreased hardness when incorporating hydrogen. However, fullerene-like films grown at 350°C in N 2 /H 2 discharges exhibit high elasticity for H 2 partial pressures as high as ϳ10 Ϫ3 Pa due to low H incorporation into these films.

Electrical properties of carbon nitride thin films: Role of morphology and hydrogen content

“…3d (rms ϭ 1 nm). 17 As discussed above, the resistivity of our nonhydrogenated CN X films as a function of N concentration changes mainly due to the changed morphology induced by the N. Hydrogen has a similar effect on the film morphology, but the electrical response is the opposite. Thus, in this case, the reduced surface roughness and number of voids do not affect as much as the increased degree of bond saturation by hydrogen.…”

“…Instead, this could be explained by a continuous change of the microstructure to shorter basal planes that become terminated by H, as previously observed by high-resolution transmission electron microscopy. 17 Another factor that may play an important role for the CN X H Y films, as for the nonhydrogenated CN X , is the film morphology and surface roughness. Figure 3 shows cross-sectional SEM micrographs of different films, which illustrates the main trends for how the morphology changes depending on gas mixtures.…”

“…Film composition was determined by Rutherford backscattering spectrometry and by nuclear reaction analysis (NRA), as described previously. 17 The film morphology was analyzed with a LEO 1550 scanning electron microscope (LEO Electron Microscopy Ltd., Cambridge, U.K.) operated at 2 kV. The acceleration voltage thus selected for SEM investigation was the highest one compatible with substrate noncharging conditions during imaging with a beam current of 0.20 mA/cm 2 .…”

“…The details of the film grown have been reported elsewhere, together with detailed analyses of the film composition, bonding configuration, and mechanical and tribological properties. [16][17][18] The dark electrical resistivity of films deposited on SiO 2 substrates was measured in vacuum at room temperature using a four-point probe. The film thickness values used for determining the film resistivity (ϳ400 nm) were measured by a stylus profilometer; the resulting uncertainty in the resistivity values was estimated to Ϯ10%.…”

Super-Lubricious, Fullerene-like, Hydrogenated Carbon Films

“…Interestingly, the growth of FL-C:H films show a conflicting to Hellgren's work [43] that intentional hydrogen addition to the discharge will terminate potential bonding sites for CNx precursors and hinder the growth of fullerene-like structures. But it seem that during growth FL-C:H films, hydrogen atoms during the deposition process may affect the produc- …”