Characterization of hydrogenated amorphous carbon thin films by end-Hall ion beam deposition

Abstract

Pure hydrogenated amorphous carbon (α-C:H) and nitrogen doped hydrogenated amorphous carbon (α-C:H:N) thin films were prepared using end-Hall (EH) ion beam deposition with a beam energy ranging from 24eV to 48eV. The composition, microstructure and mechanical properties of the films were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning probe microscopy (SPM), and nano-scratch tests. The films are uniform and smooth with root mean square roughness values of 0.5–0.8nm for α-C:H and 0.35nm for α-C:H:N films. When the ion energy was increased from 24eV to 48eV, the fraction of sp3 bonding in the α-C:H films increased from 36% to 55%, the hardness increased from 8GPa to 12.5GPa, and the Young's modulus increased from 100GPa to 130GPa. In the α-C:H:N films, N/C atomic ratio, the hardness and Young's modulus of the α-C:H:N films are, 0.087, 15 and 145GPa, respectively. The results indicate that both higher ion energy and a small amount of N doping improve the mechanical properties of the films. The results have demonstrated that smooth and uniform α-C:H and α-C:H:N films with large area and reasonably high hardness and Young's modulus can be synthesized by EH ion source.