Influence of bias voltage on the structure and deposition mechanism of diamond-like carbon films produced by RF (13.56 MHz) CH4 plasma

• Published in: Physica status solidi. A, Applications and materials science Vol. 207; no. 10; pp. 2311 - 2318
• Main Authors: Ouchabane, M., Salah, H., Herrmann, M., Tabet, N., Henda, K., Touchrift, B., Kechouane, M.
• Format: Journal Article
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.10.2010; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: amorphous semiconductors; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); chemical vapour deposition; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; diamond-like carbon; Exact sciences and technology; infrared spectra; Materials science; Mechanical and acoustical properties of condensed matter; mechanical properties; Mechanical properties of solids; Methods of deposition of films and coatings; film growth and epitaxy; Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Physics; Tribology and hardness; Elastic modulus; Voltage dependence; Nanoindentation; Diamond-like carbon; Hardness; Energy gap; Elastic recoil detection analysis method; Amorphous hydrogenated material; Chemical bonds; PECVD; Absorption spectra; Fourier-transformed infrared spectrometry; Spectrophotometry; X-ray photoelectron spectra
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.200925581

Plasma enhanced chemical vapour deposition technique (PECVD) was used to grow diamond‐like carbon films using pure methane gas plasma. Structural, optical and mechanical properties of the obtained a‐C:H films were investigated as a function of bias voltage in the range 120–270 V, using different techniques. Elastic recoil detection analysis (ERDA) was employed to determine the hydrogen content and Fourier transform infrared spectroscopy (FTIR) was used to analyse the absorption of optically active hydrogen in the deposited films. The relative concentrations of sp2 and sp3 groups were determined from fitting of both X‐ray photoelectron spectroscopy (XPS) and FTIR spectra. Mechanical hardness and optical transmission were determined using nanoindentation and spectrophotometry, respectively. The results showed that the structure and properties of the films formed strongly depended on the applied bias voltage. In the range of energy considered the growth of the films was governed by a competition between both chemical and physical processes, with a dominance of physical process (subplantation) above 240 V, the energy at which more than 90% sp3 hybridization was obtained. Nanoindentation tests revealed hardness and Young's modulus of the films ranging from 12–15 and 116–155 GPa, respectively. The optical gap values deduced from the optical transmission spectra varied between 1.13 and 1.60 eV.