Highly porous carbon films fabricated by magnetron plasma enhanced chemical vapor deposition: Structure, properties and implementation

The new method is suggested of formation of highly porous graphite-like thin films by radio frequency magnetron plasma enhanced chemical vapor deposition from argon-methane gas mixture. The prepared films were characterized before and after thermal annealing by XPS, XES, FTIR, Raman spectroscopy, XRD, XRR, AFM, and electrical measurements. Deconvolution of XPS spectra has demonstrated a significant growth of sp²/sp³ ratio from 1 for as-deposited films to 12 for the films annealed at 650 °C for 5 min. FTIR spectra have confirmed that thermal annealing results in reduction of H– and OH– functional groups and formation of СС bonds. The analysis of Raman spectra has shown that the annealing incorporates additional defects in graphite plane. XRD has shown that films are amorphous. Estimation of porosity from XRR measurements gave values of about 59% for as-deposited films and 34% for annealed films. AFM has shown that roughness of the films decreases from 3.3 to 0.6 nm during treatment at 650 °C in inert atmosphere. The size of pores was found to be few tens of nanometers. The electrical measurements have shown that after annealing the resistivity decreases by up to 5 orders of magnitude. Annealed films have demonstrated perceptible sensitivity to ammonia and water vapor.