Linear antenna microwave plasma CVD deposition of diamond films over large areas

Diamond thin films were grown by linear antenna microwave plasma CVD process over large areas (up to 20 × 10 cm2) from a hydrogen based gas mixture. The influence of the gas composition (H2, CH4, CO2) and total gas pressure (0.1 and 2 mbar) on the film growth is presented. For CH4/H2 gas mixtures, the surface crystal size does not show dependence on the methane concentration and total pressure and remains below 50 nm as observed by SEM. Adding CO2 (up to 10%) significantly improves the growth rate. However, still no significant change of morphology is observed on films grown at 2 mbar. The crucial improvement of the diamond film purity (as detected by Raman spectroscopy) and crystal size is found for deposition at 0.1 mbar. In this case, crystals are as large as 500 nm and the growth rate increases up to 38 nm/h.

► We report a growth of diamond films by linear-antenna microwave plasma CVD technique. ► The used CVD technique allows large area deposition. ► Diamond film morphology and quality are strongly related to gas mixture and total gas pressure. ► Lowering gas pressure from 2 to 0.1 mbar significantly influenced the growth kinetics resulting in a formation of large well-faceted diamond crystals.