Si-doped nano- and microcrystalline diamond films with controlled bright photoluminescence of silicon-vacancy color centers

Nanocrystalline diamond (NCD) and microcrystalline diamond (MCD) films with bright photoluminescence (PL) of silicon-vacancy (SiV) color centers at 738nm have been grown using a microwave plasma CVD technique. The films were doped with Si via adding silane to CH4–H2 reaction gas mixture in the course of the deposition process. The dependence of SiV PL intensity on silane concentration in gas shows a maximum at SiH4/CH4 ratios of 0.2% and 0.6% for NCD and MCD films, respectively, the maximum intensity for MCD being an order of magnitude stronger compared with that for NCD. The PL quenching at higher CH4 addition occurs, however, no significant degradation of the film structure, such as Si-induced amorphous carbon formation, was observed within the SiH4 concentration range studied (0%–0.9%). The higher PL efficiency of the MCD films is related to their less defective structure, as deduced from Raman spectroscopy analysis.