Origin of the asymmetric zero-phonon line shape of the silicon-vacancy center in nanocrystalline diamond films

The spectral line shape of the 1.68 eV (738 nm) emission line – usually associated with the negatively charged silicon-vacancy (SiV) center in diamond and promoted as a strong candidate for many quantum technology and nanobiology related applications – was studied by luminescence spectroscopy in different nanocrystalline diamond films prepared by MW CVD technique. An asymmetric line profile, expressed as a long tail on the low-energy side of the narrow luminescence band located around 1.68 eV, have been observed in all samples.