Low-Temperature Spectroscopy of Single CVD Microdiamonds with GeV Color Centers

We presented the results of low-temperature photoluminescence (PL) spectra investigations of diamond microcrystals with germanium-vacancy GeV color centers. The microdiamonds were synthesized by plasma chemical vapor deposition (CVD) using gaseous germanium as an impurity source. The PL spectra of single microdiamonds at 8 K contain either a single or a few narrow lines spreading between 600 and 606 nm instead of zero-phonon line quartet characteristic for GeV-centers. The observed 100% polarization contrast of individual spectral line is indirect evidence that the corresponding emission originates from single GeV-center. The deviations of the obtained PL peak positions from the expected ones are explained by the lattice stresses, introduced during the synthesis of microcrystals. The widths of the observed spectral lines appear to be significantly smaller than the characteristic values obtained for ensembles of GeV-centers earlier.