Fig. 8

PL spectra of various submicron fractions of Microdiamant™ polycrystalline diamond particles: blue—DP 0–0.05 (mean size 25 nm), green—DP 0–0.2 (mean size 100 nm), red—DP 0–0.35 (mean size 175 nm). Excitation wavelength λ = 488 nm. The prominent peak at 738 nm marked by the vertical dashed line is the zero-phonon line of negatively charged SiV⁻ centres, which can be observed in all polycrystalline diamond fractions. For better comparison, the spectra are specially normalized for PL intensity at λ = 590 nm. Normalising coefficients are indicated in the figure