Temperature dependence of optical centres in ultrapure diamond after 200 keV electron irradiation

In this work, we conduct a temperature-dependent study of optical centres in ultrapure diamond after 200 keV irradiation by photoluminescence spectra, which are performed in a temperature range of 80-200 K. The zero phonon lines (ZPLs) include sizes of 550.3 nm, 593 nm, and 741 nm (GR1 centre). With an increase in measurement temperature, the ZPLs shift to the lower energy side, together with intensity quenching and an increase in the full width at half maximum. These results are noted in models of lattice contraction and electron-phonon coupling, and their inhomogeneous and homogeneous broadening mechanisms are also carefully distinguished by the Voigt function. The 550.3 nm and 593 nm emissions present harder bonds than the GR1 centre, close thermal quenching energies to the interstitial-related defect, a lower thermal softness than that of the ideal diamond, weak phonon bands at each lower energy side, and different broadening mechanisms with the GR1 centre, indicating that the 550.3 nm and 593 nm lines are possibly interstitial-related.