Photoluminescence spectra of xenon implanted natural diamonds

The natural diamonds were implanted with 500 keV Xe ions within the dose range 1×1013–5×1014 cm−2. The post-implantation thermal annealing was carried out gradually at temperatures between 300°C and 1400°C. Photoluminescence spectra were measured after each annealing step in the temperature range 1.5–200 K. The spectra featured the Xe-related zero phonon line (ZPL) at 811.6 nm (1.527 eV) and a vibronic sideband with several quasilocal and phonon peaks. The Huang–Rhys factor was determined to be exp(−S)=0.5±0.1. The ZPL at 1.5 K is inhomogeneously broadened and has line width in the range 5.5–15 cm−1 depending on the implantation dose. It was concluded that the vacancy is involved in the Xe center formation. The photoluminescence is significantly quenched by the irradiation-induced defects. A growth of the second ZPL at 793.3 nm was observed at elevated temperatures. The excited state energy level splitting of ΔE=128±20 cm−1 was found by studying the temperature behavior of these ZPLs. It was concluded that the excited state, as well as the ground state of the optical transition, has a double level structure, and that ZPL at 811.6 is not, likely, a resonance 0–0 line.