Atomic displacement effects on the cathodoluminescence of zinc selenide implanted with ytterbium ions

The cathodoluminescence emission spectrum of Yb$^{3+}$ in zinc selenide has been observed following ion implantation. The complexity of the resulting spectrum has been interpreted in terms of several distinct trigonally distorted lattice sites. The crystal field parameters obtained in this way indicate an appreciable degree of covalency between the rare-earth ions and the lattice. It has been found that all Yb$^{3+}$ spectra in zinc selenide are damage-sensitive and the resulting effects can be interpreted on the assumption that the excitation mechanism is indirect, resonance transfer between like rare-earth ions is occurring and the concentration of centres is being changed. In turn, these concentration changes are used to determine a threshold energy of 8.0 eV ($\equiv $ 199 keV for the incident electron energy) for zinc displacement and an activation energy for thermal annealing of 0.14 $\pm $ 0.01 eV, tentatively assigned to zinc interstitial motion.