Due to its potential applications for electroluminescent devices the doping of wide band-gap materials, such as GaN and ZnO, with rare earth (RE) ions is actually an interesting field of study. Trivalent RE ions like Eu3+, Er3+ and Tm3+ are known to be suitable dopants for red, green, and blue emitters, respectively. Moreover Er3+ and Tm3+ emissions in the middle infrared have promising applications as fiber amplifiers and optical switches in optical fiber communication technology.
In this work Tm+ ions with 150 keV energy were implanted with different fluences, from 4x1015 to 5x1016 ions/cm2 on ZnO  single crystals at room temperature and 450oC. RBS/channeling results indicate that after implantation the majority of the ions are incorporated into substitutional Zn sites. After annealing the substitutional fraction decreases and is accompanied by some recovery of the lattice damage produced by the implantation.
Dependence of intraionic luminescence on the fluence and implantation temperature was observed in as-implanted samples with above band gap excitation. After implantation and following the 30 min thermal annealing in air at 800oC the samples implanted with lower dose present well-structured intraionic emission lines in the near infrared region that could be observed up to 200K. From the differences observed in the luminescence spectra of different samples it is clear that changes in the ion environment occurs.
A model for the recombination centers is proposed based on the combined experimental results.