Optical doping of ZnO with Tm by ion implantation

摘要

ZnO [0001] single-crystals were implanted at room temperature with 150keV Tm~+ ions at a fluence of 5 x10~(15)cm~(-2). Each sample was then subjected to one single 30 min air annealing at 800℃, 950℃ and 1050℃. The Tm lattice site location and defect recovery were investigated with Rutherford Backscattering/Channeling Spectro-scopy. Detailed angular scans along the [0001] direction show that 94% of the Tm ions occupy substitutional Zn sites (S_(Zn)) in the as-implanted sample. All the annealing temperatures lead to a reduction of this fraction to 30%. Also, progressive damage recovery and Tm segregation to the surface were observed, being enhanced at 1050℃. Photoluminescence (PL) studies with above band gap excitation performed on these samples revealed no luminescence on the as-implanted state. The 800℃ air annealing promotes the Tm~(3+) optical activation and a well-defined near-infrared intraionic emission is observed. For higher annealing temperatures, in spite of no change of the Tm fraction at S_(Zn) sites, a decrease of the Tm intraionic emission was observed. These results suggest that optical activation of Tm ions is related with the defect density in their environment.