Thermal stability of ion-implanted hydrogen in ZnO

The evolution of implanted ${}^{\mathrm{2}}\mathrm{H}$ profiles in single-crystal ZnO was examined as a function of annealing temperature $\text{(500–700\hspace{0.05em}°}\mathrm{C})$ by secondary ion mass spectrometry. The as-implanted profiles show a peak concentration of ${\text{∼2.7×10}}^{19}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}$ at a depth of $\text{∼0.96\hspace{0.17em}μ}\mathrm{m}$ for a dose of ${10}^{15}\hspace{0.17em}{\mathrm{cm}}^{\text{−2}}.$ Subsequent annealing causes outdiffusion of ${}^{\mathrm{2}}\mathrm{H}$ from the ZnO, with the remaining hydrogen decorating the residual implant damage. Only 0.2% of the original dose is retained after annealing at $\text{600\hspace{0.05em}°}\mathrm{C}.$ Rutherford backscattering/channeling of samples implanted with ${}^{\mathrm{1}}\mathrm{H}$ at a dose of ${10}^{16}\hspace{0.17em}{\mathrm{cm}}^{\text{−2}}$ showed no change in backscattering yield near the ZnO surface, but did result in an increase near the end-of-range from 6.5% of the random level before ${}^{\mathrm{1}}\mathrm{H}$ implantation to $\text{∼7.8\%}$ after implantation. Results of both cathodoluminescence and photoluminescence studies show that even for a ${}^{\mathrm{1}}\mathrm{H}$ dose of ${10}^{15}\hspace{0.17em}{\mathrm{cm}}^{\text{−2}},$ the intensity of the near gap emission from ZnO is reduced more than 2 orders of magnitude from the values in unimplanted samples. This is due to the formation of effective nonradiative recombination centers associated with ion-beam-induced defects.