Investigation of structural and photoluminescence properties of gas and metal ions doped zinc oxide single crystals

Highlights: • Ion species and annealing dependent structural and PL properties of ZnO crystals. • Vacuum annealing resulted in complete recovery of implantation induced disorders. • Red- and blue-shift observed in deep level emissions due to N and Na implantation. • N/Na implantation suggested p-type behavior evident from a slight band-edge shift. - Abstract: We report the structural and photoluminescence properties of annealing dependent and gas and metal ion implanted zinc oxide (ZnO) single crystals. Gd, Na and N ions were implanted into ZnO at an average implantation depth of 12, 24, and 38 nm, respectively from the surface layer. The samples were annealed under high vacuum or oxygen at 650 °C and their effects were studied. Raman spectra of Gd implanted and oxygen annealed ZnO revealed the A₁ longitudinal optical, A₁(LO) mode, usually assigned to intrinsic defects, which suggested a partial recovery of implantation induced disorders, unlike ion implanted and vacuum annealed ZnO. Low temperature photoluminescence spectra from unimplanted and Gd implanted ZnO revealed transitions from neutral bound exciton, two electron satellites (TES) and LO phonon replicas. Deep level transitions in unimplanted and Gd implanted ZnO were affected by the annealing atmosphere, and oxygen annealing reduced the deep level emission, suggesting oxygen vacancy related emissions. A small red-shift in the near-band edge emission and a blue-shift in deep level emissions were observed in N and Na implanted and annealed ZnO, indicating slight changes in their band gap energies