The origin of additional modes in Raman spectra of N⁺-implanted ZnO

Raman measurements were performed on ZnO single crystals before and after implantation with N⁺, O⁺, Si⁺, and Ga⁺ ions. It is found that the broad Raman band at 576 cm^-1 appears in all spectra of implanted ZnO, independent of the ion species, and thus it is attributed to disorder-activated Raman scattering. Two extra peaks at 275 and 510 cm^-1 are observed only in Raman spectrum of N⁺-implanted ZnO. The dependence of intensity on doses indicates that the origin of these two modes is different from that of 576 cm^-1 peak. We assign the additional modes to N⁺-related local vibrational modes.