Fig. 1. PL spectra at room temperature before and after Ar⁺ plasma treatment

Fig. 2. Temperature-dependent PL spectra of ZnO nanowires. (a) PL spectra before Ar⁺ plasma treatment; (b) peak position versus temperature under different treatment time

Fig. 3. PL spectra of ZnO nanowires at low temperature of 10 K under different Ar⁺ plasma treatment time

Fig. 4. Surface states and energy bands of ZnO nanowires under different Ar⁺ plasma treatment time. (a)(b)(c) Surface states; (d)(e)(f) energy bands

Fig. 5. SEM images of ZnO nanowires under different Ar⁺ plasma treatment time. (a) 0 s; (b) 60 s; (c) 90 s; (d) 120 s