Study of excitonic emission in highly faceted ZnO rods

We report a detailed photoluminescence study of ZnO rods which exhibit 18 side surfaces. The photoluminescence studies reveal excellent optical quality of the rods, comparable to that of thin films in spite of their large surface area. The low-temperature PL spectra are dominated by a narrow and very intense bound exciton emission. Time resolved PL results show very long decay time of spontaneous emission, with the time constants of biexponential decay equal to 116 ps and 1.2 ns. The stimulated emission spectra reveal very narrow lasing modes with widths of 0.4-0.5 nm and decay times of 4-5 ps.