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(a) Plan-view FE-SEM images of Au nanoparticles on a substrate. (b) ZnO nanowires grown on (a) at 550 °C.
(a) High-resolution plan-view FE-SEM image of ZnO nanowires grown at 550 °C; (b) SEM-EDX spectrum recorded from the top surface [the point marked by a circle in (a)] of a single nanowire; (c) and (d) show ZnO nanorods (FE-SEM image taken at a tilt angle of 45°) and nanowires (plan-view FE-SEM image) grown on the substrate represented at Fig. 1(a) at 400 and 900 °C, respectively; (d) is a FE-SEM image of a tip area in one of the nanowires grown at 900 °C. Scale bar in the inset indicates 50 nm.
(a) Band-edge PL spectra of, at various temperatures, for the ZnO-nanowire sample [shown in Fig. 1(b)]. With an increase in temperature, the EX band becomes clear, while the intensity of the peak gradually decreases; (b) integrated PL intensity as a function of temperature.
PL spectra measured at 77 K under various excitation intensities. The bottom most curve shows a PL spectrum obtained using a He–Cd (325 nm) laser. The remaining curves show PL spectra under high excitation obtained by a mode-locked laser with a repetition rate of 80 MHz and 1 kHz REGEN with excitation densities of (a) 0.64 and (b) . A pump pulse of 330 nm was obtained from an OPA.
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