Scanning electron microscopy images of ZnO nanorods with different diameters of (a) 300 to 350 nm, (b) 150 to 250 nm, and (c) 70 to 100 nm. An image of the ZnO nanoribbons is shown in (d). One can use the scale bars in (a) and (b) to discern the sizes of the nanorods.
(Color online) (a) Photoluminescence spectra of thin ZnO nanorods obtained with a 325 nm UV pumping source applied while the below-gap source at 532 nm switches on/off at 12 K. The inset shows the time evolution of the band-edge emission as the second beam (532 nm) was switched on and off. (b) A comparison of the optical quenching and the thermal quenching. (c) The spectral distribution of the excitation and quenching of the band-edge emission from ZnO nanorods at 12 K. The inset shows the dependence between the Rw ratio and the diameter of the ZnO nanorods.
(Color online) (a) Scheme of the device profile to illustrate the experimental process of the quenching effect in the ZnO nanoribbons. (b) Spectral distribution of the excitation and quenching of the photocurrent in the ZnO nanoribbons at 12 K. The dashed line shows the constant current excited by the 325 nm laser. The inset shows the time evolution of the photocurrent as the second beam (532 nm) was switched on and off.
(Color online) (a) Illustration of the carrier transitions that can explain the quenching effect of the NBE emission by the below-gap illumination. (b) Quenching ratios as a function of the below-gap excitation power density in three different sizes.
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