SEM images and schematic illustration of the cross section of ZnO MWs. (a), (b), low- and medium-magnification SEM image of the hexagonal sample collected at ∼ 700 °C; (d), (e), low- and medium-magnification SEM image of the dodecagonal sample collected at ∼ 850 °C; (g), (h), low- and medium-magnification SEM image of the circular sample collected at ∼ 900 °C; (c), (f), (i) illustrate cross sections of ZnO MWs with different growth temperatures; the inset in (b) shows a high-magnification SEM image of one side face of the MW.
(Color online) (a) A typical unpolarized spectra from a hexagonal ZnO MW with diameter D = (4.55 ± 0.02) μm; the inset shows the corresponding SEM image. (b) The dependences of the resonant wavelength of TM polarization on the interference order N for different wire diameters. Solid lines are the predicted theoretical values using theoretical diameter values with error <1% to the values measured by SEM; the symbols represent the experimentally observed peaks. (c) Polarization resolved micro-PL spectra of an individual ZnO MW, the topmost, green curve is unpolarized. The spectra detected for TM and TE polarizations are shown in the lower two curves. (d) The enlarged spectra of the peaks in the blue rectangle in (c) show that the positions of unpolarized peaks match well with the positions of the TM polarized peaks.
(Color online) The typical emission spectra from individual ZnO MWs with different cross sections: (a) dodecagon, D = (2.28 ± 0.01) μm. (b) circle, D = (1.87 ± 0.01) μm, the labeled red peaks display the results using theoretical diameter values with error <1% to the values measured by SEM. The inset is the corresponding SEM image. The peak marked by arrows in (a) and (b) is from the laser source.
(Color online) The bright-field image (a), dark-field PL image (b), and PL spectrum (c) of an individual dodecagonal ZnO MW of ∼160 μm in length and ∼4 μm in width; PL mapping image in the regions of 522–530 nm (d) and 518–520 nm (e).
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