SEM and HRTEM images of ZnO NWs. (a) SEM image of ZnO NWs grown at 1 atm. The SEM images were taken at a tilt angle of 20°. Inset image is the top view of single NW which has the hexagonal shape. (b) SEM image of ZnO NWs grown at 0.17 atm. (c) HRTEM image of ZnO NWs. Inset image is the corresponding diffraction pattern.
(Color online) Relationship between the length and the diameter of the ZnO NWs grown under different pressures from 0.13 to 1 atm. The solid curves are fits to Eq. (2) for each pressure.
SEM images of Al doped ZnO NWs grown at the pressure of 0.13 atm with different amount of Al power in the source material: (a) 0.5 g, (b) 1.0 g, (c)1.5 g.
(Color online) Ellingham diagram of ZnO and Al2O3 shows the temperature dependence of Gibbs free energy.
Typical I–V curve for individually contacted ZnO NWs. The inset shows the SEM image of the NW contacted by two Pt bars along with a schematic diagram.
(Color online) Raman spectra of undoped ZnO NWs and Al-doped ZnO NWs with 1.2 and 1.8 at. % Al concentrations. All nanowires were grown at 0.13 atm. The curves are vertically shifted for clarity. The inset shows zoomed-in spectra around the dominant peak E2 at 438 cm−1 in log scale.
(Color online) PL spectra of undoped and Al-doped ZnO NWs with different Al concentrations, showing an increase (resp. decrease) in the NBE (resp. green) emission intensity with Al content. All nanowires were grown at 0.13 atm. The inset shows a normalized near band edge emission peak that is blue shifted with an increase of Al concentration.
(Color online) Dependence of peak position and FWHM on Al concentration of the NBE emission. The values were obtained through a Gaussian fit of the NBE emission peak.
Fitting parameters of the relationship between length and diameter of the ZnO NWs grown at different pressures.
Al atomic concentration as determined by EDS and the corresponding estimated resistivity of Al-doped ZnO NWs grown with different amount of Al in the source material. The nanowires were grown at 0.13 atm.
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