Probing surface structure quality of ZnO nanorods by second harmonic generation

The surface quality of ZnO nanorod after postannealing was inspected by second harmonic generation (SHG) with the assistance of photoluminescence (PL) spectra, and the X-ray photoelectron (XPS) spectroscopy. The SHG is sensitive to the quality of the surface structure, which involves the elimination of surface defects and restructuring. Oxygen (O)-deficient defects and surface defects were generated during the growth of ZnO nanorods. The PL and XPS analyses indicate that the surface defects on ZnO nanorods were reduced at annealing temperatures above 600^{\circ}{\rm C}. The bulk crystal structure was repaired for higher activation temperatures ({>}{\rm 700}^{\circ}{\rm C}) concluded by X-ray diffraction. Results from SHG revealed the relationship between surface restructuring of ZnO nanorods and annealing temperature.