Microstructural and optical characteristics of solution-grown Ga-doped ZnO nanorod arrays

Highly oriented Ga-doped zinc oxide (ZnO) nanorod arrays have been prepared on a ZnO-buffered silicon substrate in an aqueous solution, which is a mixture of methenamine (C(6)H(12)N(4)), zinc nitrate hexahydrate (Zn(NO(3))(2)·6H(2)O), and gallium nitrate hydrate (Ga(NO(3))(3)·xH(2)O). The microstructure characteristics and optical properties of the nanorod arrays were analyzed using different characterization techniques including field-emission scanning electron microscopy (FESEM), x-ray photoelectron spectroscopy (XPS), and photoluminescence (PL). The experimental results show that the morphology, density, and surface compositions of ZnO nanorod arrays are sensitive to the concentration of gallium nitrate hydrate. The PL spectra of all ZnO nanorod arrays show three different emissions, including UV (ultraviolet), yellow, and NIR (near infrared) emissions. With the increase in the Ga doping level, the luminescence quality of ZnO nanorods has been improved. The peak of UV emission has a small redshift, which can be ascribed to the combined effect of size and Ga doping. Furthermore, Ga doping has caused defects that respond to NIR emission.