Electrical and optical properties of well-aligned Al doped ZnO nanorod arrays annealed at different temperatures

Hexagonal Al doped ZnO nanorod arrays have been prepared via a simple low-temperature sonicated sol-gel immersion method on Al doped ZnO nanoparticle thin film coated glass substrates. The nanorod arrays were annealed at the temperatures between 300 to 500°C in ambient. The properties of the nanorods have been investigated using field-emission microscope (FESEM), X-ray diffractometer (XRD), photoluminescence (PL) spectrofluorometer and current-voltage (I-V) measurement system. It was found that the electrical resistivity of the sample decreased with annealing temperatures from 2920 Ω cm (as-grown) to 58 Ω cm (500°C). The ratio of ultraviolet (UV) emission peak to visible emission peak of the samples as measured using PL spectrofluorometer also improved at higher annealing temperature. These trends indicate annealing process plays important role to diffuse Al dopant in the ZnO lattice and improves the electrical and optical properties of the nanorod arrays.