Synthesis of photoconducting ZnO nano-needles using an unbalanced magnetron sputtered ZnO/Zn/ZnO multilayer structure

The synthesis of ZnO nano-needles using unbalanced magnetron sputtering is reported. A multilayer structure comprised of ZnO(50 nm)/Zn(20 nm)/ZnO(2 µm) was grown on a stainless steel substrate without substrate heating. The growth of ZnO nano-needles was observed on the surface of the multilayer structure after post-annealing treatment at 300–400 °C. The nano-needles were distributed randomly over the entire surface and had an average diameter of 20 nm; their length varied from 2 to 5 µm. The ultra-thin Zn layer (20 nm) in the multilayer structure is attributed to act as a nucleating centre and it activates the coalescence process for the growth of ZnO nano-needles. The ZnO nano-needles showed enhanced ultraviolet photoresponse with an initial fast rise and decay. The origin of the photoconductivity is due to the bulk related process. Results show the myriad application of ZnO nano-needles in ultraviolet light detection.