Structure and photoluminescence of arrayed Zn1−xCoxO nanorods grown via hydrothermal method

High density arrays of Zn 1− x Co x O ( x = 0.05, 0.10, 0.15, denoted by ZnCoO) nanorods were vertically grown on glass coated ZnO films via hydrothermal reaction at 70 °. The structures and morphology of the arrays were studied by x-ray diffraction, photoluminescence (PL) spectroscopy and field emission scanning electron microscopy, which show that the nanorods of 150 nm diameter and 4.5 nm length grow along the [0 0 0 1] direction. X-ray photoemission spectroscopy demonstrated that Co was successfully doped into the nanorods. Ammonia concentration and ZnO buffer were found to play a very important role in the nucleation and growth of the ZnCoO nanorods. PL spectra were composed of broad ultraviolet (UV) emission and visible light. Using Gaussian simulation, the UV band was separated into two peaks, both of which were characteristic of redshift with the increase in Co concentration. The effect of the Co dopant on the broad ultraviolet emission peak and the formation mechanism of ZnCoO arrays were also discussed.