Characteristics of Ni-doped TiO2 nanorod array films

Abstract

In this work, un-doped and Ni-doped titanium dioxide nanorod (TiO2 NR) arrays were synthesized by using a hydrothermal method in a Teflon-lined autoclave, on a fluorine tin oxide (FTO) substrate, at different Ni content (XNi = 0, 0.025, 0.05, 0.075, and 0.1). The grown nanorod array samples were studied by XRD, FESEM, DC conductivity, Hall effect measurements, ultraviolet-visible (UV-Vis) spectroscopy, and vibrating-sample magnetometer (VSM) measurements. Pure rutile phase with preferred orientation along (002) was noticed, indicating that the vertical growth of nanorods for the un-doped sample converts to the (101) direction with increasing doping content. The sharp (002) peaks compared with the broad behavior for other peaks indicate the longitudinal growth along this direction. The lattice constant (a), for tetragonal structure, increased with increasing Ni content, while small increment showed along the (c) direction. Uniformly distributed nanorod arrays with 2000-nm length and 200-nm diameter for the un-doped sample. The nanorod length decreases and their diameters increase with increasing Ni doping content. All the prepared samples showed that they behave like n-type semiconductors with a high carrier concentration and this can be attributed to the present of oxygen vacancies. DC conductivity increases due to increasing carrier concentration, while the charge carriers’ mobility decreases with increasing doping content from 0 to 0.1. Increasing Ni content enhances the TiO2 NR magnetic properties, where the residual magnetization increased from 0.0001 to 0.0058 emu/g, while the saturation magnetization increased from 0.0304 to 0.2652 emu/g with increasing Ni content from 0 to 0.1.