Effect of Ni thickness on electronic and optical properties of the (TiO₂/Ni) x 10 multilayer

Transition-metal doped TiO₂ is a class of materials with promising applications as diluted magnetic semiconductors, photocatalysis and gas sensing etc. because doping alters the structural as well as electronic and optical properties of the material. Ni doping in TiO₂ enhances the effective utilization of TiO₂ thin film in the visible range in place of UV range. In this work, we have studied the influence of Ni thickness on the optical and its electronic properties of the (TiO₂/Ni)x10 multilayer prepared by Pulsed Laser deposition at room. For deposition of [TiO₂/ Ni] x10 multilayer thin film, we have used TiO₂ (1000 Laser pulses) and Ni (100, 200, 400 and 800 laser pulses), these samples are denoted as TNi-0, TNi-1, TNi-2, TNi-4 and TNi-8 respectively. From X-ray reflectivity measurement, the thickness of Ni layer is found to be varying from ∼1.5 — 5 nm while the individual layer of TiO₂ is ∼ 6.0 nm. The optical band gap energy (E_g) measured for pure TiO₂ film is found to be 3.2eV. As a function of Ni thickness, the band gap energy of TiO₂ has reduced. The value of crystal field splitting (which is less than 2.0 eV) obtained from the soft X-ray absorption spectroscopy measurement indicates the amorphous nature of the film. (author)