Paper EN+SE+SS+TF-WeM3
Titanium Doped Tungsten Oxide (WO₃) Thin Films for Application in Photovoltaic Devices

Wednesday, October 30, 2013, 8:40 am, Room 101 A

Tungsten oxide (WO₃) is a fascinating material, which has potential for integration into a wide range of technological applications. Most recently, it has been considered for use in photoelectrochemical cells due to the associated photocatalytic properties. However, the optical, photochemical and electrical properties of W-oxide thin films grown from either chemical or physical vapor deposition methods are sensitive to the physical and chemical characteristics, which in turn depend on the processing conditions and precursor materials. In this work, titanium (Ti) doping into WO₃ has been considered to fabricate transparent conducting oxides (TCO) for photovoltaic devices. Ti-doped WO₃ (W-Ti-O) films were grown by sputter-deposition onto silicon, Si (100), and optical grade quartz wafers. Co-sputtering of Ti and W metal targets was performed in a wide growth temperature range (room temperature (RT)-500 ⁰C). The thin films were deposited for 1 hour, resulting in a thickness ranging from 80-90 nanometers. The structure and optical properties were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and the spectrophotometry measurements. The films are optically transparent and a correlation between the growth conditions and optical properties is derived. The XRD results show Ti-doped WO₃ films grown are amorphous and crystalline. A decrease in the peak intensity implies that the crystallinity decreases with an increase in titanium (Ti) along with a phase change at higher substrate growth temperatures. The optical results show the transparency of the films is well above 80% and the energy band gap is ~3 eV, which meet the criteria TCO parameters. The effect of Ti concentration on the structure and optical properties of W-Ti-O films grown at various temperatures is presented and discussed.