Effect of Annealing on the Optical and Structural Properties of TiO2 RF Sputtered Thin Films

Titanium dioxide (TiO2) thin films were prepared by RF magnetron sputtering technique at an argon flow rate of 4.9 sccm and room temperature during 4 h. These films were deposited on pyrex substrates with an RF power of 300 W and annealed at different temperatures (500, 600, 700 and 800 °C). The optical and structural properties were studied by spectrophotometry and X ray Diffractometry respectively. The obtained results show an amorphous structure for the unheated TiO2 films and an apparition of an anatase phase after the annealing process. The transmittance is increased with an annealing of 500°C from 45 to 80 % in the visible and near-infrared regions. The direct band gap, refractive index, extinction coefficient and grain size were investigated. The reflection in the visible range for a silicon (Si(p)) substrate covered by TiO2 thin films is decreased to be about 20%. The results of this work suggest that the variation of the annealing temperature allow the control of the physical properties of TiO2 thin films as antireflective coating for silicon solar cells.