The effect of repeated annealing temperature on the structural, optical, and electrical properties of TiO2 thin films prepared by dip-coating sol–gel method

In this study, we have studied the effect of repeated annealing temperatures on TiO2 thin films prepared by dip-coating sol–gel method onto the glasses and silicon substrates. The TiO2 thin films coated samples were repeatedly annealed in the air at temperatures 100, 200, and 300 °C for 5 min period. The dipping processes were repeated 5 to 10 times in order to increase the thickness of the films and then the TiO2 thin films were annealed at a fixed temperature of 500 °C for 1 h period. The effect of repeated annealing temperature on the TiO2 thin films prepared on glass substrate were investigated by means of UV–VIS spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM). It was observed that the thickness, average crystallite size, and average grain size of TiO2 samples decreased with increasing pre-heating temperature. On the other hand, thickness, average crystallite size, and average grain size of TiO2 films were increased with increasing number of the layer. Al/TiO2/p-Si metal–insulator–semiconductor (MIS) structures were obtained from the films prepared on p-type single silicon wafer substrate. Capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements of the prepared MIS structures were conducted at room temperature. Series resistance (Rs) and oxide capacitance (Cox) of each structures were determined by means of the C–V curves.