Effects of Annealing Temperature on Optical and Electrical Properties of Different Multilayer Film Structures for Photoelectric Sensors

In this study, multilayer transparent conductive films were formed by depositing titanium dioxide (TiO2) and zinc oxide (ZnO) or indium tin oxide (ITO) on a glass substrate by radio-frequency magnetron sputtering using different sputtering parameters, and by depositing niobium (Nb) of 99.99% purity as an intermediate layer between the two oxide layers by DC magnetron sputtering. It was found that the amount of crystals in all the multilayer film structures increases with the annealing temperature, the TiO2/Nb/ITO (TNI) multilayer film structure has the best electrical properties when annealed at 500 °C, with the resistivity being 9.22 × 10−4 Ω-cm (with the highest average transmittance being 87.85% at the annealing temperature of 300 °C), and the TNI multilayer film structure also has the highest figure of merit (FOM), i.e., 3.88 × 10−3 Ω−1. However, the TiO2/Nb/ZnO (TNZ) film annealed at 500 °C had the resistivity of 1.63 × 10−2 Ω-cm, the transmittance of 81.20%, and the FOM of 1.66 × 10−8 Ω−1. The results showed that the TNI multilayer film had the best optical and electrical properties. The results of this study indicate that such multilayer film structures are suitable for use as photoelectric sensors.