Amorphous TiO2 films with high refractive index deposited by pulsed bias arc ion plating

Uniform and transparent TiO2 films were successfully prepared on glass by pulsed bias arc ion plating. The influence of pulsed substrate bias on film optical property was investigated by varying pulsed negative biases from 0 V to − 900 V. Film structure, surface morphology, and optical properties were measured with X-ray diffraction, SEM, AFM, and UV–VIS transmittance spectroscope. The results show that the as-deposited films are amorphous. The film deposited at − 300 V is atomically smooth in droplet-free zone with Rrms 0.113 nm, which results in a high refractive index, 2.51 at 550 nm, close to the maximum values reported to date. With increasing biases, the absorption edge first shifts to longer wavelengths, then to shorter ones. The band gap is nearly constant, at 3.27 eV.