Fabrication and characterisation of TiO 2 anti‐reflection coatings with gradient index

Abstract

Nano-textured anti-reflection (AR) films are designed elaborately to improve the transmittance character and to reduce the surface reflection loss. This work reports the gradient-index titanium dioxide (TiO2) AR coatings (ARCs) with the thickness of 50–400 nm, which was deposited by radio-frequency magnetron sputtering-assisted with the oblique-angle deposition technique on the low-iron glass substrates. The technological parameters related with this deposition were discussed such as the base pressure and target–substrate distance, as well as the vapour incident angle. Then, optical characteristics of the graded-index coating were discussed. An ellipsometric model was built to account for the structural and optical differences. The optimal thickness of the TiO2 ARC was about 250 nm. It exhibited a higher transmittance at the visible light regions over a large wavelength range than that of the primitive glass substrate. The value of refractive index for the TiO2 ARC was 2.245 at the wavelength of 632.8 nm.