Increasing the refractive index of materials via nanolamination: a-IGZO/TiO2 nanolaminates

Abstract

We investigate nanolamination as a means of increasing the refractive index of materials, with a focus on [amorphous InGaZnO (a-IGZO)/${\mathrm{TiO}}_{2}{]}_{i}$ nanolaminates as composite transparent conducting oxides with a tunable index. We demonstrate that by periodic layering with ${\mathrm{TiO}}_{2}$ the refractive index of a-IGZO can be increased by up to $\mathrm{\ensuremath{\Delta}}n\ensuremath{\approx}0.39$ while the carrier mobility and conductivity retain 70% of their original values. This is shown to be a result of the alignment of the conduction bands of a-IGZO and ${\mathrm{TiO}}_{2}$. We also use optical modeling to verify the integral refractive index behavior of the nanolaminates and outline its range of applicability.