Enhanced optical properties of aluminum-doped zinc oxide thin films fabricated via twist substrate-assisted glancing angle deposition

Abstract

This study presents a methodology termed Twist Substrate-Assisted Glancing Angle Deposition (TSA-GLAD) for the fabrication of nanocolumnar aluminum-doped zinc oxide (AZO) thin films on borosilicate glass substrates. By integrating substrate twisting into the deposition process, we achieved enhanced control over the nanostructural characteristics of the films. The TSA-GLAD technique combines radio-frequency sputtering with controlled precession substrate rotations at varying speeds of 15, 30 and 45 rpm and a twist frequency of 0.5 Hz over a 40-minute deposition period. Our results demonstrate a remarkable reduction in Solar Weighted Reflectance (SWR) from 20 % in single-layer films to as low as 13 % in multilayer configurations, indicating superior anti-reflective capabilities. The films exhibit a minimum refractive index of 2.16 at 550 nm, increasing to 2.79 at 800 nm, and maintaining over 80 % transparency in the visible spectrum. Additionally, the average porosity of the films was quantified at 12.3 %, 13.2 %, and 14.1 % for samples M4, M5, and M6, respectively, highlighting the impact of substrate rotation on structural characteristics. The films exhibit remarkable ultraviolet (UV) absorption, blocking over 90 % of radiation below 335 nm, and attenuating approximately 23 % of near-infrared (NIR) radiation within the 700 nm to 1100 nm range. The findings reveal the TSA-GLAD technique capability in enhancing the optical properties of AZO thin films. Future challenges include refining morphology control, exploring different substrates, and assessing durability under varying environmental conditions for practical applications in solar cells and smart windows.