Electron beam ion-assisted deposition of SiO₂–TiO₂ broadband antireflection coatings: Substrate temperature effect on optical properties

Antireflection coatings dominate a critical role in enhancing optical efficiency across a wide range of technologies, particularly top layer in high-performance solar energy systems and advanced laser optics. In this study we
report fabricating low-loss SiO₂–TiO₂ based antireflection coating by using electron beam ion-assisted deposition
and analysing their optical transmission evolved through microstructural transformation under a varying thermal load. Multilayer antireflection films were deposited on cleaned glass substrates at temperature range from
120◦C to 240◦C, with precise control over layer thickness in-situ. Optical spectral analysis revealed average
transmission values of 99.54 ± 0.04 % in the 470–532 nm range and 98.63 ± 0.12 % in the 950–1064 nm range at substrate temperature of 160◦C and 180◦C, representing significant improvement over uncoated glass. The spectral transmission of AR coatings dropped beyond this temperature owing to increased roughness, porosity, and microstructural transformation resulting in a decreased optical efficiency. Adhesion and aging tests confirmed excellent interfacial stability and durability. Water contact angle analysis indicated the hydrophilic nature of the film surface. These findings showcase the effectiveness of electron beam ion-assisted deposition process in fabricating high-precision industrial quality antireflection coating by in-situ optimization of substrate temperature.