Characterisation of aluminium and alumina thin films coatings using different deposition methods for enhancement of optical properties

Abstract

The enhancement of optical properties such as transmittance, absorptance, and reflectance is possible by applying selective metal and ceramic coatings to the surfaces. Aluminium oxide coatings have potential advantages in this regard. The coating is used for passivation, wear resistance, anti-reflection purpose, etc. in combination with other materials. The aluminium-based coating characteristics include transmittance, reflectance, absorptance, surface roughness, etc. depending on the type of deposition method, operating principles involved, and working conditions maintained during the deposition process. In this study, aluminium and alumina thin films of different thicknesses were deposited on borosilicate glass substrates using thermal evaporation, E-beam, and sputtering method with a substrate temperature from 25°C to 100°C. The optical properties like transmittance, reflectance, and absorptance were evaluated for the thin film coating. The surface roughness of the thin film was also analysed. The Rrms values of aluminium and alumina thin films deposited using thermal evaporation and sputtering process with a coating thickness from 100 nm to 300 nm varied from 2 to 5 nm and 1 nm. An increase in reflectance of aluminium coatings was observed with surface roughness.