Synthesis and Characterization of Silica Aerogel Thin Films

This paper investigates the effect of different hydrofluoric (HF) acid catalyst concentrations on properties of silica aerogel thin films. The silica aerogel thin films were prepared by sol-gel spin on method followed by solvent evacuation from wet gel film under isopropyl alcohol supercritical conditions in autoclave. The refractive index (RI) of silica aerogel thin films observed to be reduced from 1.4 to 1.21 with increase in HF concentration. Based on RI value, porosity percentage and density of films were determined. The highest porosity of 54% and lowest density of 1.03 gm/cm³ is observed for the films deposited using 0.5 ml HF concentration. The calculated dielectric constant of the films deposited at 0.5 ml HF concentration is found to be lowered up to 2.3 for film. The incorporation of F in the film matrix is validated by using FTIR and EDAX. Peak appeared around 930 cm-1 of FTIR spectra shows the incorporation of F ion and forms Si-F bond in the silica matrix structure. Mechanical properties such as modulus and hardness of the films determined from nanoindentation technique found to be decreased from 19.33 to 14.19GPa and 2.55 to 1.45 GPa respectively.