Determination of the optical constants of HfO2–SiO2 composite thin films through reverse fitting of transmission spectra

Composite thin films of HfO2:SiO2 with wide range of relative composition from 100:0 (pure HfO2) to 10:90 have been deposited on fused silica substrates by co-evaporation technique and the optical properties of the films have been studied by measuring the transmission spectra of the samples by spectrophotometer. Different important optical parameters viz., band gap, refractive index and absorption coefficients of the samples have been obtained by fitting the measured optical spectra with theoretically generated spectra and the variation of the optical constants as a function of SiO2 content in the films have been obtained. Two different dispersion models viz., the single effective oscillator model and the Tauc–Lorentz model have been used to generate the theoretical spectra in the above fitting procedure. X-ray reflectivity (XRR) measurement technique has been used to find the densities of the films in order to explain the observed variation in optical properties of the films with increase in SiO2 content.

► Optical properties of composite thin films of HfO2:SiO2 have been studied.
► The transmission spectra of the samples have been fitted with theoretical spectra.
► The S.O. and TL models have been employed to fit the transmission spectra.
► TL model shows better agreement with the experimental spectra.
► R.I. and film density show maxima with 10% SiO2 incorporation in HfO2.