Effects of film thickness on the linear and nonlinear refractive index of p-type SnO films deposited by e-beam evaporation process

Abstract

Tin monoxide (SnO) films of different thickness have been deposited onto glass substrates at vacuum pressure of ∼ 8 × 10−6mbar using an e-beam evaporation system. A hot probe test revealed that the deposited films showed p-type conduction. The structure characterization and phase purity of the deposited films was confirmed using X-ray diffraction (XRD) and Raman spectroscopy. The optical transmission and reflection spectra of the deposited films recorded in the wavelength range 190–2500nm were used to calculate the optical constants employing the Murmann's exact equations. The refractive index dispersion was adequately described by the well-known effective-single-oscillator model proposed by Wemple–DiDomenico, whereby the dispersion parameters were calculated. The nonlinear refractive index and nonlinear optical susceptibility of the deposited films were successfully evaluated using the Miller empirical relations. The lattice dielectric constant and the carrier concentration to the effective mass ratio were also calculated as a function of film thickness using the Spitzer and Fan model. The variation of the optical band gap of the deposited films as a function of film thickness was also presented.