Optical and structural properties of flash evaporated HgTe thin films

Abstract

Thin films of HgTe were thermally flash evaporated onto glass and quartz substrates at room temperature. The structural investigations showed that stoichiometric and amorphous films were produced. The transmittance, T, and reflectance, R, of thin films of HgTe have been measured over the wavelength ranges 300–2500 nm. From analysis of the transmittance and reflectance results, the refractive index, n, and the extinction coefficient, k, has been studied. Analysis of the refractive index yields a high frequency dielectric constant, ɛ_∞, and the energy of the effective oscillator, E_o, the dispersion energy, E_d, the covalent value β and the M₋₁ and M₋₃ moments of the imaginary dielectric function of optical spectrum. Also, the dependence of the real part dielectric constant ɛ₁(hν) on its imaginary part ɛ₂(hν) of HgTe films can be used to determine the molecular relaxation time τ, the distribution parameter α^\ and the macroscopic (electronic) relaxation time τ_o. The graphical representations of surface and volume energy loss functions, dielectric constant, the optical conductivity as well as the relaxation time as a function of photon energy revealed three transitions at 0.63, 2.21 and 2.76 eV.