Determination of the optical constants of ZnSe films by spectroscopic ellipsometry

Abstract

Spectroscopic ellipsometry was used to determine the real and imaginary parts of the dielectric function of ZnSe thin films grown on (001) GaAs substrates by molecular-beam epitaxy, for energies between 1.5 and 5.0 eV. A sum of harmonic oscillators is used to fit the dielectric function in order to determine the values of the threshold energies at the critical points. The fundamental energy gap was determined to be at 2.68 eV. The E0+Δ0 and E1 points were found to be equal to 3.126 and 4.75 eV, respectively. Below the fundamental absorption edge, a Sellmeir-type function was used to represent the refractive index. At the critical points, E0 and E0+Δ0, the fitting was improved by using an explicit function combining the contributions of these two points to the dielectric function.

Influence of annealing on optical properties and surface structure of ZnO thin films

“…In addition, the thickness of the interface layer may increase with annealing time. If the interface layer is thin enough, its influence on the reflection of the polarized light is negligible [18]. However, if the thickness of the interface layer is comparable with that of ZnO film, its influence should be considered, and a further study is required.…”

Determination of the optical constants of thin films in the visible by static dispersive Fourier transform spectroscopy

“…The optical constants of ZnSe have been measured previously by spectroscopic ellipsometry of single crystals 18 and of thin films grown by MBE. 19 Measurements of n() taken from The imaginary part of the refractive index, ͑͒, is shown to be ostensibly zero between the low wave number limit of the measurement at 10 400 and 20 500 cm Ϫ1 apart from a small monotonic increase with wave number which which is probably due to scattering from surface defects and contamination. A slight peak of 0.003 in ͑͒ is apparent at 19 300 cm Ϫ1 and coincides with an increase of 0.003 above the general trend of n() at the same wave number.…”

Determination of optical constants of sol‐gel derived Zn0.9Mg0.1O films by spectroscopic ellipsometry with various models

“…In this model, the extinction coefficient is assumed to be zero and the refractive index is given by Washington et al [4,5] …”

“…In particular, the availability of a dispersion model that can flexibly account for the energy dependence of material optical properties is a critical issue. In this paper, the suitability of Sellmeier, [4,5] Cauchy, [6] and ForouhiBloomer [7,8] dispersion models for describing ellipsometric spectra of Zn 0.9 Mg 0.1 O films in the transparent region is analyzed. Samples with different annealing temperatures are characterized with these models.…”