Determination of the optical constants of zinc oxide thin films by spectroscopic ellipsometry

Abstract

Spectroscopic ellipsometry (SE) has been used to determine the complex pseudo dielectric functions, ε1(E)+iε2(E), of ZnO films on (0001) Al2O3 substrates over the spectral range of 1.33 and 4.96 eV at room temperature. The SE measurements are carried out with E⊥c at angles of incidence of 60° and 65° with respect to the surface normal. Below the band gap, the refractive index n is found to follow the first order Sellmeir dispersion relationship n2(λ)=1+1.881λ2/(λ2−0.05382). A free excitonic structure located at the band edge of 3.32 eV is clearly observed in the pseudo absorption spectrum. Elliott expression with Lorentzian broadening is used to model the pseudo absorption coefficient above the band edge.

Evidence for coupling between exciton emissions and surface plasmon in Ni-coated ZnO nanowires

“…air or ZnO), respectively [13,18]. The calculated dispersions are shown in the inset in figure 5(a).…”

Transparent conducting n-type ZnO:Sc – synthesis, optoelectronic properties and theoretical insight

“…76,82,83 However, SE data suggests that ZnO thin films should have a band gap of E opt g = 3.37 eV. 84 In a recent discussion on this dilemma, Dolgonos et al suggest that the issue arises from the fact that the Tauc method was originally developed for estimation of the band gap of amorphous Ge, a nondegenerate semiconductor. 85 Aside from the fact that assumptions regarding localisation of energy states in an amorphous material might not necessarily hold for a polycrystalline material (which instead contains far greater long-range order), accurate extraction of E g information from absorption data is further complicated by broadening of initial and final electron-hole pair states upon photon absorption arising from time-dependent perturbation theory effects.…”

Electronic structure and optical properties ofZnX(X=O,S, Se, Te): A density functional study

“…Detailed information on this subject is available for ZnOw, 1,2,3,4,5,6,7,8,9 ZnS-w, 9 ZnS-z, 9,10,11 ZnSe-z, 9,10 and ZnTe-z, 9,10,12,13 see the systematized survey in Ref. 14.…”