Complex Refractive Indices of CdxZn1−xO Thin Films Grown by Molecular Beam Epitaxy

The complex refractive indices of Cd x Zn 1-x O thin films were determined by transmission spectrophotometry. Transmission spectra were modeled from 375 nm to 800 nm for samples having cadmium concentrations ranging from 2% to 77%. The transparent and absorptive regimes were fitted separately by Sellmeier and Forouhi-Bloomer models, respectively. Real refractive indices of Cd x Zn 1-x O shift to higher values in the transparent region and the optical absorption edge shifts to longer wavelengths with increasing cadmium concentration. Spectroscopic ellipsometry was carried out on one sample from λ = 190 nm to 1.8 μm. Comparison between the two methods shows that the results are in general agreement.