Spectroscopic ellipsometry characterization of Zn_1-xCd_xO thin films

Despite previous investigations on the fabrication and optical characterization of Zn_1−xCd_xO thin films spanning the whole composition range, the permittivity has yet to be determined. In this work, we deposited Zn_1−xCd_xO alloyed thin films via the spray pyrolysis method. We optically characterized the samples through spectroscopy ellipsometry and transmittance measurements in the [300 nm – 3200 nm] wavelength range. We show that the optical band gap of ZnO is in the ultraviolet region of the electromagnetic spectrum, and while increasing Cd concentration, we notice a nonlinear red-shift. Also, we find that most of our films were conductive with a sheet resistance as low as 19.8 Ω for a composition of Zn_0.25Cd_0.75O. Moreover, the thin films have an average transmittance of 0.8 over a wide range of the electromagnet spectrum. Understanding the optoelectronic properties of Zn_1−xCd_xO thin films can pave the way to a more efficient Transparent Conducting Oxide (TCO).