Paper EL-ThA9
Far-infrared Dielectric Functions of Hg_1-xCd_xSe Thin Films Determined via Ellipsometry and Reflectivity

Thursday, October 24, 2019, 5:00 pm, Room A215

The dielectric functions of molecular beam epitaxy-grown Hg_1-xCd_xSe thin films were determined using a combination of ellipsometry and reflectivity. While we have reported the dielectric functions for this alloy system above 400 cm^-1, in the present study, by incorporating reflectivity measurements, we are able to recover the dielectric functions in a much wider spectral region (i.e., 85 cm^-1 and 50,000 cm^-1). Initially, spectroscopic ellipsometry, performed between 400 cm^-1 and 8000 cm^-1, determined the dielectric function and the thickness of Hg_1-xCd_xSe films. Ellipsometry results were then used to model the reflectivity data, which allowed us to obtain the absolute reflectance values and to map the dielectric function from the reflectivity spectra, obtained between 85 cm^-1 and 8,000 cm^-1. By representing the dielectric function as a collection of classical oscillators, we were able to recover the details of absorption due to free electrons, phonons, and band electrons in the Hg_1-xCd_xSe alloy system. Specifically, our models find two transverse phonon modes for Hg_1-xCd_xSe, where the HgSe-like mode blue-shifts and the CdTe-like mode red-shifts with increasing Cd concentration.