Kawahala, Nicolas M.Matos, Daniel A.Rappl, Paulo H. O.Abramof, EduardoBaydin, AndreyKono, JunichiroHernandez, Felix G. G.2024-05-082024-05-082023Kawahala, N. M., Matos, D. A., Rappl, P. H. O., Abramof, E., Baydin, A., Kono, J., & Hernandez, F. G. G. (2023). Thickness-Dependent Terahertz Permittivity of Epitaxially Grown PbTe Thin Films. Coatings, 13(11), Article 11. https://doi.org/10.3390/coatings13111855https://hdl.handle.net/1911/115696The exceptional thermoelectric properties of PbTe are believed to be associated with the incipient ferroelectricity of this material, which is caused by strong electron–phonon coupling that connects phononic and electronic dynamics. Here, we have used terahertz time-domain spectroscopy measurements to generate complex permittivity spectra for a set of epitaxially grown PbTe thin films with thicknesses between 100 nm and 500 nm at temperatures from 10 K to 300 K. Using a Drude–Lorentz model, we retrieved the physical parameters of both the phononic and electronic contributions to the THz permittivity. We observed a strong decrease, or softening, of the transverse optical phonon mode frequency with decreasing temperature, determining a thickness-independent negative ferroelectric-transition critical temperature, while we found a thickness-dependent anharmonic phonon decay lifetime. The electronic contribution to the permittivity was larger in thinner films, and both the carrier density and mobility increased with decreasing temperature in all films. Finally, we detected a thickness-dependent longitudinal optical phonon mode frequency, indicating the presence of plasmon–phonon coupling.engExcept where otherwise noted, this work is licensed under a Creative Commons Attribution (CC BY) license. Permission to reuse, publish, or reproduce the work beyond the terms of the license or beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.Journal articlecoatings-13-01855-v3https://doi.org/10.3390/coatings13111855