Broadband Optical Characterization of Epitaxial Two-Dimensional Tellurium thin Films

Tellurene, the two-dimensional counterpart of bulk Tellurium, is a semiconductor with intriguing properties for optoelectronic applications. In this work, the optical properties of epitaxial Tellurene thin films, approaching the two-dimensional limit, were investigated over a broad spectral range spanning from Terahertz to Ultraviolet frequencies. Transmittance and reflectance measurements were combined to extract the optical conductivity and the dielectric function for films of different thicknesses. The evolution of both interband and free-carrier responses with thickness is discussed. A pronounced free-electron response was observed in the thickest Te film, characterized by high carrier mobility and high DC conductivity, making it a promising candidate for the development of innovative infrared detectors and other optoelectronic devices, due to the thicknesstunable optical response and enhanced transport properties achieved by epitaxial growth.