Pb/FeSe Interfaces Designed for Optical Communication Technology

Abstract

Herein, thin films of FeSe are coated onto glass and semitransparent Pb substrate of thicknesses of 200 nm. The produced glass/FeSe (GFS) and Pb/FeSe (PFS) are structurally, compositionally, and optically characterized. It is observed that Pb substrates induced the crystallinity of cubic FeSe and cubic PbSe. On average, 21% of the phases in FeSe films are identified as PbSe. Due to the strong orbital overlapping between Pb and FeSe, Pb substrate increases the light absorption, the dielectric constant, the optical conductivity, and the terahertz cutoff frequency by ≈150 %, 180 %, 263 %, and 101 %, respectively. In addition the direct and indirect energy bandgaps shrink from 2.49 and 2.80 to 2.41 and 2.50 eV, respectively. Moreover, treating GFS and PFS as terahertz optical resonators have shown that Pb substrates enhanced the drift mobility and increased the plasmon frequency making it adequate for 6G technology applications. An important feature of the PFS optical resonator is the stability of the terahertz cutoff frequency at 16 THz in the visible range of light. This feature together with the enhanced optical absorption in the visible light region makes the PFS films attractive for visible light communication technology.