Synthesis of Copper Nanosheets Coatings onto Glass and Glass/CrSe₂ Substrates Using Ion Coating Technique for Terahertz Technology

Abstract

In this study, copper (Cu) nanosheets are utilized as semitransparent conducting optical windows for the fabrication of terahertz band filters based on chromium selenide (CrSe2). The deposition of CrSe2 thin films onto glass substrates is performed via the thermal evaporation technique followed by the application of Cu nanosheets using the ion coating technique. The interaction between Cu windows and CrSe2 films resulted in a slight widening of the energy bandgap and a remarkable reduction in the Urbach tail states from 2.24 to 1.23 eV. Furthermore, the coating of CrSe2 with Cu optical windows led to a decrease in the dielectric constant values of more than 35% and an increase in the terahertz cutoff frequency by more than 70%. The application of Cu windows increased the cutoff frequency to 23 THz. The correlation between electrical and optical conduction in the terahertz band filters is investigated through the utilization of Drude–Lorentz models, revealing that although Cu windows reduced the free carrier density and conductivity, they enhanced drift mobility, resulting in more efficient terahertz filter properties. The calculated optical constants and optical conductivity parameters provided evidence of the suitability of Cu‐coated CrSe2 films for applications in terahertz technology.