Investigation of conductivity and shielding efficiency of the free-standing PVA–GO–Ag composite thin films in terahertz regime using time-domain terahertz spectroscopy

Terahertz time-domain spectroscopy has been used to study the THz optical properties of polyvinyl alcohol–graphene oxide–silver (PVA–GO–Ag) composite films with varying weight fractions of silver nanoparticles in the range of 0.0–0.64%. The measured THz AC conductivities are analyzed using the formalisms based on universal dielectric response and Drude-Smith models. The outputs from the analysis of these two formalisms are compared and used to get accurate physical insights into charge transport. The samples being lightweight and flexible and having sub-100 μ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\upmu }$$\end{document}m thickness, show electromagnetic interference shielding efficiency (SE) of ∼\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sim$$\end{document} 2–3 dB below 1 THz that increases linearly between 4 and 8 dB above 1 THz. These SE values are found to arise mainly from the absorption and they are estimated to increase to ∼\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sim$$\end{document} 10–50 dB of magnitude when the thickness is ∼\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sim$$\end{document} 500 μ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\upmu }$$\end{document}m indicating potential application of these composite films as THz shielding materials and THz filters.