Electrochemically and optically-switched terahertz electromagnetic interference shielding using MXenes

MXenes, a growing family of two-dimensional transition metal carbides and nitrides, have demonstrated substantial potential for terahertz (THz) electromagnetic interference (EMI) shielding. The adjustable and high electrical conductivity of titanium carbide, coupled with its absorption capabilities in the THz range, is utilized in the development of electrochemically and optically controlled devices, making them ideal for dynamic EMI shielding control. The sufficient EMI shielding effectiveness (SE) of $2.5\ifmmode\times\else\texttimes\fi{}{10}^{4}\phantom{\rule{0.16em}{0ex}}\mathrm{dB}\phantom{\rule{0.16em}{0ex}}{\mathrm{g}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{2}$ can be enhanced through electrochemical doping, reaching levels as high as $4\ifmmode\times\else\texttimes\fi{}{10}^{4}\phantom{\rule{0.16em}{0ex}}\mathrm{dB}\phantom{\rule{0.16em}{0ex}}{\mathrm{g}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{2}$ (at $+2\phantom{\rule{0.16em}{0ex}}\text{V}$). Furthermore, this initial EMI shielding can be improved by increasing the thickness, achieving an SE of 27 dB. With ultrafast optical pulses at 800 nm, tunability is achieved through a novel photoinduced enhancement in transparency, a phenomenon known as negative photoconductivity. A micron-thick film exhibits a long-lived photoinduced change in SE of $\ensuremath{-}0.25\phantom{\rule{0.16em}{0ex}}\text{dB}$. Our research enables the advancement of adaptable electromagnetic interference shielding components, which are ideally suited for the design and fabrication of innovative THz devices, including highly responsive detectors with both optical and electrical control capabilities.