Xi Ling1
Boston University1
The discovery of MXenes expands the 2D family by adding desirable highly conductive and stable members, providing more building blocks for ubiquitous electronics. In addition to the widely used selective etching method to synthesize MXenes in liquid phase, several other methods such as chemical vapor deposition (CVD) and atomic substitution method are also developed recently to synthesize MXenes on solid state substrates. In the first part of my talk, I will first discuss our recent progress on the synthesis of nitride MXenes and related ultrathin metal nitrides through the atomic substitution of ultrathin layered metal chalcogenides.<sup>1</sup> This approach allows us to prepare the self-aligned 2D lateral heterostructures between nitride MXenes and the metal chalcogenides such as MoN<sub>x</sub> and MoS<sub>2</sub>, which is a metal-semiconductor junction. We further apply this structure to field-effect transistors with MoN<sub>x</sub> as metallic contacts and MoS<sub>2</sub> as the semiconducting channel material. In the second part of my talk, I will introduce the synthesis of 2D transition metal oxides (TMOs, e.g. TiO<sub>2</sub>) through the oxidation of MXenes (e.g. Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub>) and the liquid-liquid self-assembly method to fabricate large-area films of both 2D TMOs and MXenes.<sup>2</sup> We further demonstrate flexible, fast, and high-coloration-efficiency EC devices based on self-assembled 2D TiO<sub>2</sub>/Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> heterostructures, with the Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> layer as the transparent electrode, and the 2D TiO<sub>2</sub> layer as the EC layer. Benefiting from the well-balanced porosity and connectivity of these assembled nanometer-thick heterostructures, they present fast and efficient ion and electron transport, as well as superior mechanical and electrochemical stability. We further demonstrate large-area flexible devices which could potentially be integrated onto curved and flexible surfaces for future ubiquitous electronics.<br/>References:<br/>(1) Cao, J.; Li, T.; Gao, H.; Lin, Y.; Wang, X.; Wang, H.; Palacios, T.; Ling, X. Realization of 2D Crystalline Metal Nitrides via Selective Atomic Substitution. <i>Sci. Adv.</i> <b>2020</b>, <i>6</i> (2), eaax8784.<br/>(2) Li, R.; Ma, X.; Li, J.; Cao, J.; Gao, H.; Li, T.; Zhang, X.; Wang, L.; Zhang, Q.; Wang, G.; Hou, C.; Li, Y.; Palacios, T.; Lin, Y.; Wang, H.; Ling, X. Flexible and High-Performance Electrochromic Devices Enabled by Self-Assembled 2D TiO2/MXene Heterostructures. <i>Nat. Commun.</i> <b>2021</b>, <i>12</i> (1), 1587.