Direct visualization of out-of-equilibrium structural transformations in atomically thin chalcogenides
Year: 2020
Type: article
Abstract: Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been the subject of sustained research interest due to their extraordinary electronic and optical properties. They also exhibit a wide range of structural phases because of the different orientations that the atoms can have within a single layer, or due to the ways that different layers can stack. Here we report a unique study involving direct visualization of structural transformations in atomically thin layers under highly non-equilibrium thermodynamic conditions. We probe these transformations at the atomic scale using real-time, aberration-corrected scanning transmission electron microscopy and observe strong dependence of the resulting structures and phases on both heating rate and temperature. A fast heating rate (25 °C/sec) yields highly ordered crystalline hexagonal islands of sizes of less than 20 nm which are composed of a mixture of 2H and 3R phases. However, a slow heating rate (25 °C/min) yields nanocrystalline and sub-stoichiometric amorphous regions. These differences are explained by different rates of sulfur evaporation and redeposition. The use of non-equilibrium heating rates to achieve highly crystalline and quantum-confined features from 2D atomic layers present a new route to synthesize atomically thin, laterally confined nanostructures and opens new avenues for investigating fundamental electronic phenomena in confined dimensions.
Institution: University of Pennsylvania
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,790
Funders: National Science Foundation, University of Pennsylvania, Materials Research Science and Engineering Center, Harvard University, Center for Undergraduate Research and Scholarship, Bowling Green State University, Vagelos Institute for Energy Science and Technology, University of Pennsylvania, Division of Materials Research, Division of Civil, Mechanical and Manufacturing Innovation, Army Research Office
Awards: G1051554911, G1461678227, G155958390, Materials Research Science and Engineering Center, G1659969087, G2022074885, NNCI: Mid-Atlantic Nanotechnology Hub (MANTH) for Research, Education, & Innovation, G2567800894, G4469591436, Real Time Quantification of Diffusion and Alloying in Atomically Thin Capillaries, G584641232, Collaborative Research: Rational Design and Engineering of Atomically Thin Interfaces for Electronic Devices, G643866923, Quantifying the Coarsening Kinetics of Supported Metal Nanoparticles Using Time-resolved Electron Microscopy, Data Analytics and Simulations, G6995622194, G7012716497, G7125181322, G8171373877, G8980839182
OpenAlex ID: W3035459578