Direct visualization of out-of-equilibrium structural transformations in atomically thin chalcogenides

This research directly visualizes structural transformations in atomically thin layers of transition metal dichalcogenides (TMDCs) under non-equilibrium thermodynamic conditions using real-time, aberration-corrected scanning transmission electron microscopy. The study reveals a strong dependence of resulting structures and phases on heating rate and temperature. Fast heating (25 °C/sec) produces highly ordered crystalline hexagonal islands ( <20 nm) of 2H and 3R phases, while slow heating (25 °C/min) yields nanocrystalline and sub-stoichiometric amorphous regions. These differences are attributed to varying sulfur evaporation and redeposition rates. The ability to achieve highly crystalline, quantum-confined features using non-equilibrium heating rates offers a new synthesis route for atomically thin, laterally confined nanostructures.

Pawan Kumar, James P. Horwath, Alexandre C. Foucher, Christopher C. Price, Natalia Acero, Vivek B. Shenoy, Eric A. Stach, Deep Jariwala