Sub-2-nm-droplet-driven growth of amorphous metal chalcogenides approaching the single-layer limit.

Atom-thin amorphous materials (for example, amorphous monolayer carbon) offer a designable material platform for fundamental studies of the disorder system, as well as the development of various applications. However, their growth at a single layer remains challenging since their thermodynamically favourable grains are neither two dimensional nor layered. Here we demonstrate the growth of 1-nm-thick, amorphous metal chalcogenides at a wafer scale using a nanodroplet-driven nanoribbon-to-film strategy. Metal clusters are initially liquified into 1-2 nm droplets at 120 °C, and they then orchestrate the growth of amorphous single-layer nanoribbons, which eventually merge into a continuous centimetre-scale film. Phase-field simulations, combined with our characterizations, suggest a non-equilibrium kinetic growth mechanism, which can be applicable to various films, for example, PtSe, IrSe, PdSe and RhSe. The synthesized films exhibit a range of unique properties, including tunable conductivity through disorder modulation, high work functions and remarkable catalytic activity, making them promising candidates for hole-injection contacts in p-type transistors and hydrogen production applications. This work opens a pathway for the synthesis of non-layered materials approaching the single-layer limit.