Substrate surface modification for enlarging two-dimensional SNS grains at low temperatures

Grain enlargement is a crucial requirement to synthesizing two-dimensional (2D) metal chalcogenides because it can minimize the effects of carrier scattering at the grain boundaries. To this end, researchers have used a high processing temperature to enlarge grains, which makes it difficult to implement novel electronics employing 2D metal chalcogenides. This work proposes an alternative method to enlarge grains of 2D SnS at low temperatures via ligand-mediated surface modification. A priming method using hexamethyldisilazane vapor makes the substrate surface inert via the replacement of a functional group with a methyl group. Atomic layer deposition is performed at low temperatures (<300 °C) to grow the SnS grains. The grains exhibit small irregular shapes of approximately 200 nm when grown on pristine SiO₂, but show single-crystalline and rectangular shapes of approximately 1 μm when formed on hexamethyldisilazane-primed SiO₂. Such a morphological change is attributed to the increase in the surface diffusivity of the adsorbate, resulting from the decrease in the surface migration activation barrier via surface modification. This approach may provide the possibility of employing 2D metal chalcogenides in future electronics, which requires strictly low-temperature processing.