Colloidal\nAtomic Layer Deposition with Stationary\nReactant Phases Enables Precise Synthesis of “Digital”\nII–VI Nano-heterostructures with Exquisite Control of Confinement\nand Strain

Abstract

In contrast to molecular systems,\nwhich are defined with atomic\nprecision, nanomaterials generally show some heterogeneity in size,\nshape, and composition. The sample inhomogeneity translates into a\ndistribution of energy levels, band gaps, work functions, and other\ncharacteristics, which detrimentally affect practically every property\nof functional nanomaterials. We discuss a novel synthetic strategy,\ncolloidal atomic layer deposition (c-ALD) with stationary reactant\nphases, which largely circumvents the limitations of traditional colloidal\nsyntheses of nano-heterostructures with atomic precision. This approach\nallows for significant reduction of inhomogeneity in nanomaterials\nin complex nanostructures without compromising their structural perfection\nand enables the synthesis of epitaxial nano-heterostructures of unprecedented\ncomplexity. The improved synthetic control ultimately enables bandgap\nand strain engineering in colloidal nanomaterials with close to atomic\naccuracy. To demonstrate the power of the new c-ALD method, we synthesize\na library of complex II–VI semiconductor nanoplatelet heterostructures.\nBy combining spectroscopic and computational studies, we elucidate\nthe subtle interplay between quantum confinement and strain effects\non the optical properties of semiconductor nanostructures.