Colloidal Atomic Layer Deposition on Plasmonic Metal Oxide Nanocrystals

Abstract

Colloidal atomic layer deposition (c-ALD) has emerged as a powerful technique for enhancing the functional properties of nanocrystals (NCs) while preserving their solution dispersibility. Previous studies have shown that the deposition of amorphous metal oxide shells via c-ALD can passivate surface states in NCs, resulting in improved stability, photoluminescence, conductivity, and energy transfer. However, its application to doped metal oxide NCs, such as tin-doped indium oxide (ITO), which exhibit surface depletion due to surface hydroxyls, remains unexplored. In this work, we implement a c-ALD strategy using ligand-modified precursors to grow amorphous Al2O3, TiO2, and Ga2O3 shells on ITO NCs. We reveal how these coatings influence the plasmonic response and mitigate surface depletion, which we ascribe to surface state passivation. Energy-dependent X-ray photoelectron spectroscopy (XPS) reveals a reduction in band bending, indicating a modification of the near-surface electronic structure. Furthermore, we demonstrate that control over shell thickness enables tunability of the collective plasmonic resonances in assembled ITO NC superlattices. This work expands the scope of c-ALD and establishes a versatile approach for tailoring the optoelectronic properties of doped metal oxide NCs in solution-processable systems.