0D Nanocrystals as Light‐Driven, Localized Charge‐Injection Sources for the Contactless Manipulation of Atomically Thin 2D Materials

Abstract

We report a new localized and electrodeless charge injection scheme that quasi-permanently modifies monolayer (1L-)MoS2 doping levels to extents competing with electrostatic gating. The key innovation is to use Sn-doped In2O3 (ITO) nanocrystals (NCs) as contactless light-driven charge injection sources triggered solely by light. Each nanocrystal can store and transfer multiple charges after ultraviolet illumination within the diffraction limited laser spot. This results in reductions in carrier density in the underlying 1L-MoS2 up to 1×1013 cm-2 and is observed throughout the extent of the 2D material flake. The long-distance charge separation proliferates up to 40 µm away from the localized charge injection and persists over months. The apparent driving force for carrier relocation is the initial inhomogeneous electronic landscape of the 2D material. These studies demonstrate a novel all-optically controlled tool to locally inject carriers with sub-micrometer precision. This new ability allows us to extract important aspects of inhomogeneity in 2D materials undisturbed by bulky electronic contacts and indicates that local 2D material manipulation can serve as a key element for novel nanoscale device design.