Contactless photo-induced carrier density control in nanocrystal MoS2 hybrids

TL;DR

This paper introduces a novel photo-doping method for monolayer MoS2 using indium tin oxide nanocrystals, enabling contactless, long-range, and quasi-permanent control of carrier density with potential applications in optoelectronics and energy storage.

Contribution

It demonstrates a new all-optical doping technique that achieves significant and persistent carrier density modulation in monolayer MoS2 via nanocrystal coupling.

Findings

Carrier density reduced by ~6x10^12 cm^-2

Stored ~40 electrons per nanocrystal

Long-range effects up to 40 micrometers

Abstract

The ultrathin nature of two-dimensional monolayer semiconductors yields optoelectronic properties which are highly responsive to changes in free-carrier density, making it imperative to masterfully control their doping levels. We report a new photo-doping scheme that quasi-permanently dopes the monolayer MoS2 to extents competing with electrostatic gating. The photo-doping is achieved by coupling monolayer MoS2 with indium tin oxide nanocrystals that can store multiple electrons per nanocrystal after UV illumination. In the hybrid structure, the photo-generated valence band holes in the nanocrystals are filled by MoS2 electrons, photo-doping the MoS2 with holes. Reductions in carrier density by ~6x10^12 cm^-2 are observed, equivalent to the storage of ~40 electrons per nanocrystal. Long-range changes proliferating up to 40 micrometers away from the localized photodoping result from local bandstructure variations in MoS2. These studies reveal novel all-optical carrier density control in monolayer semiconductors, enabling remote-control of local charge density and innovative energy storage technologies.