Photo-physics and electronic structure of lateral graphene/MoS2 and metal/MoS2 junctions

TL;DR

This study uses advanced microscopy and theoretical methods to analyze charge transfer and electronic properties at graphene/MoS2 and metal/MoS2 interfaces, revealing significant differences in photocurrent and Schottky barriers.

Contribution

It provides direct visualization and quantitative analysis of Schottky barriers and charge transfer at 2D material interfaces using nano-ARPES, DFT, and photocurrent mapping.

Findings

Photocurrent at EG/MoS2 interface is 10x higher than at Ti/Au/MoS2.

Schottky barrier at EG/MoS2 is approximately half that of Ti/MoS2.

Valence band bending of ~500 meV observed over 2-3 micrometers.

Abstract

Integration of semiconducting transition metal dichalcogenides (TMDs) into functional optoelectronic circuitries requires an understanding of the charge transfer across the interface between the TMD and the contacting material. Here, we use spatially resolved photocurrent microscopy to demonstrate electronic uniformity at the epitaxial graphene/molybdenum disulfide (EG/MoS2) interface. A 10x larger photocurrent is extracted at the EG/MoS2 interface when compared to metal (Ti/Au) /MoS2 interface. This is supported by semi-local density-functional theory (DFT), which predicts the Schottky barrier at the EG/MoS2 interface to be ~2x lower than Ti/MoS2. We provide a direct visualization of a 2D material Schottky barrier through combination of angle resolved photoemission spectroscopy with spatial resolution selected to be ~300 nm (nano-ARPES) and DFT calculations. A bending of ~500 meV over a length scale of ~2-3 micrometer in the valence band maximum of MoS2 is observed via nano-ARPES. We explicate a correlation between experimental demonstration and theoretical predictions of barriers at graphene/TMD interfaces. Spatially resolved photocurrent mapping allows for directly visualizing the uniformity of built-in electric fields at heterostructure interfaces, providing a guide for microscopic engineering of charge transport across heterointerfaces. This simple probe-based technique also speaks directly to the 2D synthesis community to elucidate electronic uniformity at domain boundaries alongside morphological uniformity over large areas.