Investigation of Band-Offsets at Monolayer-Multilayer MoS2 Junctions by Scanning Photocurrent Microscopy

TL;DR

This study investigates the electronic properties of monolayer-multilayer MoS2 junctions using microscopy, electrical measurements, and simulations, revealing a type II band alignment and hot carrier effects at the interface.

Contribution

It provides new insights into the band offsets and photocurrent mechanisms at MoS2 heterojunctions through combined experimental and simulation approaches.

Findings

Rectifying I-V characteristics at monolayer-multilayer junctions

Bias-dependent photocurrent observed at the junction

Type II band alignment explains electrical and photocurrent behavior

Abstract

The thickness-dependent band structure of MoS2 implies that discontinuities in energy bands exist at the interface of monolayer (1L) and multilayer (ML) thin films. The characteristics of such heterojunctions are analyzed here using current versus voltage measurements, scanning photocurrent microscopy, and finite element simulations of charge carrier transport. Rectifying I-V curves are consistently observed between contacts on opposite sides of 1L-ML junctions, and a strong bias-dependent photocurrent is observed at the junction. Finite element device simulations with varying carrier concentrations and electron affinities show that a type II band alignment at single layer/multi-layer junctions reproduces both the rectifying electrical characteristics and the photocurrent response under bias. However, the zero-bias junction photocurrent and its energy dependence are not explained by conventional photovoltaic and photothermoelectric mechanisms, indicating the contributions of hot carriers.