# Internal Interfaces in Exfoliated MoS2 Exhibit Junction-like Behavior

## TL;DR

This paper shows that internal interfaces in exfoliated MoS2 behave like electronic junctions, offering new opportunities for quantum device engineering.

## Contribution

The study reveals that natural layer transitions in MoS2 form quasi-heterojunctions with measurable electronic properties.

## Key findings

- Band offsets of 22 and 24 meV were observed in conduction bands at internal MoS2 interfaces.
- Line defects and bandgap variations influence the rectification properties of the junctions.
- Finite element modeling reconstructs surface potential to detail electronic structures.

## Abstract

Mechanical exfoliation
remains a ubiquitous method for
material
deposition in van der Waals layered semiconductors, despite usually
producing terraced structures where the layer count changes across
the flake, resulting in variations in the band gap magnitude across
the device. While most published studies circumvent this phenomenon
using sophisticated fabrication processes, these internal interfaces
present a unique opportunity for the realization of engineered quantum
building blocks within single-crystalline materials. The electronic
structure of internal interfaces in MoS2, termed here “quasi-heterojunctions”,
is studied using a combination of photoluminescence and Raman spectroscopies,
Kelvin probe force microscopy, and macroscopic transport measurements.
In the transition between 5 to 2 to 1 layers within a single crystal,
heterojunctions form, with band offsets of 22 and 24 meV in the conduction
bands of the respective junctions. Variations of bandgap and electron
affinity, as well as the formation of line defects, are shown to be
the primary cause determining the rectification properties of the
two junctions in series. Moreover, the formation of a line defect
results in a space-charge region that introduces nonlinear properties
to its response (I–V) curves.
Finally, computational reconstruction of the measured surface potential
using a finite element Poisson solver enables the determination of
detailed electronic structures of the constituent segments and their
quasi-heterojunctions.