Imaging Electron Motion in a Few Layer MoS2 Device

TL;DR

This paper demonstrates imaging of electron flow in a few-layer MoS2 device using a cooled Scanned Probe Microscope, revealing current patterns crucial for advancing 2D material-based nanoelectronics.

Contribution

It introduces a novel application of SPM to visualize electron trajectories in MoS2, a new 2D semiconductor, providing insights into current flow in ultrathin devices.

Findings

Electron flow patterns in MoS2 are imaged at different densities.

SPM tip influences resistance by blocking electron flow.

Current patterns are similar for different contact geometries.

Abstract

Ultrathin sheets of MoS2 are a newly discovered 2D semiconductor that holds great promise for nanoelectronics. Understanding the pattern of current flow will be crucial for developing devices. In this talk, we present images of current flow in MoS2 obtained with a Scanned Probe Microscope (SPM) cooled to 4 K. We previously used this technique to image electron trajectories in GaAs/AlGaAs heterostructures and graphene. The charged SPM tip is held just above the sample surface, creating an image charge inside the device that scatters electrons. By measuring the change in resistance {\Delta}R while the tip is raster scanned above the sample, an image of electron flow is obtained. We present images of electron flow in an MoS2 device patterned into a hall bar geometry. A three-layer MoS2 sheet is encased by two hBN layers, top and bottom, and patterned into a hall-bar with multilayer graphene contacts. An SPM image shows the current flow pattern from the wide contact at the end of the device for a Hall density n = 1.3x10^12 cm^-2. The SPM tip tends to block flow, increasing the resistance R. The pattern of flow was also imaged for a narrow side contact on the sample. At density n = 5.4x10^11 cm^-2; the pattern seen in the SPM image is similar to the wide contact. The ability to image electron flow promises to be very useful for the development of ultrathin devices from new 2D materials.