Electrostatic Imaging of Encapsulated Graphene

TL;DR

This paper demonstrates that conductive scanning probe techniques like electrostatic and Kelvin force microscopy can effectively visualize and assess the quality of encapsulated graphene layers without direct electrical contact, aiding in device fabrication.

Contribution

It introduces a non-invasive method to image and evaluate encapsulated 2D materials, revealing defects and charge environments prior to device processing.

Findings

Successful visualization of encapsulated graphene layers.

Detection of local defects such as cracks and bubbles.

Assessment of charge environment without electrical contact.

Abstract

Devices made from two dimensional materials such as graphene and transition metal dichalcogenides exhibit remarkable electronic properties of interest to many subdisciplines of nanoscience. Owing to their 2D nature, their quality is highly susceptible to contamination and degradation when exposed to the ambient environment. Protecting the 2D layers by encapsulation between hexagonal boron nitride layers significantly improves their quality. Locating these samples within the encapsulant and assessing their integrity prior to further processing then becomes challenging. Here we show that conductive scanning probe techniques such as electrostatic force and Kelvin force microscopy makes it possible to visualize the encapsulated layers, their charge environment and local defects including cracks and bubbles on the sub-micrometer scale. Our techniques are employed without requiring electrical contact to the embedded layer, providing valuable feedback on the local electronic quality prior to any device etching or electrode deposition. We show that these measurement modes, which are simple extensions of atomic force microscopy, are perfectly suited for imaging encapsulated conductors and their local charge environments.