Topography preserved microwave plasma etching for top-down layer engineering in MoS2 and other van der Waals materials

TL;DR

This paper introduces a scalable microwave plasma technique for layer-by-layer etching of van der Waals materials like MoS2, preserving material quality and topography, enabling precise layer control for advanced 2D electronics.

Contribution

The authors develop a universal, non-reactive microwave plasma method for controlled layer removal in van der Waals materials, compatible with existing semiconductor processes.

Findings

Effective layer-by-layer etching down to monolayer achieved

Material properties and topography are preserved post-etching

Technique applicable to various layered materials like graphene and h-BN

Abstract

A generic and universal layer engineering strategy for van der Waals (vW) materials, scalable and compatible with the current semiconductor technology is of paramout importance in realizing all-two-dimensional logic circuits and move beyond the silicon scaling limit. In this letter, we demonstrate a scalable and highly controllable microwave plasma based layer engineering strategy for MoS2 and other vW materials. Using this technique we etch MoS2 flakes layer-by-layer starting from arbitrary thickness and area down to the mono- or the few-layer limit. From Raman spectroscopy, atomic force microscopy, photoluminescence spectroscopy, scanning electron microscopy and transmission electron microscopy, we confirm that the structural and morphological properties of the material have not been compromised. The process preserves the pre-etch layer topography and yields a smooth and pristine-like surface. We explore the electrical properties utilising a field effect transistor geometry and find that the mobility values of our samples are comparable to those of the pristine ones. The layer removal does not involve any reactive gasses or chemical reactions and relies on breaking the weak inter-layer vW interaction making it a generic technique for a wide spectrum of layered materials and heterostructures. We demonstrate the wide applicability of the technique by extending it to other systems such as Graphene, h-BN and WSe2. In addition, using the microwave plasma in combination with standard lithography, we illustrate a lateral patterning scheme for device fabrication.