# Conformality limits of 2D WS2 on 3D nanostructures

## TL;DR

Researchers found a 4 nm radius limit for conformal WS2 deposition on 3D nanostructures, helping design better nanoelectronic and catalytic devices.

## Contribution

The study identifies a critical radius of curvature for conformal 2D WS2 deposition on 3D structures, enabling design guidelines for nanoscale applications.

## Key findings

- A minimum radius of curvature of 4 nm ensures consistent conformality of WS2 on 3D nanostructures.
- Conformality is only observed in about half of the cases for radii smaller than 4 nm.
- The tipping point aligns with the balance between adhesion and stiffness forces.

## Abstract

3D nanostructures are a vital part of various applications envisaged for two-dimensional transition metal dichalcogenides (2D TMDs), such as nanoelectronics and catalysis. However, achieving conformal deposition of 2D TMD films on 3D nanostructures is challenging due to the requirement for bending the basal planes of the 2D TMDs. Here, the limits of conformality of 2D WS2 deposited by atomic layer deposition on SiO2 3D nanostructures are investigated through cross-sectional transmission electron microscopy imaging. A minimum radius of curvature of 4 nm is identified above which basal plane conformality is almost always observed, while for smaller radii conformality is only observed in approximately half of the cases. We show that the observed tipping point agrees with the balance between the adhesion and stiffness forces, which allows for the estimation of the critical radius of curvature for other 2D TMDs and substrates. These results provide guidelines for the design of 3D nanostructured devices and substrates on which conformality of 2D materials is desired.

A critical radius of curvature of 4 nm for conformal deposition of WS2 on 3D nanostructures was identified, offering design guidelines for integrating 2D transition metal dichalcogenides in advanced nanoelectronic and catalytic applications.