New Technique for Controllable Tuning and Instability Assessment in 2D Materials

New Technique for Controllable Tuning and Instability Assessment in 2D Materials
by Simon Mansfield
Sydney, Australia (SPX) Jul 23, 2024

Two-dimensional (2D) materials, known for their atomic-level thickness and excellent mechanical and physical properties, are gaining traction in various fields, including semiconductors, flexible devices, and composite materials.

These single-layer 2D materials often experience out-of-plane deformation, such as ripples, buckling, or wrinkling, due to their extremely low bending stiffness. This deformation can significantly impact their mechanical, electrical, and thermal properties, directly influencing the lifespan and performance of devices like micro/nanoelectromechanical systems (M/NEMS), resonators, nano kirigami/origami, proton transport membranes, and nanochannels.

Understanding and controlling the mechanical stability and instability behaviors of 2D materials is crucial for their mechanical applications. A team led by Professor Yang Lu from the Department of Mechanical Engineering at the University of Hong Kong (HKU) has introduced a novel method for assessing instability in these atomically thin films.

Collaborating with researchers from the University of Science and Technology of China, Professor Lu's team proposed a "push-to-shear" strategy for in situ observation of in-plane shear deformation in single-layer 2D materials, enabling controllable tuning of their instability characteristics. Through theoretical analysis and molecular dynamics simulations, they revealed the mechanical principles and control mechanisms of multi-order instability in these films.

The findings have been published in the journal Nature Communications in the paper titled "Tuning Instability in Suspended Monolayer 2D Materials".

The team aims to work with industrial partners to develop a new mechanical measurement platform for atomically thin films. This platform will use in-situ micro/nanomechanical techniques to achieve high-throughput mechanical property measurements and enable deep strain engineering of the materials' physical properties.

Professor Lu highlighted the significance of their research, noting that it addresses the challenge of controlling instability in single-atom-layer 2D materials. Their method has enabled the measurement of bending stiffness in materials like single-layer graphene and molybdenum disulfide (MoS2). According to him, this study opens new possibilities for manipulating the nano-scale instability morphology and physical properties of atomically thin films.

In addition, Professor Lu explained that their MEMS-based in-situ shearing device can control instability in suspended single-layer 2D materials and other atomically thin films. The team examined how wrinkle morphology in these materials evolves due to instability, uncovering various instability and recovery paths. This approach provides a new experimental mechanics method for assessing the instability behavior and bending performance of atomically thin films. The local stress/strain and curvature changes associated with the instability process have significant applications in fields such as electronics and chemistry, by adjusting the wrinkled morphology to alter electronic structures and create efficient proton transport channels.

Dr. Hou Yuan, the first author of the paper and a postdoctoral fellow in Professor Lu's group, added that their research has achieved controllable modulation of instability in atomically thin materials. He emphasized that compared to traditional tensile strain engineering, shear strain can deeply influence the band structure of 2D materials. Dr. Yuan expressed their future goal of integrating mechanical design and functionality in low-dimensional materials under deep strain.

Research Report:Tuning instability in suspended monolayer 2D materials