Biaxial strain effects in 2D diamond formation from graphene stacks

TL;DR

This paper demonstrates that biaxial strain and water interaction can induce the formation of nanodiamond-like structures from graphene at room temperature, revealing new pathways for phase control in 2D materials.

Contribution

It uncovers the role of biaxial strain in stabilizing sp3 carbon structures in graphene stacks, a novel insight for phase engineering of 2D nanomaterials.

Findings

Biaxial strain facilitates nanodiamond formation at low pressure.

Water interaction stabilizes sp3 carbon structures.

Experimental and simulation results confirm strain's pivotal role.

Abstract

Discovering innovative methods to understand phase transitions, modify phase diagrams, and uncover novel synthesis routes poses significant and far-reaching challenges. In this study, we demonstrate the formation of nanodiamond-like sp3 carbon from few-layer graphene (FLG) stacks at room temperature and relatively low transition pressure (~7.0 GPa) due to chemical interaction with water and physical biaxial strain induced by substrate compression. By employing resonance Raman and optical absorption spectroscopies at high-pressure on FLG systems, utilizing van der Waals heterostructures (hBN/FLG) on different substrates (SiO2/Si and diamond), we originally unveiled the key role of biaxial strain. Ab initio molecular dynamics simulations corroborates the pivotal role of both water and biaxial strain in locally stabilizing sp3 carbon structures at the graphene-ice interface. This breakthrough directly enhances nanodiamond technology but also establishes biaxial strain engineering as a promising tool to explore novel phases of 2D nanomaterials.