Spin defects in hexagonal boron nitride as two-dimensional strain sensors

Lattice deformation is a powerful way to engineer the properties of two-dimensional (2D) materials, making their precise measurement an important challenge for both fundamental science and technological applications. Here, we demonstrate that boron-vacancy (V$\text{B}^-$) color centers in hexagonal boron nitride (hBN) enable quantitative strain sensing with sub-micrometer spatial resolution. Using this approach, we precisely quantify the strain-induced shift of the E${\rm 2g}$ Raman mode in a multilayer hBN flake under uniaxial stress, establishing V$\text{B}^-$ centers as a new tool for strain metrology in van der Waals heterostructures. Beyond strain sensing, our work also highlights the unique multimodal sensing functionalities offered by V$\text{B}^-$ centers, which will be valuable for future studies of strain-engineered 2D materials.

💡 Research Summary

The authors present a novel approach for high‑resolution strain metrology in two‑dimensional (2D) materials by exploiting the spin‑triplet boron‑vacancy (V_B⁻) color centers in hexagonal boron nitride (hBN). After creating an ensemble of V_B⁻ defects via 30 keV nitrogen implantation (10¹⁴ cm⁻²) in a ~20 nm thick hBN flake, the sample is clamped onto a polyimide (PI) substrate, coated with a 100 nm Au layer, and integrated into a custom strain cell comprising three parallel piezoelectric actuators. By applying voltages from 0 to 5 V, the PI substrate is stretched, delivering a controllable in‑plane tensile strain (up to ~1 %) to the hBN layer.

Optically detected magnetic resonance (ODMR) is used to monitor the spin Hamiltonian of the V_B⁻ ground state, which is described by
H =