Continuously tunable uniaxial strain engineering of two-dimensional materials under scanning probe microscopy

Abstract

Uniaxial strain has emerged as a powerful technique for manipulating quantum phenomena in van der Waals (vdW) materials. However, most existing strain-engineering approaches face critical limitations: (i) incompatibility with real-time nanoscale characterization, (ii) restricted maximum strain, and (iii) discontinuous strain application. To overcome these challenges, we develop NanoGap, a piezoelectric-driven strain platform that achieves full compatibility with scanning probe microscopy (SPM) techniques while enabling continuous strain in multilayer vdW crystals. Applying this methodology to hexagonal boron nitride flakes (20–50 nm thickness), we achieve 1.2% uniaxial tensile strain, as quantified through in situ atomic force microscopy measurements. Moreover, our strain-SPM integration reveals the direct correlation between progressive lattice deformation and phonon polariton dispersion alterations, as demonstrated through photo-induced force microscopy. This synergistic methodology establishes a paradigm for strain engineering by enabling simultaneous real-time nanoscale characterization and continuous strain manipulation.