Cooling-induced Strains in 2D Materials and Their Modulation via Interface Engineering

Abstract

2D materials exhibit unique properties for next-generation electronics and quantum devices. However, their sensitivity to temperature variations, particularly concerning cooling-induced strain, remains underexplored systematically. This study investigates the effects of cooling-induced strain on monolayer MoSe₂ at cryogenic temperatures. It is emphasized that the mismatch in thermal expansion coefficients between the material and bulk substrate leads to significant external strain, which superimposes the internal strain of the material. By engineering the material-substrate 2D-bulk interface, the resulting strain conditions are characterized and reveal that substantial compressive strain induces new emission features linked to direct-to-indirect bandgap transition, as confirmed by photoluminescence and transient absorption spectroscopy studies. Finally, it is demonstrated that encapsulation with hexagonal boron nitride can mitigate the external strain by 2D–2D interfaces, achieving results similar to those of suspended samples. The findings address key challenges in quantifying and characterizing strain types across different 2D-bulk interfaces, distinguishing cooling-induced strain effects from other temperature-dependent phenomena, and designing strain-sensitive 2D material devices for extreme temperature conditions.