Strain-dependent electronic and optical response of graphene–Ti₃C₂O₂ MXene heterostructures: A sequential DFT-to-FDTD computational study

Abstract

Graphene–MXene heterostructures have emerged as promising platforms for strain-sensitive optoelectronics, yet a methodologically transparent link between mechanical deformation and optical response has not yet been established. In this work, we present a sequential multiscale DFT–FDTD study of a graphene–Ti₃C₂O₂ heterostructure under 0% to 1% biaxial tensile strain. Using density functional theory with dispersion corrections, we demonstrate that biaxial tension induces a quadratic bandgap widening from 0.18 eV at equilibrium to 0.43 eV at 1% strain. This opening arises primarily from strain-induced breaking of graphene sublattice symmetry alongside modest interlayer orbital hybridization. Incorporating the strain-dependent complex dielectric functions into FDTD simulations yields a refractive-index sensitivity of approximately −14 per unit strain, roughly twofold higher than that of isolated pristine graphene. Because environmental substrate interactions, phononic stability, and finite carrier transport were not explicitly modeled, the device-level metrics provide an order-of-magnitude computational baseline rather than absolute experimental limits. These findings establish a transferable framework for the design and performance prediction in strain-tunable 2D nanophotonics.