Effects of strain on electronic and optic properties of holey two-dimensional C₂N crystals

A two-dimensional (2D) material, the holey 2D C₂N (h2D-C₂N) crystal, has recently been synthesized. Here, we investigate the strain effects on the properties of this material by first-principles calculations. We show that the material is quite soft with a small stiffness constant and can sustain large strains ≥ 12 %. It remains a direct gap semiconductor under strain, and the bandgap size can be tuned in a wide range as large as 1 eV. Interestingly, for biaxial strain, a band crossing effect occurs at the valence band maximum close to a 8% strain, leading to a dramatic increase of the hole effective mass. Strong optical absorption can be achieved by strain tuning with absorption coefficient ∼ 10 6 cm^-1 covering a wide spectrum. Our findings suggest the great potential of strain-engineered h2D-C₂N in electronic and optoelectronic device applications.