Ferroelastic phase transition-modulated electronic transport and photoelectric properties in monolayer 1T' ZrCl₂

Monolayer 1T' ZrCl₂ exhibits unique ferroelastic behavior with three structurally distinct variants (O1, O2, and O3), demonstrating potential for next-generation nanoelectronic and optoelectronic devices. This study investigates the electronic transport and optoelectronic properties of the O1 and O3 variants, with O3 serving as a representative for both O2 and O3 due to their structural symmetry. First-principles calculations and non-equilibrium Green's function analysis reveal that the O1 variant possesses exceptional electronic properties, including high electron mobility (1.44 × 10⁴ cm² V^-1 s^-1) and a large current on/off ratio (10⁶), while the O3 variant shows high conductivity in both crystallographic directions. Optoelectronically, the O1 variant demonstrates strong anisotropy with a maximum photocurrent density of 6.57 µA mm^-2, photo responsivity of 0.37 A W^-1, and external quantum efficiency of 41.08% along the a direction, outperforming many 2D materials, whereas there is negligible response along the b direction. In contrast, the O3 variant exhibits a more balanced photoresponse with comparable performance in both directions. These findings provide insights into structure-property relationships in ferroelastic 2D materials and pave the way for developing phase transition-based multifunctional devices for applications in information processing, energy conversion, and sensing.