Two-Dimensional Auxetic GeSe2 Material with Ferroelasticity and Flexoelectricity

It has been a long-time pursuit to design two-dimensional (2D) semiconductors with multi-functions in material science. In this work, using first-principles calculations, we propose a novel 2D semiconductor, GeSe2, with excellent energetic, dynamical, and thermal stabilities as proved by the formation energy, phonon spectrum, and ab initio molecular dynamics. Our calculation indicates that the GeSe2 monolayer simultaneously has auxeticity, ferroelasticity, and flexoelectricity. To guide future experimental synthesis, we further demonstrate that MoSe2 should be an ideal substrate for epitaxial growth via chemical vapor deposition/molecular beam epitaxy techniques thanks to its slight lattice mismatch and robust thermal stability. Considering its rich and extraordinary properties, the GeSe2 monolayer is predicted to be a potential candidate for nanomechanics and nanodevices, especially for designing nonvolatile memory and energy conversion devices.