Size-dependent ferroic phase transformations in GeSe nanoribbons

Ferroic phase transformation in monolayer nanosheets or nanoribbons endows 2D nanoelectronic devices with novel functionalities. However, less is known how the phase transformation behaves with the system size. Combined with molecular dynamic simulations and a machine learning model, we systematically investigate the temperature induced ferroic phase transformation in monolayer GeSe nanoribbons, which exhibits remarkable size effect. Specifically, the transformation hysteresis is found continuously decreased with ribbon width at the investigated scales. In contrast, the transformation temperature of monolayer GeSe nanoribbons shows non-monotonic size-dependency, i.e., it is first increased and then decreased as we narrow the GeSe nanoribbons. We attribute this to a competition between the enhanced ripple deformation, which will promote phase transformation upon cooling, and the stronger edge effect that can suppress phase transformation. In addition, the two factors are well captured by the Landau model, which will deepen our understanding of phase transformation behaviors in 2D ferroic materials.