Phase and polarization modulation in two-dimensional In(2)Se(3) via in situ transmission electron microscopy

Phase transitions in two-dimensional (2D) materials promise reversible modulation of material physical and chemical properties in a wide range of applications. 2D van der Waals layered In(2)Se(3) with bistable out-of-plane ferroelectric (FE) α phase and antiferroelectric (AFE) β′ phase is particularly attractive for its electronic applications. However, reversible phase transition in 2D In(2)Se(3) remains challenging. Here, we introduce two factors, dimension (thickness) and strain, which can effectively modulate the phases of 2D In(2)Se(3). We achieve reversible AFE and out-of-plane FE phase transition in 2D In(2)Se(3) by delicate strain control inside a transmission electron microscope. In addition, the polarizations in 2D FE In(2)Se(3) can also be manipulated in situ at the nanometer-sized contacts, rendering remarkable memristive behavior. Our in situ transmission electron microscopy (TEM) work paves a previously unidentified way for manipulating the correlated FE phases and highlights the great potentials of 2D ferroelectrics for nanoelectromechanical and memory device applications.