Optical Effects on Polarization States in van der Waals Ferroelectric α-In2Se3

Optically controlled ferroelectricity represents a scalable approach to engineering desirable ferroelectric properties for various device applications. With van der Waals ferroelectric α-In2Se3 being extensively explored for optoelectronic memory and photonic neuromorphic computing technologies, an understanding of the light–ferroelectric interactions is necessary but has not been clearly established. In this study, we show the significant effects of optical illuminations on ferroelectric properties in α-In2Se3, particularly the changes from monodomain to disordered polarization states and associated variations of surface electric potentials. We attribute these photoinduced changes to the screening effects from photogenerated carriers that allow for the formation of domain walls and the corresponding multidomain state. These multidomains are metastable under ambient conditions, persisting for tens of days, but begin to disappear after ∼100 days. In addition, they can be returned to the aligned polarization state through external electrical poling. We also demonstrate the reversible optical modulation of device electrical resistance, which is promising for reconfigurable electronics. These findings reveal rich and new phenomena of light–ferroelectric interactions and provide critical microscopic insight that forms the basis for future explorations of novel device concepts based on ferroelectric α-In2Se3.