Photonic Control of the Ferroelectric State in van der Waals Compound CuInP₂S₆

Layered van der Waals (vdW) ferroelectric semiconductors such as CuInP₂S₆ (CIPS) exhibit strong coupling between electronic and polar degrees of freedom. Here, we present nanoscale effects of visible light on this coupling in exfoliated CIPS nanoflakes using atomic force microscopy to locally probe the ferroelectric polarization, switching dynamics, and surface potential. CIPS demonstrates light-induced modulation of polarization through ionic displacement and charge redistribution. The vdW nature of this material allowed investigations of the photo-effects as a function of thickness down to a few monolayers limit. Under illumination with photons of energy exceeding the bandgap of CIPS, the photo-generated carriers alter the surface potential and partially screen the ferroelectric polarization, modulating domain contrast and reducing the coercive field. Upon removal of light, partial recovery of the initial potential reveals persistent photo-induced charge trapping, which is a function of the layer thickness. This work reveals optoelectronic control of ferroelectric state and switching dynamics, establishing CIPS as a promising material for photoferroelectric devices.