Lowering the coercive field of van der Waals ferroelectric NbOI2 with photoexcitation

Polarization switching in van der Waals ferroelectric materials driven by an electric field remains robust even at the atomic layer limit, paving the way for advances in the miniaturization and integration of ferroelectric devices. Thus, understanding the modulation of ferroelectric properties in two-dimensional ferroelectric materials is essential for their efficient nanoscale applications. NbOI2, a recently confirmed van der Waals ferroelectric, offers an ideal platform for investigating in-plane spontaneous polarization at the nanoscale. We explored the influence of laser excitation on the ferroelectric polarization properties of NbOI2. In multilayer NbOI2 devices with in-plane configurations, no significant current signals were detected along the c-axis or b-axis (the ferroelectric polarization axis) in the absence of illumination. However, under laser excitation, the material exhibited clear hysteresis loop behavior along both the c-axis and b-axis, indicating that laser excitation effectively reduces the coercive voltage. Furthermore, at the same excitation wavelength, the current peak along the c-axis was larger, with more pronounced hysteresis loops. Our experimental findings demonstrate that laser excitation can lower the coercive field in multilayer NbOI2 and induce different electrical hysteresis behavior along different crystallographic orientations, providing valuable insights for the development of NbOI2-based optoelectronic devices.