Optoelectronic Ferroelectric Domain-Wall Memories Made from a Single Van Der Waals Ferroelectric

Due to the potential applications in optoelectronic memories, optical control of ferroelectric domain walls has emerged as an intriguing and important topic in modern solid-state physics. However, its device implementation in a single ferroelectric, such as conventional BaTiO₃ or PZT ceramics, still presents huge challenges in terms of the poor material conductivity and the energy mismatch between incident photons and ferroelectric switching. Here, using the generation of photocurrent in conductive α-In₂Se₃ (a van der Waals ferroelectric) with a two-terminal planar architecture, the first demonstration of optical-engineered ferroelectric domain wall in a non-volatile manner for optoelectronic memory application is reported. The α-In₂Se₃ device exhibits a large optical-writing and electrical-erasing (on/off) ratio of >10⁴, as well as multilevel current switching upon optical excitation. The narrow direct bandgap of the multilayer α-In₂Se₃ ferroelectric endows the device with broadband optical-writing wavelengths greater than 900 nm. In addition, photonic synapses with approximate linear weight updates for neuromorphic computing are also achieved in the ferroelectric devices. This work represents a breakthrough toward technological applications of ferroelectric nanodomain engineering by light.