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

Abstract

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 BaTiO 3 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-In 2 Se 3 (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-In 2 Se 3 device exhibits a large optical-writing and electrical-erasing (on/off) ratio of >10 4 , as well as multilevel current switching upon optical excitation. The narrow direct bandgap of the multilayer α-In 2 Se 3 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.

Optically Controlled Ferroelectric Nanodomains for Logic-in-Memory Photonic Devices With Simplified Structures

“…These peaks, particularly the one at 89 /cm, assign our used -In2Se3 to hexagonal structure, which is distinguishable from rhombohedral counterpart [24]. As previously reported [14], the hexagonal -In2Se3 has a direct bandgap of ~1.45 eV, very suitable for photoactive materials and optical devices with visible light sensing [25,26].…”

“…2c) exhibits dramatic reversal. Upon light illumination, the domain wall that is parallel with the channel almost shows no change, in contrast with the reported optical-controlled domain wall motion [14]. As the illumination time is raised to 10 s, the white and bright area is further reduced (left-bottom panel of Fig.…”

“…Here, we report a novel mechanism of optoelectronic memories at the device level whose operation only relates to the channel ferroelectric -In2Se3 with its two metal terminals. Upon light irradiation ferroelectric nanodomain reversal in -In2Se3 channel is observed, which is distinct from the domain wall motions in our published paper [14]. The nanodomain flipping exhibits non-volatile properties and can be used to store light information.…”

“…The charge trapping effect under light illumination has been ruled out for -In2Se3 optoelectronic devices [14] The origin of our observations in this work (i.e., optically controlled nanodomain reversal) can be ascribed to the unbalanced screening effect on ferroelectric bound charges at the nanodomain walls. The nanodomain wall across -In2Se3 channel is unusually stabilized by absorbed compensation charges, which, however, are prone to be disturbed by photogenerated carriers.…”

“…Using the as-fabricated -In2Se3 optoelectronic memories, we demonstrate the functionality of logic-in memory. The -In2Se3 is a vdW ferroelectric crystal with switchable polarization down to the monolayer limit, which has gained considerable interest since its stable polarization was theoretically predicted in 2017 [14][15][16][17][18][19][20][21][22][23][24]. Using Scotch tape method, it can be easily exfoliated to ultrathin flakes.…”