NbSe₂/Ta₂NiS₅ Interface-Engineered Schottky Heterojunctions for Near-Infrared Polarization-Sensitive Visual Synapses

To meet the urgent demand for high-performance, low-power hardware devices for near-infrared polarization-sensitive neuromorphic vision in infrared detection, robot perception, and other fields, this work develops a two-dimensional heterojunction-based visual synapse with efficient near-infrared polarization response and flexible regulation. Benefiting from the high carrier mobility of NbSe₂ and the strong in-plane optical anisotropy as well as the narrow direct bandgap of 0.36 eV in Ta₂NiS₅, the two materials synergistically form an atomically sharp Schottky barrier at the NbSe₂/Ta₂NiS₅ interface. This barrier effectively promotes the separation of photogenerated electron-hole pairs and directional interfacial charge transport, endowing the heterojunction with superior photoelectric response properties. Accordingly, the heterojunction exhibits stable polarization-dependent synaptic responses across the 1064-2200 nm near-infrared window, whereby photoinduced synaptic weight can be precisely modulated by three independent parameters: incident optical power, light pulse duration, and applied bias voltage. Benefiting from these features, the heterojunction successfully emulates critical neuroplasticity behaviors, including paired-pulse facilitation, paired-pulse depression, the activity-dependent transition from short-term plasticity to long-term plasticity, and Hebbian learning. At the representative wavelength of 1550 nm, the heterojunction delivers an outstanding optical anisotropy ratio of 16.3. This work provides a promising hardware platform for next-generation infrared polarization vision and adaptive robotic perception systems, exhibiting important theoretical significance and practical application value.