Synaptic devices based on two-dimensional layered single-crystal chromium thiophosphate (CrPS 4 )

Two-dimensional (2D) van der Waals (vdW) materials have recently attracted considerable attention due to their excellent electrical and mechanical properties. TmPS x (where Tm = a transition metal), which is a new class of 2D vdW materials, is expected to show various physical phenomena depending on the Tm used. In this paper, the unprecedented synaptic behavior of a vertical Ag/CrPS 4 /Au capacitor structure, where CrPS 4 is a single-crystalline 2D vdW layer, is reported. Multi-stable resistive states were obtained using an external voltage of less than 0.3 V. Both short-term plasticity and long-term potentiation were observed by controlling the interval of the external voltage pulse. Simple mechanical exfoliation was used to develop a synaptic device based on a very thin CrPS 4 layer with a thickness of ~17 nm. Therefore, it was demonstrated that vertical Ag/CrPS 4 /Au capacitors could be promising inorganic synaptic devices compatible with next-generation, flexible neuromorphic technologies.