Emulating Synaptic and Nociceptive Behavior via Negative Photoconductivity of a Memristor

In comparison to electrical memristive synapses, photoelectric synapses have the capability for ultrafast computing with less power consumption. In this work, a photoelectric synaptic memristor (PSM) based on Zn<inline-formula> <tex-math notation="LaTeX">$_{{\text{2}}}$</tex-math> </inline-formula>SnO<inline-formula> <tex-math notation="LaTeX">$_{{\text{4}}}$</tex-math> </inline-formula> (ZSO)/cuprous oxide (Cu<inline-formula> <tex-math notation="LaTeX">$_{{\text{2}}}$</tex-math> </inline-formula>O) heterostructure is fabricated. This two-terminal PSM device with a simple structure exhibits primary synaptic functions such as long-term potentiation (LTP)/long-term depression (LTD), and spike-timing-dependent plasticity (STDP) by electrical stimulation. Under the exposure of violet light, the observed negative persistent photoconductivity (NPPC) of our PSM is associated with inhibitory synaptic plasticity, which leads to synaptic performances such as short to long-term memory (STM-LTM) transition, learning experience behavior, and a transition from post-tetanic potentiation (PTP) to post-tetanic depression (PTD). Furthermore, this PSM mimics the five essential features of a nociceptive receptor (nociceptor) like threshold, relaxation, no-adaptation, hyperalgesia, and allodynia in response to violet light pulse-induced NPPC phenomenon. These results provide a new path to propel the development of neuro-inspired perceptual systems.