Novel Optical Functionalities in Memristors

ABSTRACT

We present an electronic memristor with expanded optical functionalities enabled by integrating an ultrathin 3 nm cadmium sulfide (CdS) film as a tunnel junction barrier with a La _0.7 Sr _0.3 MnO ₃ (LSMO) bottom electrode. A transparent In ₂ O ₃ :SnO ₂ (90:10) (ITO) upper electrode provides direct optical access to the junction area. In the dark, the device exhibits non‐volatile electrical resistive switching with robust intermediate states. When illuminated with UV light (3.3 eV) between 50 and 150 K, the resistive switching remains unchanged; however, a photovoltaic response emerges, correlating linearly ‐via the open circuit voltage V _oc ‐ with the resistance of each intermediate state. This behavior enables electro‐optical sensing of each state. In contrast, at 10 K, photogenerated carriers enter a high injection regime and modify the device's electrical behavior in the dark, leading to a volatile suppression of the high‐resistance states as illumination power reaches 26 mW cm ⁻² . The equilibrium dark resistance of the memristor states is restored upon removing illumination, with long characteristic recovery times (∼100 s). This slow response can be leveraged in very high‐resistance states of 30 GΩ to induce voltage accumulation through low‐intensity UV pulses of 0.13 mW cm ⁻² . Integrating these innovative optoelectronic functionalities, photovoltaic sensing and hybrid electro‐optical voltage accumulation, into memristive devices opens exciting possibilities for the development of advanced bioinspired computing architectures.