Visible Light Detection and Memory Capabilities in MgO/HfO₂ Bilayer-Based Transparent Structure for Photograph Sensing

Photograph response in transparent devices has been a hot area of investigation, with several material systems being used to generate a response to illumination. In this study, we propose an ITO/MgO/HfO
₂
/ITO bilayer (BL) transparent resistive switching (RS) device that exhibits a photograph response through defect engineering in the switching layer, which resulted in a subsurface active RS location in the formed conductive filament, thus reducing the loss of oxygen through the polycrystalline electrode. We observe that the switching performance is enhanced in the ITO/MgO/HfO
₂
/ITO BL device as compared to the ITO/HfO
₂
/ITO single-layer device with the insertion of MgO layer between the ITO top electrode and HfO
₂
RS layer. The device shows excellent ON/ OFF ratio (~10
⁷
), high and stable dc electrical set and optical reset endurance (>1000 cycles without degradation), excellent retention (>10
⁴
s at 85 °C), high transparency (>85% transmittance in the visible spectrum), and a response time of 30 μs for the optical reset. This study lays the foundation for future work involving oxide defect-based optical functionalization in RS devices with the possibility for being used in photograph sensing.