Charge-Trapping-Enhanced Resistive Switching and Charge Storage in Silk Fibroin-TiO2 Composite Memristors.

Silk fibroin (SF) is a promising bio-compatible material for transient and bio-integrated memory devices; however, its relatively high leakage current and limited resistance state stability remain critical issues. In this study, Ag/SF-TiO2/Pt bio-memristors were fabricated using SF-TiO2 composite films with TiO2 nanoparticle concentrations of 0, 0.25, 0.5, and 1.0 wt%. SEM analysis showed that TiO2 incorporation increased particle aggregation while maintaining continuous film morphology. Optical analyses revealed that TiO2 nanoparticles reduced the apparent optical gap, enhanced sub-bandgap absorption, and suppressed photoluminescence intensity, indicating the formation of defect- and trap-related states. Electrical measurements demonstrated that TiO2 incorporation effectively reduced leakage current and stabilized the high-resistance state. The devices exhibited stable bipolar resistive switching within ±1 V, with enhanced Ion/Ioff ratios of approximately 104-105 after TiO2 addition. Endurance and retention measurements confirmed reliable switching over 100 cycles and stable resistance states up to 104 s. Capacitance analysis further revealed resistance state-dependent charge storage behavior, with higher capacitance in the low-resistance state due to conductive filament formation and TiO2-assisted interfacial polarization. These results indicate that TiO2 nanoparticles effectively modulate charge trapping, leakage suppression, and memory stability in SF-based bio-memristors.