Size and Temperature Dependent Memristive Behavior of ZnO Nanoparticles Synthesized via Chemical Bath Deposition

Memristors, theoretically postulated by Leon Chua in 1971 and experimentally realized by Stanley Williams and co-workers at HP Labs in 2008, represent the fourth fundamental passive circuit element and have emerged as promising candidates for next-generation non-volatile memory and neuromorphic systems. In this work, zinc oxide (ZnO) nanoparticles with controlled sizes were synthesized using a polyvinyl pyrrolidone (PVP)-assisted chemical bath deposition (CBD) method. The influence of nanoparticle size and operating temperature on memristive performance was systematically investigated. Structural analysis confirmed the formation of hexagonal wurtzite ZnO with average crystallite sizes of 64.6 nm, 37.3 nm, and 12.1 nm corresponding to 1%, 2%, and 3% PVP concentrations, respectively. Optical band gap values showed slight size dependence, varying from 3.02 to 3.04 eV. Memristive devices fabricated in Ag/ZnO/Ag configuration exhibited clear pinched hysteresis loops. A strong size dependence of the resistance switching ratio (R_OFF/R_ON) was observed, increasing significantly to 22.96 for 12 nm nanoparticles. Temperature-dependent studies (100–300 °C) revealed thermally enhanced switching, with the resistance ratio increasing to 6.7 at 300 °C. The results demonstrate that both nanoparticle size and thermal activation critically govern resistive switching in ZnO-based memristors, highlighting their potential for scalable nanoelectronic and neuromorphic applications.