Low-Cost Spin-Coating Process for SnO 2 -Based Memristors: Comparative Study of Different Solvent Systems and Device Performance

Abstract

Solution-based deposition of SnO2 thin films is a promising low-cost alternative to vacuum-based techniques, offering scalability and compatibility with various substrates. However, achieving uniform film quality, controlled defect concentrations, and stable resistive switching behavior remains challenging due to the influence of precursor chemistry. This study investigates a low-cost, scalable solution-based fabrication approach for SnO2-based memristors, comparing three distinct precursor-solvent systems: SnCl2• 2H2O dissolved in pure ethanol, aqueous hydrochloric acid with deionized water, and ethanol with ammonium hydroxide using the sol-gel method. Spin-coated SnO2 films were deposited on patterned ITO-glass substrates, followed by annealing and thermal evaporation of silver top electrodes. Comprehensive electrical characterization revealed significant impacts of precursor chemistry on memristor performance. Devices fabricated using pure ethanol exhibited moderate switching voltages around ±1 V but suffered from poor stability due to rapid solvent evaporation and high defect density. Devices prepared with hydrochloric acid and deionized water showed enhanced film uniformity and stable high-resistance states, yet exhibited limited filament formation and lower on-off ratios of approximately five. In contrast, devices derived from the sol-gel method with ethanol and ammonium hydroxide demonstrated the best overall performance, including wide operating voltages around ±2 V, significantly improved on-off ratios exceeding 100, and excellent switching stability. These improvements result from controlled hydrolysis and condensation reactions, which produce uniform films with optimized oxygen vacancy concentrations and consistent filament formation. This work establishes the sol-gel process as an optimal strategy for low-cost, large-area, and highperformance memristor fabrication, providing essential guidelines for scalable manufacturing and practical applications.

Keywords: SnO2 memristors, non-volatile memory, solution process, sol-gel deposition