Crystallization control of Cu(i)-halide via thermal evaporation for improving resistive switching memory performance

Abstract

CsCu₂I₃ is considered a promising material for lead-free resistive switching (RS) memory devices due to its low operating voltage, high on/off ratio, and excellent thermal and environmental stability. However, conventional lead-free halide-based RS memory devices typically require solvent-based thin-film formation processes that involve toxic organic and acidic solvents, and the effects of process conditions on device performance are often not fully understood. This study investigates the effect of crystallinity on CsCu₂I₃-based RS memory devices fabricated via thermal evaporation. Crystallinity increases with higher substrate deposition temperatures but decreases with increasing post-annealing temperatures, leading to film decomposition. At a substrate deposition temperature of 180 °C, without post-annealing, the CsCu₂I₃-based device demonstrates enhanced performance, including an endurance of 190 cycles and a retention time of 6500 s. The devices operate through a space-charge-limited conduction mechanism, as shown by logarithmic I–V characteristics. Trap density calculations reveal that higher crystallinity reduces defects, leading to improved endurance and retention by promoting the formation of stable conductive filaments. This study establishes a relationship between crystallinity and the enhanced endurance and retention of CsCu₂I₃-based RS memory devices prepared using thermal evaporation as a function of deposited substrate temperature and post-annealing temperature.