Capacitance-induced non-zero crossing hysteresis in CoWO4 thin-film resistive memory

Abstract

This study investigates the influence of capacitance on the non-zero crossing hysteresis observed in Ag/CoWO₄/FTO devices. This work successfully synthesized uniform and adherent cobalt tungstate (CoWO₄) film using spray pyrolysis at 350 ℃. The results revealed a pure, monoclinic polycrystalline phase with a crystallite size of ∼50 nm. The electrical properties demonstrated that a typical capacitive behavior characterizes current-voltage (I-V) hysteresis. The non-pinched hysteresis curve is observed from ±0.5 V to ±3 V, while the non-zero crossing hysteresis curve is obtained at ±4 V and ±5 V. The device demonstrates low power consumption, ranging from 0.3 nW to 310 nW across the tested voltage range. Reliability studies show minimal cycle-to-cycle variation (coefficient of variance <10 %) in SET and RESET currents, except at ±5 V. A higher Weibull β indicates more stable and uniform resistive switching. The β values for SET and RESET currents range from 10.06 to 58.06, excluding 146 at +3 V. Further, the fabricated device showed stable performance over 10³ switching cycles without degradation. The Ag/CoWO₄/FTO device exhibits double-valued charge-flux characteristics, suggesting it is a non-ideal memristor. The results suggest uniformity and reliability during the RS process. This work gives new insight into developing the metal tungstates-based memristive device based on the capacitive effect for non-volatile memory application.