Coexistence of Write Once Read Many Resistive Switching with Negative Differential Resistance in Bi‐Rich Bi12FeO20 Ideal Sillenite

Abstract

The materials showing write once read many (WORM) types of resistive switching characteristics are potential candidates for permanent storage. The negative differential resistance‐based memory devices have the potential to perform like nonlinear systems together with resistive switching simultaneously. The successful synthesis of Bi‐rich Bi12FeO20 sillenite material as phase pure thin film on fluorine tin oxide (FTO) using a solution process together with thermally deposited copper (Cu) as the top contact is demonstrated. Cu/Bi12FeO20/FTO/Glass resistive random‐access memory (RRAM) devices show the WORM characteristics with Ion/Ioff ratio103 and negative differential resistance simultaneously. Further, Bi12FeO20 active material also shows nonvolatile characteristics with analog switching for 200 cycles or more with large retention time, ≈5 × 103 s, and endurance for 103 cycles, substantiating the stability of the device. The space charge limited conduction and Schottky mechanisms explain the formation of a conductive filament in a high resistance state (HRS) and rupturing of a conductive filament in a low resistance state (LRS). The observed negative differential resistance is attributed to trapping, detrapping, and Schottky barrier interface between the top electrode and active layer together with ambient humidity.