Enriching oxygen vacancies in hematite (α-Fe₂O₃) films with Cu impurities for resistive switching applications

Resistive-switching memory device is a promising candidate for the quest in areas of non-volatile memory. Herein, iron (III) oxide (hematite, α-Fe₂O₃) and Cu-doped Fe₂O₃ were employed as active layers in solution processed resistive random-access memory devices (s-RRAM). The fabricated device follows MIM (metal/semiconductor/metal) configuration with the fluorine-doped tin oxide-coated (FTO) glass plate as the bottom electrode and gold (Au) as the top electrode in a cross-pin configuration. Raman analysis revealed that if Cu dopant concentration increased beyond 3% in the Fe₂O₃ matrix, structural defects are dominated in the film. The photoluminescence spectroscopy identifies that the structural defects are attributed to the reinforced oxygen vacancies (O_V) and 5% Cu-doped Fe₂O₃ was observed to have more O_V. 5% Cu-doped Fe₂O₃ outperform Fe₂O₃ as an active layer, and it demonstrated to have lower operational voltage (~ 0.6 V) in RESET operation. The Au/Fe_1.90Cu_0.10O₃/FTO device had optimum resistive switching characteristics such as 6 × 10³ s retention time and stable under 1000 endurance cycles. The conduction mechanisms involved behind switching were found to be Schottky and space charge limited current (SCLC). This work elucidates the mechanism pertaining to oxygen vacancies in resistive switching in conjunction with Cu doping in a hematite structure.