Fabrication of Transparent AZO/ZnO/ITO Resistive Random Access Memory Devices and Their ZnO Active Layer Deposition Temperature-Dependent Switching Characteristics

The resistive switching characteristics in resistive random access memory (RRAM) devices based on metal oxide materials are strongly influenced by the qualities of the metal oxide film, such as the defect density and grain size. In this report, we demonstrate the deposition-temperature-dependence of the resistive switching properties of the ZnO active layer in an AZO/ZnO/ITO transparent RRAM device. As we increase the deposition temperature of ZnO to 300 degrees C, the forming voltage and the resistance in the low resistance state increase from 2 V and 0.3 m Omega to 6 V and 4.3 m Omega, respectively, owing to the decrease of oxygen vacancies that play a critical role in the conduction mechanism. However, the stability of the device improves owing to the enhancement of the crystallinity of the ZnO thin film. For the film deposited at 450 degrees C, the resistance in the low resistance state decreases to the value of the sample prepared at room temperature and the resistance ratio between the high resistance state and the low resistance state is fairly depressed, which results from inter-diffusion of indium or tin atoms into the ZnO layer at high deposition temperatures. Our devices have potential for transparent nonvolatile memory applications because the transmittance is measured to be approximately 80% in all cases.