Digital-to-analog resistive switching depending on thickness of CeO2-x-TiO2 films

Abstract

The resistive switching layer of CeO2-x-TiO2 film was prepared on the FTO substrate by the sol-gel method and spin coating technique, and the Al/CeO2-x-TiO2/FTO resistive switching device was fabricated by depositing thin Al top electrode on the surface of the CeO2-x-TiO2 film. The crystal phase composition and crystal structure of CeO2-x-TiO2 thin films were characterized by XRD and XPS. The results show that the resistive switching layer is mainly composed of TiO2 and CeO2-x. Compared with Al/CeO2/FTO devices, the electrical performance of Al/CeO2-x-TiO2/FTO device is improved. I-V test shows that Al/CeO2-x-TiO2/FTO device has bipolar resistance variation characteristics without forming process. The resistive behavior with different CeO2-x-TiO2 thicknesses was carried out. The results show that the low resistance state of Al/CeO2-x-TiO2/FTO device shows ohmic conduction mechanism under different CeO2-x-TiO2 film thicknesses. As the thickness of CeO2-x-TiO2 increases, the essential change of resistance mechanism occurs in high resistance state. The resistance mechanism of the device changes from oxygen vacancy conductive filament mechanism to charge trapping/releasing mechanism by defect controlled. It was found that the AlOxlayer at the Al/CeO2-x-TiO2 interface is critical to the transformation of resistance mechanism, and the thickness of AlOx layer changes the device from "digital type" to "analog type".

Keywords

• resistive memory
• ceo2-x
• conductive filament
• tio2
• oxygen vacancy