Resistance switching of transition metal oxide thin films and its application to memory devices

Abstract

Recently, the study on the application of the resistance switching (RS) in oxides to the memory device has been intensively conducted. The RS is the phenomenon that the resistance of the oxide is altered by applying electrical stimuli. To make a higher density of the capacitance-based memory device, the Flash memory and the DRAM, the innovative development of the lithography is required. The resistance random access memory is applicable to the cross-point structure which is possible to stack three-dimensionly. And the multi-level cell is relatively easily obtained. These two factors can make a higher density memory device than other concept memory. However, the switching mechanism of the RS is not understood perfectly yet and the property that the value of the switching parameters widely scattered should be resolved. In addition, a thorough study of the multi-level cell (MLC) is required. In Chapter 2, the switching mechanism with microscopic change of the conducting filament in bipolar RS will be given by using the impedance spectroscopy. The qualifications for the MLC are proposed and then, the MLC satisfying these qualifications will be shown in Chapter 3. In Chapter 4, the physical origin of the wide spread of the switching parameters in unipolar RS are investigated and the solution to random nature of the switching parameters is suggested.