The resistive switching mechanisms of ZrO 2 memory films are proposed to explain why resistive switching characteristics of Ti/ZrO 2 /Pt device are more stable than those of Pt/ZrO 2 /Pt and Al/ZrO 2 /Pt devices in this study. Different from the Pt/ZrO 2 /Pt and the Al/ZrO 2 /Pt devices, the carrier conduction mechanisms in the Ti/ZrO 2 /Pt device obey space charge limited current theory, which may be caused by the formation of the interface layer between Ti and ZrO 2 . Moreover, the resistive switching mechanisms are proposed to be related to the filament formation/rupture theory and oxygen ion migration. The location where filament formation/rupture takes place should be confined near the interface between Ti and ZrO 2 , leading to the stable resistive switching characteristics and a better endurance performance. During successive resistive cycles at room temperature and 150°C, the fatigue behaviors are observed due to the degradation of both two memory states, which might be related to the transformation of the interface layers between Ti and ZrO 2 and the coalescence of ZrO x clusters.

This study investigates the resistive switching behavior of Ga-doped ZnO (GZO) nanorod thin films with various Ga/Zn molar ratios. Vertically well-aligned and uniform GZO nanorod thin films were successfully grown on Au/Ti/SiO(2)/p-Si substrates using an aqueous solution method. X-ray diffraction (XRD) results indicate that GZO nanorods have [0001] highly preferred orientation. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show the formation of highly ordered and dense nanorod thin films. These compact GZO nanorod thin films can be used to make resistive switching memory devices. Such memory devices can be reversibly switched between ON and OFF states, with a stable resistance ratio of ten times, narrow dispersion of ON and OFF voltages, and good endurance performance of over 100 cycles. The resistive switching mechanism in these devices is related to the formation and rupture of conducting filaments consisting of oxygen vacancies, occurring at interfaces between GZO nanorods (grain boundaries). Results show that the resulting compact GZO nanorod thin films have a high potential for resistive memory applications.

Resistive switching behaviors are studied for the rapid thermal annealing (RTA) Ga 2 O 3 thin film embedding a Cr metal layer. By modifying the thickness, area, and RTA temperature of the device, the thermal-induced resistive switching is similar to those induced by the electrical forming process. The conducting filaments composed of oxygen vacancies are created by the Cr diffusion and oxidization during RTA. The related carrier conduction mechanism obeys space charge limited conduction theory accompanied by the formation/rupture of the conducting filaments at the interface between Ti and Cr:Ga 2 O 3 film. This study demonstrates a convenient process to fabricate forming-free resistive switching memory devices. V

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