Influence Of Preparation Method And Doping On Resistance Switching Properties In Ag/TiO₂/Pt Heterostructures

With the rapid development of modern science and technology, the memory device cannot meet the high demand of the people. The non-volatile resistance random access memory（RRAM） device is attracting more and more attention due to its good performance, such ashigh-speed, high density, low power consumption and simple preparation. The RRAM ishopeful to be used as the major general-purpose memory of next generation. Nowadays, theRRAM is still in the development phase and has not been put into practical application. Theresearch hotspots of RRAM are focused on their memory properties and their mechanism. Inthis paper, using TiO₂as the resistance switching layer, the resistance switching behavior andmechanism of Ag/TiO₂/Pt heterojunction was studied. The main contents of this thesis are asfollows:1. The TiO₂thin films with an anatase structure are deposited on Pt/Ti/Si/SiO2substrateusing the sol-gel method and magnetron sputtering method. Ag top electrode is prepared bythe magnetron sputtering. All samples prepared by two methods show a stable bipolarresistive switching behavior. All the samples show good retention and fatigue property. Thisphenomenon can be explained by the formation and rupture of conductive filaments in theheterojunction owing to field-induced oxygen ion migration. The yield of the sample preparedby magnetron sputtering is higher than that prepared by sol-gel method. We think that thesurface roughness of TiO₂prepared by magnetron sputtering is better than that of the sol-gelmethod, therefore improves the yield of the sample. This result indicates that the state ofelectrode/film contact surface influences the resistance switching behavior.2. The resistance switching properties of Mg, Al-doped TiO₂thin films are investigated.The experimental results show that the surfaces of undoping and a small amount of Mg-dopedTiO₂thin films are quite rough, that weakens the effect of Schottky barrier at electrode/filminterface. Conductive filaments model is the mainly Resistance switching mechanism. Whendoping quantity increases, the film surface defects decreased, and the Schottky barrier atmetal electrode/film interface become the dominant role in resistance switching. Researchshows that Mg-doping in TiO₂film improves the state of the electrode/film contact surface, leading to the enhancement of sample yield and the fatigue property. Al-doped TiO₂modulates the oxygen vacancy concentration, results in easier formation of the conductivefilaments, and reduces the threshold voltage.3. When prepare Ag electrode using magnetron sputtering, the electrode/film contactsurface has too many defects, which results in the metal electrode/film to be an ohm contact.With heating of the electrode during the growth of the electrode process, the sample’s yieldincreases. We think that the enhancement of growth temperature of the electrode is conduciveto the infiltration and diffussion of Ag in Ag/TiO₂contact surface, ameliorates the contactsurface state of the electrode/film, thereby increases the sample yield.