Influence Of Electrode And Interface Modification On Resistance Switching Properties In PCMO And ZnO Films

With the development of the flying technology and the acceleration of the pace of life,people receive a huge amount of date every day. High performance memory device isbecoming more and more important. Emerging of the resistance random access memory（RRAM） is attractive for today’s semiconductor technology due to its simple sandwichstructure, high writing/erasing speed, high storage density, low power consumption and theCOMS compatibility. Although various models have been proposed in the past decade toexplain the resistance switching behaviors, the essential mechanism of resistance switchinghas not yet been clarified, currently, a lot of problems such as yield, endurance and stabilitystill impede the application of RRAM device. Aiming at the research hotspot in RRAM, thePr_0.7Ca_0.3MnO₃（PCMO） and ZnO films were selected as the research object in this paper.1. Fix Pt as the bottom electrode, various active metal top electrodes have been depositedon the same PCMO film to investigate the influence of the top electrodes on the resistanceswitching behaviors. The results of all electrical measurements indicated that Ti is the bestmaterial as top electrodes. Then by using Ti as the top electrode, La_0.67Sr_0.33MnO₃（LSMO）films with appropriate thickness were deposited on Pt/Ti/SiO2/Si substrates as bottomelectrode. Since the lattice constants of LSMO is very close to that of PCMO, it is effective toavoid the interface defects between PCMO and LSMO films. In addition, LSMO bottomelectrode also serves as a reservoir of the oxygen for PCMO films and provides oxygen ionsfor the system. The thickness of TiOxlayer between Ti top electrodes and PCMO filmsincreases with the increase of oxygen ions. The switching rate and endurance were effectivelyimproved by using the LSMO bottom electrode.2. Research results from the resistance switching properties of ZnO films show that theformation and rupture of the electrically conducting filament are random, which leads toAg/ZnO/Pt heterojunctions show dispersive distribution on SET and RESET voltages andinferior endurance. In view of the above serious problems, we added Ag, Al or Tinanoparticles between Pt bottom electrodes and ZnO films using a pulsed-laser depositiontechnique, to research the influence of Ag, Al and Ti nanoparticles on resistance switchingproperties in ZnO films. The experimental results show that the randomicity of the conductingfilament were reduced by adding small amount of Ag nanoparticles, while further increase Agnanoparticles led to instability for conducting filament which triggered high resistance stateuncertainty and inferior. The resistance switching properties can be also improved by Al nanoparticles. Since Al is quite active, it is easy to be oxidized, so only a small number of Alnanoparticles played its role in the resistance switching properties. Ti nanoparticles weremore effective than Ag and Al to improve the resistance switching properties. Low switchingvoltage and good endurance were effectively improved by Ti nanoparticles.Metal nanoparticles provides an easy path for the formation and rupture of filament inthe ZnO thin films and gives rise to a more stable resistance switching behavior.