Investigation On The Novel Binary Oxide Thin Film Based Resistance Change Device

As the building block of semiconductor electronics approaches the22nm regime, a number of fundamental and practical issues start to emerge. In terms of nonvolatile memory, it is generally believed that transistor based flash memory will be close to the end of scaling within about a decade. The novel, non-FET based devices and architectures are likely be needed to satisfy the growing demands for high performance memory and logic electronics applications, In recent years, resistive random access memory (RRAM) has gained significant attention as one of the promising candidates for next generation memory applications. This is due to its anticipated advantages versus flash technology with respect to high density, low power and fast read and write speeds. The main operation mechanism of these devices is a resistance change induced by filament formation and rapture through metal-cations or oxygen vacancies. The resistive swithing phenomeon has been observed in many materials. In this thesis, we focus our attention mainly on the binary transition metal oxide owing to the simple structure, easy fabrication process and compatibility with the complementary metal-oxide semiconductor (CMOS) technology. We have fabricated a series of resistive switcing memories using binary metal oxide, and the electrical performances and the resistive switching mechanism are investigated. The contribution of the current work is how to improve the resistive switching performances of the binary metal oxide based RRAM. The main contents of the thesis are as follows:(1) We fabricate the dysprosium oxide based RRAM device. The effects of Ti embedding layer, Pt nanocrystal layer, and different electrode materials on the resistive switching behavior of dysprosium oxide film are systematically investigated.(2) The Ag/Dy2O3/Pt structure devices are fabricated and the electrical parameters are investigated. Through STEM and EDX technology, we analysis the phenomenon of Set voltage increseaing with the cycle number increased in Ag/Dy2O3/Pt device with unipolar resistive switching behavior. And we found that the movement of oxygen vacancies is responsible for the resistive switching and failure behavior of Ag/Dy2O3/Pt device.(3) The interface between a metal electrode and a metal oxide has important influence on the resistive switching behavior of the RRAM device. We proposed a new way to fabticate super-thin-film based RRAM by using a Dy2O3layer as the oxygen supporting layer to make an active metal Ti layer be oxidized. The electrical parameters indicate the Pt/TiOx/DyOx/Pt structure device has stable resistive switching behavior. And we capture transmission electron microscopy (TEM) images of conductive filaments formation and rupture in the Pt/TiOx/DyOx/Pt device which is the reason of the reversible resistive switching behavior.(4) We have investigated the characteristics and mechanism of Pt/La2O3/Pt resistance switching memory with a set of measurements. La2O3were determined as5-10nm nano-polycrystalline with XRD and HRTEM analysis. The Pt/La2O3/Pt device exhibits excellent resistive switching properties, including low switching voltage (<2V), large low/high resistance ratio (>10-8), and good cycling endurance property. The conduction mechanisms of the Pt/La2O3/Pt device were revealed with current-voltage characteristics, which are different in low/high resistance states. Furthermore, XPS analysis and temperature-dependent resistance measurement in low resistance state show that the conducting filaments in Pt/La2O3/Pt device are mainly affected by oxygen-defects rather than metallic La.(5) The effects of an intentional interface engineering of a heterogeneous CeO2-Nb:SrTiO3interface on the switching uniformity has been investigated to obtain HfO2-based RRAM with excellent switching characteristics. Switching parameters including set voltage, reset votage, low resistance state, high resistance state, are greatly improved by the interface engineering.(6) Flexible RRAM devices, using Gd2O3as the switching layer, are fabricated on plastic substrates at room temperature. The device shows high performance, excellent flexibility, and mechanical endurance in bending tests. No performance degradation occurs, and the stored information is not lost after bending the device to different angles and up to104times. Studies on the temperature-dependent electrical properties reveal that the conducting channels of the low-resistance state are composed of Cu conductive filaments, and the rupture of the Cu conductive filaments switches the device to the high-resistance state.(7) The multilayer graphene (MLG)/Dy2O3/ITO device is fabricated which shows unipolar resistance switching with a low operation current (<100μA), low operation voltage (<1V), low power consumption (<100μW), high resistance ratio (>104), fast switching speed (<60ns), reliable data retention and promising cycle endurance properties (>200cycles), which makes a step toward the realization of low-power transparent electronics for next-generation nonvolatile memory application. Raman spectra obtained in pristine state, high resistance state and low resistance state indicate that the lower power consumption of MLG/Dy2O3/ITO device is attributable to the formation of graphene oxide layers.