Fabrication Of Memristive Device Based On Metal Oxides And Study On Resistive Switching Memory And Synaptic Emulation

Memristor is regarded as the fourth fundamental electrical element besides resistor,capacitor, and inductor. The memristor can be changed with the current flew it and rememberthe states. Recently, the study of memristor has attracted great interest due to the specificnonlinear electrical properties, and the application of memristor involves several areas,especially in resistive random access memory (RRAM) and synapse emulation. Thememristor has the characteristic which can switch its state between high resistance state andlow resistance state. It has the potential application on the next generation nonvolatilememory due to its characteristics of high operation speed, high density, and low energyconsume. On the other hand, the memristor can tune its resistance continuously, whichshows the similar transmission characteristic with the synapse in biology. Thus, the memristoralso has the great potential application value on the area of synapse emulation.In this thesis, we develop the memristor device based on the metal oxides materials. Westudy the application of memristor on the RRAM and synapse emulation based on itscharacteristics of resistive switching and continuous resistance states. We also research themechanism of devices in detail. The primary contents are decrisbed as follows:The resistive switching based RRAM device faces a key problem: the electricalparameters shows big fluctuation in the device operation, which is the biggest obstacle forpractical application of RRAM devices. To solve the key problem, we study some work asfollows:(i) we investigated the effect of compliance current on the conducting filaments(CFs), and obtained that the net-like CFs are easily formed under the higher compliancecurrents. In contrast, the simple CFs can be achieved under lower compliance currents. Wechose the appropriate compliance current to control the CFs and reduce the parameters’ sfluctuation;(ii) we investigate the effect of voltage polarity on the structure of CFs. Theresults indicated the voltage polarity can affect the structure of CFs. Especially, the resetvoltage polarity affect the switching location of CFs;(iii) we fabricated the electrode with tipshape by migrating the Ag and forming Ag nanoclusters in the switching layer. The enhancedlocal electric field around the tip of the Ag nanoclusters can control the CFs, which canreduce the randomicity of CFs and improve the performance of RRAM devices.We fabricated stable dual-layer memristor based on amorphous InGaZnO films withdifferent oxygen contents. The resistance states of memristor can be tuned continuously andthe device can response the signal spike quickly. We study the analogy between the memristor and synapse, and achieved the synaptic device with inherent learning abilities. Severalessential learning abilities of synapse can be achieved, including the nonlinear transmissioncharacteristic, synapse plasticity, long-term/short-term plasticity, and learning behavior withexperience. Furth, we also investigate the mechanism of short-term plasticity by studying itstemperature dependence. The results indicate its mechanism can be attributed to the diffusionof oxygen ions. Then, the operation mechanism of memristor can be explained by themigration/diffusion of oxygen ions.Based on our previous works, we develop the memristor device with one dimensionnanostructure materials and its application on synapse emulation. We grew the TiO2nanowirearrays on the FTO substrate, and fabricated the memristor device. By sputtering the TiO2nanowire using H2plasma, we can get the stable memristor device. Further, we use the TiO2nanowire based memristor to study its synaptic learning abilities. We also investigate itsmechanism in detail by using the techniques, e.g. XPS and TEM. In comparison with thememristor fabricated by films, the TiO2nanowire based memristor may have high potentialapplication on high density integration.