Study Of Zno Based Thin Films And Resistive Random Access Memory

Among various new non-volatile memories, resistive random access memory (RRAM) regarded as next-generation nonvolatile memory devices in the storage field has been widely investigated due to its simple structure, excellent scalability, low operation current, low power consumption, high speed, and well compatibility with complementary metal oxide semiconductor (CMOS) technology. In this thesis, we focus on improving the switching performance of ZnO-RRAM devices. The main contents are as follows:The ZnO thin films were deposited on quartz substrates by radio frequency magnetron sputtering. The effects of sputtering oxygen gas flow on the structure and optical properties of ZnO thin films were investigated. Then the performances of RRAM devices depend on different substrate temperature were also studied. The results reveal that when oxygen flow is25SCCM, argon flow is30SCCM and ZnO thin films grow at400℃, the ZnO-RRAM devices have better switching performance. The ratio of high resistance state to low resistance state is50. The operation voltages and operation currents are very low, which are2V and200μA, respectively.The ZnO-RRAM devices were prepared on Si substrates by radio frequency magnetron sputtering. We originally grew a Zn buffer layer between the ZnO thin film and metal bottom electrodes (BE). Through this method, we improved the quality of the ZnO films. Then the performance of ZnO-RRAM devices as a function of ZnO substrate temperature, the thickness of Zn buffer layer, and ZnO annealing temperature were systematically investigated. The results exhibit that the RRAM devices based on ZnO film grown at400℃, the Zn buffer layer at20nm, and the ZnO film annealed at330℃have better performance. The ratio of high resistance state to low resistance state is1X103. The resistive switch became more stable. The threshold voltages of OFF state and ON state were very uniform, which maintained at±1V. Then the effects of top electrode size were studied, we found that the conductive filament formation and rupture controlled by electrochemical redox-reaction are proposed to explain the resistive switching phenomenon.The resistive switching properties of GZO-RRAM devices fabricated on Si substrates were systematically studied. By comparing the data with ZnO-RRAM, we found the memory window is bigger and the switch became more stable. It reveals that effective doping can improve the performance of RRAM device. The effects of GZO substrate temperature, the thickness of ZnO buffer layer, and GZO annealing temperature on GZO-RRAM devices were investigated. The results show that the GZO-RRAM devices based on GZO film grown at400℃, the ZnO buffer layer at15run and the GZO film annealed at330℃had better performance. The ratio of high resistance state to low resistance state is1X104. The threshold voltages of OFF state and ON state were maintained at±1V, and resistance switching is very uniform.