Research On Resistive Switching Memories Based On ZnO Nano-materials

Because of high density and low energy consumption, the metal-oxide-semiconductor Silicon-based floating Flash memory, not only has been the most advanced non-volatile memory, but also accounted for about forty percent of semiconductor memory share. Although, it has disadvantages such as slow operating speed, poor endurance, high write voltage. Meanwhile, due to the high drain current caused by the physical limit, it will approaching the integration limit in recent years. So new non-volatile memories arise at the historic moment, among all the new memories, non-volatile resistive switching random access memory(RRAM) will be the powerful competitor to be the most popular non-volatile memory because of the advantages such as high density, fast operating speed, high endurance.In this thesis, not only the background, but also the research status and problems existing of the new non-volatile memories and the non-volatile RRAM were reported. RRAM device unit based on ZnO nanowire and ZnO thin film were prepared. The microstructure of the device unit were characterized by Scanning Electron Microscope, Transmission Electron Microscope, Photoluminescence, X-ray diffraction. Resistive switching phenomena and resistive switching mechanism based on ZnO nanowires and ZnO thin films were investigated and analyzed.The results obtained in this thesis are as follows:1. In the device of Au/ZnO/Au based on ZnO nanowires, bipolar resistive switching was observed. The migration of oxygen vacancies on the surface of ZnO nanowires played an important role in resistive switching. More work needed to be done because of the high switching voltage, non-ideal cycling stability and resistance retention time.2. In the device of Ti/ZnO/Pt based on ZnO thin films, bipolar resistive switching was observed, which was caused by the migration of oxygen vacancies in ZnO thin films. It had advantage of relatively high On/Off ratio, meanwhile the cycling was not stable enough and the resistance retention time was not long enough, which need further improvement. What’s more, resistive switching was observed when the thickness of the ZnO thin films was 35nm. However, when the thickness was 90nm, none resistive switching was observed. It is obvious that the thickness of ZnO thin film plays an important role in resistive switching.