Investigations On Transparent And Flexible Resistive Random Access Memory Devices Based On Metal-Oxide Thin Films

As the technology node for semiconductor manufacturing approach to22nm, and the floating-gate, channel and dielectric layer are scaling down, it will result in flash memory devices meet its limitation of physics and fabrication, so it becomes urgent to develop novel non-volatile memory. Owing to the simple structure, high speed, low power consumption, the resistive random access memory shows a potential for next generation non-volatile memory and attracts extensive researches. However, with a detailed study, the mechanism of resistive switching, the option and fabrication of resistive switching layer has become inevitable issues, and it will impede further progress. So, in this dissertation, it demonstrat the resistive switching polarity, the preparation and characterization of transparent and flexible resistive random access memory based on metal-oxide films. The main contents of the thesis are as follows:(1) The effects of anion and cation on resistive switching polarity were studied. In this part, the resistive switching polarity from unipolar to bipolar in a simple Al/ZnOx/Al structure by moderating the oxygen content in the ZnO sputtering process were achieved. In pure Ar sputtering, Al/ZnO/Al showed unipolar resistive switching behavior, as oxygen partial increase, the polarity change to bipolar, and the switch current decreased by about five orders of magnitude. The current transport properties of unipolar device showed ohmic behavior under both high resistance state and low resistance state, but the bipolar device showed Schottky barrier modulated current transport properties. The types of defects in the unipolar and bipolar devices were characterized through photoluminescence spectra. It showed that the interstitial zinc and interstitial oxygen was dominant in unipolar and bipolar device, respectively. It demonstrated that Zni and O; played an important role in URS and BRS, respectively.(2) The memory devices based on transparent resistive switching layer of SnO2:Mn films were prepared and the resistive switching behaviors were studied. Resistive switching cells using Al/SnO2:Mn/FTO capacitor were fabricated and studied. It exhibited an optical transmittance of approximately75%in the visible region (550nm) in the structure of SnO2:Mn/FTO. The interface modified space charge limited conduction were indicated in bipolar resistive switching in the Al/SnO2:Mn/FTO structure. The results showed that the ON/OFF ratio between high resistance state and low resistance state exceeds103at+1V and-1V. And the devices also showed a fast reset speeding (100ns).(3) The deep ultraviolet photochemical activated solution-processed films at low temperature for resistive random access memory applications have been studied. The photochemical activated solution-processed ZnO and Mn-doped based devices were fabricated under the temperature of145℃. The characteristics of resistive switching of prepared devices were also studied. The characteristic of carrier transport in high resistance state was dominated by Frenkel-Poole emission, whereas in low resistance state followed Ohm’s law. In the last part of the study, the photochemical activated solution-processed ZnO films for flexible resistive switching access memory applications on polyethylene terephthalate substrate were fabricated and the characteristics of resistive switching and mechanical endurance were demonstrated as well.