Study On Resistance Switching Characteristics Of Perovskite Metal Oxides La₀.67Sr₀.33MnO₃ Thin Films

While traditional memories are approaching their scaling limits, the next generation nonvolatile memory has attracted extensive attention which is included magnetic random access memory (MRAM), phase change memory (PRAM) and resistance change memory (RRAM). The resistive random access memory (RRAM) is one of the promising candidates due to its superior characteristics including simple structure, high density integration, low power consumption and fast write/erase operation in these memory devices. Recently, resistive switchings in complex Perovskite oxides, such as La0.67Sr0.33MnO3 (LSMO), Pr0.67Ca0.33MnO3 (PCMO) and SrTiO3, have induced great interest for a possible application in nonvolatile memory devices. However, many models leave unanswered questions. Despite its fundamental importance, our understanding of the underlying physics of the RS effect is still poor. In the papers, we have mostly investigated the resistive switching properties of LSMO nanostructure grain films, and obtained the significant experimental results which showed a high potential for nonvolatile memory application.In Chapter 2, the pure LSMO thin films deposited on conduct glass were prepared by pulsed laser deposition. A vacuum DC sputtering system was used to deposit Au nanaoparticles on LSMO thin films. The crystalline structure of LSMO was characterized by X-ray diffractometer (XRD). The surface morphology was observed by an atomic force microscope (AFM). Cyclic voltammetry and electric measurements were undertaken by using a Chi660B electrochemical workstation.In Chapter 3, the LSMO thin film was grown on SnO2:F (FTO) substrates by pulsed laser deposition. Resistive switching characteristics of Au/LSMO/FTO sandwich structure were tested by direct current voltage at room temperature. The results show the bipolar reversible resistive switching. Analysis of I-V behaviors were carried out. The switching process between high resistive state and low resistive state is explained in terms of space-charge-limited-current conduction in higher voltage region caused by asymmetric electron trapping centers.In Chapter 4, Au top electrodes with different areas are patterned on LSMO films to form sandwiched structure. LSMO thin films show nonvolatile and reversible resistance switching characteristics. The resistive switching behaviors can change by the application of different voltage at room temperature. It is interesting that theâ… -â…¤curve in the low resistance state (LRS) is almost a straight line, which suggests the ohmic characteristic. The resistance of the high resistance state (HRS) is sensitive to the top electrode area, but that of LRS hardly changes, indicating a filament conducting in low resistance state, and a uniformly conducting in high resistance state. The conducting may be the interface-type conducting path, which plays a key role in the resistive switching characteristics of the LSMO films.