基于Au/TiO_2/FTO结构忆阻器的开关特性与机理研究

Resistive switching characteristics and resistive switching mechanism of Au/TiO_2/FTO memristor

采用简单的一步水热法在FTO导电玻璃上外延生长了锐钛矿TiO_2纳米线,制备了具有Au/TiO_2/FTO器件结构的锐钛矿TiO_2纳米线忆阻器,系统研究了器件的阻变开关特性和开关机理.结果表明,Au/TiO_2/FTO忆阻器具有非易失的双极性阻变开关特性.同时,在103s的时间内,器件在0.1 V的电阻开关比始终保持在20以上,表明器件具有良好的非易失性.此外,器件在低阻态时遵循欧姆导电特性,而在高阻态时则满足陷阱控制的空间电荷限制电流传导机制,同时提出了基于氧空位导电细丝形成与断开机制的阻变开关模型.研究结果表明Au/TiO_2/FTO忆阻器将是一种很有发展潜力的下一代非易失性存储器.

Resistance random access memory is regarded as one of the most promising candidates for the future nonvolatile memory applications due to its good endurance, high storage density, fast erase speed and low power consumption.As one of the most important transition-metal oxides, the anatase TiO2 has received intense attention due to its inexpensive cost, strong optical absorption, favorable band edge positions and superior chemical stability. In the last decade, the nanometer-sized TiO2 has been shown to exhibit a wide range of electrical and optical properties, such as nanoscale electronics and optoelectronics, which rely mainly on the unique size and shape. Recently, various anatase TiO2 based devices such as the anatase TiO2 nanotube based memristor and the anatase TiO2 nano-film based memristor have been intensively studied due to their nonvolatile resistive switching performances. Furthermore, many conduction mechanisms have been used to elucidate the resistive switching behaviors of the anatase TiO2 based devices. However, the direct growth of anatase TiO2 nanowire arrays（NWAs） on the FTO substrate is still a challenge since there exists a large lattice mismatch of about 19% between the anatase TiO2 NWAs and the FTO substrate. Moreover,the Au/TiO2/FTO based device has not been reported and the resistive switching mechanism of the anatase TiO2 NWAs based memristor is still unclear. In this work, the anatase TiO2 NWAs with（101） preferred orientation are successfully grown on the FTO substrate by a facile one-step hydrothermal process. The resistive switching characteristics and resistive switching mechanism of the as-fabricated Au/TiO2/FTO memristor are investigated systemically. The result indicates that the Au/TiO2/FTO memristor exhibits nonvolatile bipolar resistive switching behavior. Meanwhile, the resistance ratio between high resistance state and low resistance state exceeds 20 at 0.1 V,which can be maintained over 103 s without significant degradation. In addition, the conduction mechanism of the low resistance state is governed by the ohmic conduction mechanism, while the trap-controlled space charge limited current conduction mechanism dominates the high resistance state. The resistive switching model of the Au/TiO2/FTO memristor is developed, and the resistive switching mechanism could be attributed to the formation and rupture of the conductive filaments relating to the localized oxygen vacancies. It demonstrates that the Au/TiO2/FTO memristor may be a potential candidate for the future nonvolatile memory applications.