金属基底层上NiO(111)外延薄膜的变温电阻开关特性与隧穿机制

利用射频磁控溅射方法在Pt层上制备了沿<111>晶向外延生长的NiO薄膜,研究了其晶体微结构和变温电阻开关特性.微结构观测分析发现, NiO(111)薄膜与Pt层满足"立方-立方"晶格生长关系.在周期性外电场作用下,薄膜中氧空位的定向漂移和电极附近银离子的氧化还原反应相互促进,使得在较低的翻转电压下即可在薄膜中形成周期性导通/截断的氧空位导电丝通道,从而使得Ag/NiO(111)/Pt存储单元在室温至80°C测试温度范围里的电流-电压曲线均呈现稳定的双极性电阻开关特性.运用Arrhenius作图法以及肖特基热激发隧穿公式拟合薄膜高阻态电流-温度曲线符合线性关系,表明薄膜高阻态漏电流符合肖特基热激发隧穿机制.

Temperature-dependence of resistive switching behaviors and tunneling mechanism of (111) epitaxial NiO films on metal seed layer

Since 2000,resistive switching random access memory(ReRAM)based on binary metal oxide has become one of potential candidates for next generation of nonvolatile memory due to its simple structure,high writing/read speed(~5 ns),good endurance(~109 cycles),long retention time(~10 years)and low energy consumption(~dozens of pJ).NiO has been extensively studied as one of promising materials applied for commercial ReRAMs.However,it exhibits diverse resistive switching(RS)behaviors that heavily dependent on fabrication technologies,methods and conditions.Up to now,RS performances and mechanisms of polycrystalline NiO films have been extensively investigated,while there are few discussions on RS performances of epitaxial NiO films,especially on metal seed layer.On the other hand,with the expanding scope of human activities,researches on stabilities of ReRAM devices under extreme environmental conditions are necessary.In this paper,temperature-dependence of RS behaviors and tunneling mechanism of epitaxial NiO(111)films on Pt seed layers have been discussed.A set of highly textured NiO(111)films on Pt seed layers were prepared by means of Radio Frequency magnetron sputtering.Their microstructural characteristics and temperaturedependence of RS performance were investigated.Microstructural investigation demonstrated the"cube-to-cube"lattice relationship of NiO(111)/Pt(001)interfaces.Under the applied electric field,the drift of oxygen ions in NiO film and the redox of Ag ions near upper electrodes result in the formation/rupture of oxygen-vacancy conductive filaments at a set/reset voltage lower than±1 V.Moreover,current-voltage(I-V)curves of Ag/NiO(111)/Pt memory cells exhibit stable bipolar switching behaviors in the temperature range from RT to 80℃.Moreover,their Arrhenius form(ln I vs.1000/T)and Schottky tunneling(ln(I/T^2)vs.1000/T)plots are the best linear fitting relationship.It reveals that the leakage current of Ag/NiO(111)/Pt memory cell on high resistance state can be explained by the Schottky tunneling mechanism.