Cu/TiO_2/ITO薄膜元件阻变性能与机理研究

Resistive switching behaviors and mechanism study on Cu/TiO_2/ITO element

以磁控溅射方法沉积TiO2薄膜和Cu上电极层,制备Cu/TiO2/ITO阻变存储器元件。采用原子力显微镜、X射线衍射仪、X射线光电子能谱仪对薄膜材料进行性能表征,测试结果表明:TiO2薄膜表面平整、致密;结构以非晶为主,仅有少量金红石相TiO2(110)面结晶;钛氧比为1:1.92(at%),说明薄膜内部存在少量氧空位。在阻变性能测试中,元件呈现双极阻变现象,阻变窗口值稳定,数据保持特性良好,但未出现Forming过程。通过对阻变元件I-V曲线线性拟合结果的分析,得出阻变机理由导电细丝理论和普尔-法兰克效应共同控制。进一步分析发现,被氧化的Cu离子在偏压作用下很容易在TiO2薄膜内迁移并形成直径较大且较为稳定的导电细丝。

Magnetron sputtering was utilized to prepare Cu/TiO2/ITO resistive random access memory （RRAM）; including TiO2 film and Cu top electrode layers. The film was characterized by atomic force microscopy （AFM）, X-ray diffraction （XRD）and X-ray photoelectron spectroscopy（XPS）. Testing results showed that the surface morphology of TiO2 film is smooth and dense, the structure of the film is mainly amorphous phase with a small amount of crystallized futile TiO2（ 110）planes, and the ratio of titanium and oxide is 1：1.92 （at % ）meaning there are a few oxygen vacancies in the film. Testing results of resistive switching behaviors indicated the element displayed bipolar resistive switching property, stable resistive switching window and good data retention although no Forming process existed. Through the analysis of I-V curve linear fitting results, resistive switching mechanism was detected as common controlled by conduction filament theory and Poole-Frenkel effect. It was also found that oxidized Cu ion is very easy to migrate in the TiO2 film under bias and then to form stable conducton filament with large diameter.