基于CeO_(2-x)-TiO_(2)薄膜厚度的数模阻变转换机理

Digital-to-analog resistive switching depending on thickness of CeO_(2-x)-TiO_(2) films

采用溶胶凝胶法和旋涂工艺在FTO衬底制备阻变层CeO_(2-x)-TiO_(2)薄膜,通过在CeO_(2-x)-TiO_(2)薄膜表面热蒸镀Al电极制备Al/CeO_(2-x)-TiO_(2)/FTO阻变器件,采用XRD和XPS表征CeO_(2-x)-TiO_(2)薄膜的晶相组成和晶体结构。结果表明:阻变层中主要由TiO_(2)和CeO_(2-x)组成。与Al/CeO_(2)/FTO器件相比,Al/CeO_(2-x)-TiO_(2)/FTO阻变器件的电学性能得到提升。I-V测试表明Al/CeO_(2-x)-TiO_(2)/FTO器件具有无初始化过程的双极性阻变特性。对不同CeO_(2-x)-TiO_(2)厚度下的阻变器件进行电学分析,研究表明Al/CeO_(2-x)-TiO_(2)/FTO器件在不同CeO_(2-x)-TiO_(2)膜厚下其低阻态呈欧姆导电机制。随着CeO_(2-x)-TiO_(2)厚度的增加,高阻态的阻变机制会发生本质变化,器件的阻变机制从氧空位导电细丝机制转变为缺陷对电荷的捕获/释放机制。研究发现Al/CeO_(2-x)-TiO_(2)界面处的AlO_(x)层是阻变机制转变的关键,AlO_(x)层的增厚使器件从“数字型”转变为“模拟型”。

The resistive switching layer of CeO_(2-x)-TiO_(2) film was prepared on the FTO substrate by the sol-gel method and spin coating technique,and the Al/CeO_(2-x)-TiO_(2)/FTO resistive switching device was fabricated by depositing thin Al top electrode on the surface of the CeO_(2-x)-TiO_(2) film.The crystal phase composition and crystal structure of CeO_(2-x)-TiO_(2) thin films were characterized by XRD and XPS.The results show that the resistive switching layer is mainly composed of TiO_(2) and CeO_(2-x).Compared with Al/CeO_(2)/FTO devices,the electrical performance of Al/CeO_(2-x)-TiO_(2)/FTO device is improved.I-V test shows that Al/CeO_(2-x)-TiO_(2)/FTO device has bipolar resistance variation characteristics without forming process.The resistive behavior with different CeO_(2-x)-TiO_(2) thicknesses was carried out.The results show that the low resistance state of Al/CeO_(2-x)-TiO_(2)/FTO device shows ohmic conduction mechanism under different CeO_(2-x)-TiO_(2) film thicknesses.As the thickness of CeO_(2-x)-TiO_(2) increases,the essential change of resistance mechanism occurs in high resistance state.The resistance mechanism of the device changes from oxygen vacancy conductive filament mechanism to charge trapping/releasing mechanism by defect controlled.It was found that the AlO_(x) layer at the Al/CeO_(2-x)-TiO_(2) interface is critical to the transformation of resistance mechanism,and the thickness of AlO_(x) layer changes the device from“digital type”to“analog type”.