镶嵌金属纳米微粒铪基氧化物薄膜微结构调控的磁电性能

Today, the further scaling down and increase of memory density for the nonvolatile memory(NVM)device based on charge storage are becoming more and more difficult, and the multifunctional memory device is becoming the main trend for future research. Hf-based oxides exhibits both excellent dielectric properties and unexpected weak ferromagnetism at room temperature; where its excellent dielectric properties make it good candidate for next generation tunnel barrier in NVM devices, but the potential application of its magnetism is unclear due to its too weak saturated magnetic moment. If its saturated magnetic moments can be improved, it should be able to be applied in magneto-electric combined memory devices. Our pilot research work has demonstrated that embedding metal nanoparticles can increase the both charge storage and nanomagnetism properties of the Hf-based oxide film. In this project, through comparison work, we will identify those metal nanoparticles who can improve both the charge storage characteristics and magnetic properties of the Hf-base oxide film, and study the physical mechanism behind. Through optimizing the fabrication process and modifying the nanoparticles size and density, we will try to realize the magneto-electric charge storage induced memory in a single capacitor cell and study their coupling effect. The results may open another new approach to realize the new generation of multifunctional memory devices.

基于电荷存储的非易失性记忆体(NVM)器件在今天面临着尺寸难以更小，存储密度很难进一步提高的困境，多功能存储器件将成为未来研究的主流趋势。铪基氧化物同时具有优异的介电性能与奇特的室温弱铁磁性，优异的介电性能使其成为下一代NVM器件隧穿势垒层候选材料之一；而其室温弱铁磁性，却因饱和磁矩过小而应用前景不明。若能提高其室温饱和磁矩，则其有可能应用于未来的磁电多功能存储器件。我们前期研究发现镶嵌金属纳米微粒对铪基氧化物薄膜电荷存储特性和饱和磁矩都有所增益。因此我们拟通过对比实验，筛选出能同时增益薄膜磁/电性能的金属纳米微粒种类，先分别研究其对薄膜电荷存储特性和纳米磁性的增益影响以及物理机制；然后优化整合制备工艺，通过调控纳米微粒的尺寸以及分布密度，在同一个悬浮式栅极电容器结构中实现磁/电性能的共存；最后探测二者之间可能存在的耦合效应，为新一代磁电多功能存储器件提供新的研究思路。

随着现代社会生活的快速化和高度信息化，对下一代非易失性存储器件提出了尺寸更小，读写更快，存储容量更大，存储稳定性更高和功耗更低的要求, 以金属纳米微粒为存储节点，高介电氧化物为隧穿/栅控层的纳米浮栅电容器结构的电荷存储器件和氧化物电阻开关存储器件是有望实现以上要求的主要候选者。本项目主要研究了以下内容: (1)对比研究了硅基衬底上以铪基氧化物为隧穿/栅控层，金属Ag，半导体Ge和磁性金属Ni纳米微粒为纳米存储节点的电容器结构的电荷存储特性。通过优化制备工艺，在掺锗 HfOx薄膜中获得了3.2V的电荷存储窗口宽度和3.5×10^12/cm2的电荷存储密度，实验测量到5×10^4次稳定读写次数和长达10年的存储时效推算值，完全满足下一代非易失性存储器件的性能参数要求。在优化光辐照条件下，镶嵌Ni 纳米微粒HfOx薄膜的电荷存储窗口宽度从2V最高提高到7.2V，电荷存储密度从6.0×10^12/cm2提高到了3.44×10^13/cm2，提高了近一个数量级；(2) 研究了扫描电压幅度，薄膜厚度和测量温度对磁性氧化物r-Fe2O3和NiOx薄膜的电阻开关特性的影响。在优化制备条件下，既保持了可观的饱和磁矩，同时获得了>70的高低电阻比；(3) 通过调控氧分压，利用磁控溅射方法在氧化物衬底上生长出高质量的Pt外延薄膜，并以之为种子层，成功制备出Pt/NiOx外延异质堆栈结构，该结构具有高低电阻比大于20, 稳定循环次数大于5000次的优异电阻开关性能，可应用于下一代电阻开关存储器件; (4) 利用溶胶-凝胶法，旋涂法和磁控溅射法，将“有机-无机”杂化钙钛矿薄膜和掺镍HfOx薄膜复合在一起，形成无硅基的“1电池+1电容器”的构型，该器件在光辐照条件下可获得高低电阻比大于10^4，开启电压小于1V的电阻开关性能，相比传统电阻开关器件在高低电阻比和开启电压性能方面大幅提高，有望应用开发研究新型光敏电阻开关器件。