基于拓扑绝缘体的自旋霍尔纳米振荡器的制备及其微波发射性能研究

With the advantages of small size, easy integration and wide-band current modulation, spin nano-oscillator（SNOs） is expected to be the basis of the next generation of microwave devices. The Spin Hall effect (SHE) - driven microwave emission nanostructured oscillators (SHNOs) have attracted a lot of attention due to their simple structure and easy preparation of synchronous arrays. At present, the microwave emission of SHNOs is faced with a series of shortcomings, such as low output power, large linewidth and high critical driving current. In view of this key problem, this project will prepare topological insulator / ferromagnetic thin film multilayers by using magnetron sputtering, and use the huge current-spin current conversion efficiency of topological insulator and the synchronous coupling effect between nano-oscillators to prepare high output power, high quality factor, low power consumption topological insulator based-SHNOs. At the same time, the influence of the synchronous effect on the microwave emission performance of the nano-oscillators will be studied, and the synchronous coupling mechanism between the nano-oscillators will be clarified. The development of this project will provide a new idea for the practical application of topological insulator, and provide a basis for the realization of high-performance microwave devices.

自旋纳米振荡器具有尺寸小、易于集成化和可以实现电流宽频调制等优点，有望成为下一代微波技术的核心元件。基于自旋霍尔效应（SHE）驱动微波发射的自旋霍尔纳米振荡器（SHNOs）由于结构简单和容易制备同步阵列受到人们的广泛关注。目前SHNOs器件的微波发射面临着功率较低、线宽较大和临界驱动电流偏高等一系列不足。针对这些关键问题，本项目提出采用磁控溅射制备拓扑绝缘体/铁磁薄膜多层膜，利用拓扑绝缘体巨大的电流-自旋流转换效率和纳米振荡器间的同步耦合效应，制备出高性能和低功耗的拓扑绝缘体-SHNOs，研究同步效应对纳米振荡器微波发射性能的影响规律，并探究拓扑表面态在同步耦合时的物理机制。本项目的开展将为拓扑绝缘体的应用提供新的思路，同时为实现高性能的微波器件提供基础。

基于自旋霍尔效应驱动微波发射的自旋霍尔纳米振荡器（SHNOs）具有尺寸小、易于集成化和可以实现电流宽频调制等优点，有望成为下一代微波技术的核心元件。本项目采用磁控溅射制备拓扑绝缘体/铁磁薄膜多层膜，利用拓扑绝缘体巨大的电流-自旋流转换效率，从而降低SHNOS驱动电流和器件功耗。.首先，利用室温磁控溅射制备出具有三角相Bi2Te3合金，基于自旋轨道-铁磁共振（ST-FMR）测得5nm PtBi2的自旋扭矩效率SOT 高达0.2，它的自旋霍尔电导约为105 ℏ/2e S/m, 与PtTe2和拓扑绝缘体等拓扑材料的自旋霍尔电导率相当。同时PtBi2 的电阻率比其它 Bi 基拓扑绝缘体材料的电阻率低得多，使得它更有利于降低SHNOS驱动电流和器件功耗。.其次，利用磁控溅射在Al2O3单晶衬底上制备出表明平整、高质量外延的Bi2Te3薄膜，利用自旋轨道-铁磁共振（ST-FMR）等手段测得Bi2Te3的自旋霍尔角为0.13左右。.综上，我们基于磁控溅射制备出高质量的 Bi2Te3、PtBi2 两种薄膜，具有较高的自旋霍尔角和电导率。本项目的开展为拓扑绝缘体是应用提供新的路径，同时为实现高性能的自旋霍尔纳米振荡器提供材料基础。