半导体表面上极薄材料和纳米自旋结构的计算研究与功能探索

With semiconductor electronic devices getting ever smaller, and two-dimensional materials, such as grapheme and MoS2, and surface functional nano-structures coming into action, quasi-two-dimensional materials and nano-structures on semiconductor surfaces become more and more important. This project is aimed to study single-unit-cell-thin materials and sub-monolayer spin nano-structures on semiconductor surfaces. Essentially, these are composite materials & structures made of single-unit-cell overlayers & sub-monolayer nano-structures and semiconductor substrates. We shall choose grapheme and other single-unit-cell-thin materials (usually different from corresponding bulk forms) as overlayers, and match semiconductor surfaces (including reconstruction) as substrates, and then explore and optimize their structures, study their electronic and magnetic properties, including electric field manipulation, and finally explore the relationship between their structures and functions. Putting suitable magnetic adatoms on appropriate semiconductor surfaces, we look for strong single-ion magnetic anisotropy and good interaction between spins, study their quantum dynamical behaviors, and seek promising spin systems that can be used to store and process information. Furthermore, we shall thereby seek novel electronic and spintronic devices. With our long-time effort and some preliminary research, we already have enough experience and capability and therefore shall certainly accomplish the tasks and goals of this project, making our contribution to the emerging field.

随着半导体电子器件越来越小型化，以及石墨烯与MoS2等二维材料和半导体表面上功能纳米结构的出现，半导体表面上的准二维材料和纳米结构变得越来越重要，本项目拟研究半导体表面上的单胞层厚度的材料和亚单层纳米自旋结构。这实际上是单胞覆盖层与亚单层纳米结构和半导体基底构成的复合材料与结构。我们拟选用石墨烯和其它合适的单胞层材料（通常与相应块体形态不同）作为覆盖层，配上适当的半导体表面（包括重构表面），通过第一原理计算探索和优化其结构，研究其电和磁性质、电场调控，探索其结构与性能的关系。在合适的半导体表面上放置适当的磁性原子，寻求强单轴磁各向异性和有利的自旋相互作用，研究其量子动力学行为，探索可用于信息存储和处理的自旋系统。进一步，开展新型电子和自旋电子学器件探索。通过多年的积累和一些前期工作，我们已经具备了足够的经验和能力，定会顺利完成项目任务、达到项目目标，为这个新兴领域做出应有的贡献。

随着半导体器件的尺度越来越小，场效应晶体管等器件的导电层需要越来越薄；石墨烯等高性能二维材料的出现，有望使得器件导电层进入亚纳米阶段。这些使得单胞层厚度的二维材料和结合半导体的异质结构的研究越来越重要。根据项目研究计划，我们研究了适合放在半导体上的二维电子功能材料、钙钛矿氧化物半导体中的界面/表面二维电子系统、基于半导体的量子自旋和电子系统，所用方法是第一原理计算和模型研究。我们发现了GaTeCl单层的高性能铁电性、PdSe2单层的载流子铁磁性、Mo6Br6S3的载流子高迁移率，还发现了应力诱导的BiTeI单层的各向异性Rashba效应和自旋流、KTaO3表面二维电子和空穴气的载流子类型反转、SrTiO3/YTiO3超晶格的电子绝缘体-金属相变，对金刚石NV自旋系统给出了一个快速磁场调控方案并且厘清了相应的非绝热几何相位，得到了半导体表面的量子自旋链的长尼尔态寿命。这些对于探索高性能的二维电子系统和纳米量子自旋系统具有参考价值。我们完成了项目研究任务，达到了项目目标，做出了应有的贡献。

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