二维半导体量子阱超晶格结构与物性的原子尺度研究

The structural similarity among different semiconducting two-dimensional materials (2D) has made it feasible to construct high quality 2D lateral semiconductor heterostructures and superlattices via lateral epitaxy growth. This provides a way to fine tune the band structure and carrier transport properties of 2D semiconductors via interfacial coupling and quantum confinement effects, which is of great scientific significance to understand the structure-property relationships in 2D materials and to expand their applications in optoelectronics. In early 2018, we reported a novel mechanism for the growth of 2D semiconductor quantum well superlattices using misfit dislocations formed at the lattice-mismatched 2D hetero-interface (Science Advances 4, eaap9096, 2018), where the feature width of the quantum wells is comparable to the de Broglie wave length of electrons. This new class of 2D superlattices provides new opportunities for the use of quantum confinement effects to modulate the physical properties of 2D materials. This proposal explores the controlled growth of these novel 2D quantum well superlattices by optimizing growth conditions and probes the structure-propertiy relationships using the state-of-the-art low-voltage monochromated and aberration corrected scanning transmission electron microscopy (STEM) and ultra-low temperature scanning tunning microscope (STM). We propose a systematic atomic scale study of the atomic structure, chemical composition, lattice strain distribution, electronic structure and local optical properties of these 2D semiconductor quantum well superlattices using high precision quantitative STEM imaging and meV energy resolution electron energy-loss spectroscopy (EELS) techniques. These will allow us to explore the effects of interfacial coupling, quantum confinement, and lattice strain on the physical properties of 2D quantum well superlattices, and provide guidance for the design and optimization of novel 2D materials.

利用二维半导体材料晶体结构的相似性构筑二维异质结及二维超晶格结构，通过界面耦合作用和量子限域效应等对材料的能带结构和载流子输运特性进行精准调控，对于认识二维材料中的基本物理现象和规律以及拓展其在纳米光电子器件中的应用具有非常重要的科学意义。2018年初，我们报道了利用二维平面异质结界面处形成的失配位错催化生长二维半导体量子阱超晶格的新机制，所构筑的二维量子阱超晶格的特征宽度与载流子的德布罗意波长相当，为利用量子限域效应调制二维材料物性开启了新的方向。本项目通过优化生长条件探索二维量子阱超晶格的可控生长；结合低电压单色仪球差校正扫描透射电子显微学分析，在原子尺度深入研究二维量子阱超晶格的原子结构、化学成分、晶格应力、电子结构以及局域光学特性，探究界面耦合、量子限域效应、晶格应变对二维量子阱超晶格物性的精准调控，为新型二维材料的设计和优化提供重要基础支持。

利用二维异质结超晶格结构的界面耦合作用和量子限域效应等，对材料的能带结构和载流子输运特性进行精准调控，这对于认识二维材料中的基本物理现象和规律以及拓展其在纳米光电子器件中的应用具有非常重要的科学意义。本项目基于低电压单色仪球差校正扫描透射电子显微学技术，主要研究内容涵盖二维量子阱超晶格的可控生长、二维半导体量子阱超晶格的高精度定量结构分析、探索局域物性的实验测量并揭示材料物性和结构的本征关联。取得以下主要结果：1）利用低电压单色仪球差校正STEM的高精度成像，结合图像降噪及畸变消除技术，将基于STEM高分辨图像的原子定位精度提高到1-2皮米量级，用于分析量子阱和异质结等器件中的应变分布；2）优化生长条件探索二维量子阱超晶格的可控生长，利用不同旋转角的晶界作为模板实现量子阱超晶界的周期和取向调控，并首次获得量子阱网络结构，为量子阱及其超晶格在宏观器件中的应用奠定基础；3）综合多种电镜表征手段，包括原位加热技术、四维扫描透射电子显微技术、单原子精度、毫电子伏分辨的电子能量损失谱等，揭示二维材料的应力、结构和化学键合等对材料本征物性的调控机制。项目成果共发表高水平论文7篇，包括Nature、Nature Materials等，并有1篇论文在审稿、多篇论文在整理撰写。申请发明专利2项。