应变和掺杂对二维过渡金属硫族晶体物性调控的理论研究

Two-dimensional materials are attractive for use in next-generation nanoelectronic devices because, compared to one-dimensional materials, it is relatively easy to fabricate complex structures from them. The most widely studied two-dimensional materials is graphene, both because of its rich physics and its high mobility. However, graphene does not have a bandgap, which is essential for many applications. Recently, it was found that single-layer MoS2 crystal is a direct semiconductor with a band gap of 1.8 eV and presents rich physical properties,which ignite intense research interests on two-dimensional transition metal dichalcogenides (TMDCs) experientally and theoretically. Although there are some theoretical and experimental researches for them, it is still lack of enough theoretical research for understanding their physical properties. This project will systematically and deeply study the structural, electronic, and dynamical properties of stressed and doped TMDCs using the first-principles methods in conjunction with structural prediction scheme based on the evolusionary algorithm. In detail, we will firstly determine the stable structures of systems by using evolusionary algorithm. When determining the stable structure, we will discuss the influence of temperature and anharmonic effect. Then, electronic structure calculations will be performed to discern bandgap's feature modulated by strain and thus disclose stress-induced phonon soften behavior which points to peculiar phase transition. Further, we will explore optimum dopant concentration and mechanism of doping and co-doping controlling photocatalysis. Fourthly, we will discuss superconductivity behavior of doped TMDCs and find the relation between critical temperature and layer numbers. Lastly, we will uncover the law of molecular obsorbed on surface of TMDCs by calculating volt-ampere characteristic curve and Raman spectrum. All these results will serve as a theoretical basis for experimental researches on TMDCs and for designing field-effect transistors, gas detectors, sensors, and nanometer quantum coherent devices.

对二维晶体的物性及其性能调控的研究是近年来多学科领域研究热点。最近，实验上成功剥离单层MoS2晶体，其良好的物理性能，使其在纳米电子学、光电子学和谷电子学等方面具有重要应用。尽管人们对其已进行一定的研究，但在应变和掺杂调控电子结构和物性方面的研究仍较为薄弱。本项目拟利用第一性原理方法，结合遗传算法，围绕应变和掺杂对二维过渡金属硫族晶体物性的调控这一关键科学问题展开系统而深入的理论研究。在确定结构的基础上，逐步揭示应变和掺杂对结构、电子和动力学行为的调控机理。研究内容包括：确定应变对带隙的调制行为；揭示应力引起的结构相变行为；确定掺杂对光催化分解水制氢和制氧的调控机理和最佳掺杂浓度；揭示掺杂引起的超导电性的机制，确定超导临界温度与掺杂浓度间关系；揭示分子吸附特性，确定伏安曲线；探索温度效应和非谐效应的影响。本项目可为后续的研究和工业应用提供理论支撑，为新材料和新能源领域的发展提供知识储备。

对二维晶体的物性及其性能调控的研究是凝聚态物理领域研究热点。最近，实验上成功剥离单层MoS2晶体，其良好的物理性能，使其在纳米电子学、光电子学和谷电子学等方面具有重要应用。本项目利用第一性原理方法，结合遗传算法，围绕应变和掺杂对二维过渡金属硫族晶体和单层黑磷晶体的物性的调控这一关键科学问题展开系统而深入的理论研究。在确定稳定结构的基础上，揭示了应变对结构、电子和动力学行为的调控机制。研究内容包括：确定应变对带隙的调制行为；揭示应力引起的结构相变行为；确定光催化分解水制氢和制氧的调控机理和最佳掺杂浓度。我们指出特定应变条件下的单层ReS2和单层黑磷是良好的光催化剂。应光催化科学与技术期刊编辑邀请，撰写综述论文对二维单层材料在光催化领域应用进行了评述。此外，我们探讨了压力对Ca-C、LiC6、KN3、Ca2Si、Zn-O和YB4等系统的结构、动力学和电子特性的调制作用。对于Ca-C系统，我们确定了压力下的热动力学稳定相图，预测了5个热动力学稳定化合物，其中Ca2C和Ca2C3被实验所证实。本项目研究成果可为后续的研究和工业应用提供理论支撑，为新材料和新能源领域的发展提供知识储备。