TMD/石墨烯的叠层结构稳定性及其光电特性的应变调控研究

The successful fabrication of graphene through mechanical or chemical exfoliation and the findings of its novel properties attracted more and more research interests in two-dimensional (2D) crystals from the communities of physics, chemistry and material science all over the world. In fact, any bulk materials with layered structures and bonded through van der Waarls forces could be seperated into graphene-like 2D crystals. The typical one is transition metal dichalcogenides (TMDs). The elastic strain they can sustain exceeds 10%, much higher than those of the counterpart bulks. This provides the congenital condition to explore and utilize the coupling effects of mechanical/optical as well as mechanical/electronic properties of 2D crystals. Some research works have been conducted in this field, but mainly focused on the single-component systems. As for the hetergeneously layered structure with interlayer coupling, the behaviors under stress are extremely more complicated than those of the single-layer ones and, it can not be obtained through simple superposition or extrapolation. In this proposal, taking typical TMD/graphene heterogeneous structures as examples, we will systematically study the stress/strain effects on the structural stablity and the optical properties from both theoretical and experimental aspects. The stable configurations as well as the stable photoelectric properties under "internal strain coordination" and "external stress intervention" will be explored at first. Accordingly, we would like to analyze and uncover the changes in electronic states, band edges and the Dirac energy as a result of electron transfer across the heterogeneous interface, establish the relationship between the heterojunction nature and the external stress. Based on this, it is expected to illustrate the physical mechanisms for the enhanced photoelectric properties under both the interlayer coupling and strain effect. This might present us new ideas to develop high-performance photovoltaic cells, photocatalysis and photodetector devices and to engineer the physical properties by mechanical straining.

石墨烯的成功分离和新奇物性的发现极大推动了人们对二维晶体的研究热潮。超过10%的弹性应变极限是探索和利用其力/光和力/电耦合特性的先天特有条件。就此已有研究工作涉足，但多围绕单组元单片层结构来开展。具有层间耦合作用的异质叠层体系在外加应力作用下的行为远比单片层体系复杂，且不能进行简单叠加或推演。本项目拟以典型过渡族金属硫系化合物（TMDs）与石墨烯所形成的异质叠层结构为例，结合理论模拟计算和实验表征分析，考察并明确在层间"内应变协调"和"外应力干预"下的结构"稳态化"及其与光电功能特性"稳定化"的关系；研究和探讨界面电荷转移可能引起的电子态、带边位置及狄拉克能级的变化，建立TMD/石墨烯异质结属性与外加应力之间的关联关系；揭示在层间耦合与应变效应交互作用下TMD/石墨烯叠层结构的光电特性增强或调控的物理机制，为新型高效光伏、光催化、光探测器件的探索及其性能的应力/应变调控提供新思路。

石墨烯的成功分离和新奇物性的发现极大推动了人们对二维晶体的研究热潮。超过10%的弹性应变极限是探索和利用其力/光和力/电耦合特性的先天特有条件。本项目以典型过渡族金属硫系化合物（TMDs）与石墨烯所形成的异质叠层结构为例，考察并明确在层间“内应变协调”和“外应力干预”下的结构“稳态化”及其与光电功能特性“稳定化”的关系，已顺利完成了各项研究内容，达到预期目标。部分研究结果已在Journal of Materials Chemistry A, The Journal of Physical Chemistry Letters，Journal of Power Sources, Journal of Materials Chemistry C，Applied Physics Letters, Carbon, Physical Chemistry Chemical Physics等国际期刊发表学术论文62篇，其中SCI检索61篇，申请技术发明专利8件，授权技术发明专利3件。培养博士生8名，硕士生9名。应邀参加相关学术会议并作特邀报告8人次。取得的重要进展有：(1) 考察并阐明了二维晶体力致微结构转变特征及变形行为，揭示了拉伸应力致二维材料的褶皱结构形貌特征及其影响因素；(2) 阐明了单层MoS2电子态、磁化特性及晶格振动的应变效应和掺杂效应，发现掺杂原子最外层电子数的奇偶性是控制其磁性的本质因素，建立了掺杂原子之间的双交换与超交换竞争关系；(3)阐明了AlN/MoS2和MoS2/SiC二维异质结构电子态、磁极化及电输运特性的掺杂效应和界面效应，揭示了TMDs二维材料与金属的垂直/横向接触特性及界面电子的费米钉扎效应；(4) 采用SiC高温热解方法制备出高质量大面积的单层外延石墨烯并揭示了其生长机制，阐明了外延石墨烯与缓冲层及金属的交互作用机制，揭示了金属岛状结构择优生长的物理本质；(5) 制备出石墨烯/MoS(Se)2异质叠层结构并阐明了光催化特性增强机制，提出以导电性优异的多孔碳纤维纸为基体构建MoSe2/NiSe2二维复合结构的思路，该结构表现极高的电催化析氢性能及循环稳定性；(6) 以CeO2与石墨烯复合形成的纳米结构为例，发现界面结构及电子态对气敏特性也产生显著影响。充分揭示了界面和应力对于二维材料特性的调控作用，完成预期目标。