二维晶体材料表面结构-性能耦合与调控的物理力学研究

Two dimensional crystal materials such as graphene and hexagon boron nitride (h-BN) hold great potential for various applications. However, surface geometry and defects,surface adsorption and wetting as well as multi-field coupling significantly influence the actual properties and behaviors of those dimensional materials when they are integrated into nano-electromechanical system (NEMS). By using and combining mechanical modeling, molecular dynamics simulations, first-principles calculations, and experimental methods, this proposal is to extensively study and investigate how to modify and control surface structure and properties of graphene and h-BN under coupled multi fields. The main research includes surface wrinkles and defects as well as their influence on the electronic and mechanical properties of substrate-supported graphene and h-BN in the presence of thermal, mechanical and electric fields, and the surface adsorption and wettability properties of substrate-supported two-dimensional crystals under coupled multi fields. Our studies are to unveil the mechanisms for external field modifying surface morphology, and tuning the physical and mechanical properties of substrate-supported two-dimensional crystals by surface wrinkle, defect and adsorption. Furthermore, we will present the feasible ways to change and control the surface adsorption and wettability of two-dimensional crystals by considering the effects of temperature, wrinkles, electric field and charge injection. The corresponding works and findings will prompt advance in nanoscale physical mechanics and provide new routes for the development of novel nanodevices based on two-dimensional crystal materials.

石墨烯、六方氮化硼等类石墨烯二维晶体是目前最具应用潜力的纳米材料。本项目针对这类二维晶体材料在纳机电系统应用时所面临的表面结构影响与性能调控等实际问题，拟采用力学建模、分子动力学模拟、基于量子力学的第一原理计算，并结合实验表征与测试等多学科方法，对力电热等多场耦合条件下的基底支撑石墨烯、六方氮化硼表面结构和形貌控制及对自身性能影响、改变和控制其表面吸附和润湿性能、表面吸附、外场与表面结构变化的耦合作用对二维晶体物理力学性能影响等重要的科学问题进行深入研究。揭示利用表面形貌变化与外场耦合作用调控类石墨烯二维晶体力学、电学性能的机制，揭示褶皱、缺陷等结构形貌因素与电场、电荷注入、力场等外场影响和改变基底上二维晶体表面吸附和润湿性能的原理；揭示利用表面吸附和基底、电场、电荷注入等多场耦合作用调控二维晶体力学和电学性能的原理和途径。为基于类石墨烯材料的纳机电系统的发展和创新提供理论依据和基础。

本项目采用力学建模、分子动力学模拟、基于量子力学的第一原理计算对二维晶体材料在纳机电系统应用时所面临的表界面结构影响与性能调控等重要的科学问题进行深入研究。发现铜基底上的六方氮化硼表面吸附O3和O-H2时会表现出铁磁性、反铁磁性和亚铁磁性，以及镍和铜基底上的六方氮化硼表面氧化后会使水分子发生分解，从而形成羟基化的六方氮化硼；发现了氧化和氟化可以显著降低公度堆垛的石墨烯和氮化硼之间层间滑动的能垒；提出了估算少层石墨烯和六方氮化硼弯曲刚度的方法；揭示了受限于石墨烯与铜基底之间的单层水在低温和室温下的结构变化和摩擦性能变化规律；揭示了“双面神”过渡族金属硫族化合物（TMD）双层的摩擦压电性和单层TMD的挠曲电效应。相关研究结果为基于二维晶体材料的新型纳功能器件和纳机电系统的设计和构筑提供了新的原理和思想。本项目到目前为止已在Nano Energy、J. Phys. Chem. Lett.等国际刊物上发表11篇SCI学术论文。项目负责人2016年入选江苏省第五期“333高层次人才培养工程”第三层次；2016年获得国家自然科学基金优秀青年科学基金和江苏省自然科学基金杰出青年基金；2018年入选江苏省“333高层次人才培养工程”第二层次；2017年入选教育部“长江学者奖励计划”青年学者。