外电场下二维材料表面纳米摩擦机制与主动调控研究

二维材料优异的机械、电学和润滑性能应用于微/纳机电系统(MEMS/NEMS)中摩擦组件、移动部件和固体润滑层，有望为MEMS/NEMS表面粘着和摩擦问题提供解决方案，表面纳米摩擦动态可控十分重要。项目基于纳米摩擦声子电子能量耗散理论，提出通过外电场对二维材料载流子浓度控制进而对表面纳米摩擦主动调控方法；首先基于AFM测试外电场下二维材料表面粘着和纳米摩擦特性，归纳电场对二维材料表面纳米摩擦影响规律；然后研究电场对原子尺度粘滑行为、表面势垒和能量耗散影响，建立电场下二维材料表面原子尺度摩擦模型；进一步设计和微纳制造二维材料场效应器件，建立外电场下二维材料电输运特性和表面纳米摩擦性能关联，确立载流子浓度对表面纳米摩擦影响；最后探索外电场对二维材料表面纳米摩擦大小、动态和往复调控规律。项目将丰富和完善二维材料表面纳米摩擦理论，发展为MEMS/NEMS应用基于二维材料的主动设计与调控纳米摩擦表面。

Existed problems of adhesion and friction at the frictional interface in MEMS/NEMS limit the potential application as the dimension decrease to nanoscale. The atomically thin two-dimentional(2D) materials with excellent tribological, electrical and mechanical properties have much potential application as moving parts, sliding surface and solid lubricant in micro/nano-electromechanical systems (MEMS/NEMS). To improve the performance and extend the lifetime of MEMS/NEMS, the nanofriction mechanism and actively regulating the nanofriction of atomically thin 2D materials is proposed using external electrical field based on electron and photon energy consumption.Firstly, the nanotribological properties including adhesion and nanofriction of the atomically thin 2D materials on silicon substrate with 300nm silicon oxide(Si/SiO2) will be investigated using the calibrated atomic force microscopy(AFM) tip under the electric field with different size and direction. Then, the influence law of electric field on the adhesion and nanofriction of the atomically thin 2D materials will be summarized further. The nanofriction on atomically thin 2D materials including conductive, semi-conductive, insulative and super-conductive such as graphene, molybdenum disulfide (MoS2), niobium diselenide (NbSe2), and hexagonal boron nitride(h-BN) with different thickness will be investigated further. Secondly, a systematic and abundant measurements of atomic-scale frictional behavior on atomically thin 2D materials with evidently different electric properties will be conducted under electric field. The atomic-scale stick-slip frictional behavior on atomically flat surfaces of atomically thin 2D materials including the amplitude and distance will be measured to investigate the energy dissipation of the lateral force acting on an AFM tip sliding forward and backward. The interaction between the tip and the substrate will be modeled by a surface corrugations potential which has a sinusoidal form for a perfectly atomically thin 2D materials. An extension of the original Prandtl-Tomlinson model that the tip may move in two-dimensions will be proposed and established to explain the effects of electric field on atomic-scale friction behavior. Thirdly, the quantitative analysis of energy dissipation including electronic and photonic dissipation can provide us a deeper and more accurate comprehension of the nanofriction. The field effect transistor based on 2D materials will be fabricated using the micro/nano fabrication process. The electron transport and nanofriction of atomically thin 2D materials will be investigated under the same electric field. The nanofriction on the surface of atomically thin 2D materials with controllable electron carrier will be studied using the AFM. The quantified mapping between the nanofriction and electron transporting of 2D materials with typically different electric properties will be built to assure the role of electron carrier in nanofriction of atomically thin 2D materials. Lastly, regulating of nanofriction on atomically thin 2D materials will be optimized base on the electric properties of the 2D materials by change the insulting materials and thickness. Also the systematic evaluation for regulating nanofriction of atomically thin 2D materials will be established by adjusting the electric field. The controllable regulation of the nanofriction on atomically thin 2D materials with electronic structure will be obtained. The success of this project will also make significant impacts on the efficient and reliable utilization of atomically thin 2D materials as solid lubricants in MEMS/NEMS. Also the fulfillment of this project will be of great importance of better and deeper fundamental understanding and enriching nanotribological fundamentals of atomically thin 2D materials.