电场下悬浮六方氮化硼摩擦特性的研究

Tribological properties of suspended hexagonal boron nitride under electric field

六方氮化硼(hexagonal boron nitride, h-BN)因其良好的润滑性和绝缘性,在微纳机电系统中有巨大的应用潜力.本文通过基底刻蚀的工艺,在SiO_2/Si基底上制备了微孔阵列,然后将h-BN转移到微孔基底上形成悬浮结构,利用原子力显微镜研究电场对悬浮h-BN摩擦特性的影响.结果表明:悬浮状态的h-BN的表面摩擦力小于有基底支撑的h-BN的表面摩擦力,原因是更大的面内拉伸削弱了褶皱效应.电场作用下,针尖与h-BN之间的静电相互作用增强,悬浮h-BN表面的摩擦力随偏压的增大而增大,且正偏压的影响大于负偏压的影响.同时,在电场下针尖在悬浮h-BN表面的黏滑行为出现单步黏滑向多步黏滑的转变.此外,与有基底支撑的h-BN相比,悬浮状态的h-BN受电场的影响更大,这是由于针尖与基底界面距离的缩小以及基底氧化层的缺失导致静电力增强.本文提出了通过施加外电场来调节悬浮h-BN表面摩擦的方法,对研究二维材料摩擦特性提供了一定的理论指导.

Hexagonal boron nitride(h-BN)has huge potential applications in micro-nano electromechanical system due to its good lubricity and insulation.In this paper,a microporous array is prepared on a SiO2/Si substrate by the substrate etching process,and then the h-BN is transferred to the microporous substrate to form a suspension structure.The effect of electric field on tribological properties of suspended h-BN is studied by atomic force microscopy.The results show that the friction of the suspended h-BN is smaller than the friction on the h-BN supported by the substrate,because the greater in-plane stretch weakens the puckering effect.The electric field increases the friction of the suspended h-BN,and the influence of positive bias is greater than that of negative bias.The application of the electric field increases the electrostatic force on the tip,thereby increasing the additional load and the interface barrier in the friction process.The electric field causes the stickslip behavior to change from single-slip to multi-slip.Compared with the h-BN supported by the substrate,hBN in the suspended state is strongly affected by the electric field.The reduction of the interface distance and the absence of the substrate oxide layer lead the electrostatic force to increase.This paper proposes a method to adjust h-BN’s friction by electric field,which provides theoretical guidance for studying the friction characteristics of two-dimensional materials.