Tribological properties of suspended hexagonal boron nitride under electric field

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 stick-slip behavior to change from single-slip to multi-slip. Compared with the h-BN supported by the substrate, h-BN 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.