Study on the friction characteristics of supported and suspended h-BN flake based on AFM

Abstract The realization of ultra-low friction is one of the core goals for promoting the development of micro-nano electromechanical systems (M/NEMS). Among them, the use of suspended two-dimensional materials is a key technical approach to achieving this goal. Hexagonal boron nitride (h-BN) has shown great application potential in this field due to its excellent lubricity and insulation. In order to explore the friction characteristics of suspended h-BN flake and the traditional support state. In this study, microporous arrays were prepared on SiO2/Si substrates through an etching process. Then, h-BN flakes were transferred to the microporous region (forming a suspended state) and the non-porous region (forming a supporting state) using a mechanical stripping method. The friction characteristics of the flakes in two states were investigated using atomic force microscopy (AFM). The experimental results show that the friction coefficients of h-BN flakes in suspension state and support state are 0.0007909 and 0.002, respectively. The friction coefficient of the suspension state is significantly reduced by approximately 60.5%, exhibiting improved anti-friction performance. According to the analysis, the ultra-low friction mechanism is attributed to the in-plane stretching effect caused by the suspension structure. This effect significantly reduces the wrinkles of the flakes, thereby decreasing the real contact area between the AFM tip and the sample. This study provides an important experimental basis for the application of h-BN as a high-performance lubricating material in M/NEMS.