Tuning friction behaviors of supported nanofilms via multiscale roughness of underlying substrate

CC Xu and ZJ Ye and SM Hua and P Egberts, CARBON, 243, 120607 (2025).

DOI: 10.1016/j.carbon.2025.120607

Substrate roughness plays a critical role in governing the interfacial friction of supported nanofilms, yet the underlying mechanism remains unclear. Here, we systematically investigate how roughness affects the friction and hysteresis behavior of graphene and MoS2 films using atomic force microscopy (AFM) and molecular dynamics (MD) simulations. Experiments reveal that smoother substrates lead to lower friction and a distinct transition from positive to negative hysteresis. Phase imaging and contact stiffness measurements indicate that this transition corresponds to a sudden increase in nanofilm-substrate conformity. Simulations further show that in rough systems, two key factors contribute to enhanced positive hysteresis: persistently low interface conformity and a gradual, irreversible increase in nanofilm roughness during repeated sliding. In contrast, smooth substrates enable stable, highly conformal interfaces, resulting in negative hysteresis. Additionally, thicker nanofilms exhibit reduced conformability under the same roughness. These findings highlight roughness-governed conformity and morphological evolution as the dual mechanisms controlling nanoscale frictional behavior.

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