Ultra-low friction and patterning on atomically thin MoS2via electronic tight-binding

Abstract

Atomically thin two-dimensional molybdenum disulfide (MoS₂) is well known for its excellent lubrication characteristics and is usually used as a solid lubricant in diverse micro/nanoelectromechanical systems (MEMS/NEMS). The friction on atomically thin MoS₂ deposited on a SiO₂/Si substrate is reduced almost five times to achieve an ultra-low friction state (coefficient of friction nearly 0.0045) by rubbing the surface with an AFM tip under the electric field. The electric field leads to a shift and accumulation of charges at the interface between MoS₂ and the SiO₂/Si substrate. Then, electronic tight-binding with high interfacial bonding strength is experimentally found by the charges transferring during the rubbing process. The ultra-low friction state of atomically thin MoS₂ could attribute to the electronic tight-binding between MoS₂ and the SiO₂/Si substrate, which suppresses the atomic-scale deformation and limits the local pinning capability of MoS₂. The ultra-low friction state on atomically thin MoS₂ is patterned further by controllably regulating position, time, and electric field during the rubbing process. This approach can provide an additional channel to achieve ultra-low friction on MoS₂ related two-dimensional materials with semiconductor properties. The nanopatterning of ultra-low friction could promote and expand engineering applications of MoS₂ as lubricants in various MEMS/NEMS with nano-scale components.