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

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.