Friction on a single MoS2 nanotube
1 Jozef Stefan Institute, Jamova 39, Ljubljana SI-1000, Slovenia
2 Center of Excellence NAMASTE, Jamova 39, Ljubljana SI-1000, Slovenia
Nanoscale Research Letters 2012, 7:208 doi:10.1186/1556-276X-7-208Published: 10 April 2012
Friction was measured on a single molybdenum disulfide (MoS2) nanotube and on a single MoS2 nano-onion for the first time. We used atomic force microscopy (AFM) operating in ultra-high vacuum at room temperature. The average coefficient of friction between the AFM tip and MoS2 nanotubes was found considerably below the corresponding values obtained from an air-cleaved MoS2 single crystal or graphite. We revealed a nontrivial dependency of friction on interaction strength between the nanotube and the underlying substrate. Friction on detached or weakly supported nanotubes by the substrate was several times smaller (0.023 ± 0.005) than that on well-supported nanotubes (0.08 ± 0.02). We propose an explanation of a quarter of a century old phenomena of higher friction found for intracrystalline (0.06) than for intercrystalline slip (0.025) in MoS2. Friction test on a single MoS2 nano-onion revealed a combined gliding-rolling process.
PACS, 62.20, 61.46.Fg, 68.37 Ps