Nanoscale friction behavior of monolayer MoxW1−xS2 alloy

We synthesized MoxW1−xS2 alloy by chemical vapor deposition. Raman characterization results showed that the sample is a monolayer with a special structure which transforms from MoS2 to WS2. Atomic force microscopy measurements suggested that the friction force decreases from MoS2 region to WS2 region. Molecular dynamics simulations verified that interfacial interaction is the determining factor resulting in the variation in the friction properties of monolayer MoxW1−xS2. Green’s function calculations demonstrated that phonons are excited at both washboard frequency and its harmonics. Besides, the number and total energy of the excited phonons were calculated. The decreasing of the number and total energy of the excited phonons with the weakening interfacial interaction, leading to the decreasing dissipated energy and reduced friction force.