Fig. 2
Stress-activation length and crossover velocity. a Schematics of the shear-promoted thermally activated slip in the IS regime (σn ~ 200–400 MPa). b Stress-activation length λ obtained from fitting Eq.(2) to the velocity-dependent friction force in the IS regime. The error bars show the root-mean-square error of the fits. The region under the gray dashed line shows the range of λ in dry experiments, which is described here by the shear-promoted thermally activated slip of the surface atoms for comparison purposes. Tip radius = 150 nm. c Crossover velocities vc in the HS regime (σn > 400 MPa); tip radius = 100 nm. The results in b, c are shown for the selected CaCl2 concentrations displayed in the legends
