Self-assembly of semifluorinated $n$-alkanethiols on {111}-oriented Au investigated with scanning tunneling microscopy experiment and theory

The adsorption of semifluorinated alkanethiols on Au/mica was studied by scanning tunneling microscopy (STM). The adlayer structure produced is based on a $p(2×2)$ structure though lines of molecules displayed extensive kinks and bends. In addition, a considerable variation in the contrast of molecular features is found. Molecular modeling calculations confirm that, for the fluorinated thiols, inequivalently adsorbed molecules within a $p(2×2)$ registry are present, an aspect that endows the local structure of the adlayer with a higher flexibility in comparison to nonfluorinated thiols, where one adsorption site is strongly favored in a $(√3×√3)R30°$ structure. Simulated STM imaging on the optimized systems successfully recovered the effects on the molecular feature contrast induced by the flexibility of the fluorinated thiol adlayer.