Two-Dimensional Phase Diagram of Decanethiol on Au(111)

On the basis of variable-temperature ultrahigh vacuum scanning tunneling microscopy data, we propose a two-dimensional phase diagram of monolayer decanethiol on Au(111). Four triple-point temperatures were determined: T1 at ≈27 °C, T2 at ≈33 °C, T3 at ≈35 °C, and T4 at ≈56 °C. T1 defines the lowest temperature melting point, and T4 defines the temperature above which striped phases are metastable. These data provide a fundamental framework to understand and control mesoscale monolayer structure; moreover, they provide fundamental insight into the two-dimensional phase behavior of molecules with many degrees-of-freedom.