Displacement Processes of 1-Adamanetanethiol Self-Assembled Monolayers on Au(111) by 1-Hexanethiol

Displacement processes of pre-adsorbed 1-admanetanethiol (ADT) self-assembled monolayers (SAMs) on Au(111) by 1-hexanethiol (HT) at room temperature were investigated by scanning tunneling microscopy (STM) and cyclic voltammetry (CV). Molecular-scale STM imaging clearly revealed that phase transitions from the (7 x 7) phase for ADT SAMs to the c(4 x 2) phase for HT SAMs via intermediate phase including bright aggregated islands and disordered phase. Moreover, it was found that ADT SAMs were completely displaced by HT molecules with a short hexyl chain within an hour. The CV measurements showed that cathodic peaks for SAM-modified Au(111) electrodes as a function of displacement time were varied with the structural change of displaced SAMs. Our results provide new insight into understanding the displacement processes of ADT SAMs on Au(111) by HT.