INDIRECT VISUALIZATION OF DEFECT STRUCTURES CONTAINED WITHIN SELF-ASSEMBLED ORGANOMERCAPTAN MONOLAYERS - COMBINED USE OF ELECTROCHEMISTRY AND SCANNING-TUNNELING-MICROSCOPY

Adventitious defects within self-assembled monolayers of 1-octadecanethiol confined to Au substrate have been studied by a new method, which takes advantage of the high spatial resolution of scanning tunneling microscopy (STM) and the molecular specificity of electrochemistry. The method permits direct visualization of the defect density and provides information about the chemical and structural nature of the defects. CN- was used to electrochemically etch Au from surface regions near defects. This leads to the formation of triangular etch pits, which exhibit a uniform in-plane orientation. A point-defect model is proposed to explain the orientation of the triangular pits. The model also predicts that the organomercaptan molecules occupy particular 3-fold hollow sites on a Au(111) surface.