Growth processes and control of two-dimensional structure of carboxylic acid-terminated self-assembled monolayers on Au(111)

The growth processes and solvent effects on the two-dimensional structure of self-assembled monolayers (SAMs) formed by 6-mercaptohexanoic acid (MHA) on An(111) were examined by scanning tunneling microscopy (STM) and contact angle (CA) measurements. The STM study revealed for the first time that the striped phases of 6-mercaptohexanoic acid (MHA) on Au(111) are preferentially formed near the step edges of gold terraces in the initial stage of SAM growth. In addition, it was found that MHA SAMs prepared from a polar aprotic solvent form a more well-ordered structure and a better hydrophilic surface than those prepared from a polar protic solvent. From this study, we clearly demonstrated that the properties of solvents are very important factors in controlling the two-dimensional structure of carboxylic acid-terminated SAMs.