Self-assembly and scanning tunneling microscopy tip-induced motion of ferrocene adamantane trithiolate adsorbed on Au(111)

We have studied the self-assembled monolayers (SAMs) of adamantane-based trithiolate, which consists of a ferrocene derivative at the head (ferrocene adamantane trithiolate; ferrocene-ATT), on Au(111) using low temperature scanning tunneling microscopy (STM). It was found that the adsorption behavior of ferrocene-ATT is similar to that of bromine adamantane trithiolate (BATT) adsorbed on Au(111). This indicates that adsorption of adamantane-based trithiol is controlled by three legs (CH₂S) connected to bridgehead positions of the adamantane cage. Molecules, which form an ordered structure, are stable under low-bias-voltage scanning, i.e., a sample bias voltage lower than 1 V. STM tip-induced diffusion, however, was observed both for small clustered molecules and for molecules bound around the edge of an ordered molecular island. Furthermore, applying a high bias voltage (5 V) resulted in the destruction of SAMs structures.