Structures and Stability of Ferrocene Derivative Monolayers on Ag(110): Scanning Tunneling Microscopy Study

Abstract

A scanning tunneling microscopy (STM) study of an unsaturated long-chain-bridged diferrocene, Fc(CH2)6HCCH(CH2)6Fc (u-diFc, Fc = ferrocenyl), on Ag(110) reveals three ordered molecular phases, α, β, and β‘. It is found that the α and the β phase are predominant on the ordered structures with the Fc group neighboring to the center of the hydrocarbon chain in the former phase but with the Fc group arranging into a row-like structure in the latter phase. High-resolution STM images also show that the β‘ structure is analogous to the β phase but is not well-defined and exhibits the zigzag shape because of the variable distance between two neighboring molecular rows and molecular arrangement shifted along the molecular row. Interestingly, the irreversible phase transition from α to β‘ has been observed in the recorded regions by using the real-time STM. On the basis of the experimental results, three molecular models are provided, and the stability of these three structures has been investigated as well.