Structures and stability of ferrocene derivative monolayers on ag(110): Scanning tunneling microscopy study

Dou RF, Zhong DY, Wang WC, Wedeking K, Erker G, Chi LF, Fuchs H

Abstract

A scanning tunneling microscopy (STM) study of an unsaturated long-chain- bridged diferrocene, Fc(CH2)(6)-HC=CH(CH2)(6)Fc (u-diFc, Fc = ferrocenyl), on Ag(110) reveals three ordered molecular phases, alpha, beta and beta'. It is found that the R and the, 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, beta' structure is analogous to the, 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 R to, beta' 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.