Adsorption of substituted bistable [5]Phenacene Precursor on Ag(111)
Yu-Lun Hung1*, Paul Yu-Hsiang Yen1, Hideki Okamoto2, Germar Hoffman1
1Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
2Department of Chemistry, Okayama University, Japan
* Presenter:Yu-Lun Hung,
[5]Phenacene, a poly-aromatic hydrocarbon with five fused carbon rings shows interesting properties – high charge mobility and chemical stability – and is relevant for application in organic field effect transistors[1]. As such, substituted Phenacenes and their precursors are focus of our current research.
In a recent work, we studied Di-Naphtalene-Ethylene (DNE) with a structurally flexible Ethylene bridge, which can be activated by the local injection of hot electrons. Here, we address a functionalized precursor with a methyl-acetate group and the respective bistable ethylene bridge (DNEMAc).
In an initial study, DNEMAc is prepared on Ag(111) by thermal deposition[2]. Surfaces with one and two monolayers are investigated with Scanning Tunneling Microscopy at low temperatures. DNEMAc forms well ordered structures with two different phases present. A rich bias dependent intramolecular contrast can be observed. The contrast, which reflects a strong localization of occupied and unoccupied molecular states, can be traced back to the strongly ionic character of DNEMAc. With Oxygen being a strong electron acceptor, the naphtalene entities become electron donors. This property make connect way between the molecule and molecule become special.
We will give an interpretation of observed molecular structures, its properties and a comparison with previous results on the unsubstituted DNE.

[1]Song-Wen chen et al. Adsorption of Phenacenes on a Metallic Substrate: Revisited, J. Phys. Chem. C 2017, 121, 21, 11390-11398(2017)
[2] Yasuo Yoshida et al. Scanning tunneling microscopy/spectroscopy of picene thin films formed on Ag(111). J. Chem. Phys. 141, 114701 (2014)

Keywords: Scanning Tunneling microscope, Scanning Tunneling Spectroscopy