Influence of Molecular Ordering on Electrical and Friction Properties of ω-(trans-4-Stilbene)Alkylthiol Self-Assembled Monolayers on Au (111)
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- 作者：Yabing Qi ; Xiaosong Liu ; B. L. M. Hendriksen ; V. Navarro ; Jeong Y. Park ; Imma Ratera ; J. M. Klopp ; C. Edder ; Franz J. Himpsel ; J. M. J. Frchet ; Eugene E. Haller ; Miquel Salmeron
- 刊名：Langmuir
- 出版年：2010
- 出版时间：November 2, 2010
- 年：2010
- 卷：26
- 期：21
- 页码：16522-16528
- 全文大小：1096K
- 年卷期：v.26,no.21(November 2, 2010)
- ISSN：1520-5827
文摘
The electrical and friction properties of ω-(trans-4-stilbene)alkylthiol self-assembled monolayers (SAMs) on Au(111) were investigated using atomic force microscopy (AFM) and near edge X-ray absorption fine structure spectroscopy (NEXAFS). The sample surface was uniformly covered with a molecular film consisting of very small grains. Well-ordered and flat monolayer islands were formed after the sample was heated in nitrogen at 120 °C for 1 h. While lattice resolved AFM images revealed a crystalline phase in the islands, the area between islands showed no order. The islands exhibit substantial reduction (50%) in friction, supporting the existence of good ordering. NEXAFS measurements revealed an average upright molecular orientation in the film, both before and after heating, with a narrower tilt-angle distribution for the heated fim. Conductance-AFM measurements revealed a 2 orders of magnitude higher conductivity on the ordered islands than on the disordered phase. We propose that the conductance enhancement is a result of a better π−π stacking between the trans-stilbene molecular units as a result of improved ordering in islands.