Observation of stable mixed alkanethiolate-chloride adlayer on Ag(1 1 1): structural correlation with pure alkanethiolate monolayers |
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Authors: | Mitsuo Kawasaki Hiromichi Nagayama |
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Affiliation: | Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Katsura, Nishigyo-ku, Kyoto 615-8510, Japan |
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Abstract: | The self-assembly of 1-alkanethiols, CH3(CH2)n−1SH (n=2-16), on Ag(1 1 1) film initially covered with a native oxide monolayer and that on a chloride-covered Ag(1 1 1) were comparatively studied by X-ray photoelectron spectroscopy and scanning tunneling microscopy. The native oxide monolayer was readily substituted completely by thiolates irrespective of chain length, leading to a dense (√7×√7)R19.1° monolayer for n<3, or a distorted (√7×√7)R19.1° structure for n>3 accompanied by distinct island and fine domain structures previously reported by other groups. In contrast, the chloride-to-thiolate conversion was far from complete for long alkanethiols (n?8), and at sufficiently high conversion temperature (>50 °C), we found a highly stable mixed thiolate-chloride monolayer with a well-defined 2:1 S/Cl atomic ratio, suggesting the occurrence of a mixed (√7×√7)R19.1° adlayer ordering. The combined effects of substrate-molecule and intermolecular interactions behind these contrastive phenomena are discussed. |
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Keywords: | X-ray photoelectron spectroscopy Scanning tunneling microscopy Chemisorption Self-assembly Silver Halides Sulphides |
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