Bond Insertion, Complexation, and Penetration Pathways of Vapor-Deposited Aluminum Atoms with HO- and CH3O-Terminated Organic Monolayers

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• 作者：Gregory L. Fisher ; Amy V. Walker ; Andrew E. Hooper ; Timothy B. Tighe ; Kevin B. Bahnck ; Hope T. Skriba ; Michael D. Reinard ; Brendan C. Haynie ; Robert L. Opila ; Nicholas Winograd ; and David L. Allara
• 刊名：Journal of the American Chemical Society
• 出版年：2002
• 出版时间：May 15, 2002
• 年：2002
• 卷：124
• 期：19
• 页码：5528 - 5541
• 全文大小：229K
• 年卷期：v.124,no.19(May 15, 2002)
• ISSN：1520-5126

文摘

The interaction of vapor-deposited Al atoms with self-assembled monolayers (SAMs) of HS-(CH₂)₁₆-X (X = -OH and -OCH₃) chemisorbed at polycrystalline Au{111} surfaces was studied usingtime-of-flight secondary-ion mass spectrometry, X-ray photoelectron spectroscopy, and infrared reflectancespectroscopy. Whereas quantum chemical theory calculations show that Al insertion into the C-C, C-H,C-O, and O-H bonds is favorable energetically, it is observed that deposited Al inserts only with the OHSAM to form an -O-Al-H product. This reaction appears to cease prior to complete -OH consumption,and is followed by formation of a few overlayers of a nonmetallic type of phase and finally deposition of ametallic film. In contrast, for the OCH₃ SAM, the deposited Al atoms partition along two parallel paths:nucleation and growth of an overlayer metal film, and penetration through the OCH₃ SAM to the monolayer/Au interface region. By considering a previous observation that a CH₃ terminal group favors penetration asthe dominant initial process, and using theory calculations of Al-molecule interaction energies, we suggestthat the competition between the penetration and overlayer film nucleation channels is regulated by smalldifferences in the Al-SAM terminal group interaction energies. These results demonstrate the highly subtleeffects of surface structure and composition on the nucleation and growth of metal films on organic surfacesand point to a new perspective on organometallic and metal-solvent interactions.