Study of self-assembled triethoxysilane thin films made by casting neat reagents in ambient atmosphere

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• 作者：Yongan Yang ; Alex ; er M. Bittner ; Steve Baldelli ; Klaus Kern
• 关键词：Self-assembly ; Silane ; Atomic force microscopy ; Water contact angle ; Ellipsometry ; Sum frequency generation
• 刊名：Thin Solid Films
• 出版年：2008
• 期刊代码：78_00406090
• 类别：ph
• 出版时间：30 April 2008
• 卷：516
• 期：12
• 页码：3948-3956
• 文件大小：1115 K

摘要

We studied four trialkoxysilane thin films, fabricated via self-assembly by casting neat silane reagents onto hydrophilic SiO_x/Si substrates in the ambient. This drop-casting method is simple, yet rarely studied for the production of silane self-assembled monolayers (SAMs). Various ex-situ techniques were utilized to systematically characterize the growth process: Ellipsometry measurements can monitor the evolution of film thickness with silanization time; water droplet contact angle measurements reveal the wettability; the change of surface morphology was followed by Atomic Force Microscopy; the chemical identity of the films was verified by Infrared–Visible Sum Frequency Generation spectroscopy. We show that the shorter carbon chain (propyl-) or branched (2-(diphenylphosphino)ethyl-) silane SAMs exhibit poor ordering. In contrast, longer carbon chain (octadecyl and decyl) silanes form relatively ordered monolayers. The growth of the latter two cases shows Langmuir-like kinetics and a transition process from lying-down to standing-up geometry with increasing coverage.