Near-Ideal Complete Coverage of CD3 onto Si(111) Surfaces Using One-Step Electrochemical Grafting: An IR Ellipsometry, Synchrotron XPS, and Photoluminescence Study

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• 作者：Florent Yang ; Katy Roodenko ; Ralf Hunger ; Karsten Hinrichs ; Klaus Rademann ; J枚rg Rappich
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：September 6, 2012
• 年：2012
• 卷：116
• 期：35
• 页码：18684-18690
• 全文大小：365K
• 年卷期：v.116,no.35(September 6, 2012)
• ISSN：1932-7455

文摘

A one-step electrochemical grafting process using Grignard reagents has been performed to achieve a complete monolayer methyl-terminated Si(111) surfaces. Anodic treatment (0.5 mA/cm² for 300 s) has been applied to atomically flat H-terminated Si(111) surfaces in methylmagnesium bromide (CH₃MgBr), methylmagnesium iodide (CH₃MgI), and methyl-d₃-magnesium iodide (CD₃MgI) to obtain methylated Si(111) surfaces. Infrared spectroscopic ellipsometry (IRSE) clearly reveals a vibrational shift of the symmetric 鈥渦mbrella鈥?mode characteristic for methyl groups (CH₃ and CD₃) with a preferential z-orientation. Additionally, X-ray photoelectron spectroscopy using synchrotron radiation (SXPS) shows a well-defined splitting of the Si 2p core level spectra from the methylated Si(111) surfaces. This splitting is more pronounced for the CD₃-terminated Si(111) surfaces. Moreover, the C 1s spectra also confirm the well-defined structure of the CD₃-terminated Si(111) surfaces by the presence of C鈥揇 vibrational stretching features. Photoluminescence (PL) measurements reveal better surface passivation in the case of CD₃-terminated Si(111) surfaces. Finally, the quality of the surfaces depends strongly on the counterions. Grignard reagents containing iodine show the best performance in the formation of complete monolayer methylated Si(111) surfaces.