Measurements of Electron-Transfer Rates of Charge-Storage Molecular Monolayers on Si(100). Toward Hybrid Molecular/Semiconductor Information Storage Devices

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• 作者：Kristian M. Roth ; Amir A. Yasseri ; Zhiming Liu ; Rajeev B. Dabke ; Vladimir Malinovskii ; Karl-Heinz Schweikart ; Lianhe Yu ; Hugo Tiznado ; Francisco Zaera ; Jonathan S. Lindsey ; Werner G. Kuhr ; and David F
• 刊名：Journal of the American Chemical Society
• 出版年：2003
• 出版时间：January 15, 2003
• 年：2003
• 卷：125
• 期：2
• 页码：505 - 517
• 全文大小：199K
• 年卷期：v.125,no.2(January 15, 2003)
• ISSN：1520-5126

文摘

Redox kinetics were measured for two electroactive molecules attached to Si(100) surfaces, aferrocene (Fc-BzOH) and a Zn(II) trimesitylporphyrin (Por-BzOH). Each molecule was derivatized with abenzyl alcohol linker for attachment to the Si surface via the formation of a Si-O bond. A complete protocolwas developed for the preparation of stable Si(100) surfaces derivatized with the electroactive molecules.The redox-kinetic measurements were performed on the resulting Fc-BzOH and Por-BzOH monolayersto probe (1) the rate of electron transfer (k⁰) for oxidation in the presence of applied potentials and (2) therate of charge dissipation after the applied potential is disconnected (in the form of a charge-retentionhalf-life t_1/2). The k⁰ values for the two types of monolayers were found to be similar to one another aswere the t_1/2 values. Perhaps more importantly, the electron-transfer rates for both the Fc-BzOH and thePor-BzOH monolayers differ from the charge-dissipation rates by ~6 orders of magnitude and are stronglydependent on the surface concentration of the electroactive species. For the Por-BzOH monolayers onSi(100), the k⁰ and t_1/2 values and their trends as a function of surface coverage were determined to besimilar to those previously measured for the analogous thiol-derivatized molecule assembled on Au(111).In contrast, the Fc-BzOH monolayers on Si(100) were found to exhibit much slower electron-transfer andcharge-dissipation rates than those in the corresponding thiol-Au(111) case. Two alternative hypothesesare advanced to explain both the diminution in rates with increased surface coverage and the contrastingbehavior with the analogous thiols on Au, one based on space-charge effects at the monolayer-solutioninterface, and a second relying on changes in distance of the redox centers from the surface as modulatedby the orientation of the linking chains. Collectively, the ability to prepare and study stable, electroactivemolecular media on Si(100) is likely to be key in the development of hybrid molecular/semiconductor devices.