Synthesis, Characterization, and Reactivity of Ethynyl- and Propynyl-Terminated Si(111) Surfaces

详细信息    查看全文

• 作者：Noah T. Plymale ; Youn-Geun Kim ; Manuel P. Soriaga ; Bruce S. Brunschwig ; Nathan S. Lewis
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：August 27, 2015
• 年：2015
• 卷：119
• 期：34
• 页码：19847-19862
• 全文大小：741K
• ISSN：1932-7455

文摘

Ethynyl- and propynyl-terminated Si(111) surfaces synthesized using a two-step halogenation/alkylation method have been characterized by transmission infrared spectroscopy (TIRS), high-resolution electron energy-loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), atomic-force microscopy (AFM), electrochemical scanning鈥搕unneling microscopy (EC-STM) and measurements of surface recombination velocities (S). For the ethynyl-terminated Si(111) surface, TIRS revealed signals corresponding to ethynyl 鈮鈥揌 and C鈮 stretching oriented perpendicular to the surface, HREELS revealed a Si鈥揅 stretching signal, and XPS data showed the presence of C bound to Si with a fractional monolayer (ML) coverage (桅) of 桅_Si鈥揅CH = 0.63 卤 0.08 ML. The ethynyl-terminated surfaces were also partially terminated by Si鈥揙H groups (桅_Si鈥揙H = 0.35 卤 0.03 ML) with limited formation of Si³⁺ and Si⁴⁺ oxides. For the propynyl-terminated Si(111) surface, TIRS revealed the presence of a (C鈥揌)_CH3 symmetric bending, or 鈥渦mbrella,鈥?peak oriented perpendicular to the surface, while HREELS revealed signals corresponding to Si鈥揅 and C鈮 stretching, and XPS showed C bound to Si with 桅_Si鈥揅CCH3 = 1.05 卤 0.06 ML. The LEED patterns were consistent with a (1 脳 1) surface unit cell for both surfaces, but room-temperature EC-STM indicated that the surfaces did not exhibit long-range ordering. HCC鈥揝i(111) and CH₃CC鈥揝i(111) surfaces yielded S values of (3.5 卤 0.1) 脳 10³ and (5 卤 1) 脳 10² cm s^鈥?, respectively, after 581 h exposure to air. These observations are consistent with the covalent binding of ethynyl and propynyl groups, respectively, to the Si(111) surface.