Electronic properties of Au nano-particles supported on stoichiometric and reduced TiO2 (110) substrates
Electronic properties of Au nano-particles supported on stoichiometric and reduced TiO2 (110) substrates
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DOI：
10.1016/j.susc.2006.07.012
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发表时间：
2006-10-01
期刊：
影响因子：
1.9
通讯作者：
Kido, Y.
中科院分区：
文献类型：
--
作者：
Okazawa, T.;Kohyama, M.;Kido, Y.
使用同步辐射光，通过中能离子散射（MEIS）和光电子能谱（PES）分析了在化学计量和还原的TiO2（110）基底上生长的An纳米粒子的生长模式和电子性质。最初，具有一层和两个原子层高度的二维岛(213)生长，并且更高的覆盖率增加了岛的高度，以形成用于化学计量的TiO2(110)基底的三维(3D)岛。相反，3D 岛从初始阶段开始生长，An 覆盖范围较小（>= 0.1 ML，1 ML = 1.39 x 1015 原子/cm(2) : Au(111)），这可能是由于 O 空位充当成核位点。超过 0.7 ML，所有的岛都变成 3D 岛，呈部分球体形状，并且两个基板的 Au 团簇都变成金属。我们观察了 Au 4f 和 Ti 3p 核心能级移动以及价带光谱。与化学计量表面相比，O 缺陷表面的 Ti 3p 峰向更高的结合能移动 0.25 +/- 0.05 eV，表明电子电荷从 O 空位引起的表面态带转移到 n 型 TiO2 基底导致能带向下弯曲。在两种基材上观察到的 Au 4f 峰的较高结合能变化揭示了电子电荷从 Au 到 TiO2 基材的转移。化学计量和还原的 TiO2 基底上负载的金纳米粒子的功函数也被确定为金覆盖率的函数，并通过上述表面和界面偶极子清楚地解释。 (c) 2006 Elsevier B.V. 保留所有权利。
Growth modes and electronic properties were analyzed for An nano-particles grown on stoichiometric and reduced TiO2(110) substrates by medium energy ion scattering (MEIS) and photoelectron spectroscopy(PES) using synchrotron-radiation-light. Initially, two-dimensional islands (213) with a height of one and two atomic layers grow and higher coverage increases the islands height to form three-dimensional (3D) islands for the stoichiometric TiO2(110) substrate. In contrast, 3D islands start to grow from initial stage with a small An coverage (>= 0.1 ML, 1 ML = 1.39 x 1015 atoms/cm(2) : Au(111)) probably due to O-vacancies acting as a nucleation site. Above 0.7 ML, all the islands become 3D ones taking a shape of a partial sphere and the Au clusters change to metal for both substrates. We observed the Au 4f and Ti 3p core level shifts together with the valence band spectra. The Ti 3p peak for the O-deficient surface shifts to higher binding energy by 0.25 +/- 0.05 eV compared to that for the stoichiometric surface, indicating downward band bending by an electron charge transfer from an O-vacancy induced surface state band to n-type TiO2 substrate. Higher binding energy shifts of Au 4f peaks observed for both substrates reveal an electron charge transfer from Au to TiO2 substrates. The work functions of Au nano-particles supported on the stoichiometric and reduced TiO2 substrates were also determined as a function of Au coverage and explained clearly by the above surface and interface dipoles. (c) 2006 Elsevier B.V. All rights reserved.