使用求和频率生成成像显微镜对微晶铜表面上烷硫醇单层的表面诱导异质性进行分析,The Journal of Physical Chemistry C

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使用求和频率生成成像显微镜对微晶铜表面上烷硫醇单层的表面诱导异质性进行分析
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2017-01-17 00:00:00 , DOI: 10.1021/acs.jpcc.6b09403
Ming Fang ₁ , Steven Baldelli ₁

Affiliation

通过求和频率产生（SFG）成像显微镜和电子背散射衍射（EBSD）研究了微晶铜上的十八烷硫醇（ODT）自组装单层。整个畴边界的强烈SFG信号对比度表明铜表面上存在晶粒结构，这已通过EBSD测量进一步证实。SFG响应的非共振贡献显示出相对于样品相对于表面法线的面内旋转的各向异性，并在每个晶畴区域中变化。单层的共振贡献，例如CH ₃ -sym / CH ₃的振幅比-asym，方位角几乎各向同性。由于非线性磁化率的zzz张量分量起主导作用，因此金属表面上SFG光谱的共振部分不会显示任何各向异性。此外，基于统计分布分析确定了局部金属结构与顶部单层堆积行为之间的强相关性。以甲基为例，在SFG图像中可视化了不同晶粒的甲基倾斜角的变化，表明下面的局部晶粒结构对宏观测量的整体单层堆积行为有很大贡献。

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Surface-Induced Heterogeneity Analysis of an Alkanethiol Monolayer on Microcrystalline Copper Surface Using Sum Frequency Generation Imaging Microscopy

An octadecanethiol (ODT) self-assembled monolayer on microcrystalline copper is investigated by sum frequency generation (SFG) imaging microscopy and electron backscattering diffraction (EBSD). The strong SFG signal contrast across the domain boundary indicates the existence of grain structures on copper surface, which is further verified by EBSD measurements. The nonresonant contribution of SFG response shows anisotropy with respect to the in-plane rotation of the sample relative to the surface normal and varies in each crystal domain area. The resonant contribution of the monolayer, such as the amplitude ratio of CH₃-sym/CH₃-asym, is azimuthally nearly isotropic. Since the zzz tensor component of nonlinear susceptibility dominates, the resonant part of SFG spectra on the metal surface does not show any anisotropy. Further, a strong correlation between the local metal structures with the top monolayer packing behaviors is identified based on the statistical distribution analysis. Using the methyl group as an illustrative case, the variations in tilt angle of methyl group for different crystal grains, visualized in the SFG image, suggest that the underneath local grain structure contributes significantly to the overall monolayer packing behaviors measured on the macroscale.

更新日期：2017-01-17

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