Electronic and vibrational surface-enhanced Raman scattering: from atomically defined Au(111) and (100) to roughened Au,Chemical Science

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Electronic and vibrational surface-enhanced Raman scattering: from atomically defined Au(111) and (100) to roughened Au
Chemical Science ( IF 7.6 ) Pub Date : 2020-08-03 , DOI: 10.1039/d0sc02976a
Motoharu Inagaki _{1,

2,

3,

4} , Taichi Isogai _{1,

2,

3,

4} , Kenta Motobayashi _{1,

2,

3,

4} , Kai-Qiang Lin _{5,

6,

7,

8} , Bin Ren _{9,

10,

11,

12,

13} , Katsuyoshi Ikeda _{1,

2,

3,

4,

14}

Affiliation

In surface-enhanced Raman spectra, vibrational peaks are superimposed on a background continuum, which is known as one major experimental anomaly. This is problematic in assessing vibrational information especially in the low Raman-shift region below 200 cm⁻¹, where the background signals dominate. Herein, we present a rigorous comparison of normal Raman and surface-enhanced Raman spectra for atomically defined surfaces of Au(111) or Au(100) with and without molecular adsorbates. It is clearly shown that the origin of the background continuum is well explained by a local field enhancement of electronic Raman scattering in the conduction band of Au. In the low Raman-shift region, electronic Raman scattering gains additional intensity, probably due to a relaxation in the conservation of momentum rule through momentum transfer from surface roughness. Based on the mechanism for generation of the spectral background, we also present a practical method to extract electronic and vibrational information at the metal/dielectric interface from the measured raw spectra by reducing the thermal factor, the scattering efficiency factor and the Purcell factor over wide ranges in both the Stokes and the anti-Stokes branches. This method enables us not only to analyse concealed vibrational features in the low Raman-shift region but also to estimate more reliable local temperatures from surface-enhanced Raman spectra.

中文翻译：

电子和振动表面增强拉曼散射：从原子定义的Au（111）和（100）到粗糙的Au

在表面增强的拉曼光谱中，振动峰叠加在背景连续体上，这被称为一种主要的实验异常。这在评估振动信息时尤其是在低于200 cm ^-1的低拉曼位移区域中是有问题的，其中背景信号占主导。在这里，我们提出了正常的拉曼光谱和表面增强的拉曼光谱，对有原子吸附和无分子吸附的Au（111）或Au（100）的原子定义表面进行了严格的比较。清楚地表明，背景连续体的起源很好地解释了Au导带中电子拉曼散射的局部场增强。在低拉曼位移区域中，电子拉曼散射获得了额外的强度，这可能是由于通过表面粗糙度的动量传递而使动量规则的守恒松弛了。基于产生光谱背景的机制，我们还提出了一种实用的方法，可以通过降低热因子来从测量的原始光谱中提取金属/介电界面的电子和振动信息，斯托克斯分支和反斯托克斯分支中的散射效率因子和珀塞尔因子在很宽的范围内。这种方法不仅使我们能够分析低拉曼位移区域中的隐藏振动特征，而且能够根据表面增强拉曼光谱估计更可靠的局部温度。

更新日期：2020-09-23

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