Effect of Bias Voltage on a Single-Molecule Junction Investigated by Surface-Enhanced Raman Scattering
Effect of Bias Voltage on a Single-Molecule Junction Investigated by Surface-Enhanced Raman Scattering
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通过表面增强拉曼散射研究偏置电压对单分子结的影响
DOI：
10.1021/acs.jpcc.9b02286
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Kiguchi M.
中科院分区：
文献类型：
--
作者：
Yasuraoka K.;Kaneko S.;Fujii S.;Nishino T.;Tsukagoshi K.;Juhasz G.;Kiguchi M.
我们使用表面增强拉曼散射 (SERS) 研究了偏置电压对 1,4-苯硫醇 (BDT) 单分子结的影响。通过测量相同样品的 SERS 偏压依赖性，我们可以清楚地观察到施加偏压时 355 cm-1 处振动模式的蓝移。通过使用通过光刻技术制造的高度稳定的纳米间隙电极可以进行这种测量。同时，其他振动模式的能量不随偏置电压的变化而变化。键合强度的变化可以通过在单分子结上施加偏压引起的电荷转移来解释。理论计算结果表明，偏置电压的影响是π体系重排的结果。 355 cm–1 模式是芳环的面外模式。在BDT单分子连接中，π系统在硫原子上离域。这种离域通过施加偏置电压而被抑制，因此，芳环更像“苯”，并且平面外振动转移到更高的能量。
We have investigated the effect of the bias voltage on the 1,4-benzenethiol (BDT) single-molecule junction using the surface-enhanced Raman scattering (SERS). By measuring the bias voltage dependence of SERS for the identical sample, we can clearly observe the blue shift of the vibrational mode at 355 cm–1by the application of the bias voltage. This measurement is possible by using a highly stable nanogap electrode which is fabricated with lithographic techniques. Meanwhile, the energy of other vibrational modes does not change with the bias voltage. The change in the bond strength can be explained by the charge transfer induced by the application of the bias voltage on the single-molecule junction. The theoretical calculation result reveals that the effect of bias voltage is a result of the rearrangement of the π system. The 355 cm–1mode is an out-of-plane mode of the aromatic ring. In the BDT single-molecule junction, the π system is delocalized on the sulfur atom. This delocalization is suppressed by the application of the bias voltage, and thus, the aromatic ring is more “benzene-like” and the out-of-plain vibration shifts to higher energy.