Interplay of Bias-Driven Charging and the Vibrational Stark Effect in Molecular Junctions

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• 作者：Yajing Li ; Pavlo Zolotavin ; Peter Doak ; Leeor Kronik ; Jeffrey B. Neaton ; Douglas Natelson
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：February 10, 2016
• 年：2016
• 卷：16
• 期：2
• 页码：1104-1109
• 全文大小：395K
• ISSN：1530-6992

文摘

We observe large, reversible, bias driven changes in the vibrational energies of PCBM based on simultaneous transport and surface-enhanced Raman spectroscopy (SERS) measurements on PCBM-gold junctions. A combination of linear and quadratic shifts in vibrational energies with voltage is analyzed and compared with similar measurements involving Cb>60b>-gold junctions. A theoretical model based on density functional theory (DFT) calculations suggests that both a vibrational Stark effect and bias-induced charging of the junction contribute to the shifts in vibrational energies. In the PCBM case, a linear vibrational Stark effect is observed due to the permanent electric dipole moment of PCBM. The vibrational Stark shifts shown here for PCBM junctions are comparable to or larger than the charging effects that dominate in Cb>60b> junctions.