Effect of graphene Fermi level on the Raman scattering intensity of molecules on graphene.
Effect of graphene Fermi level on the Raman scattering intensity of molecules on graphene.
复制标题
DOI：
10.1021/nn103237x
复制
发表时间：
2011-06
期刊：
影响因子：
17.1
通讯作者：
Hua Xu;Liming Xie;Hao‐Li Zhang;Jin Zhang
中科院分区：
文献类型：
--
作者：
Hua Xu;Liming Xie;Hao‐Li Zhang;Jin Zhang
利用电场效应（EFE）对石墨烯费米能级进行调谐，研究了石墨烯表面分子的拉曼散射强度的调制。采用一系列具有不同能级的金属酞菁（M = Mn，Fe，Co，Ni，Cu，Zn）分子作为探针分子。所有这些M-Pc分子的拉曼强度在石墨烯费米能级通过施加正栅极电压而上移时变得较弱，而它们在石墨烯费米能级通过施加负栅极电压而下移时变得较强。然而，这种拉曼强度调制仅在施加具有快扫描速率的栅极电压时发生，而在施加具有慢扫描速率的栅极电压时几乎不存在，这可能是由于石墨烯EFE中的滞后效应的出现。此外，由于石墨烯与M-Pc分子之间能量排列的差异，具有较小能隙的M-Pc分子的拉曼调制能力大于具有较大能隙的M-Pc分子。此外，这种调制在单层石墨烯上显示出最大的调制，并且主要来自与石墨烯直接接触的第一层分子。用EFE对GERS中分子的拉曼调制表明，GERS的拉曼增强是通过化学增强机制发生的。
We studied the modulation of Raman scattering intensities of molecules on graphene by tuning the graphene Fermi level with electrical field effect (EFE). A series of metal phthalocyanine (M-Pc) molecules (M = Mn, Fe, Co, Ni, Cu, Zn), which have different molecular energy levels, were used as probe molecules. The Raman intensities of all these M-Pc molecules become weaker when the graphene Fermi level is up-shifted by applying a positive gate voltage, while they become stronger when the graphene Fermi level is down-shifted by applying a negative gate voltage. However, this Raman intensity modulation only occurs when applying the gate voltage with a fast sweep rate, while it is nearly absent when applying the gate voltage with a slow sweep rate, which is likely due to the arising of the hysteresis effect in the graphene EFE. In addition, the Raman modulation ability for M-Pc molecules with smaller energy gaps is larger than that with larger energy gaps due to the difference in the energy alignment between graphene and these M-Pc molecules. Furthermore, this modulation shows the greatest one on single-layer graphene and mainly comes from the first layer of molecules which are in direct contact with graphene. The Raman modulation of molecules in GERS with the EFE suggests that the Raman enhancement for GERS occurs through a chemical enhancement mechanism.