Competition between the Spring Force Constant and the Phonon Energy Renormalization in Electrochemically Doped Semiconducting Single-Walled Carbon Nanotubes
Competition between the Spring Force Constant and the Phonon Energy Renormalization in Electrochemically Doped Semiconducting Single-Walled Carbon Nanotubes
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DOI：
10.1021/nl801637h
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发表时间：
2008-10-01
期刊：
影响因子：
10.8
通讯作者：
Dresselhaus, M. S.
中科院分区：
文献类型：
--
作者：
Kalbac, M.;Farhat, H.;Dresselhaus, M. S.
详细分析了单个半导体单壁碳纳米管(SWCNTs)的原位拉曼光谱电化学行为。特别注意了切向(Tg)模频率的发展，它随着外加电势V-e从V-e=0移开而移动。切向模带的大小和方向(上移或下移)取决于半导体管的直径。对于负充电，小口径管表现为降档，而大口径管表现为升档。这一现象可以通过两种效应之间的竞争来解释，这两种效应在负电荷过程中导致了Tg模频率的相反移动：声子重整化效应和充电过程中C-C键的减弱。正充电总是导致TG模式频率的上移。然而，上移的大小取决于管子直径。
A detailed analysis of the in situ Raman spectroelectrochemical behavior of individual semiconducting single-walled carbon nanotubes (SWCNTs) is presented. Special attention has been paid to the development of the tangential (TG) mode frequency, which shifts when the externally applied potential V-e is shifted away from V-e = 0. The magnitude and direction (upshift or downshift) of the tangential mode band has been found to be dependent on the diameter of the semiconducting tubes. For negative charging, the small-diameter tubes exhibit a downshift while the large-diameter tubes exhibit an upshift. This behavior is explained by a competition between two effects which cause opposite shifts in the TG mode frequency during negative charging: a phonon renormalization effect and a C-C bond weakening during the charging process. Positive charging always causes an upshift of the TG mode frequency. However, the magnitude of the upshift is dependent on the tube diameter.