Frequency-Modulated, Single-Molecule Absorption Detected by Scanning Tunneling Microscopy

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• 作者：Erin S. Carmichael ; Joshua B. Ballard ; Joseph W. Lyding ; Martin Gruebele
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：March 1, 2007
• 年：2007
• 卷：111
• 期：8
• 页码：3314 - 3321
• 全文大小：332K
• 年卷期：v.111,no.8(March 1, 2007)
• ISSN：1932-7455

文摘

We image frequency-modulated single-molecule optical absorption using a scanning tunneling microscopeas the detector (SMA-STM). As a first example of the technique, a semiconducting carbon nanotube adsorbedon a silicon surface is studied. Excitation is achieved using laser amplitude as well as frequency modulation,and these two complementary approaches are compared. Detection is achieved via the resulting change intunneling current through the excited molecule. We distinguish three mechanisms, direct, relaxed, andbolometric, for detecting single-molecule absorption spectra. Kinetic models for these mechanisms as well asfor surface heating are presented. The latter effect can be eliminated by frequency modulation, keeping thelaser power density on the surface constant.