科研之友
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摘要
We studied the morphological changes of "hot" spots in gap-mode tip-enhanced Raman spectroscopy (TERS) experiments by monitoring both the Raman spectra and topographic images of amorphous Au surfaces that were covered with a benzenethiol monolayer. Significant roughness reduction of the Au surfaces in the vicinity of the location of the TERS measurement together with irreversible signal loss was observed: To understand this phenomenon, a numerical simulation was performed and the result implies that it was the Joule heating generated by the highly enhanced electromagnetic field in the "hot" tip-sample nanogap that locally annealed the Au surface. Considering that the mobility of the atoms on top of an Au surface is high and the reduction of the local roughness is significant, we propose that the TERS signal loss is mainly caused by two mechanisms: reduction of electromagnetic enhancement caused by the degradation of the "hot" site and concomitant surface diffusion of the adsorbates.
- 出版日期2008-2-14
