Department of Electrical Engineering and Computer Science, University of California , Irvine, California 92697, United States.
ACS Nano. 2014 Apr 22;8(4):3421-6. doi: 10.1021/nn406263m. Epub 2014 Mar 11.
A billion-fold increase in the Raman signal over conventional tip-enhanced Raman spectroscopy/microscopy (TERS) is reported. It is achieved by introducing a stimulating beam confocal with the pump beam into a conventional TERS setup. A stimulated TERS spectrum, closely corresponding to its spontaneous TERS counterpart, is obtained by plotting the signal intensity of the strongest Raman peak of an azobenzene thiol self-assembled monolayer versus the stimulating laser frequency. The stimulated TERS image of azobenzene thiol molecules grafted onto Au ⟨111⟩ clearly shows the surface distribution of the molecules, whereas, when compared to the simultaneously recorded surface topography, it presents an image contrast of different nature. The experimentally obtained stimulated gain is estimated at 1.0 × 10(9), which is in reasonable agreement with the theoretically predicted value. In addition to the signal increase, the signal-to-noise ratio was 3 orders of magnitude higher than in conventional spontaneous TERS. The proposed stimulated TERS technique offers the possibility for a substantially faster imaging of the surface with respect to normal TERS.
研究报告称，拉曼信号的增强幅度比传统的针尖增强拉曼光谱/显微镜（TERS）提高了 10 亿倍。这是通过在传统的 TERS 装置中引入与泵浦光束共焦的激发光束来实现的。通过绘制偶氮苯硫醇自组装单层的最强拉曼峰的信号强度与激发激光频率的关系，可以得到与之对应的受激 TERS 光谱。偶氮苯硫醇分子接枝在 Au ⟨111⟩上的受激 TERS 图像清晰地显示了分子的表面分布，而与同时记录的表面形貌相比，它呈现出不同性质的图像对比度。实验获得的受激增益估计为 1.0×10(9)，与理论预测值相当吻合。除了信号增强之外，信号与噪声的比值比传统的自发TERS 高 3 个数量级。所提出的受激TERS 技术为相对于普通TERS 更快地对表面成像提供了可能。
