Antenna-mediated back-scattering efficiency in infrared near-field microscopy
Antenna-mediated back-scattering efficiency in infrared near-field microscopy
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DOI：
10.1364/oe.16.011203
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发表时间：
2008-07-21
期刊：
影响因子：
3.8
通讯作者：
Keilmann, F.
中科院分区：
文献类型：
--
作者：
Brehm, M.;Schliesser, A.;Keilmann, F.
我们评估了接触平面样品的标准悬臂 AFM 探针的背向散射效率 eta(B)，以及背向散射相位。这两个量均通过相干频梳傅立叶变换光谱 (c-FTIR) 在 9-12 μm 宽波长范围内进行光谱测定。虽然菲涅耳反射率是 SiC Reststrahlen 边缘在 975 cm(-1) 处的关键因素（如先前记录的那样），但我们观察到涉及轴、悬臂和样品的天线谐振引起的光谱效应。最引人注目的是在 955 cm(-1) 处的强共振反向散射 (.B = 13%)，当尖端探测 SiC/Au 边界附近的区域时，该频率表明涉及表面声子极化子激发。通过对近场、辐射区场和远场散射分布进行数值模拟来阐明探头的天线特性。模拟是针对具有三个数量级尺度变化的真实尖端/样品配置进行的。结果表明，沿轴存在固定表面等离子体激元极化图案，以及随样品介电特性变化的远场天线波瓣。 (C) 2008 年美国光学学会。
We evaluate the efficiency of back-scattering, eta(B), from a standard cantilevered AFM probe contacting a flat sample, and also the back-scattering phase. Both quantities are spectroscopically determined over a broad 9-12 mu m wavelength range by coherent frequency-comb Fourier-transform spectroscopy (c-FTIR). While Fresnel reflectivity contributes a key factor with the SiC Reststrahlen edge at 975 cm(-1) as previously documented, we observe spectral effects ascribable to antenna resonances involving the shaft, cantilever, and sample. Most conspicuous is strong (. B = 13%), resonant back-scattering at 955 cm(-1), a frequency that suggests the involvement of surface-phonon-polariton excitation, when the tip probes the area near a SiC/Au boundary. The probe's antenna properties are elucidated by numerically simulating the near fields, the fields in the radiation zone, and the far-field scattering distributions. The simulations are performed for a realistic tip/sample configuration with a three-orders-of-magnitude scale variation. The results suggest a standing-surface-plasmon-polariton pattern along the shaft, as well as far-field antenna lobes that change with the sample's dielectric properties. (C) 2008 Optical Society of America.