Nanooptics Group, CIC nanoGUNE Consolider, 20018 Donostia-San Sebastián, Spain.
Nat Mater. 2011 May;10(5):352-6. doi: 10.1038/nmat3006. Epub 2011 Apr 17.
Fourier-transform infrared (FTIR) spectroscopy is a widely used analytical tool for chemical identification of inorganic, organic and biomedical materials, as well as for exploring conduction phenomena. Because of the diffraction limit, however, conventional FTIR cannot be applied for nanoscale imaging. Here we demonstrate a novel FTIR system that allows for infrared-spectroscopic nanoimaging of dielectric properties (nano-FTIR). Based on superfocusing of thermal radiation with an infrared antenna, detection of the scattered light, and strong signal enhancement employing an asymmetric FTIR spectrometer, we improve the spatial resolution of conventional infrared spectroscopy by more than two orders of magnitude. By mapping a semiconductor device, we demonstrate spectroscopic identification of silicon oxides and quantification of the free-carrier concentration in doped Si regions with a spatial resolution better than 100 nm. We envisage nano-FTIR becoming a powerful tool for chemical identification of nanomaterials, as well as for quantitative and contact-free measurement of the local free-carrier concentration and mobility in doped nanostructures.
傅里叶变换红外（FTIR）光谱学是一种广泛用于无机、有机和生物医学材料化学鉴定的分析工具，也可用于探索传导现象。然而，由于衍射极限，传统的 FTIR 无法应用于纳米尺度成像。在这里，我们展示了一种新型的 FTIR 系统，该系统允许对介电性质进行红外光谱纳米成像（nano-FTIR）。基于红外天线的热辐射超聚焦、散射光的检测以及采用非对称 FTIR 光谱仪的强信号增强，我们将传统红外光谱的空间分辨率提高了两个数量级以上。通过对半导体器件进行映射，我们证明了通过光谱学可以识别氧化硅，并对掺杂 Si 区域中的自由载流子浓度进行定量，空间分辨率优于 100nm。我们预计 nano-FTIR 将成为纳米材料化学鉴定的有力工具，以及对掺杂纳米结构中局部自由载流子浓度和迁移率进行定量和非接触测量的有力工具。
