CIC nanoGUNE, 20018 Donostia-San Sebastián, Spain.
ACS Nano. 2014 Jul 22;8(7):6911-21. doi: 10.1021/nn5016314. Epub 2014 Jul 1.
The increasing complexity of composite materials structured on the nanometer scale requires highly sensitive analytical tools for nanoscale chemical identification, ideally in three dimensions. While infrared near-field microscopy provides high chemical sensitivity and nanoscopic spatial resolution in two dimensions, the quantitative extraction of material properties of three-dimensionally structured samples has not been achieved yet. Here we introduce a method to perform rapid recovery of the thickness and permittivity of simple 3D structures (such as thin films and nanostructures) from near-field measurements, and provide its first experimental demonstration. This is accomplished via a novel nonlinear invertible model of the imaging process, taking advantage of the near-field data recorded at multiple harmonics of the oscillation frequency of the near-field probe. Our work enables quantitative nanoscale-resolved optical studies of thin films, coatings, and functionalization layers, as well as the structural analysis of multiphase materials, among others. It represents a major step toward the further goal of near-field nanotomography.
纳米尺度复合材料结构的日益复杂性要求高度灵敏的分析工具来进行纳米级化学识别，理想情况下是在三维空间中。虽然近场红外显微镜在二维空间中提供了高的化学灵敏度和纳米级的空间分辨率，但尚未实现对三维结构样品的材料特性进行定量提取。在这里，我们介绍了一种从近场测量中快速恢复简单 3D 结构（如薄膜和纳米结构）的厚度和介电常数的方法，并首次进行了实验验证。这是通过对成像过程的新型非线性可逆模型来实现的，该模型利用近场探针的振荡频率的多个谐波记录的近场数据。我们的工作使得对薄膜、涂层和功能化层的纳米级分辨光学研究以及多相材料的结构分析等成为可能。这是朝着近场纳米层析术的进一步目标迈出的重要一步。
