"Development of Near-Field Infrared Scanning Analyzing Microscope with Sub-Micro Spatial Resolution"

通过这个研究项目，我们研究了一种高分辨率红外光学显微镜的可能性，它的空间分辨率比阿贝衍射极限确定的分辨率极限高10到100倍。虽然红外光谱仪对固体样品的材料分析迫切需要红外显微镜的发展，但由于红外光的波长较长，其空间分辨率不足以用于当前电子器件的材料分析。我们研究的这台显微镜配备了探针，但没有物镜或反射镜。探针尖端在探针尖端的近场中向样品表面提供一种倏逝波。光通过与样品的局部区域相互作用而被调制，并且证明在样品表面被扫描以形成图像。本文的研究结果如下：1)理论分析：基于Marchand和Wolf的衍射理论和角谱表示，分析了在直径小于红外波长但实际可实现（约为红外波长的十分之一）的小孔径下的衍射效应，并分析了探针尖端的倏逝波和传播波之间的耦合。通过我们的分析，获得了开发显微系统的一些新知识。2)计算机模拟：利用实际参数，通过计算机模拟计算出小孔径下的衍射。3)针尖加工：对ZnSe衬底和AgCl-AgBr红外光纤的探针针尖端部进行研磨加工。4)实验：测量近场针孔衍射的空间分布，对显微镜的仪器进行检验。采用CO_2红外激光器作为光源，利用3轴PZT平台扫描探针尖端，检测了针孔的近场分布。结果表明，该方法需要双锁相检测，该双锁相检测必须与轴向尖端激活和源调制同步。利用装有一对卡塞格伦物镜、针孔和探针尖端的FT-IR光谱仪，通过一个小孔径测量了薄膜的多层分布。测量了波长大于针孔直径的光谱。少

Through this research project we investigated the possibility of a high-resolution infrared optical microscope which has a spatial resolution of ten to one hundred times higher than the resolution limit determined by the Abbe's diffraction limit. Although a development of infrared microscopes is strongly required for material analysis of solid-state samples with an infrared spectrometer, its spatial resolution is insufficient for material analysis of current electronic devices because of the long wavelength of infrared light. This microscope that we investigate is equipped with a probe, but not objective lens or mirror. The probe tip provides an evanescent wave of the light onto the sample surface in the near-field of the tip. The light is modulated by interacting with the local area of the sample, and the prove is scanned across the sample surface to form the image. The result through this research is as follows :1) Theoretical analysis : The diffraction effect for a small aperture wh … More ose diameter is sufficiently smaller than the infrared wavelength but is realistically achievable (approximately one-tenth of the wavelength) and the coupling between the evanescent wave and the propagating wave in the probe tip were analyzed based on the diffraction theory by Marchand and Wolf and the angular spectrum representation. Through our analyses, several new knowledges for developing the microscopy system were obtained.2) Computer simulation : The diffractions from the small aperture were calculated by computer simulation with the real parameters.3) Machining of tips : Probe tips of a ZnSe substrate and AgCl-AgBr infrared fiber were made by grinding their ends.4) Experiments : Spatial distribution of near-field diffraction by a pinhole was measured for examining the instrumentation of the microscope. A infrared CO_2 laser was used as a source and the near-field distribution of the pinhole was detected by scanning the probe tips with a 3-axis PZT stage. It was found that double lock-in detection which synchronizes with both the tip activation in axial direction and the modulation of the source is required.Multi-layer distribution of a film was measured through a small aperture using an FT-IR spectrometer which was equipped with a pair of Cassegrain objectives, a pinhole and the probe tip. The spectrum whose wavelength is longer than the pinhole diameter were measured. Less