Ultra high-resolution scanning near-field optical microscope for direct gene reading

本研究的目的是开发一种扫描近场光学显微镜（SNOM），以实现对DNA特定基因上荧光分子的超高分辨率观察。结果概要如下所示。(1)制备用于样品周围近场光散射的微型SNOM探针的基本制造技术。电子束沉积法是一种新型的制备高纵横比尖端长度为1微米、直径为20纳米的微SNOM探针的方法。我们制作了一个500纳米方形孔径的微型SNOM探针的原型，利用聚焦离子束制造了一个AFM悬臂。(2)为了进一步实现SNOM探针尖端的小型化，我们开发了一种新的电子束沉积方法，既可以生产非晶碳，也可以生产结晶碳。试验结果表明，制备结晶碳的最佳条件为温度900℃，压力1托。为了实现扫描电镜（SEM）腔内的最佳条件，我们开发了一种局部加热和压缩设备，并证实了在扫描电镜（SEM）腔内产生了结晶碳。提出了通过施加磁场来控制结晶碳的方向和长度，使结晶碳在理想的位置上具有理想的形状。(3)通过对SNOM原型探针的荧光观察，确定了在各波长下获得最高信噪比和分辨率的最佳探针形状。优化了滤光片的激发光强度、辐照面积、透过率等参数，降低了噪声。结果证实，降低激发光强度可提高信噪比，降低激发光可形成荧光图像。这些结果表明了仅对荧光粒子进行观察的可行性。

The objective of this research is developing a scanning near-field optical microscope (SNOM), to realize ultra high-resolution observation of fluorescent molecules on a specific gene of a DNA. The outline of the results is shown below.(1)Fundamental fabrication technique which produces micro SNOM probe for scattering near-field light around a specimen. Electron beam deposition method has been newly developed for fabricate a micro SNOM probe with a high aspect ratio tip end with 1 micrometer length and 20 nanometer diameter. And we have prototyped a micro SNOM probe with 500 nanometer square aperture, fabricating an AFM cantilever using focused ion beam.(2)For further miniaturization of the SNOM probe tip, we develop a new electron beam deposition method that produces not only amorphous carbon but also crystalline carbon. A examination result shows the optimum condition for producing crystalline carbon was 900 degrees temperature and 1 torr pressure. To realize the optimum condition in a scanning electron microscope (SEM) chamber, we developed a local heating and compression equipment, and confirmed that crystalline carbon was produced in the SEM camber. And it was proposed to control the direction and length of the crystalline carbon by applying magnetic field, to produce crystalline carbon with a desired shape at a desired position.(3)Through a fluorescent observation using prototyped SNOM probe, the optimum probe shape to get the highest S/N ratio and resolution at each wavelength. We optimized the parameters of excitation light strength, irradiation area, transmissivity of the filter, and reduce the noise. As the result, it was confirmed that reducing excitation light strength improved the S/N ratio, and reduced excitation light made a fluorescent image. These results showed feasibility of the observation of only fluorescent particle.