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特定基因上的荧光分子的超高分辨率观察。实验结果概述如下：(1)制作微型近场光学显微镜探头的基本制造技术。电子束沉积法是一种新发展起来的用于制作长度为1微米、直径为20纳米的高深宽比针尖微探针的新方法。利用聚焦离子束制作了原子力显微镜悬臂梁。(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，不仅可以制备无定形碳，还可以制备晶态碳。实验结果表明，制备结晶炭的最佳条件为温度900℃、压力1Torr。为了实现在扫描电子显微镜(SEM)腔内的最佳条件，我们开发了一种局部加热和压缩设备，并证实了在扫描电子显微镜(SEM)腔内生成了结晶碳。并提出了通过施加磁场来控制晶态碳的方向和长度，在理想的位置制备出具有所需形状的晶态碳。(3)通过对样机的荧光观察，得出了在各个波长下获得最高S/N比和分辨率的最佳探头形状。对滤光片的激发光强、照射面积、透过率等参数进行了优化，降低了噪声。结果证实，降低激发光强度可以提高S/N比，并且减少激发光可以得到荧光图像。这些结果表明，只观测荧光颗粒是可行的。

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.