Development of a photon scanning tunneling microscope for nondestructive measurements of bio-particles

点击翻译按钮获取中文摘要

Fabrication process of an optical fiber probe was developed, which is an essential device for the photon scanning tunneling microscope (PSTM). By extending chemical etching process we have developed previously, the two-step etching was developed. As a result, the cladding diameter was reduced to 1/20 times that of the conventional fiber. By utilizing a high sensitivity of this slender fiber to the atomic force between the probe and sample, a servo-control system was developed to control the sample-probe separation with high accuracy.The PSTM system was assembled by using this probe and its performance was evaluated. Flagellar filaments of salmonella were used as a reference sample for the evaluation, which has the 25 nm diameter. Collection-mode measurement obtained the image with the resolution of about 5 nm. It was found that the resolution of the image was reduced by increasing the aperture diameter of the probe, and by increasing the sample-probe separation. This dependency agreed … More with the theoretical results based on the "virtual photon" model, which we have proposed previously. Futhermore, it was found that the resolution also depended on the polarization-state of the incident light. This dependency was explained based on the spatial distribution of the light-induced polarization on the surface.To evalute the performance of the illumination-mode PSTM,neurons were used as a reference sample. The bundle of microtubulines (nominal diameter observed by an electron microscope was 25 nm) in the branching axon was successfully imaged without taking them out from the axon. The measured diameter was 25 nm, which is exactly the same as the nominal diameter. From this result, it was confirmed that the present PSTM has the resolution as high as that of the electron microscope for diagnosing biological samples.Although the experimental results described above was obtained in the air, we have also succeeded in imaging the polyhooks of the flagellar filaments of salmonella in the water. Less