Advanced Electron Holography Applied to Electromagnetic Field Study in Materials Science

Abstract

Advances and applications of electron holography to the study of electromagnetic fields in various functional materials are presented. In particular, the development of split-illumination electron holography, which introduces a biprism in the illumination system of a holography electron microscope, enables highly accurate observations of electromagnetic fields and the expansion of the observable area. First, the charge distributions on insulating materials were studied by using split-illumination electron holography and including a mask in the illumination system. Second, the three-dimensional spin configurations of skyrmion lattices in a helimagnet were visualized by using a high-voltage holography electron microscope. Third, the pinning of the magnetic flux lines in a high-temperature superconductor YBa Cu O was analyzed by combining electron holography and scanning ion microscopy. Finally, the dynamic accumulation and collective motions of electrons around insulating biomaterial surfaces were observed by utilizing the amplitude reconstruction processes of electron holography.

Electron Holography Study of Secondary Electron Distribution around Charged Epoxy Resin

“…The decrease of visibility of interference fringes results from the electric field fluctuation, which was discussed in previous paper. 33) On the other hand, this low…”

“…Phase and amplitude information can be extracted by processing these holograms through the Fourier transform operation. 31,33) Reconstructed phase images clarify the electric potential distribution, while reconstructed amplitude images detect the fluctuation of electric field due to the motion of secondary electrons. Figure 3 shows a low-magnification TEM image of an epoxy resin specimen shaped by FIB.…”

“…The Y-shape epoxy resin imitates the shape of the biological specimen observed in the previous study. 32,33) Figure 4(a) shows a hologram of the specimen, and Fig. 4(b) shows the reconstructed phase image, where the purple region corresponds to the epoxy resin.…”

“…Figure 5(a) shows a reconstructed amplitude image, where the dark regions correspond to fluctuations in electric field due to the motion of secondary electrons. 31,33) Color images are presented in Fig. 5(b), where the color scale bar in the lower part indicates the relation between the visibility of the interference fringes and the contrast of the reconstructed amplitude images.…”

“…The accumulation of secondary electrons in the branched regions of microfibrils was also studied. 32,33) These studies observed the motion and accumulation of secondary electrons in the upper-edge regions of microfibrils that were far from the supporting film. The reason for this precaution is that charging of insulating materials is strongly affected by the irradiation of secondary electrons from the substrate and/or supporting film, as reported elsewhere.…”