Development of electron differential interferometry and its application to magnetic materials

点击翻译按钮获取中文摘要

Electron holography, which enables us to measure the electron phase shift with high precise and high resolution, requires a well-defined reference wave. This restricts the application to materials science. The theme of this research is to develop a new electron differential microscopy to overcome this disadvantage of electron holography and a system which makes a real time observation possible.Following results have been obtained in this project :i) In order to compensate for the lack of sensitivity in differential interferometry for weak phase objects, we proposed electron phase differential micrography that is realized by means of digital reconstruction method. For convenience an electron trapezoidal prism has been invented and replaced electron biprism.ii) We successfully observed directly the magnetic vectors in ferromagnetic thin films and that leaking from single magnetic domain particles by the two dimensional differentiation. It has been found that the reference phase reconstructed from all holograms should be coincident to each other, and an effect of Fresnel diffraction at an electron prism is important, too.iii) A complete simulation of electron holograms which include Fresnel effects, the quantum noise and the coherency of electrons has been accomplished.iv) Applying an additional square-wave voltage to the electron trapezoidal prism and recording double-exposure holograms on videotape, we confirmed that the real time observation in electron differential interferometry is available, though the time resolution obtained is about 1 sec. so far.