Development of electron differential interferometry and its application to magnetic materials

电子全息术是一种高精度、高分辨率的电子相移测量技术，它需要一个清晰的参考光。这就限制了它在材料科学中的应用。本研究的主题是发展一种新的电子微分显微术，以克服电子全息术的这一缺点，并使真实的时间观测成为可能，在本项目中取得了以下成果：1）为了弥补微分干涉术对弱相位物体灵敏度的不足，我们提出了用数字重建方法实现的电子相位微分显微术。（2）利用二维微分法，我们成功地直接观测到了铁磁薄膜中的磁矢量和单磁畴粒子的磁矢量泄漏。我们发现，从所有全息图中再现的参考相位应彼此一致，电子棱镜的菲涅耳衍射效应也是重要的。iii）对包含菲涅耳效应的电子全息图进行了完整的模拟，iv）在电子梯形棱镜上加一个方波电压，记录双-通过在录像带上曝光全息图，证实了电子差分干涉术中的真实的时间观测是可行的，虽然所获得的时间分辨率约为1秒。迄今

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.