%0 Journal Article
%T Resolution Improvement in Stage-Scanning Electron Holography: Comparison with Conventional Electron Holography
%A Dan Lei
%A Kazutaka Mitsuishi
%A Ken Harada
%A Masayuki Shimojo
%A Dongying Ju
%A Masaki Takeguchi
%J ISRN Nanotechnology
%D 2013
%R 10.1155/2013/368671
%X Electron holography provides information on the phase and amplitude of electron wave passing through a specimen. The recently proposed stage-scanning electron holography technique should improve the spatial resolution of phase and amplitude images compared to the conventional electron holography based on the Fourier transformation method. To demonstrate the resolution improvement, cobalt nanoparticles were observed using the stage-scanning holography and the conventional holography, and significantly sharper images were obtained with the former technique. 1. Introduction Electron holography [1¨C3] is a transmission electron microscopy (TEM) technique that uses a biprism to mix an object wave passing through a specimen with the reference wave passing through vacuum. Interaction of the two waves produces a pattern containing interference fringes. In contrast to conventional TEM techniques, which only record the spatial distribution of image intensity, electron holography yields information on both the phase and amplitude of the object wave through reconstruction of the interference pattern, or hologram. The phase distribution can then be used to provide information about the magnetic and electrostatic fields in the specimen. To obtain information on the phase and amplitude, a reconstruction process is necessary such as the Fourier transformation method [4, 5], in which the electron hologram is Fourier-transformed, and then its selected sideband is inversely Fourier-transformed. In this approach, the spatial resolution of the reconstructed phase image is limited by the fringe spacing in the hologram [6¨C10]. This spacing determines the separation of center band and side band in Fourier space and thus the resolution of resultant phase and amplitude images. However, the use of small fringe spacing, aiming for higher resolution, results in a lower fringe contrast and signal-to-noise ratio. Many efforts have been spent to overcome this difficulty. For example, Ru et al. [6, 7] developed a phase-shifting electron holography technique, where the incident beam is tilted to obtain a series of holograms with different initial phases. With this method, the object wave passing through the specimen can be determined independently of the fringe spacing without requiring Fourier transformation. We presented an electron holography technique using a stage-scanning system [11]. In this method, line intensities are acquired from a series of holograms recorded at different specimen positions, and an interferogram that corresponds to the phase distribution can be obtained
%U http://www.hindawi.com/journals/isrn.nanotechnology/2013/368671/