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On the phase problem in electron microscopy: The relationship between structure factors, exit waves, and HREM images
Author(s) -
Zou Xiaodong
Publication year - 1999
Publication title -
microscopy research and technique
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 118
eISSN - 1097-0029
pISSN - 1059-910X
DOI - 10.1002/(sici)1097-0029(19990801)46:3<202::aid-jemt4>3.0.co;2-8
Subject(s) - phase (matter) , diffraction , confusion , resolution (logic) , electron microscope , phase problem , electron diffraction , structure factor , crystal structure , crystallography , optics , materials science , physics , chemistry , computer science , artificial intelligence , quantum mechanics , psychology , psychoanalysis
In electron microscopy, the word phase is used for different physical phenomena, including crystallographic structure‐factor phases and the electron wave phases. This has resulted in great confusion, as to whether the phase information is present or lost when an image is recorded. The aim of this paper is to solve this phase confusion problem by studying the relationships between structure factors, exit waves, and high‐resolution electron microscopy (HREM) images. Three approaches are taken. First phases at different stages of the imaging processes are compared analytically for a crystal that can be considered a weak phase object (WPO). Then these different phases are calculated by the multi‐slice method based on dynamical diffraction theory, and their numerical values are compared. Finally, the validity of the theoretical description is checked by comparison with experimental data on a real crystal, Ti 2 S. It is demonstrated that it is possible to obtain accurate structure factor‐phases directly from HREM images by crystallographic image processing. The two major methods for structure determination from HREM images—exit wave reconstruction and crystallographic image processing—are compared. It is shown that the information utilised by the two methods as well as the results are essentially the same. Microsc. Res. Tech. 46:202–219, 1999. © 1999 Wiley‐Liss, Inc.