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Reduction of Contrast in ADF-STEM Images Due To Amorphous Layer

Published online by Cambridge University Press:  01 February 2011

Sara Maccagnano-Zacher
Affiliation:
sem55@cornell.edu, Cornell University, Applied and Engineering Physics, Ithaca, NY, 14853, United States
Andre Mkhoyan
Affiliation:
kam55@cornell.edu, Cornell University, Applied and Engineering Physics, Ithaca, NY, 14853, United States
John Silcox
Affiliation:
js97@cornell.edu, Cornell University, Applied and Engineering Physics, Ithaca, NY, 14853, United States
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Abstract

A study of high-resolution ADF imaging in uncorrected and aberration-corrected STEMs was carried out by multislice simulation. The presence of amorphous layers at the surface of a crystalline specimen is shown to significantly alter the visibility of the atomic columns in ADF images. After propagating through an amorphous layer a portion of the beam passes without any alteration while scattered electrons introduce a Gaussian background. An amorphous layer at the beam entry surface appears to have slightly more of an effect on the ADF image contrast than that of an amorphous layer at the exit surface, and this difference increases with increasing atomic number. With constant crystal layer thickness, the reduction of contrast as a function of increasing amorphous layer is found to have the same behavior, regardless of the thickness of the initial crystal layer thickness.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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