Effects of amorphous layers on ADF-STEM imaging

K. A. Mkhoyan, S. E. Maccagnano-Zacher, E. J. Kirkland, J. Silcox

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

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. After propagating through an amorphous layer a portion of the beam passes without any alteration while scattered electrons introduce a Gaussian background. The dependence of the image contrast on the crystal structure, orientation and the types of the atoms present in the crystal was studied. In the case of uncorrected probes an amorphous layer thicker than 200 Å is necessary to achieve considerable reduction of the visibility of the atomic columns, but with aberration-corrected probes only 60 Å is necessary. With changes in defocus, crystalline specimens with amorphous layers on the top can also be imaged and high-resolution ADF images can be obtained. An amorphous layer at the beam entry surface affects the ADF image more than that of an amorphous layer at the exit surface. Approximately linear reduction of the contrast (with a slop of 1) is expected with increased thickness of amorphous layer.

Original languageEnglish (US)
Pages (from-to)791-803
Number of pages13
JournalUltramicroscopy
Volume108
Issue number8
DOIs
StatePublished - Jul 1 2008

Keywords

  • ADF imaging
  • Aberration correction
  • Multislice simulation
  • STEM
  • Si

Fingerprint Dive into the research topics of 'Effects of amorphous layers on ADF-STEM imaging'. Together they form a unique fingerprint.

Cite this