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Title: Contrast and resolution versus specimen thickness in low energy scanning transmission electron microscopy

Abstract

A theoretical and experimental investigation of contrast and resolution versus specimen thickness in scanning transmission electron microscopy at low energy is reported. Due to absence of postspecimen imaging lenses it is possible to have images with a resolution defined by the probe size using very wide collection angles and independent of the energy loss of the transmitted electrons. The fundamental limitation in observable specimen thickness is represented by the signal to noise ratio, i.e., the intensity of the beam current. The investigated specimens are semiconductor multilayers and Sb precipitates in a Si implanted specimen. The observations of layers crossing the whole specimens parallel to the electron beam point out that only a small portion of them, the one close to the surface, causes the image contrast, while the portion below, where the probe diameter, as a consequence of the broadening, is larger than the layer itself, reduces the contrast. A similarity with recent results, achieved in scanning transmission electron microscopy at high energy, where the layers are represented by atomic columns, is pointed out. The image contrast depends on the angular distribution of the transmitted electrons, and for thick specimens it is always of bright field type, independent of themore » collection angle of the transmitted electrons. The observation of Sb precipitates, distributed along the specimen thickness, evidences the role of beam broadening on the resolution and contrast.« less

Authors:
;  [1]
  1. CNR-IMM, Sezione di Bologna, via Gobetti 101, 40126 Bologna (Italy)
Publication Date:
OSTI Identifier:
20979430
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 11; Other Information: DOI: 10.1063/1.2745333; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM COMPOUNDS; ANGULAR DISTRIBUTION; ANTIMONY; BEAM CURRENTS; ELECTRON BEAMS; ELECTRONS; ENERGY LOSSES; IMAGES; LAYERS; PRECIPITATION; RESOLUTION; SEMICONDUCTOR MATERIALS; SIGNAL-TO-NOISE RATIO; THICKNESS; TRANSMISSION ELECTRON MICROSCOPY

Citation Formats

Morandi, Vittorio, and Merli, Pier Giorgio. Contrast and resolution versus specimen thickness in low energy scanning transmission electron microscopy. United States: N. p., 2007. Web. doi:10.1063/1.2745333.
Morandi, Vittorio, & Merli, Pier Giorgio. Contrast and resolution versus specimen thickness in low energy scanning transmission electron microscopy. United States. doi:10.1063/1.2745333.
Morandi, Vittorio, and Merli, Pier Giorgio. Fri . "Contrast and resolution versus specimen thickness in low energy scanning transmission electron microscopy". United States. doi:10.1063/1.2745333.
@article{osti_20979430,
title = {Contrast and resolution versus specimen thickness in low energy scanning transmission electron microscopy},
author = {Morandi, Vittorio and Merli, Pier Giorgio},
abstractNote = {A theoretical and experimental investigation of contrast and resolution versus specimen thickness in scanning transmission electron microscopy at low energy is reported. Due to absence of postspecimen imaging lenses it is possible to have images with a resolution defined by the probe size using very wide collection angles and independent of the energy loss of the transmitted electrons. The fundamental limitation in observable specimen thickness is represented by the signal to noise ratio, i.e., the intensity of the beam current. The investigated specimens are semiconductor multilayers and Sb precipitates in a Si implanted specimen. The observations of layers crossing the whole specimens parallel to the electron beam point out that only a small portion of them, the one close to the surface, causes the image contrast, while the portion below, where the probe diameter, as a consequence of the broadening, is larger than the layer itself, reduces the contrast. A similarity with recent results, achieved in scanning transmission electron microscopy at high energy, where the layers are represented by atomic columns, is pointed out. The image contrast depends on the angular distribution of the transmitted electrons, and for thick specimens it is always of bright field type, independent of the collection angle of the transmitted electrons. The observation of Sb precipitates, distributed along the specimen thickness, evidences the role of beam broadening on the resolution and contrast.},
doi = {10.1063/1.2745333},
journal = {Journal of Applied Physics},
number = 11,
volume = 101,
place = {United States},
year = {Fri Jun 01 00:00:00 EDT 2007},
month = {Fri Jun 01 00:00:00 EDT 2007}
}