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First Observation of InxGa1−xAs Quantum Dots in GaP by Spherical-Aberration-Corrected HRTEM in Comparison with ADF-STEM and Conventional HRTEM

Published online by Cambridge University Press:  22 January 2004

Nobuo Tanaka ,
Jun Yamasaki ,
Shingo Fuchi  and
Yoshikazu Takeda
Nobuo Tanaka
Affiliation:
Center of Integrated Research in Science and Technology, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
Jun Yamasaki
Affiliation:
Center of Integrated Research in Science and Technology, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
Shingo Fuchi
Affiliation:
Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
Yoshikazu Takeda
Affiliation:
Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
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Abstract

InxGa1−xAs quantum dots in GaP(100) crystals prepared by the OMVPE technique are observed along the [011] direction with a newly developed 200-kV spherical aberration(Cs)-corrected HRTEM, a 200-kV annular dark-field (ADF)-STEM, and a 200-kV conventional HRTEM equipped with a thermal field-emission gun. The dots are 6–10 nm in size and strongly strained due to the misfit of about 9% with the GaP substrate and GaP cap layer. All of the cross-sectional high-resolution electron micrographs show dumbbell images of Ga and P atomic columns separated by 0.136 nm in well-oriented and perfect GaP areas, but the interpretable images are limited to those taken with the Cs-corrected HRTEM and ADF-STEM with Fourier filtering of the images. The Cs-corrected HRTEM and ADF-STEM are comparable from the viewpoint of interpretable resolution. A detailed comparison between the Cs-corrected HRTEM images and the simulated ones with electron incidence tilted by 1° to 5° from the [011] zone axis gives information on local lattice bending in the dots from the images around 0.1 nm resolution. This becomes one of the useful techniques newly available from electron microscopy with sub-Ångstrom resolution.

Keywords

InGaAsquantum dotsGaP substrateCs-corrected HRTEMADF-STEM
Type
Research Article
Information
Microscopy and Microanalysis , Volume 10 , Issue 1 , February 2004 , pp. 139 - 145
Copyright
© 2004 Microscopy Society of America

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