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X-Ray Absorption Spectroscopy from H-Passivated Porous Si and Oxidized Si Nanocrystals

Published online by Cambridge University Press:  15 February 2011

S. Schuppler ,
S. L. Friedman ,
M. A. Marcus ,
D. L. Adler ,
Y.-H. Xie ,
F. M. Ross ,
T. D. Harris ,
W. L. Brown ,
Y. J. Chabal  and
P. J. Szajowski
...Show all authors
S. Schuppler
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
S. L. Friedman
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
M. A. Marcus
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
D. L. Adler
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
Y.-H. Xie
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
F. M. Ross
Affiliation:
National Center for Electron Microscopy, Lawrence Berkeley Laboratory, Berkeley, CA 94720
T. D. Harris
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
W. L. Brown
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
Y. J. Chabal
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
P. J. Szajowski
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
E. E. Chaban
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
L. E. Brus
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
P. H. Citrin
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974
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Abstract

Quantum confinement in nanoscale Si structures is widely believed to be responsible for the visible luminescence observed from anodically etched porous silicon (por-Si), but little is known about the actual size or shape of these structures. Extended x-ray absorption fine structure data from a wide variety of por-Si samples show significantly reduced average Si coordination numbers due to the sizable contribution of surface-coordinated H. (The H/Si ratios, as large as 1.2, were independently confirmed by ir-absorption and α-recoil measurements.) The Si coordinations imply very large surface/volume ratios, enabling the average Si structures to be identified as crystalline particles (not wires) whose dimensions are typically <15 Å. Comparison of the size-dependent peak luminescence energies with those of oxidized Si nanocrystals, whose shapes are known, shows remarkable agreement. Furthermore, near-edge x-ray absorption fine structure measurements of the nanocrystals shows the outer oxide and interfacial suboxide layers to be constant over a wide range of nanocrystal sizes. The combination of these results effectively rules out surface species as being responsible for the observed visible luminescence in por-Si, and strongly supports quantum confinement as the dominant mechanism occurring in Si particles which are substantially smaller than previously reported or proposed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 375: Symposia AA – Applications of Synchrotron Radiation Techniques to Materials Science , 1994 , 113
Copyright
Copyright © Materials Research Society 1995

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References

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