Oxygen '96

Early Stages of Oxygen Precipitation in Silicon

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THE NITROGEN-PAIR OXYGEN DEFECT IN SILICON

F. Berg Rasmussen(a), R. Jones (b), S. Öberg(c), C. Ewels(b), J. Goss(b),
J. Miro(d), and P. Deák(d)

(a)Van der Waals-Zeeman Laboratorium, Universiteit van Amsterdam,
Valckenierstraat 65-67, NL-1018 XE Amsterdam, THE NETHERLANDS
(b)Department of Physics, University of Exeter, Exeter EX4~4QL, UK
(c)Department of Mathematics, University of Lule\aa ,Lule\aa, S95187, SWEDEN
(d)Department of Atomic Physics, Technical University of Budapest,
Budafoki út 8, H-1111 Budapest, HUNGARY.

Keywords: nitrogen, oxygen, infrared absorption, ab-inito theory.

The properties of nitrogen in silicon have attracted much attention during the years. In oxygen-lean silicon the dominant nitrogen defect is a nitrogen pair consisting of two neighbouring <100> oriented N-Si split interstitials bonded into a squarelike configuration lying on a {011} plane. Of special interest is the interaction between the nitrogen pair and oxygen in oxygen-rich material. Three infrared absorption lines at 1026, 996 and 801 cm^-1, resp., were observed in N- and O-implanted FZ-Si [1]. They were ascribed to a nitrogen-pair oxygen defect but no microscopic model of the defect could be given. In this study we combined measurements of the isotopic shift of the infrared absorption lines with ab initio cluster calculations to deduce the microscopic structure of the defect.

Infrared absorption measurements have been carried out on FZ silicon samples implanted with various combinations of ¹⁶O, ¹⁷O, ¹⁴N and ¹⁵N. The observed isotopic shifts are consistent with a defect containing two nitrogen atoms and one oxygen atom and show that the local modes of the three impurity atoms are only weakly dynamically coupled.

Ab initio local density functional cluster calculations were carried out on various models of nitrogen-pair oxygen defects and the impurity-related vibrational modes were evaluated in each case.

A model consisting of a bridging oxygen atom adjacent to the nitrogen pair, accounts for the dynamic properties of the observed defect with fair agreement between measured and calculated isotopic shifts and is suggested as a model of the defect.

[1]: H. J. Stein, in Oxygen, Carbon, Hydrogen and Nitrogen in Crystalline Silicon, ed. J. C. Mikkelsen et al. (MRS, Pittsburgh, PA, 1985) Vol. 59, p. 523

Last modified: Sun Mar 17 15:09:59 GMT 1996 JG