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NiAl3 formation in Al/Ni thin-film bilayers with and without contamination

Ma, E. and Nicolet, M-A. and Nathan, M. (1989) NiAl3 formation in Al/Ni thin-film bilayers with and without contamination. Journal of Applied Physics, 65 (7). pp. 2703-2710. ISSN 0021-8979. http://resolver.caltech.edu/CaltechAUTHORS:MAEjap89

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Abstract

The interfacial reactions induced by vacuum furnace annealing and rapid thermal annealing in sequentially deposited Al/Ni bimetallic thin-film diffusion couples have been investigated with MeV 4He+ backscattering spectrometry, cross-sectional transmission electron microscopy, and Auger electron spectroscopy. Upon annealing, NiAl3 is the first aluminide phase to grow. In uncontaminated samples, the NiAl3 growth proceeds in uniform planar fashion, governed by diffusion-limited kinetics. The kinetics data fit well with those for NiAl3 growth on large-grained Al substrates, yielding a common kinetics law of x2=kt, where x is the thickness of the NiAl3 grown at the interface, t is the annealing duration, and k is the growth constant, which is given by k=2.24(cm2/s) exp(−1.5±0.1 eV/kBT), in which T is the annealing temperature and kB is the Boltzmann constant. Microscopic examination reveals slight nonuniformity at the Al/NiAl3 interface resulting from shallow local protrusions of NiAl3 grains into the Al layer at grain boundaries. When either the Al film or the Al/Ni interface is purposely contaminated during sample preparation, the roughness at this Al/NiAl3 interface becomes very pronounced, and the reaction rate is significantly reduced. Meanwhile, Ni motion becomes appreciable as NiAl3 grains and/or Ni severely penetrate the Al layer. In contrast, the NiAl3/Ni interface remains sharp in all samples. The irregular morphology and nonuniform reaction cannot be attributed uniquely to the presence of grain boundaries in the Al film, but rather are a combined effect of impurities and Al grain boundaries. Short-term rapid thermal annealing at elevated temperatures appreciably alleviates the nonuniformity at the Al/NiAl3 interface in contaminated samples.


Item Type:Article
Additional Information:Copyright © 1989 American Institute of Physics (Received 26 August 1988; accepted 6 November 1988) The authors wish to thank Professor W.L. Johnson of Caltech for helpful discussions on the results and on the general topic of reactions in thin-film diffusion couples, and Dr. E. Colgan of IBM East Fishkill for useful comments and suggestions. We appreciate the technical assistance of G. Mendenilla and K. Olver of Martin Marrietta Laboratories. This work was suuported at Caltech in part by the National Science Foundation - MRG Grant No. DMR-8811795 and by a grant from Intel Corporation.
Subject Keywords:ALUMINIUM; NICKEL; THIN FILMS; NICKEL COMPOUNDS; ALUMINIUM COMPOUNDS; HELIUM IONS; ANNEALING; TRANSMISSION ELECTRON MICROSCOPY; FILM GROWTH; INTERFACE STRUCTURE; GRAIN BOUNDARIES; MICROSTRUCTURE; MORPHOLOGY; BACKSCATTERING; AUGER ELECTRON SPECTROSCOPY; ROUGHNESS; IMPURITIES; BILAYERS; MEV RANGE 01−10
Record Number:CaltechAUTHORS:MAEjap89
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:MAEjap89
Alternative URL:http://dx.doi.org/10.1063/1.342756
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8557
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:20 Aug 2007
Last Modified:26 Dec 2012 09:40

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