H. Wang et al., Phase transformation of (Ni66Fe22Co12)(x)C1-x nanocomposite films preparedby d.c. magnetron co-sputtering, THIN SOL FI, 382(1-2), 2001, pp. 133-138
(Ni66Fe22Co12)(x)C1-x nanocomposite films with x = 10-75 at.% were prepared
by d.c. magnetron co-sputtering. Subsequent thermal annealing was performe
d in a vacuum (<2X10(-3) Pa) furnace for 1 h at various temperatures. The m
icrostructure evolution of the as-deposited and annealed films was characte
rized by non-Rutherford backscattering spectroscopy, X-ray photoelectron sp
ectroscopy, X-ray diffraction, Raman spectroscopy, and atomic force microsc
opy. Results showed that the phase transition with the increase of annealin
g temperature was closely dependent on the composition. Films with less tha
n 20 at.% NiFeCo showed an amorphous structure in the as-deposited and up t
o 400<degrees>C annealed samples. After annealing at 500 degreesC, a small
amount of face-centered-cubic (fcc) crystalline NiFeCo precipitated while c
arbon remained amorphous. For the films with NiFeCo concentration in the ra
nge of 30-55 at.%, the as-deposited films were found to consist of very sma
ll NiFeCo nanocrystals encapsulated in amorphous carbon. After annealing, t
he crystal grain size of the alloys increased with the increase of annealin
g temperature while carbon was graphitized. For the films with more than 62
at.% NiFeCo, the as-deposited films went through a meta-stable stage at wh
ich a rhombohedral Ni3C phase and fee NiFeCo co-existed upon annealing to a
temperature between approximately 300 and 400 degreesC (dependent on compo
sition). Upon further annealing to a sufficiently high temperature between
approximately 350 and 500 degreesC, the carbide phase decomposed and only t
he fee NiFeCo nanocrystals encapsulated in graphite existed in the films. (
C) 2001 Elsevier Science B.V. All rights reserved.