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MÖSSBAUER SPECTROSCOPY OF IRON IMPLANTED COPPER, SILVER AND GOLD
ALLOYS
G. Longworth, R. Jain
To cite this version:
G. Longworth, R. Jain. MÖSSBAUER SPECTROSCOPY OF IRON IMPLANTED COPPER, SILVER AND GOLD ALLOYS. Journal de Physique Colloques, 1979, 40 (C2), pp.C2-608-C2-610.
�10.1051/jphyscol:19792211�. �jpa-00218591�
JOURNAL DE PHYSIQUE Colloque C2, suppl6ment au no 3, Tome 40, mars 1979, page C2-608
MOSSBAUER S?ECTROSCO?Y O F I R O N I M P L A N T E D COPPER, S I LVER AND GOLD A L L O Y S
G. Longworth and R.
aid
Nuclear Physics Division ( 8 ) , Atomic Energy Research EstabZishmcnt, Hamell, Oxfordshire OX11 ORA,
u. K.
R6sumB.- La detection des 6lectrons de conversion (CEMS) dans une experience Mijssbauer est utilisiie pour Btudier la composition des phases cuivre-fer, argent-fer et or-fer, implantds avec du 5 7 ~ e Zi des doses 2x10'~ ions ~ m - ~ . Les spectres sont interpretds en supposant l'existence d'atomes de fer isolEs ou en amas ainsi que celle de pr6cipiths a et y de fer. Les intensites respectives dBduites, tiennent compte des effets de pulv6risation ainsi que de l'accroissement de la diffusion induit par les radiations. Pour des doses comprises entre 10" et 5x1016 Fe cm-2 les effets des d6fauts de structure sur la valeur des paramstres hyperfin sont discutes. Enfin on mentionne l'btude de la mi- gration du fer, dans et hors la zone d'implantation, causee par un recuit.
Abstract.- ~ijssbauer conversion electron scattering (CEMS) is used to study the phase co ositions of copper-, siluer- and gold-iron alloys produced by 17pe implantation at a dose of 2x10' ions
The spectra are explained in terms of contributions from isolated iron atoms, iron clusters and from a- and y-iron precipitates, whose relative intensities are accounted for by a considera- tion of sputtering effects and of radiation enhanced diffusion. For doses between 1 0 1 5 and 5 x 1 0 ' ~ ions ~ m - ~ the effects on the hyperfine parameters of defect structures are discussed. Finally the use of post-anneals to study the migration of iron atoms within and away from the implanted layer is mentioned.
Introduction.- The use of ion implantation /I/ Experimental technique.- The alloys discussed here allows the equilibrium solubilities in alloys to be were prepared by implanting 85 kev iron-57 ions into exceeded although a limit to the implanted ion so- the metal foils using the Harwell variable geometry lubility is set by the sputtering of target atoms magnetic isotope separator. In the absence of sput- from the host surface. In the alloys considered tering the mean projected range is 100-200
1
which here : copper, silver and gold iron, the saturation is a convenient depth for Mzssbauer conversion elec- concentration expected is of the order of 5-10 ato- tron scattering (CEMS). The spectra (Fig.1) obtained mic percent which apart from the case of gold iron for copper, silver and gold iron alloys for a common is much greater than the equilibrium solubilities. dose of 2x10'~ ions cm-2 are compared, and the re-The lattice defects formed due to radiation sults for different doses in the range 10"
-
5 x 1 0 ' ~ damage during implantation may also be studied and ions ~ m - ~ , and for the effect of post-annealing are if the implanted atom is a Mgssbauer atom then we outlined. In the case of copper and silver iron a may look for a perturbation of the hyperfine in- fuller treatment of the latter aspects has been pre- teractions due to the effects of such defects. The sented elsewhere /2,3,4/. The spectra were fitted implanted ions will displace the host atoms in to Voigt profiles apart from those for &Fe where elastic collisions and since the displaced atoms Lorentzian profiles were used, and the main hyper- frequently have sufficient energy to displace fur- fine parameters are listed in table I.ther atoms, a cascade of atomic collisions is set up
with the production of large numbers of vacancies Table I : Hyperfine components derived from least- squares fits to GEMS spectra for copper, and interstitials. Although many of these recombine, silver and gold iron alloys. Shifts are the remainder will either condense into defect clus-
ters or if sufficiently mobile will diffuse away from the damaged region. Such mobile vacancies lead 'to radiation enhanced diffusion which may result in clustering or in precipitation of new phases which are expected only at higher temperatures according to the phase diagram.
I On leave from Indian Institute of Technology, New Delhi 110029, India.
quoted with respect to that for a-iron.
: I s o l a t e d i r o n ; I r o n c l u s t e r : a o r y l r o n
A l l o y :--- ;
---.---..----.---
* ---: S h l f t : : S h i f t ; S p l i t t i n g ; : S h i f t :
/
m s - ~;
a r e a ms-l : ms-,;
a r e a : , mns-l j a r e a CuFei
0.239/
20 X j 0.233 j 0.56 : 63 Xi
-0.11 : 11 X -3 F e
i
0 . S : 27 X1
0.17 : 0.88i
23 1 j 0.31 j 43 X A u F e j 0 . 6 4 ; 6 5 1i
0 . 6 0 i 0 . 7 4 ; 2 8 %i
-1
--
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792211
Fig. I : CEMS spectra for implanted copper iron (A), silver iron (B) and gold iron alloys (C), for dose of 2x10'~ iron-57 ions cm-'. The solid lines are the re- sult of leastsquares fits and the zero of the velo- city scale corresponds to the shift of a-iron.
Results and discussion.- Although the spectra appear to have different overall shapes they may be fitted essentially to three components 1. an isolated iron singlet, 2. a cluster doublet and 3. an alpha or gamna iron singlet, similar to those used for the spectra of solution quenched alloys of copper iron 151. Using a simple sputtering model 161 retained doses of 1.8~10'~. 9.8x1015 and 6 . 3 ~ 1 0 ' ~ ions were calculated for &Fe, &Fe and &Fe resulting in peak Fe atomic concentrations of 6,5 and 4 %. The isolated line due to iron atoms with 12 host nearest neighbours has a shift and width in agreement with those measured for solution quenched alloys or in the case of &Fe for "CO in silver since iron is insoluble in silver. The narrow width implies that these iron atoms are situated at undamaged regions of the lattice, The cluster doublet is made up of contributions from iron clusters of different sizes and shapes and as such the parameters for the re- sultant component are difficult to interpret althougb in the case of e F e the shift is larger than obser- ved in solution quenched alloys which may suggest that the clusters are situated near small disloca- tion loops. When the clusters are sufficiently large
there is also a contribution from iron atoms with 12 iron neighbours which gives rise to a singlet in CuFe characteristic of y-iron. The decomposition of
-
copper iron solid solutions is known to proceed via formation of coherent y-iron precipitates /5/ which may form due to the similarity in lattice parameters of y-iron and copper. This matching is not as close for silver and it is suggested that the precipitates here transform to a-iron before they can grow above about 20-30
1,
as revealed by the superparamagnetic a-iron singlet (table I) and the low cluster frac-tion. The singlet identification is confirmed by observation of a magnetic spectrum at 4.2 K in the absorption spectrum and also in the scattered spec- trum after post annealing of the sample. Only for AuFe where the iron solubility is -15 % is the iso-
-
lated fraction ( ~ 6 0 %) consistent with a random solid solution. For S F e and &Fe the enhanced dif- fusion coupled with a tendency to short range order produces pronounced iron clustering.
In addition to the components in table I there is a weak component at 4 . 9 mms-' for g e and &Fe and a weak doublet (Fig. 1) for &Fe. Theie are associated with iron oxides formed from recoil im- planted oxygen impurity atoms. For a dose of 5x1016
iron-57 ions cm-' in silver a spectral component from FesC was observed which was due to recoil im- planted carbon, from an adsorbed hydrocarbon layer.
The variation in the relative component frac- tions over doses 10"
-
5x10'~ ion for copper, silver and gold can be explained in terms of the above model allowing for changes in the implantation profile with dose due to sputtering effects. An *no- malous isolated iron component was observed in thespectrum for 5x10'~ ions cme2 for copper, with a shift of 0.34 mms-' and width of 0.5 nuns-'. After annealing at 2 4 5 " ~ for one hour, this line reverted to its expected position and width and it seems li- kely that the iron atoms were situated originally near a small vacancy cluster /2,3/. The effect of post-anneals on the samples is to allow the iron atoms both to diffuse within the implanted layer, with changes in the component fractions, and also ultimately into the bulk of the host at temperatures ranging from about 400°C for copper and about 600°c for silver and gold iron.
These measurements suggest that &ssbauer spec- troscopy can play an important role in the determi- nation of the phase composition and metallurgical state of implanted alloys when the implanted ion is a Mgssbauer atom. This is also true to a lesser ex- tent when non-KGssbauer ions are implanted into iron 171.
JOURNAL DE PHYSIQUE References
/I/ Dearnaley, G., Freeman, J.H., Nelson, R.S. and Stephen, J., Ion Implantation (Amsterdam : North Holland) 1973.
/2/ Longworth, G. and Jain, R., J. Phys F : Metal Phys.
8
(1978) 351./3/ Jain, R. and Longworth, G., J. Phys. F : Metal Phys.
8
(1978) 363./ 4 / Longworth, G. and Jain, R.J. Phys. Metal Phys.
8
(1978) 993.
/5/ Window, B. Philos, Mag.
26
(1972) 681.161 Bett. R. and Charlesworth, J.P. UKAEA Report AERE- R7052 (1973).
/7/ Longworth, G. and Hartley, N.E.W., Thin Solid Films 48 (1978) 95.
