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Effect of swift heavy ion irradiation in Fe/W multilayer structures
Sharmistha Bagchia, S. Potdara, F. Singhb, and N. P. Lallaa
a) UGC-DAE Consortiums for Scientific Research, Khandwa Road, Indore 452001. INDIAb) Inter University Accelerating Center (IUAC), Aruna Asaf Ali Marg, New Delhi 110067. INDIA
Abstract
The present study reports the effect of swift heavy ion irradiation on structural and magnetic properties of sputtered Fe/W multilayer structures (MLS) having bilayer compositions of [Fe(20Å)/W(10Å)]5BL and [Fe(20Å)/W(30Å)]5BL. These MLS were subjected to 120 MeV Au9+ ion irradiation up to fluence of 4×1013 ions/cm2. Pristine and irradiated MLS were subjected to structural and magnetic characterization employing wide-angle x-ray diffraction (WAXD), cross-sectional transmission electron microscopy (X-TEM) and magneto optical Kerr effect (MOKE).
Tailoring the properties of functional materials at atomic scale represents the ultimate goal in material science research. The most desirable approach is to artificially fabricate the structures with atomic precision, i.e. in layer-by-layer growth. For GMR application interface quality plays a decisive role in achieving the optimum performance. In order to optimize and understand these properties; structural studies regarding interface stability, against swift heavy ion-irradiation are done. To the best of our knowledge there is almost no reports of swift heavy ion irradiation study on immiscible systems like W/Fe [1, 2].
E-mail –[email protected]
EXPERIMENTAL-DETAILES
W/Fe multilayer with composition [W(10,20,30)Å/Fe(20)Å]×5BL were deposited on Si-substrates by ion beam sputtering technique. The sample were irradiated by 120 MeV Au9+ ions at fluences between 5×1012 to 4×1013 ions/cm2. The irradiation was performed using the 15UD Pelletron accelerator at IUAC, New Delhi.The specimens were characterized before and after irradiation, using WAXD, XRR, X-TEM and MOKE.
E. Majkova, S. Luby, M. Jergel, A. Anopchenko, Y. Chushkin, G. Barucca, A. Cristoforo, P. Mengucci, E. D. Anna, A. Luches, M. Martino and H. Y. Lee Materials Science and Engineering C 19, (2002) 139. E. Majkova, S. Luby, M. Jergel, Y. Chushkin, E. D. Anna, A. Luches, M. Martino, P. Mengucci, G. Majni, Y. Kuwasawa and S. Okayasu Applied Surface Science 208, (2003) 394. S. Bagchi and N. P. Lalla, Thin Solid Films 515, (2007) 5227. S. Bagchi, S. Potdar, F. Singh and N. P. Lalla J. App. Phys. 102, (2007) 074310.S. Bagchi and N. P. Lalla. J. Phys.: Condens. Matter 20, (2008) 235202.
www.csr.ernet.in
IRRADIATION - STUDIES
The W-Fe system, with increasing bilayer thickness shows a weakly textured multilayer structure consisting of W layers oriented along [110] direction.
The SHI affects the inter-layer and intra-layer features in different ways. On irradiation the Fe-layers of the multilayer recrystallized of the individual layers into randomly oriented nano-crystals.
MOKE results show the change in coercivity and saturation value with irradiation dose, which is also consistence with the X-TEM data.
For direct observation and better understanding of the irradiation-induced microstructural changes, plane and cross-sectional TEM investigation on pristine as well as irradiated multilayer of W/Fe was carried out The observed alternate black and white layer-contrast is Z-contrast due to W and Fe layers [3, 4, 5].
INTRODUCTION OF SWIFT HEAVY ION IRRADIATION
REFERENCES
CONCLUSION
INTRODUCTION
This dominates at an energy of 1 keV
This dominates at an energy of 1 MeV or
more
Electronic Energy Loss (dE\dx)e
Nuclear Energy Loss (dE\dx)n
Thermal Spike Model
Energetic Ions
Coulomb Explosion
Magnetic Field (Oe)-1000 -500 0 500 1000
Pristine(a)
(c)
4x1013 ions/cm2
(b)
Ker
r int
ensi
ty (a
rb. u
nits
)
5x1012 ions/cm2
FeW10-5BL-Si FeW20-5BL-Si FeW30-5BL-Si
0.1 0.2 0.3 0.4 0.5
(a)
FeW10-5BL
4x1013 ions/cm2
5x1012 ions/cm2
pristine
Re
fle
ctivity
q(Å)-1
0.1 0.2 0.3 0.4
(b)
4x1013 ions/cm2
5x1012 ions/cm2
Pristine
FeW30-5BL
Ref
lect
ivity
q(Å)-1
Ref
lect
ivity
527101FeW30- 4×1013
35442FeW30- 5×1012
584132 FeW30- Pristine
59168FeW10- 4×1013
32959FeW10- 5×1012
46082 FeW10- Pristine
Saturation Field Value (Oe)
Coercivity Hc (Oe)
Multilayer Structure
FeW20-5BL
W(220)
W(110)/Fe(110)
W(200)W(211)/Fe(200)
W(321)W(400)
(b)(a)
1st
10nm
1st
(c) 10nm
W(220)W(211)
(d)
W(110)/Fe(110)W(200)
W(321)W(400)
W(110)/Fe(110)
W(200)W(211)
(f)
(a)
1st2nd
10nm
(d)
W(110)/Fe(110)
W(211)
W(110)/Fe(110)
Fe(200)
W(211)
(b)
W(110)/Fe(110)
W(200)
W(211)
(f)
(c)10nm
1st
2nd
(e)20nm
1st
(e)20nm
1st
2nd
Irradiated MLS
36 38 40 42 44 46
(a)
5x1012 ions/cm2
4x1013 ions/cm2
Pristine
Inte
nsi
ty (
arb
. u
nits
)
2 (Degree)
FeW10-5BL
38 40 42 44 46 48
Pristine
5x1012 ions/cm2
FeW30-5BL
4x1013 ions/cm2
Inte
nsi
ty (
arb
. u
nits
)
2 (Degree)
40 45
Inte
nsi
ty (
arb
. units
)FeW20-5BL
4x1013 ions/cm2
5x1012 ions/cm2
Pristine
2(degree)
FeW10
FeW10
Irradiated
FeW20 FeW20
Irradiated
FeW30
Irradiated
FeW30