IAEA CRP: Ion Beam Modification of Insulators
RCM, Dec. 10-14, 2007, FNRC, Uni. Chiang Mai, Thailand
Study of the formation of ferro-, para- and superparamagnetic nano clusters by ion implantation itno suitable
insulators
Principal investigators : Prof. K. Bharuth-Ram , University of KwaZulu-Natal, Durban
and iThemba LABS, Faure. S. Africa
Prof. Dr. Hans Hofsaess, Universitaet Goettingen, Germany
+ Carsten Ronning, Peter Schaaf, Michael Uhrmacher, Uni-Goettingen.
Terry Doyle, Cebo …, iThemba LABS, South Africa.
+ Uli Wahl: Emission channeling
Gerd Weyer et al., MS following Mn57 implantation
Introduction
Nanoclusters of Fm atoms have high proportion of surface atoms
• increase spin magnetic moment towards high spin limit
• reduction in effective quenching of the orbital magnetic moment.
+ quantum size effects + modified valence electron screening
Novel properties:
magnetic moments enhanced by up to 35%
superparamagnetic behaviour in clusters below a critical size
magnetic behaviour in non-FM transition metals
Applications in ultra-high recording magnetic recording media,
information and telecommunications technology.
Achieved already by ion implantation at doses of 1017 cm-2.
- due to accumulation at extended lattice sites?
or diffusion and agglomeration of implanted ions?
Objective:
Investigate the implantation parameters required to achieve magnetic
nano-clusters,
i.e. energy and dose,
sample temperature and annealing characteristics,
Methods include
•
Temperature dependent Moessbauer spectroscopy and magnetization
measurements, to determine the size of clusters and their magnetic properties.
•
RBS and Raman Spectrometry, MOKE, UV-VIS Transmission Spectrometry
-- to determine implantation profile and complex formation in the host matrix.
Reported on in June 2006:
Implant of 57Fe at E = 60 keV, at Uni-Goettingen
to a dose of 5 x 1015 cm-2 .
Substrates: 3C-SiC, CVD diamond, graphite
Moessbauer spectroscopy (at UKZN) at RT and LN2 on 3C-SiC sample:
as-implanted sample, and after annealing at 400 C.
Moessbauer spectroscopy (at Uni-Goettingen) after annealing at 600 C
VSM on as-implanted and after annealing at 600 C on 3C-SiC sample
MOKE and Raman Spectroscopy on as- implanted and after annealing at
400 C and 600 C: CVD and 3C-SiC samples
Results: Mossbauer Measurements
a) SiC(Fe): as implanted)
b) SiC(Fe):TA=400 K)
57
SiC: Mn
4
a RT
3
T = 300 K
T = 300 K
Normalized Yield
Normalized Yield
2
1
4
b 700 K
3
2
T = 80 K
T = 80 K
1
-6
-4
-2
0
2
Velocity (mm/s)
4
6
-6
-4
-2
0
2
Velocity (mm/s)
4
6
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Velocity (mm/s)
Mossbauer measurements were made with a approx. 8 mCi source (30 mCi in May 2003).
Each spectrum at RT, has > 10 million events, accumulated over 4 weeks.
At LN2, longer measurement time was required.
MOKE Measurements (Magneto-Optical Kerr Effect)
b) TA = 900 K
a) As implanted
0.3
0.3
CVD 337, Fe implanted
CVD 345 not implanted
0.2
0.1
0.1
0.0
0.0
-0.1
-0.1
-0.2
-0.3
-1500
-1000
-500
0
500
1000
1500
0.3
MOKE-Signal (mV)
-0.3
0.1
0.0
0.0
-0.1
-0.1
-0.2
-0.2
-0.3
-1500
-1000
-500
0
500
HMOKE (Oe)
1000
1500
-1500 -1000
-500
0
500
1000
1500
500
1000
1500
0.3
0.1
-0.3
CVD 345 not-implanted
CVD 337 Fe implanted
-0.2
0.2
3C-SiC not implanted
57
3C-SiC Fe implanted
0.2
MOKE-Signal (mV)
MOKE signal (mV)
0.2
SiC not implanted
SiC- Fe implanted
-1500 -1000
-500
0
HMOKE (Oe)
VSM Measurements
(TB Doyle, UKZN)
• SiC(Fe) sample , Virgin SiC, Holder
3
only possible after acquisition
of a bipolar power supply for
magnet, obtained in 2005 as
donation from the Alexander
von Humboldt Stiftung.
SiC(Fe) - SiC
TA= 900 K
1
-5
m (emu X10 )
2
VSM measurements
Plot shows average of data
collected during many
measurements over several
months (TB Doyle).
0
-1
-2
-3
-3000 -2000 -1000
0
H (Oe)
1000
2000
3000
We are at the limit of
resolution of the device, but a
small ferromagnetic effect is
noticeable.
Raman Spectroscopy
1100
1200
1300
1400
Raman shift [cm^-1]
1500
diamond as grown
diamond implanted
1600
1300
Raman shift [cm^-1]
a) CVD diamond as-Implanted
1400
b) CVD diamond annealed at 900 K
SiC as grown
SiC implanted
Intensity [a.u.]
1000
Intensity [a.u.]
Intensity [a.u.]
diamond as grown
diamond implanted
c) 3C-SiC sample annealed at 900K
700
800
900
Raman shift [cm^-1]
1000
There is evidence of ferromagnetic and paramagnetic ordering,
but data with better statistics is required.
So, Plans for 2007 included:
i) obtaining new, stronger Moessbauer Sources (50 mCi)
ii) Increasing the concentration of Fe in the samples,
iii) investigating implantation induced magnetization effects in other
substrates.
Early in 2007, enriched 57Fe pellets were purchased, and implantation into
3C-SiC, CVD diamond, ZnO, SiO2 and graphite were undertaken at 60 and
80 keV energy, and up to a fluence of 1 x 1016/cm2 (at Goettingen).
Two 50mCi MS sources ordered, eventually delivered in Oct. 2007
Measurements from end October : CEMS, TMS.
Substrate
Fluence
(x1016/cm2)
Temp
(K)
MOKE
RBS
Raman
CVD
0.50
RT
600C
RT
Y
Y
Y
Y
Y
Y
1.00
3C-SiC
0.50
1.00
RT
400C
RT
300C
Graphite
0.05
0.50
ZnO
0.50
RT
1.0
RT
325C
0.50
RT
1.00
RT
SiO2
UV-VIS
MOSS
VSM
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Hyperfine Interactions and Measurables
1. Isomer Shift
3. Electric Quadrupole Interaction
d = k (rabs – rref)(<re2> – <rg2 >),
lattice site, charge state
Emag = - m . B
Emag = mI . g mN. Bz
Relative Transmission
2. Magnetic interaction
-8 -6 -4 -2
0
2
4
Velocity (mm/s)
SAIP 2007
6
8
-4
-3
-2
-1
0
1
2
Velocity (mm/s)
3
4
3C-SiC: Fe57
RBS Measurements
4
He : 2 MeV
2500
200
2 MeV 4He+
Yield
150
2000
Grazing angle = -10O
100
Yield
50
C
1500
Si
0
340
350
360
370
380
390
Channel
1000
Fe
500
0
0
100
200
300
400
500
Channel
15000
1200
ZnO
1000
4000
10000
CVD Diamond
125
800
1000
0
340
360
380
400
420
100
C
Yield
2000
Yield
Yield
Yield
3000
25
440
Channel
5000
75
50
600
0
340
400
360
380
400
Channel
Fe
200
0
0
100
200
300
Channel
400
500
0
100
200
Channel
300
400
500
3C-SiC: Fe57
UV-VIS Transmission
80
1. 3C-SiC: virgin and implanted region
60
Transmission
i) as implanted,
ii) Annealed at 350C.
2. ZnO: Implanted regions
40
Unimplanted, RT
Implanted region, as impl.
Unimplanted, TA=300 K
Implanted region, TA=300K
20
i) as implanted
0
ii) Annealed at 350 C.
400
500
600
700
800
900
Wavelength (nm)
ZnO : UV-VIS Transmission
Transmission
80
60
40
as implanted
TA= 350 K
20
0
200
400
600
800
Wavelength (nm)
1000
1000 1100
3C-SiC
57
15
1 x 1016/cm2
257
Fe: 5 x 10 /cm Fe
histogram
D1: d = 0,14 mm/s,
EQ= 0.96 mm/s
D2: d = 0.16 mm/s,
EQ=1.45 mm/s
Sxt1: d = 0.68 mm/s,
Bhf= 164 kOe
Sxt2:d = 0.58 mm/s,
Bhf= 465 kOe
Yield
Relative Yield
3C-SiC
57
16
-2
Fe: 1 x 10 cm
TA= 573 K
d (mm/s) EQ f(%)
D1: 0.19 1.10
77(5)
D2: -0.10 1.20(4) 11(3)
D1: d = 0,14 mm/s,
EQ= 0.96 mm/s
D2: d = 0.16 mm/s,
EQ=1.45 mm/s
S1: -0.23
10(3)
Bhf= 127(5) kOe.
-8
-6
-4
-2
0
2
Velocity (mm/s)
4
6
8
-10 -8
-6
-4
-2
0
2
4
Velocity (mm/s)
6
8
10
SiO2
D1: d = 0.75mm/s
EQ= 0.91mm/s, f=47(4)%
D2: d = 1.07mm/s
EQ=1.37mm/s, f=28(4)%
S1: d = 0.98mm/s
Bhf= 532kOe, f=10(3)%
S2: d = 0.46 mm/s
Bhf = 92kOe, f=15(5)%
SiO2
57
16
-2
Relative Yield
Fe: 1 x 10 cm
as implanted
D1: d = 0.71mm/s
EQ= 1.01mm/s, f=57(5)%
D2: d = 1.11mm/s
EQ=1.31mm/s, f=43(5)%
-10 -8
-6
-4
-2
0
2
4
Velocity (mm/s)
6
8
10
ZnO
3+
ZnO
57
16
2
Fe: 1x10 /cm
(Fe )
S1: IS = 0.57
2+
(Fe )
1.004 D1: IS = 0.69; QS = 0.6
D2: IS = 0.78; QS = 1.2
1.006
d
EQ
S1: 0.61
D1: 0.98
D2: 0.84
Sx1
Bhf
0.60
0.92
436
TA= 350 C
as Impl.
1.002
1.001
0.999
0.998
-8
-6
-4
-2
0
2
4
6
8
Relative Yield
Intensity
1.003
Velocity ([mm/s)
-10 -8 -6 -4 -2 0
2
4
Velocity (mm/s)
6
8 10
Moessbauer Measurements
1. CVD Diamond:
Yield
CVD Diamond
57
15
2
Fe: 5 x 10 /cm
d(mm/s)
D1: 0.54
D2: 0.33
D3: 0.31
-8
-6
EQ(mm/s) f(%)
1.08
1.93
1.15
-4
11(4)
29(4)
60(6)
-2
0
2
Velocity (mm/s)
4
6
8
Magnetization measurements ???
-- merger of UDW and UN  UKZN
- School of Physics (and Fac. of Science) to Westville
campus
VSM equipment dismantled – and still in boxes!!!
Moessbauer Studies following
57Mn
b
EC
5/2-
implantation
57Co
137 keV
1. 57Co source: 30 mCi +
Typical dose: 5 x 1014 57Fe
 tm ~ 14 days
lattice damage
CE
3/2½-
57Mn
14.4 keV, 98 ns
0
57Fe
At ISOLDE, CERN
Mass separated 57Mn* accelerated to 60 keV,
and implanted into sample held at temp T.
14.4 (+E) keV gammas detected in PPAC,
mounted directly on to MDU.
2. In-beam MS
CE and recoil implant
tm ~ 24 –36 hrs
Dose < 1010 cm-2.
teff = t .
3. 57Mn* implantation
Dose < 1013 cm-2.
b decay  57Fe*
Erecoil = 40 keV
tm~ 10 min.
57Fe*
Production of radioactive ion beams
at ISOLDE, CERN.
CVD05
300 K
414 K
90
80
Area Fraction (%)
Relative Yield
495 K
630 K
70
FeS
Fei
Fex
FeD
60
50
40
30
20
10
774 K
0
300
400
500
600
700
Temperature (K)
854 K
-4
-3
-2
-1
0
1
2
Velocity (mm/s)
3
4
800
3C-SiC
4
305 K
700 K
3
2
80
1
4
769 K
70
Normalized Yield
3
2
1
4
495 K
836 K
3
2
Areal Fraction (%)
380 K
FeS
FeD
Fei,1
Fei,2
60
50
40
30
20
10
1
4
907 K
630 K
0
300
3
400
500
600
700
Temperature (K)
2
1
-3
-2 -1 0
1
2
Velocity (mm/s)
3
-3
-2 -1 0
1
2
Velocity (mm/s)
3
800
900
Graphite
300 K
Relative emission (arb.units)
415 K
495 K
663 K
774 K
854 K
-5
-4
-3
-2
-1
0
1
Velocity (mm/s)
2
3
4
5
ZnO:Fe
730 K
Components:
594 K
S1 : Single line
D1: defect doublet
462 K
Sx1 : sharp FM sextet
Sx2 & Sx3: Broad sextets
with Eq interaction.
405 K
Effect is reversible.
350 K
 due Fe-V-O complex??
304 K
-10
-8
-6
-4
-2
0
2
4
Velocity (mm/s)
6
8
10
Conclusions
1. The lighter mass substrates ( SiC, SiO2) hold greater promise.
2. After implantation to a fluence of 1 x 1016 / cm2
 indications of magnetically split components in Moessbauer
spectra
 this fluence gives Moessbauer spectra with acceptable statistics
 higher dose implantation with Fe-56
other fm species (Mn, Co)
non-fm species (Na, C)
ACKNOWLEDGEMENTS
1. IAEA – Wulf Rosenberg and Francoise
Mullhauser
2. Hans Hofsaess, Uli wahl and colleagues in
Goettingen
3. Yu Liangden and FNRC, Chiang Mai University
4. The Group generally.
Thank You