57 mn mössbauer collaboration at isolde/cern emission mössbauer spectroscopy of advanced materials...
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57Mn Mössbauer collaboration at ISOLDE/CERN
Emission Mössbauer spectroscopy of advanced materials for opto-
and nano- electronics
Spokepersons: Haraldur Páll GunnlaugssonSveinn Ólafsson
Contact person: Karl Johnston
CERN-INTC-2010-003 (INTC-P-275)
57Mn Mössbauer collaboration at ISOLDE/CERN
Mössbauer spectroscopy
• Valence(/spin) state of probe atom (Fen+, Snn+)
• Symmetry of lattice site (Vzz)
• Diffusion of probe atoms (few jumps ~100 ns)• Debye-Waller factors• Magnetic interactions• Paramagnetic relaxations of Fe3+
• Can usually easily detect up to 5-6 spectral components (substitutional, interstitial, damage, vacancy-defects,…)
57Mn Mössbauer collaboration at ISOLDE/CERN
• Work with dilutions (< 10-4 at.%) not possible with conventional MS
• Site selective doping with different parents:
• Make use of ”special” properties- Recoil to create interstitials (57Mn, 119In)- Observe meta-stable electronic states (57Co)
57Co (271 d)
Radioactive Mössbauer spectroscopy
119mSn (290 d)
119Sb (38 h)
119Sn
119In (2.1 m)
57Fe
57Mn (1.5 m)
PACUse in homelaboratories
Off-line atISOLDE
57Mn Mössbauer collaboration at ISOLDE/CERN
This proposal
• Some basic ideas:– Growing collaboration → Do more
• Research themes:1. Paramagnetic relaxations in compound
semiconductors (diluted magnetic semiconductors)2. Vacancy diffusion in group IV semiconductors 3. Doping of Si-nano-particles 4. Investigation of phase change mechanisms in
chalcogenides
57Mn Mössbauer collaboration at ISOLDE/CERN
1. Paramagnetic relaxations in compound semiconductors (diluted magnetic semiconductors)Doping ZnO semiconductors
with few percentages of 3d metals make the material magnetic at room temperature (Dietl et al., Science, 287 (2000) 1019)
Potential multifunction material or ”Dilute Magnetic Semiconductor (DMS)” with applications in spintronics
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Publ
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Year
Inspec search: "ZnO + magnetic"
57Mn Mössbauer collaboration at ISOLDE/CERN
1. What can we do at ISOLDE
• We don’t have to worry about precipitation
-12 -9 -6 -3 0 3 6 9 12
Velocity (mm/s)
Rel
ativ
e em
issi
on (
arb.
uni
t)
B e ║ c
~ 0° g
D2D3
S Z = ±1/2 S Z = ±3/2 S Z = ± 5/2
B e ║ c
~ 60° g
0.E+00
2.E+08
4.E+08
6.E+08
8.E+08
1.E+09
1.E+09
1.E+09
300 500 700 900
Temperature (K)
Rel
axat
ion
rate
(H
z)
ExperimentalPower law
Relaxation rates
of Fe3+ in ZnO
14×108
12×108
10×108
8×108
6×108
4×108
2×108
0×108• Can measure spin-lattice relaxation rates
• Can distinguish between paramagnetism and ferromagnetism
57Mn Mössbauer collaboration at ISOLDE/CERN
1. Proposed project
• Determination of the paramagnetic properties of potential DMS and model systems (~10 samples: 6.5 57Mn shifts)
• Study paramagnetic relaxations with 57Co (~ 2 samples) : 2 shifts
• Dynamic properies by making use of 119In (~ 5 samples) : 4 shifts
• Understand the 119In data with 119mSn (2 samples): 1 shift
57Mn Mössbauer collaboration at ISOLDE/CERN
2. Vacancy diffusion in group IV semiconductors (Si-SiGe)
• Understanding diffusion mechanismes in Silicon is of fundamental importance in defect tayloring
• Vacancy of the more important defects, both intrinsic and formed upon ion implantation
• However, some gaps in our understanding
57Mn Mössbauer collaboration at ISOLDE/CERN
2. Vacancy diffusion in silicon
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1000/T (K-1)
Log
10( D
V (
cm2 /s
))
Watkins et al ., 60's-80's
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0 1 2 3 4 5 6 7 8
1000/T (K-1)
Log
10( D
V (
cm2 /s
))
Voronkov et al ., 2006 & 2009
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1000/T (K-1)
Log
10( D
V (
cm2 /s
))
Bracht et al ., 2003
Gunnlaugssonet al ., 2010 (+2003)(ISOLDE data)
57Mn Mössbauer collaboration at ISOLDE/CERN
2. What can we do at ISOLDE
• Make use of the lifetime of 57Mn and 119In to perform ”time-delayed” Mössbauer spectroscopy– Implant for short time– Measure time dependent spectra at different T’s– Repeat in different types of materials (Si-Ge, n, p)– 7.5×57Mn shifts + 4×119In shifts + 1×57Co, 2×119mSn– Do similar studies with emission channeling
57Mn Mössbauer collaboration at ISOLDE/CERN
2. Time-delayed Mössauer spectroscopy- results from test experiments -
57Mn Mössbauer collaboration at ISOLDE/CERN
3. Doping of Si-nanoparticlesSi nano-particles in SiO2 matrices have applications in opto-electronics and memory devices.
Interest in broadening the application range with tailoring doping
Sb is a possible dopant
57Mn Mössbauer collaboration at ISOLDE/CERN
3. Proposed project
Implant with 119Sb (38 h) and measure 119Sn Mössbauer spectra
-Lattice sites and annealing characteristics
-Electronic configuration (Internal pressure and Debye-Waller factors)
Need to implant into : Pure Si, Pure SiO2, at least 3 types of Si Nano-particles (differing sizes). With 2 samples per shift, 2.5 shifts are needed.
57Mn Mössbauer collaboration at ISOLDE/CERN
4. Investigation of phase change mechanisms in chalcogenides
• Ge-Sb-Te compounds• Amorphous at room temperature• Crystallize at 100ºC-150ºC with orders of magnitudes
change in resistivity and reflectivity• Used in memory applications• Very little known about structures and crystallization
mechanisms, and optimization through doping with Sn and working with off-stoichiometric compounds of interest.
From Wang et al., (2004)For Ge1.6Sn0.4Sb2Te5
57Mn Mössbauer collaboration at ISOLDE/CERN
119mSn (290 d)
4. Site selective doping of Ge-Sb-Te
119Sb (38 h)
119Te (4.7 d)
119Sn
-We can enter either Ge and/or Sb sites and monitor the changes in electronic configuration during crystallization-Implant 119Sb and 119mSn in at least 5 different types of Ge-Sb-Te compounds (2 samples/shift) : 2.5 shifts for each isotope
57Mn Mössbauer collaboration at ISOLDE/CERN
Project summary
Isotopes Theme 57Mn 57Co 119In 119Sn 119Sb Total 1. Paramagnetic relaxations in compound semiconductors
6.5 2 4 1 13.5
2. Vacancy diffusion in Si based semiconductors
7.5 2 4 1 14.5
3. Doping of Si nano-particles 2.5 2.5 4. Investigation of phase change mechanisms in chalcogenides
2.5 2.5 5
Calibration (~10%) 1.5 1 2.5 Contingency/opportunistic science (~20%)
2.5 1 2 0.5 1 7
Total 18 5 11 5 6 45
57Mn Mössbauer collaboration at ISOLDE/CERN
Beam time request
• Ask now for roughly half of the needed shifts
• Based on previous experience, this will keep us occupied for 2-3 years
• Then revise the experimental plan, give a status report and propose a addendum to conclude the plan
57Mn Mössbauer collaboration at ISOLDE/CERN
Beam request
Isotope Minimum Intensity/µC
Energy Shifts Target Ion source
57Mn (1.5 m) (2-3)×108 ≥ 50 keV 9 UCx Mn RILIS 57Co (270 d)a 9×107 ≥ 50 keV 3 ZrO2 or YtO2 VADIS 119In (2-3)×108 ≥ 50 keV 5 UCx In RILIS, or
W surf. Ionized
119mSn 1×109 ≥ 50 keV 2 UCx Sn RILIS 119Sbb 4×108 ≥ 50 keV 3 UCx Sb RILIS Total 22 aWe take all nuclei that eventually decay to 57Co ( X57
27 ). bImpurities should be below ~10%, Tellurium impurities (119Te (T½ = 4.7 d) have to be avoided.
57Mn Mössbauer collaboration at ISOLDE/CERN
2. Proposed project
• Measure time dependence in ~7 types of materials with 57Mn (~7 hours/sample + temperature mapping and test experiments) : 7.5 shifts
• Measure same effects with 119In with fewer samples: 4 shifts
• Prepeare two 57Co samples for comparison (1 sample per shift) : 2 shifts
• Make 119mSn samples : 1 shift