57 mn mössbauer collaboration at isolde/cern emission mössbauer spectroscopy of advanced materials...

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)


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,…)


• 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


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


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

0

50

100

150

200

250

300

350

Publ

icat

ions

Year

Inspec search: "ZnO + magnetic"


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


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


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


2. Vacancy diffusion in silicon

-20

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-16

-14

-12

-10

-8

-6

-4

-2

0 1 2 3 4 5 6 7 8

1000/T (K-1)

Log

10( D

V (

cm2 /s

))

Watkins et al ., 60's-80's

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0 1 2 3 4 5 6 7 8

1000/T (K-1)

Log

10( D

V (

cm2 /s

))

Voronkov et al ., 2006 & 2009

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0 1 2 3 4 5 6 7 8

1000/T (K-1)

Log

10( D

V (

cm2 /s

))

Bracht et al ., 2003

Gunnlaugssonet al ., 2010 (+2003)(ISOLDE data)


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


2. Time-delayed Mössauer spectroscopy- results from test experiments -


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


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.


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


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


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


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


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.


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

57 mn mössbauer collaboration at isolde/cern emission mössbauer spectroscopy of advanced materials...

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