(n,p) emission channeling measurements

on ion-implanted beryllium

INTC-P-233

J.P. Araujo, J.G. Correia, M. Dawson, M. Faist, H.O.U. Fynbo, C. Granja, J. Jakubek, M. Jentschel, U. Köster,

V. Nesvizhevsky, S. Pospisil, T. Soldner, J. Uher, J. Vacik, A. Van Overberghe, U. Wahl

Characteristic EC patterns for silicon lattice

Emission channeling measurements: basic principles

Elements for which emission channeling experiments have been reported

Mg IS453: EC with short-lived isotopes

Co Ni

EC with neutron-induced charged particle emission He

Li Be B

Na

Setup for neutron-induced charged particle EC

J.P. Biersack et al., Nucl. Instr. Meth. 108 (1973) 397.

J.P. Biersack et al., Nucl. Instr. Meth. 170 (1980) 151.

J.P. Biersack et al., Nucl. Instr. Meth. 188 (1981) 411.

Triton EC pattern from 6Li(n,)t in LiF crystals

Alpha EC pattern from 10B(nth,) in Si:B

1016 B/cm3 in Si

J.P. Biersack et al.,

Nucl. Instr. Meth. 170 (1980) 151.

Thermal neutron-induced particle emission

New interest: heavily boron doped silicon

Si:B with gas immersion laser doping (52)1021 B/cm3

E. Bustarret et al., Nature 444 (2006) 465.

substitutional fraction?

New interest: heavily boron doped diamond

E. Bustarret et al., Phys. Rev. Lett. 93 (2004) 237005.

T. Klein et al., Phys. Rev. B 75 (2007) 165313.

New technical possibility: intense 7Be beam at ISOLDE

PSI: 2 mA 590 MeV protons onto graphite target for pion production

Spallation products

6 C C 9 C 10 C 11 C 12 C 13 C 14

5 B B 8 B 10 B 11 B 12 B 13

4 Be Be 7 Be 9 Be 10 Be 11 Be 12

3 Li Li 6 Li 7 Li 8 Li 9 Li 11

2 He He 3 He 4 He 6 He 8

1 H H 1 H 2 H 3

ZN 0 1 2 3 4 5 6 7 8

12.3 a

807 ms 119 ms

53.3 d 1.5 Ma

178 ms840 ms

770 ms

127 ms 19.3 s 20 m

8.5 ms

5.7 ka

17 ms20 ms

13.8 s 21 ms

Procedure

1. Break graphite into pieces

2. Put into Pb-shielded container

3. Transport to ISOLDE

4. Fill ISOLDE target container

5. Heat container to 1700 °C

6. Ionize Be with RILIS

Extraction of 7,10 Be+ beams with 300 pnA (i.e. 2E12 ions per second or 1 GBq/hour) for many hours!

U. Köster et al., Nucl. Instr. Meth. B204 (2003) 343.

7Be(n,p) spectrum measured with test sample

Be doping of GaN

GaN is a wide band gap (3.39 eV) semiconductor with many applications:

• high-performance blue LEDs • long-lifetime blue/violet laser diodes (Blu-ray Disc)• UV detectors• high-speed field effect transistors• …

present p-type doping with Mg (208 meV acceptor activation energy) might be replaced by Be (90-250 meV)

Be doping of GaN

Calculated total energy surfaces for Be interstitials in GaN

C.G. Van De Walle and J. Neugebauer, J. Appl. Phys. 95 (2004) 3851.

and AlN

Ternary wide band gap alloy: BexZn1-xO

Y.R. Ryu et al., Appl. Phys. Lett. 88 (2006) 052103.

7Be half-life dependence on s-electron-density

2. Be

3. Au

4. Ta

5. Al

6. graphite

7. LiF

8. Al2O3

1. BeO, BeF2, Be(C5H5)2P. Das and A. Ray, Phys. Rev. C 71 (2005) 025801.

ILL’s Neutrograph beam line

Thermal neutron flux: 3E9 cm-2s-1

Direct view to core: fast neutrons, high gamma background

ILL’s PF1B beam line

Cold neutron flux: 2E10 cm-2s-1 (capture equivalent)

Ballistic supermirror neutron guide: excellent suppression of high energy neutrons

H. Abele et al., Nucl. Instr. Meth. A562 (2006) 407.

Test setup

Medipix2 performance

J. Jakubek et al., Nucl. Instr. Meth. A571 (2006) 69.

Cluster analysis for particle identification

J. Jakubek et al.,

Nucl. Instr. Meth. A560

(2006) 143.

Charged particle identification in high background

Cluster analysis gives peak/background ratio > 40

Sample positioning

Beam time estimations for Neutrograph beam line

Beam request

• Implantation of crystals of Al, Al2O3, AlN, Be, C, ZnO, GaN with 7Be and 9Be at GLM

• About 1E14 atoms/sample (=15 MBq, =12 uSv/h at 10 cm, if swallowed cancer risk corresponds to 1.3 cigarette packs smoked)

• 6 shifts for implantation plus 2 shifts for beam tuning and optimization of 7Be/7Li ratio

• ISOLDE beam time needs to be synchronized with availability of activated PSI graphite and ILL reactor cycles!

Sample treatment

• thermal treatment to anneal crystal damage• verify diffusion broadening of implantation peak by

neutron depth profiling

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4

0,25

0,50

0,75

1,00

1,25

1,50

1,75

2,00

2,25

2,50

2,75

3,00

3,25

3,50

out-diffusion

FWHM

Thermal annealing

0.368 m 0.460 m 0.577 m

as deposited

16800C/1 hr

21000C/1 hr

6Li depth profile in W

Co

nce

ntr

atio

n (

6 Li 1

020cm

-3)

Depth (m)

MEDIPIX2 PARTNERS- U INFN Cagliari- CEA-LIST Saclay- CERN Genève- U d'Auvergne Clermont- U Erlangen - ESRF Grenoble - U Freiburg - U Glasgow - IFAE Barcelona - Mitthoegskolan - MRC-LMB Cambridge

- U INFN Napoli - NIKHEF Amsterdam - U INFN Pisa - FZU CAS Prague - IEAP CTU in Prague - SSL Berkeley

SPOKESMAN Michael CAMPBELLDeputy Jan VISSCHERS

http://medipix.web.cern.ch/MEDIPIX/

Charged particle emission from beryllium isotopes

6 C C 9 C 10 C 11 C 12 C 13 C 14

5 B B 8 B 10 B 11 B 12 B 13

4 Be Be 7 Be 9 Be 10 Be 11 Be 12

3 Li Li 6 Li 7 Li 8 Li 9 Li 11

2 He He 3 He 4 He 6 He 8

1 H H 1 H 2 H 3

ZN 0 1 2 3 4 5 6 7 8

8.5 ms

5.7 ka

17 ms20 ms

13.8 s 21 ms

770 ms

127 ms 19.3 s 20 m

12.3 a

807 ms 119 ms

53.3 d 1.5 Ma

178 ms840 ms

2.9(5)%

770 keV

D.E. Alburger et al., Phys. Rev. C 23 (1981) 473.

GaN crystal principal axes

[0001]

[1102]

[1101] [2113]

Why Be to alloy ZnO?

Y.R. Ryu et al., Appl. Phys. Lett. 88 (2006) 052103.

Sample characterization by (RBS)

Zn RBS signal: minimum yield min=3.6% somewhat higher than the virgin sample (min1.8%) remaining damage visible but low level; relatively good crystalline quality

100 200 300 400 500 600 700 800 900

2

4

6

8

10

alinhado random

channel

yie

ld (

cou

nts

/10

00

)

ZnOFe

3.6 %

Random and[0001] aligned RBS

(2 MeV 4He) of high-dose 1.11015 cm2

implanted sample after TA=900°C