Characterization of CsI:Tl recrystalization after liquid phase deposition

Ulrik Lund Olsen, Ph.D. studentsupervisors: H.F. Poulsen, S. Schmidt

SCINT’07, Salem Winston, June 4-8 2007

Aims of project

DiffractedBeam

Grain in Aluminum Sample Scintillator

Mirror

MicroscopeLens

CCD

photons

540nm

X-rays50keV

Submicron grains structure resolved at high energy (30-100keV) at fast kinetic low flux diffraction meassurements.

fundamental relationship between scintillator thickness and resolution

Principle - Structured Scintillator

CsI:Tl

SiO2

Si

Electrochemical etching

HF solution etches surfaces with positive donors

Light induced donors are guided by an applied electric field

Field determined by silicon resistivity and bias

HF

e-e-

+

+

+ e-

R.L. Smith and J.D. Collins, J. Appl. Phys. 71, 8, R1 (1992)

Pore Structure

10µm

1µm

SiO2

Pore Filling Process

• CsI:Tl powder on Silicon surface• Sealed sample holder• Tube furnace• Controlled cooling rate

Bulk characterization

• Focused Ion Beam(FIB) milling

4µm

10µm

Ions

Crystal characterization - EBSD

Grain size Distribution

Electron Backscatter Diffraction

0 20 40 600

0.05

0.1

0.15

0.2

0.25

Grain Area [µm2]

Are

a/ T

otal

Are

a

500 1000 1500 2000 2500 30000

20

40

60

80

100

Channel No.

Ene

rgy

[keV

]

y = 0.027*x - 0.13

data linear

Compositional characterization - Fluorescence

Flourescence exited with 90keV synchrotron radiation:

•local (w/ focused beam)

•large lead(Pb) background

Au

SnKβ1

Kβ1

Kα1

Kα1Kα2

fit

9 10 11 12 13 140

200

400

600

800

Energy [keV]

Inte

nsity

[a.u

.]

Referencelow evaporationhigh evaporation

Tl -L1&2

Tl-L1&2

Compositional characterization - PIXE

0 10 20 30 400

0.5

1

1.5

2

2.5

3

3.5x 104

Energy [keV]

Inte

nsity

[a.u

.]

Referencelow evaporationhigh evaporation

Tl -L1&2

Tl-L1&2

I-K1&2

Cs - K1&2I - K1

Cs - K1

Particle induced X-ray Emission:•40keV protons•bulk information (250µm penetration)•global probe (2mm2 beam)

Compositional characterization - PIXE

0

0.02

0.04

0.06

0.08

0.1

0.12

Low evap. High evap. as recieved

Tl- c

onte

nt [w

t %]

manufacturers specs on as-received was 0.2 wt%

(GB crystals)

Composition characterization - SIMSSecondary Ion Mass Spectroscopy:

•local information•surface probing•high compositional sensitivity (>ppm)•uneven sensitivity to different species

No. Ion CentMass CI

1 I 126.8895 434

2 Cs 132.8742 564067

3 ^203Tl 203.0080 1069

4 Tl 205.0127 1362

5 Cs_2 265.7874 170843

Conclusion

• Multiple characterization tools needed• textural information from high resolution EBSD• absolute composition from PIXE• meso-scale relative composition from x-ray induced fluorescence• local composition – SIMS

Thanks to: T. Martin (ESRF)V. Honkimaki (ESRF)M. di Michiel (ESRF)X. Badel (KTH)J. Linnros (KTH)

N.B. Larsen (RISØ)J.C. Grivel (RISØ)C. Gundlach (ESRF)

Funding:

Danish FundamentalResearch Foundation &