Influence of defects and traps in  the scintillation process

Anna Vedda

University of Milano‐Bicocca, Italy

LUMDETR 2009 – July 15th, 2009

Outline•

Trapping processes during ionizing irradiation

•

De‐trapping and e‐h recombinations

•

Thermoluminescence (TSL)

•

Wavelength resolved TSL measurements

•

TSL vs RL spectra 

•

Examples of uncommon applications: amorphization, phase transitions

•

TSL equations

•

Data analysis: initial rise, variable heating rate method, curve

fitting

•

Role of traps in scintillation

•

Prediction of RT trap lifetimes

•

Slow tails in scintillation decay, afterglow, permanent trapping

•

Examples: Lead tungstate, perovskites, crystalline silicates 

Scintillation:Scintillation: Physical processesPhysical processesHi

gh E

nerg

y ph

oton

abs

orpt

ion

h

h hh

eee

e

Conduction Band

Valence Band

Eg

Luminescent Centre

Lexc

Lgnd

Traps

Photon( VIS-UV )

CONVERSION TRANSPORT LUMINESCENCE

TRAPPING-DETRAPPING PROCESSES: case of electron traps

Ionizing radiation

(X, γ…)

Valence band

Conduction band

Lground

hνRadioluminescence

A – direct process

T

B – delayed process

ET

Mean time spent in the trap

= τ

= C exp(ET

/kT)According to the ET

value (typically from 10-2

up to 100

eV) a very wide range of τcan be measured (of even less than1 s up to thousands years)

e

h

Lexc

TSL-TSC process –

simple scheme (electron traps)

Heating

Valence band

Conduction band

Lground

hνTSL

TET

TSL signal measured by a photomultiplier, no information about the recombination centre

Probability of escape from trap: P = K exp(-ET

/kT)P increases very strongly with temperatureA luminescence peak appears (thermally stimulated luminescence)

TSC

Lexc

0

200

400

0 100 200 300 400 500

Tem

pera

ture

(°C

)

Time (s)

1 104

3 104

5 104

7 104

9 104

50 100 150

TSL

inte

nsity

(arb

. uni

ts)

Temperature (°C)

Case of hole traps

Valence band

Conduction band

hνTSL

TET

TSC

1 104

3 104

5 104

7 104

9 104

50 100 150

TSL

inte

nsity

(arb

. uni

ts)

Temperature (°C)

It is not possible to determine from a simple glow curve whether

electron or holes are detrapped during heating

In a TSL process, the name “trap”

is attributed to the defect from which carriers are freed by heating

The name “recombination centre”

is attributed to the defect in which carriers are stably trapped, and in which carriers of opposite sign recombine radiatively

The same defects can act as traps or recombination centres in different temperature intervals

V.B.

C.B.

Lg

hνTSL

TETT1.

Classical recombination through conduction band

2.

Thermally assisted tunneling (trap-centre recombination)

TSC

LeETC

T1 2

Different kinds of recombination paths

Wavelength resolved TSL measurements

Study of both traps and recombination centers

link to photo-, radio-

luminescence, and scintillation

A wavelength resolved TSL measurement consists in a collection of emission spectra measured at constant temperature intervals (for example 1 K). Usually spectra are measured by a CCD.

TSL

NO

RM

ALI

ZE

0

ENERGY (eV)

1.5 2.0 2.5 3.0 3.5 4.0 4.50

4

8

12

16

20

24

(A)

(B)

(C)

(D)

TEMPERATURE (K)

25 50 75 100TS

L N

OR

MAL

IZE

D IN

TEN

SIT

Y0

20

40

60

80

100(C)

(B)(A)

An example: low T Thermally Stimulated Luminescence (TSL) of PbWO4

3D TSL measurement after x-ray irradiation at 10 K

After temperature integration

TSL emission spectra

After wavelength integration

TSL glow curves

10 K40 K

60 K

90 K

RT decay times in the micro-milli second time scale

Comparison between TSL and radio-luminescence (RL) spectraOne would expect that they are the same…

but the nature of traps as well as specific trap-centre spatial correlations makes them often different

Case of Lu2

SiO5 :RE

Significant differences between RL and TSL:

RL spectra are governed by the emissions of principal dopant ions

TSL spectra display main

ly emissions from RE which capture holes during irradiation (Ce3+,Tb3+___ Ce4+,Tb4+)

even if they are present as trace impurities

Evidence of the electronic nature of traps0

1

2

3

4

5

6

1.5 2 2.5 3 3.5 4 4.5 5

Nor

mal

ized

TSL

and

RL

ampl

itude

Energy (eV)

undoped

Ce

Tb

Tm

Sm

4G5/2

- 6Hx

3P0 - 3H

4

1D2 - 3H

6

3P0 - 3H

5

3 P0 -

3 H6

5D3 - 7F

x5D

4 - 7F

x

5d1 - 4f

620 413 310 248

Wavelength (nm)

RL TSL

Spatial correlation between Gd3+ and  traps in silica

0

2

4

6

8

10

2 2.5 3 3.5 4

RL

inte

nsity

(arb

.uni

ts)

0.1 mol% Ce,3 mol% Gd

Energy (eV)

3 mol% Gd0.1 mol% Ce RL

TSL

Gd3+

emission

The difference between RL (where both Ce3+

and Gd3+emissions are observed) and TSL spectra (featuring only Gd3+

emission line) is due to the spatial correlation between Gd3+

and oxygen-related electron traps.

0.1 mol% Ce,3 mol% Gd

5d-4f Ce3+

6P7/2

-

8S7/2 Gd3+

TSL glow curves are sensitive to material amorphization

Crystalline quartz

Amorphous silica

The amorphous structure o f a m a t e r i a l o f t e n

induces broadening of

T S L g l o w p e a k sdue to the presence of

continuous distributions o f t r a p l e v e l s

1.0

1.2

1.4

1.6

1.8

50 100 150 200 250 300 350 400TR

AP

ENER

GY

(eV)

Partial cleaning Temperature (°C)

SiO2

:500 ppmCe

0

2 105

4 105

6 105

8 105

1 106

0 50 100 150 200 250 300 350

TSL

INTE

NSI

TY (

Arb

. Un.

)

T (°C)

TSL glow curves can also be sensitive to phase transitions

P.D. Townsend et al., Rad. Meas. 27, 31 (1997)

Example of Ammonium Bromide (NH4

Br)

Modifications of trap depths

Increased effects in case of localized trap-centre recombinations

Possibility to monitor temperature lags between heater and sample, which are a common error

source in TSL measurements

T

TdTkTTE

skTTEsnTI

0

''/expexp)/exp(0)(

TSL equations

1/

0

''/exp/''11/)/exp(0'')(

bbT

TdTkTTEsbkTTEnsTI

First order recombination: no retrapping

General order recombination: non negligible probability of retrapping

0.001

0.01

0.1

1

5 10 15 20 25

Nor

mal

ized

TSL

Am

plitu

de

1000/T (1/K)

0.09

eV

0.15

eV

0.23

eV

0.26

eV

0.40

eV

0.53

eV

0.62

eV

AG F E D C B

kTEsnTI o exp)(

Data analysis:

partial cleaning and initial rise method

This procedure allows to evaluate the trap depth independently upon the kinetic order

Case of YALO3

RT X-RAY IRRADIATION

PRE-HEATING T=TSTOP

TSL GLOW CURVE

RAPID COOLINGTO RT

100

1000

104

105

106

50 100 150 200 250 300 350 400

TSL

inte

nsity

(arb

. uni

ts)

T (°C)

55

6575

250260

270

340

350

10

100

1000

104105106

1.8 2 2.2 2.41000/T (1/K)

Tstop

=260 °C

E = 1.60 eV

EVALUATION OF TRAP DEPTHSpartial cleaning of glow curves and initial rise

(104

ppm

Ce, 50 ppm

Zr)-doped LuAG

I=c·exp(-E/kb

T)

E1

=1.05 eVτRT

≈5.5 h

E2

=1.60 eVτRT

≈106

yE3

=1.92 eVτRT

≈1011

y

102

104

50 150 250 350

LYSO:Ce dose dependence

TSL

inte

nsity

(arb

. uni

ts)

Temperature (oC)

1

300

60

The presence of first order kinetics can be tested by verifying if TSL peak maxima do not vary with increasing dose. In this case,

mkTEs

mkT

E exp2

Evaluation of the frequency factor (s).

Simple case of first order kinetics

If E is already known, s can be evaluated (often only its order of magnitude due to s e v e r a l e r r o r s o u r c e s )

0

5 104

1 105

1,5 105

2 105

2,5 105

200 300 400 500 600 700 800

Lu3Ga(x)Al(1-x)

5O

12:Ce

15s 20cm 10mA

150s 20cm10mA

300s 20cm 20mA

300s 10cm 20mA

TSL

inte

nsit

y (a

rb. u

n.)

Temperature (K)

Variable heating rate method

0

2 104

4 104

6 104

8 104

1 105

1,2 105

300 350 400 450

LuGaG

1°C/s1,5°C/s2°C/s2,5°C/s3°C/s

TSL

int

ensi

ty (a

rb.u

n.)

Temperature (K)

mkTEs

mkT

E exp2

From:

Plotting lnTm2/β

vs 1/Tm

10,6

10,8

11

11,2

11,4

11,6

11,8

2,68 10-3 2,7 10-3 2,72 10-3 2,74 10-3 2,76 10-3 2,78 10-3 2,8 10-3

ln(T

m2 /

ß)

1/Tm

(1/K)

Slope = E/k

Intercept = ln (E/sk)

E = 0.92 eVs = 3x1010 s-1

Possibility to extend to general order kineticsNeed of good separation between different peaks

Glow Curve Fit

50 100 150 200 250 300

TSL

Ampl

itude

T (K)

x 100 x 3

TSL glow curve of YAP:0.1%Eu (full circles). The continuous red line represents the numerical fit of the glow curve in the framework of first order kinetics.

Made in the framework of first or general order kinetics

Difficult: E,s, and b (order of kinetic) are implicit parameters

If several overlapping peaks are present, the number of parameters can be very high

Need of preliminary information by other methods

Role of traps in scintillation If the RT decay time

is of the order of micro-

or milli-

seconds

Slow tails in the scintillation decay

Traps can be studied by heating at a constant rate after irradiation (slow scintillation tails correspond to TSL peaks at cryogenic temperatures, while afterglow and permanent trapping are related to peaks above RT)

The determination of trap parameters by some method of analysis alows the

evaluation of the order of magnitude

of the RT lifetime

(higher precision is

commonly prevented by several error sources and by the temperature dependence of the frequency factor, which is hardly predictable)

Longer

(minutes, hours)

AfterglowVery long

(days, years)

Permanent trapping

The investigation of the role of traps in scint i l lat ion involves the fol lowing steps:

Evidence of slow scintillation tails or afterglow

Need to understand the nature of responsible defects

Study of defects by an independent technique giving information about thermal stability of defects and their r a d i a t i v e r e c o m b i n a t i o n p r o p e r t i e s ( T S L )

Correlation of TSL data with other techniques which allow structural information about traps (e.g. EPR)

Tuning of material synthesis to reduce the investigated defects

100

101

102

103

104

50 100 150 200 250 300

YALO3:Ce

Lu2-x

YxSiO

5:Ce

Lu3Al

5O

12:Ce

TSL

Inte

nsity

(arb

. uni

ts)

Temperature (K)

Role of traps in scintillation time decayComparison between silicates, garnets, and perovskites

The presence of fewer shallow traps in silicates with respect to other scintillators

(very low TSL intensity below RT) is in agreement with th

e absence of slower

components in th

e scintillation decay.

100 200 300 400 500 600 700 800

lum

. int

ensi

ty [a

rb.u

nits

]

time [ns]

Photoluminescencedecay time = 54 ns

Lu3Al

5O

12:Ce (0.12%)

a - scintillationb - PL

60 ns

600-1000 ns

Ifast

= 40%

1000

100

10 10

100

1000

100 200 300 400 500 600 700 800

YAlO3:Ce

Lum

. Int

ensi

ty [a

rb. u

nits

]

time [ns]

I(t) = 954exp(-t/24ns) + 110exp(-t/60ns) + 17exp(-t/329ns)+7.89

Ifast

= 65%

10

100

1000

100 200 300 400 500 600 700 800

Lu2-x

YxSiO

5:Ce

Lum

. Int

ensi

ty [a

rb. u

nits

]time [ns]

I(t)=459exp(-t/45ns) + 4.1exp(-t/714ns)+ 14.2

Ifast

= 88%

10-9

10-7

10-5

10-3

10-1

101

103

0 50 100 150 200 250 300 350

293

K tim

e de

cay

(s)

Tmax (K)

Pb+ - V0

WO4

3 - - La3+

WO4

3 -

WO3

- - APb

MO4

3-

Present only in Mo-doped samples

Example of lead tungstate (PbWO4

– PWO)

Suppressed by trivalent ion doping

Room temperature time decays

a 460 ppm Lab 80 ppm Lac undoped

Doping with La3+

reduces slow components in the scintillation decay, as well as TSL glow

peaks at cryogenic temperatures

La3+

favours the reduction of intrinsic lattice defects

TSL of undoped PWO

Scintillation time decay

Defect structures determined by EPR measurements

Intrinsic RT scintillation decay time

S c i n t i l l a t i o n decays o f a )undopedPWO and b)PWO(2750Mo,500Nb,50Y) at RT.

TSL glow curves of differently doped PWO samples

Effect of different ion dopings in very slow decay components in

PWO

Alpha coefficient: normalized difference between the signal level before the excitation pulse and the true background (It measures the level of very slow components)

Good correlation between alpha coefficients of differently doped

samples and TSL integral intensities below RT

YAlO3

undoped crystals

Wavelength (nm)

Tem

pera

ture

(K)

1 2 3 4 5 60

0.2

0.4

0.6

0.8

1

Nor

mal

ized

TS

L A

mpl

itude

Energy (eV)

10-50 K

130-260 K

50-130 K

5d1-4f Ce3+

defects

intrinsic emissions

50 100 150 200 250 300

TSL

Am

plitu

de

Temperature (K)

154

K

190

K

232

K

66 K

89 K

110

K

30 K

Wavelength integration

Temperature integration

Several emission centres for each glow peak

Recombinations involving valence/conduction bands

50 75 100 125 150 175 200 225 250 275 3000.0

0.5

1.0

1.5

2.0

2.5

3.0 50 ppm Ce 5000 ppm Ce

EPR

, TSL

inte

nsity

(arb

. uni

ts)

T (K)

OI

OII

OIII

OIVTSL

Structural nature of trapsCorrelation with EPR signals

The TSL peaks at 154 K, 190 K, and 232 K are due to the de-trapping of holes from O-

centres followed by recombination with electrons stored in oxygen vacancies

50 100 150 200 250 300

Nor

mal

ized

TS

L A

mpl

itude

Temperature (K)

2% Yb

Undoped

0.1% Eu

x 10

x 100 x 2

Doping of YAlO3

with Yb3+, Eu3+, and Tm3+Trapping of electrons during irradiation

0.1% Tm

1 2 3 4 5 6

TSL

Am

plitu

de

Energy (eV)

2% Yb

Undoped

0.1% Eu

x 1025-100 K

140-160 K260-290 K

10-310 K

10-50 K

130-260 K

50-130 K

2F5/2

- 2F7/2

CT emissions

5D0-7F

x

defects

5d1-4f Ce3+

intrinsicemissions

0.1% Tm10-310 K

1D2 - 3H

6

3P0 - 3H

5

3P0 - 3H

6

3P0 - 3H

4

Hole traps are similar to those observed in undoped crystals. Rare earth ions compete with oxygen vacancies in electron trapping (becoming temporarily Yb2+, Eu2+, Tm2+) and act as recombination centres in the TSL process

TSL emissions

TSL peak E (eV) ν

(1/s)

at RT (s)

45 K 0.09 107 10-7

66 K 0.15 1010 10-8

89 K 0.23 1011 10-8

110 K 0.26 1010 10-6

154 K (O-) 0.40 1011 10-5

190 K (O-) 0.53 1012 10-3

232 K (O-) 0.62 1011 10-1

Detrapping and recombination: Case of YAlO3

:Yb

232

K

154

K

190

K

Due to their long RT decay times, traps responsible for the TSL peaks above 100 K (mostly O-

centres) cause slow tails in the scintillation time decay

Doping with Ce3+, Pr3+, and Tb3+Trapping of holes during irradiation –

a TSL pattern different from that occurring with Yb3+, Eu3+, Tm3+

doping is expected

50 100 150 200 250 3000

1

2

3

4

Nor

ma

lized

TSL

Inte

nsity

Temperature (K)

0.1% Tb

0.1% Pr

Undoped

0.5% Ce

Tunneling emissionTunneling emission

Evidence of one or two dominant Evidence of one or two dominant TSL peaks, similar to those TSL peaks, similar to those observed in the cases of undoped, observed in the cases of undoped, Yb, Eu, and Tm doped crystalsYb, Eu, and Tm doped crystals

TSL spectral emissions of rareTSL spectral emissions of rare-- earth ions trapping holesearth ions trapping holes

O-O- O-

CeCe3+ 3+ emissionemission

TbTb3+ 3+ emissionemission

PrPr3+ 3+ emissionemission

1 2 3 4 5 6

TSL

Ampl

itude

Energy (eV)

0.1% Tm

Undoped

0.1% Tb

defectsintrinsicemissions

5D4 - 7F

x

5D3 - 7F

x

5d1-4f

Ce traces

3P0 - 3H

4

1D2 - 3H

6

3P0 - 3H

5

3P0 - 3H

6

RE-doped YAPTSL spectra Example: 190 K peak

Emissions from electron and hole trapping RE ions observed in the same TSL peaks.

0.5% Ce5d

1-4f

1 2 3 4 5 6TS

L Am

plitu

deEnergy (eV)

2% Yb

Undoped

0.1% Eu

x 10

2F5/2

- 2F7/2

CT emissions

defectsintrinsicemissions

5d1-4f

Ce traces

5D0-7F

x

0.1% Pr 5d1-3H

4,5

3P0-3H

4,51D2-3H

4

In RE-doped YAP, traps and recombination centres do not act like separate entities, but rather as parts of defect complexes in which carriers can be transferred from intrinsic levels (O-

centres and oxygen vacancies) to the rare earth ion levels.

The observation of a nearly temperature independent TSL emission

suggests that tunnelling driven recombination processes occur in addition

to the

temperature driven recombination, supporting the existence of such complexes w i t h c l o s e s p a t i a l c o r r e l a t i o n b e t w e e n t r a p s a n d c e n t r e s .

Due to the formation of defect complexes, the kind of recombination centre (capturing holes or electrons, e.g. Ce

or Yb) is not always a proof of the nature

(electron-

or hole-kind) of a trap

The comparison of the TSL patterns of crystals doped with a variety of rare earth ions

proved to be essential in order to highlight this phenomenology,

which nevertheless could be more common in TSL experiments than expected.

50 100 150 200 250 3000.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Nor

mal

ized

TS

L A

mpl

itude

Temperature [K]

Undopedx 10

Pr-0.1%

Ce-0.1%

(RT) ~ 10-3s

(RT) ~ 10-4s

Sample Concentr.Melt (%)

Growth method

&Crucible

Nphels /MeV(phels per

MeV)

FWHM (%) at

662 keV

Nphels% of

standard

RL_intens.% of

standardYAP:Ce Ce-0.05 CZ - Ir 1978 7.3 71 81YAP:CeCzech

Ce-0.5 CZ –

Mostandard

2803 4.8 100 100

YAP:Pr Pr - 0.05 CZ - Ir 2280 7.1 81 147YAP:Pr Pr – 1.0 CZ - Ir 1026 8.9 37 113YAP:PrCzech

Pr – 0.5 CZ - Mo 975 10.3 35 130

YAP:PrCzech

Pr – 1.1 CZ - Mo 1127 9.1 40 n.m.

Consequences of trap levels RT decay times on scintillation efficiency

Ligh

t yie

ld (

1 μs

)

Stea

dy s

tate

RL

As the glow curve peak occurs at a much higher temperature in the case of Pr doping, the RT

lifetime of it main trap is a b o u t o n e o r d e r o f

magnitude larger with

respect to that of Ce-

d o p e d Y A P .

This can be one of the reasons why delayed radiative recombination processes in YAP:Pr are more pronounced and its photoelectron yield is lower with respect to that of YAP:Ce in spite of its higher steady state RL efficiency.

0

1

2

0 100 200 300 400

TSL

inte

nsity

(arb

. uni

ts)

Temperature (oC)

x 20 LSO:Ce

LYSO:Ce

Lu2

SiO5

:Ce and Lu1.96

Y0.04

SiO5

:Ce –

identification of the nature of traps thanks to their localized recombination mechanism

LSO:Ce

Recombination mechanism:Ce4+

+ e (freed from the electron trap) →

Ce3+*

(excited state) →

Ce3+

+ hν

(TSL emitted light)Evidence of the electronic nature of TSL traps

0.5

1.0

1.5

50 100 150 200 250 300 350

LSO:CeLYSO:Ce

Trap

dep

th (e

V)

Tstop (oC)

78 °C 300 °C236 °C181°C135 °C

Constant trap depth for all glow peaks except the 300 °C one

No dependence of maximum

temperatures from dose

No retrapping

rs expIn the case of a thermally assisted tunneling processWhere “s”

is the frequency factor and “r”

is the distance between the trap and the recombination centre

mm kTEs

kTE exp2

106107108109

1010101110121013

2 2.5 3 3.5 4

LSO

LYSO

Freq

uenc

y fa

ctor

(1/s

)

O-Lu distance (Angstrom)

2.0

3.0

4.0

0 2 4 6 8

Lu1-

O d

ista

nce

(A)

oxygen site no.

LSO structure

78 °

C

236

°C

181

°C

135

°C

Exponential dependence of the frequency factors from Lu1(Ce)-Oxygen distances

Oxygen vacancies act as electron traps responsible for TSL peaks

Conclusions

TSL is a powerful technique for the study of luminescent materials; especially when performed in wavelength resolved mode, it can really provide a deep insight in the t r a p p i n g - r e c o m b i n a t i o n p r o c e s s e s o c c u r r i n g i n a s c i n t i l l a t o r .

Several types of recombination mechanisms between traps and luminescent centres exist. Their comprehension needs very often the possibility to vary sample parameters like kind of doping, dopant concentration, synthesis and annealing conditions, and to probe their influence on TSL features. Anyway, in some cases only qualitative descriptions of the recombination processes remain possible.

Data analyses are delicate; the handling of trap parameters needs a clear consciousness of the error sources linked to experimental data and numerical methods. This is important especially if a comparison with similar parameters obtained by other techniques has to be performed. Such consciousness of the limits of the technique doesn’t lower, but increases its potential allowing to handle data in a critical and therefore constructive way.

References1.

M. Martini, F. Meinardi, G. Spinolo, A. Vedda, M. Nikl, Y. Usuki, “Shallow traps in PbWO4 by wavelength resolved thermally stimulated luminescence”, Phys. Rev. B 60, 4653 (1999).

2.

Vedda, M. Nikl, M. Fasoli, E. Mihokova, J. Pejchal, M. Dusek, G.

Ren, C.R. Stanek, K. J. McClellan, D.D. Byler, “Thermally stimulated tunneling in rare-earth doped Lu-Y oxyorthosilicates”, Phys. Rev. B 78, 195123 (2008).

3.

A. Vedda, N. Chiodini, D. Di Martino, M. Fasoli, L. Griguta, F. Moretti, E. Rosetta, “Thermally stimulated luminescence of Ce and Tb doped SiO2 sol-gel glasses” , Journal of Non-Cryst. Solids 351, 3699 (2005).

4.

Vedda, D. Di Martino, M. Martini, V.V. Laguta, M. Nikl, E. Mihokova, J. Rosa, K. Nejechleb, K. Blazek, “Thermoluminescence of Lu3 Al5 O12 :Ce crystals”, Physica Status Solidi A 195, R1 (2003).

5.

P.D. Townsend, A.P. Rowlands, G. Corradi, “Thermoluminescence during a phase transition”, Rad. Meas. 27, 31 (1997).

6.

M. Nikl, K. Nitsch, P. Bohacek, M. Martini, E. Mihokova, A. Vedda, S. Croci, G.P. Pazzi, P. Fabeni, S. Baccaro, B. Borgia, I. Dafinei, M. Diemoz, G. Organtini, E. Auffray, P. Lecoq, M. Kobayashi, M. Ishii, Y. Usuki, "Decay kinetics and thermoluminescence of PbWO4 :La3+", Appl. Phys. Lett. 71, 3755, (1997).

7.

V.V. Laguta, M. Martini, A. Vedda, E. Rosetta, M. Nikl, E. Mihokova, Y. Usuki, “Electron traps related to oxygen vacancies in PbWO4 ”, Phys. Rev. B 67, 205102 (2003).

8.

M. Nikl, P. Bohacek, E. Mihokova, N. Solovieva, A. Vedda, M. Martini, G.P.Pazzi, P. Fabeni, M. Kobayashi, M. Ishii, “Enhanced efficiency of PbWO4 :Mo,Nb scintillator”, J. Appl. Phys. 91, 5041 (2002).

9.

A. Vedda, M. Fasoli, M. Nikl, V.V. Laguta, E. Mihokova, J. Pejchal, A. Yoshikawa, M. Zhuravleva, “Trap-centre recombination processes by rare earth activators in YAlO3 single crystal host” , Phys. Rev. B 80, 045113 (1)-(9) (2009).

10.

V.V. Laguta, M.

Nikl, A.

Vedda, E. Mihokova, J. Rosa, K. Blazek, “Hole and electron traps in the YAlO3 single crystal scintillator”, Phys. Rev. B 80, 045114 (1)-(10) (2009).

11.

A. Vedda, M. Martini, F. Meinardi, J. Chval, M. Dusek, J.A. Mares, E. Mihokova, M. Nikl, “Tunneling process in Thermally Stimulated Luminescence of mixed Lux (Y3+)1-x AlO3 :Ce crystals”, Phys. Rev. B 61, 8081 (2000).

Influence of defects and traps in the scintillation processOutlineSlajd numer 3Slajd numer 4Slajd numer 5Slajd numer 6Slajd numer 7Slajd numer 8Slajd numer 9Slajd numer 10Spatial correlation between Gd3+ and traps in silicaSlajd numer 12Slajd numer 13TSL equationsSlajd numer 15Slajd numer 16Slajd numer 17Variable heating rate methodGlow Curve FitSlajd numer 20Slajd numer 21Slajd numer 22Slajd numer 23Slajd numer 24Slajd numer 25Slajd numer 26Slajd numer 27Slajd numer 28Slajd numer 29Slajd numer 30Slajd numer 31Slajd numer 32Slajd numer 33Slajd numer 34Slajd numer 35Slajd numer 36