Electroluminescence studies of chemically deposited (Zn-Cd)S:Cu,F films

Cryst. Res. Technol. 41, No. 7, 689 – 697 (2006) / DOI 10.1002/crat.200510650

© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Electroluminescence studies of chemically deposited

(Zn-Cd)S:Cu,F films

Ayush Khare and Shashi Bhushan*

Electro-optics Laboratory, School of Studies in Physics, Pt. Ravishankar Shukla University, Raipur (C.G.)-

492 010, India

Received 4 July 2005, revised 19 September 2005, accepted 6 October 2005

Published online 15 June 2006

Key words (Zn-Cd)S, electroluminescence, chemical deposition.

PACS 78.60.F, 81.15.H

Electroluminescence (EL) emission has been observed under AC field excitation in chemically deposited

(dipping technique) films of (Zn-Cd)S:Cu,F using substrates of conducting glass plates. Results of XRD,

SEM, absorption spectra, transmission spectra, EL emission spectra, voltage, frequency and temperature

dependence and brightness waves of EL brightness are presented and discussed. SEM studies show better

growth condition in presence of F. X-ray diffraction studies show diffraction lines due to CdS and ZnS. Both

the studies represent average particle sizes of the order of 1Å. Absorption studies show change in band gap

due to increasing concentration of ZnS. The observed EL emission (blue-green region) may be due to Cu, F

combination. Results of transmission spectra give band gap similar to those given by absorption spectra.

From voltage dependence of EL brightness acceleration-collision mechanism is found to be effective.

Frequency dependence of EL brightness shows first an increase in brightness in the lower frequency range

followed by saturation at higher frequencies. Temperature dependence of EL emission shows a maximum at

40°C. Brightness waves consist of primary and secondary waves, which depend on voltage and frequency of

excitation & the ambient temperature.

© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1 Introduction

Thin film studies of ZnS & CdS type materials are quite important because of their wide EL applications e.g.

ACTFEL panels, display systems and flat TV screen, sensitive photoconductor, IR detector, solar cells etc.

These TFEL displays have found strong acceptance in medical and industrial control applications, where the

need for wide view angle, longer life, wide temperature ranges and fast response time are critical. Above

materials have been prepared in different forms like powders, crystals, pellets, nanocrystallites and thin films.

Earlier workers used sophisticated techniques like vacuum evaporation, sputtering, chemical vapour

deposition, screen-printing, molecular beam epitaxy, multisource deposition and low pressure hydride-

transport chemical vapour deposition etc [1-10]. In recent years Bhushan and co-workers used chemical

deposition technique (dipping technique) and reported quite high photosensitivity [11-16], moderate photo

voltaic efficiency [17,18], efficient photoluminescence [13,15] and Electroluminescence (EL) [19] in CdS,

(Cd-Zn)S & (Cd-Pb)S films. Earlier Nair et al. [20] observed many fold improvement in the electro-optical

properties of solar assisted chemically deposited CdS type films. The present paper concerns with some results

of EL on (Zn-Cd)S:Cu, F films prepared by chemical deposition technique.

2 Experimental details

Film preparation The films were prepared by vertically dipping the cleaned substrates of conducting

glass plates of dimension 24 mm x 75 mm (with high transmission coefficient), prepared by depositing SnO2

conducting layer by spray-pyrolysis method [21] using SnCl2

.

2H2O as the original chemical and having

____________________

* Corresponding author: e-mail: [email protected]

690 Ayush Khare and Shashi Bhushan: Electroluminescence studies of (Zn-Cd)S:Cu,F films

© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.crt-journal.org

resistivity ≈ 80 Ω/cm2

. The substrates were cleaned with acetone and distilled water. Such non-

conducting/conducting cleaned glass slides were dipped into a mixture of appropriate amounts of 1 M solutions

of zinc acetate/cadmium acetate, thiourea, triethanolamine and 30 % aqueous ammonia (All analytical reagent

grade-99.9 % pure; mixture showed pH ∼11). In addition appropriate amounts of 0.01 M solutions of NaF (2 –

5 ml) and copper acetate (2-5 ml) were also mixed in the original mixture. The solutions of the compounds

used were prepared in double distilled water and films were prepared at a temperature of 70o

C in a water bath.

The substrates were cleaned with acetone, distilled water & by using ultrasonic cleaner. The deposition of films

is based on precipitation followed by condensation. In the beginning when precipitation started, stirring was

done. After that depositions were made in the static condition and after deposition, films were cleaned with

distilled water and then dried by keeping the films in open atmosphere at room temperature. The thickness of

the film was measured by mass difference method and was found to be between 1-2 µm.

EL Cell The construction of EL cell is shown in figure 1. For EL studies a thin layer of araldite (4 µm)

was coated on the film with the help of magnetic stirrer / centrifuge. On this a silver electrode of the area 1 cm2

was formed by coating it (thickness ∼ 100Å) with 12 //

Hind Hivac coating unit (model-12A4D). Conducting

side of the glass plate and colloidal silver paste having area 1 cm2

served the purpose of two electrodes

respectively. The thickness of different layers is also mentioned in the diagram.

Fig. 1 Construction of EL cell.

Table 1 XRD data of different (Zn-Cd)S films (Preparation time = 75 min.; Preparation temperature = 70 o

C; film

thickness ∼ 1-2 µm).

d-values (Ao

)

Obs. Rep.

Relative intensities

Obs. Rep.

hkl Lattice constant (Ao

)

Obs. Rep.

Average particle size (Ao

)

XRD SEM

A. (Zn0.7

-Cd0.3

)S

3.3600 3.360

2.0518 2.058

1.7506 1.911

100 100

35.5 80

28 74

(111)c-CdS

(220)c-CdS

(110)h-α ZnS

5.818

5.818

350 3.82

3.125 1.00

B. (Zn0.7-

Cd0.3

)S:Cu (2ml)

3.3914 3.36

2.5724 2.616

2.0799 2.058

1.9016 1.911

1.8267 1.753

100 100

45.8 100

30.5 80

35.6 74

30.5 60

(111)c-CdS

(211)-Cu

(220)c-CdS

(110)h-α ZnS

(311)c-CdS

5.87 5.818

6.30 6.690

5.82 5.818

3.80 3.820

6.05 5.818

3.254 0.91

C. (Zn0.7-

Cd0.3

)S:Cu

(2 ml), F(2 ml)

3.5311 3.583

3.3685 3.36

1.9428 2.058

1.7997 1.753

40 75

100 100

62 80

38 60

(100)h-CdS

(111)c-CdS

(220)c-CdS

(311)c-CdS

4.07 4.135

5.818

5.818

5.96 5.818

3.142 0.74

Measuring instruments The EL excitation source was an audio oscillator coupled with wide band

amplifier (50 Hz-20 KHz; 0-1000V). The light output was detected by an RCA 6217 photo multiplier (PM)

tube, which was operated by a highly regulated power supply (EHT 11, Scientific Equipments Roorkee). The

integrated light output in the form of current was recorded by a sensitive Polyflex galvanometer (10-9

A/mm).

The EL emission spectra were recorded by using a Thermo- Jarrel Ash grating monochromator (model-82415).

For optical absorption spectral studies a Varian (UV-VIS) DMS-100 spectrophotometer was used. XRD and

Cryst. Res. Technol. 41, No. 7 (2006) 691

www.crt-journal.org © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

SEM studies were performed at University of Delhi using a computerized Semadzu diffractometer (model-

98XRD with generator pw 1830 and pw 3710). The brightness waves were observed using Scientific digital

storage oscilloscope (model-HM 205-2).

Fig. 2 SEM micrographs of different (Zn-Cd)S films [a- (Zn-Cd)S; b- (Zn-Cd)S: Cu; c- (Zn-Cd)S: Cu, F].

Fig. 3 X-ray diffractograms of different (Zn-Cd)S films [a-

(Zn-Cd)S; b- (Zn-Cd)S: Cu; c- (Zn-Cd)S: Cu, F].

3 Results and discussion

3.1 Characterization studies

Scanning Electron Microscopy (SEM) The SEM micrographs of (Zn0.7

-Cd0.3

)S, (Zn0.7

-Cd0.3

)S: Cu and

(Zn0.7

-Cd0.3

)S: Cu, F, at a magnification of 5000 are shown in figure 2a-c respectively. Spherically shaped

grains are observed in different samples. The observed differences between the microstructures of (a), (b) & (c)

can presumably be attributed to addition of Cu and F. On addition of Cu & F, spherical shape changes to

irregular shape and this growth increases further, which can be seen in second and third case. It should be

noted that (Zn-Cd)S films alone didn’t show any EL. A weak EL was observed in (Zn-Cd)S: Cu film and best



emission was found in (Zn-Cd)S:Cu, F film. Thus, it is clear that the best growth condition is found in the third

case for EL emission. The particle sizes were determined by Heyn’s intercept method [22]. The average

particle size was found to be of the order of 0.74Å to 1Å. The values of particles sizes are listed in table 1.

X- Ray diffraction The X-ray diffraction (XRD) patterns of (Zn0.7

-Cd0.3

)S, (Zn0.7

-Cd0.3

)S: Cu, (Zn0.7

-

Cd0.3

)S: Cu, F films are shown in figure 3a-c respectively. Both the cubic and hexagonal phases are found. The

assignment of the peaks has been made from the comparison of ASTM data and the evaluated lattice constants

values with those of reported values. It is observed that the diffraction patterns show crystalline nature with

prominent diffraction lines of ZnS [(200)c, (110)

h] and CdS [(111)

c, (220)

c, (311)

c]. The evaluated and reported

values of the lattice constants agree well with each other.

The average particle size (D) was estimated from the full width at half-maximum (FWHM) of the

diffraction peak of different films, using Sherrer’s formula [23]

D = Kλ / (β1/2

cos θ) (1)

where ‘λ’ is the wavelength of X-ray and ‘θ’ the Bragg’s angle (in radian), K is a constant, which depends on

the grain shape (0.89 for circular grains), β1/2

is the full width at half-maximum (FWHM). It is observed that

the average particle size of the different samples lie in the range 3.125Å-3.254Å. These values are almost

similar to those obtained from SEM studies. The corresponding XRD data and particle size are summarized in

table 1.

Fig. 4 Optical absorption spectra

of different (Zn-Cd)S films: [1-

(Zn0.5

-Cd0.5

)S:Cu, F; 2 - (Zn0.6

-

Cd0.4

)S:Cu F; 3 - (Zn0.7

-Cd0.3

)S:Cu,

F].

Fig. 5 Tauc’s plots of

different (Zn-Cd)S films:

1- (Zn0.5

-Cd0.5

)S:Cu, F; 2

- (Zn0.6

- Cd0.4

)S:Cu F; 3 -

(Zn0.7

-Cd0.3

)S:Cu, F.

Fig. 6 Optical absorption spectra of differ-

rent (Zn0.7

-Cd0.3

)S:Cu, F films at varied

concentration of Cu and F: [a-Cu (3ml), F

(2ml); b- Cu (4ml), F (2ml); c- Cu (5ml), F

(2ml); d- Cu (2ml), F (3ml); e- Cu (2ml), F

(4ml); f- Cu (2 ml), F (5 ml)].

Absorption spectra / transmission spectra Results of optical absorption spectra for (Zn-Cd)S films at

varied composition of ZnS & CdS are shown in figure 4. The absorption coefficient (α) and the band gap Eg

are related by the following relation in direct band gap materials [24]

α = C (hν-Eg)1/2

/ hν (2)

where ‘Eg’ is the optical band gap and ‘C’ is a constant. Thus, as shown in figure 5, the band gap of materials

can be determined from the Tauc’s plots. The materials of present study are of direct band-gap nature and with

increase in Zn content, the band-gap is also found to increase. Those of different (Zn0.7

-Cd0.3

)S: Cu, F films at

varied concentration of Cu and F are shown in figure 6 and 7. Also the values of band-gap change slightly due

to addition of impurities (NaF). Probably it occurs due to change in lattice constants [25]. This confirms the

formation of a common lattice with higher band-gaps at increasing concentration of ZnS. These values are

summarized in table 2.



Table 2 Values of band gap energies for different (Zn-Cd)S:Cu, F films (Preparation time = 75 min.;

preparation temperature = 70°C; film thickness ∼ 1-2 µm).

S. No. Systems Band gap energy (eV) (Absorption spectra)

1. (Zn0.7

-Cd0.3

)S 2.50

2. (Zn0.7

-Cd0.3

)S: Cu (2 ml) 2.51

3. (Zn0.7

-Cd0.3

)S: Cu (2 ml), F (2 ml) 2.53

4. (Zn0.5

-Cd0.5

)S; Cu (2ml),F (2 ml) 2.43

5. (Zn0.6

-Cd0.4

)S; Cu (2ml),F (2 ml) 2.47

6. (Zn0.7

-Cd0.3

)S; Cu (2ml),F (2 ml) 2.53

7. (Zn0.7

-Cd0.3

)S; Cu (3ml),F (2 ml) 2.52

8. (Zn0.7

-Cd0.3

)S; Cu (4ml),F (2 ml) 2.50

9. (Zn0.7

-Cd0.3

)S; Cu (5ml),F (2 ml) 2.49

10. (Zn0.7

-Cd0.3

)S; Cu (2 ml),F (3ml) 2.53

11. (Zn0.7

-Cd0.3

)S; Cu (2 ml),F (4ml) 2.49

12. (Zn0.7

-Cd0.3

)S; Cu (2 ml),F (5ml) 2.53

Fig. 7 Tauc’s plots of different (Zn0.7

-

Cd0.3

)S:Cu, F films at varied concen-

tration of Cu and F: [1-Cu (3ml), F

(2ml); 2- Cu (4ml), F (2ml); 3- Cu (5ml),

F (2ml); 4- Cu (2ml), F (3ml); 5- Cu

(2ml), F (4ml); 6- Cu (2 ml), F (5 ml)].

Fig. 8 Optical transmission spectra

of different (Zn-Cd)S films: [a- (Zn-

Cd)S; b- (Zn-Cd)S: Cu; c- (Zn-Cd)S:

Cu, F].

Fig. 9 EL emission spectra of

different (Zn-Cd)S:Cu, F films: 1-

(Zn0.7

-Cd0.3

)S:Cu, F; 2- (Zn0.6

-

Cd0.4

)S:Cu, F; 3- (Zn0.5

-Cd0.5

)S :

Cu, F.

The values of absorption coefficient (α) were also estimated from transmission spectral studies (Fig. 8). Plots

obtained between (α hν)2

Vs hν gave similar values of band gaps as obtained from the measurement of ‘α’

directly.

3.2 EL emission spectra

The EL emission spectra of different (Zn-Cd)S films at varied concentrations of Zns and CdS at an excitation

frequency of 500 Hz are shown in figure 9. Similarly the EL emission spectra of different (Zn-Cd)S:Cu,F

samples at varied concentrations of Cu and F are presented in figure 10. The corresponding peak positions of

all these spectra are presented in table 3.

From figure 9 it is found that the peak positions shift with the increasing concentration of ZnS towards the

higher energy side, which obviously occurs due to increase in band gap due to its addition. This has already



been confirmed from absorption spectral study. Figure 10 shows that due to increase in concentration of Cu,

the emission peak changes which indicates that Cu is mainly responsible for the emission. F from NaF can help

in this substitution of Cu and thus the emission can be related to Cu, F combination.

Table 3 Peak positions of EL emission spectra of different (Zn-Cd)S: films (Preparation time = 75 min;

Preparation temperature = 70°C; film thickness ∼ 1-2 µm).

S. No. System Peak positions (nm)

1. (Zn0.7

-Cd0.3

)S:Cu (2 ml), F (2 ml) 480

2. (Zn0.6

-Cd0.4

)S:Cu (2 ml), F (2 ml) 505

3. (Zn0.5

-Cd0.5

)S:Cu (2 ml), F (2 ml) 522

4. (Zn0.7

-Cd0.3

)S;Cu (3 ml),F (2ml) 475

5. (Zn0.7

-Cd0.3

)S;Cu (4 ml),F (2ml) 472

6. (Zn0.7

-Cd0.3

)S;Cu, (5 ml)F (2ml) 469

7. (Zn0.7

-Cd0.3

)S;Cu (2 ml),F (3ml) 479

8. (Zn0.7

-Cd0.3

)S;Cu (2 ml),F (4ml) 477

9. (Zn0.7

-Cd0.3

)S;Cu (2 ml),F (5ml) 474

Fig. 10 EL emission spectra of

different (Zn-Cd)S:Cu, F films at

different concentrations of Cu (___

) and

F (----) (excitation frequency = 50 Hz) :

[1-Cu (3ml), F (2ml); 2- Cu (4ml), F

(2ml); 3- Cu (5ml), F (2ml); 4- Cu

(2ml), F (3ml) ;5- Cu (2ml), F (4ml); 6-

Cu (2 ml), F (5 ml)].

Fig. 11 Dependence of EL

brightness on different con-

centration of copper acetate

for (Zn0.7

-Cd0.3

)S : Cu, F

films (excitation frequency =

50 Hz).

Fig. 12 Dependence of EL bright-

ness on applied voltage for (Zn0.7

-

Cd0.3

)S : Cu, F films.

Cu can form acceptor levels whose energy levels lie in the forbidden energy gap of the material; hence shift

towards lower energy side compared to the band gap is expected. Cu can also help in forming conducting layer

for making possible the excitation of the materials with field [26]. Role of NaF in photoconducting CdS

powders prepared by firing at 500°C for 1 hr was found to be two fold [27,28]: (i) it acted as a flux because

lanthanide impurities could not become effective dopant in its absence and (ii) it acted as dopant since at its

particular concentration the highest photo response was found in this system. If it is acting as dopant in the

present system, particularly F as co-activator can help in incorporation of Cu as activator.

3.3 Voltage and frequency dependence of EL brightness

As shown in figure 11 the EL brightness is found to be maximum at a concentration of 4 ml of copper acetate.

The dependence of EL brightness on the applied voltage for the (Zn0.7-

Cd0.3

)S:Cu, F film is shown in figure 12.



It is noted that at lower voltages the increase in brightness is comparatively slow which becomes quite fast at

higher voltages. It is observed that light emission starts at a threshold voltage, first increases slowly with

voltage and finally tends towards saturation. The threshold voltage as well as maximum EL brightness depends

on the frequency of AC and saturation EL brightness is high at lower frequencies.

Plots between log B Vs 100/V1/2

(Fig. 13) show straight lines indicating that the brightness can be

represented by the relation

B = Bo exp (-b/V1/2

) (3)

where ‘Bo’ and ‘b’ are parameters, which depend on temperature and frequency of alternating voltage, the

material and other details of the construction of EL cell [29,30]. This behaviour indicates effectiveness of

acceleration – collision mechanism along with formation of a barrier of Mott-Schottky type.

The frequency dependence of EL brightness at different applied voltages for (Zn0.7

-Cd0.3

)S:Cu, F film is

shown in figure 14. It is found that the brightness first increases, which finally tends towards saturation at

higher frequencies. The increase in EL brightness with frequency can be understood on the basis that emptying

and refilling of EL centers take place more rapidly with the increase in frequency but when the time period of

applied AC cycles becomes comparable with the lifetime of excited electrons, the electron does not have

enough time to emerge out from the trap. Thus, the time-averaged brightness will not increase linearly with the

frequency.

Fig. 13 Plots between log B vs.

V-1/2

for (Zn0.7

-Cd0.3

)S:Cu, F films.

Fig. 14 Frequency dependence of

EL brightness for (Zn0.7

-Cd0.3

)S : Cu,

F films.

Fig. 15 Temperature dependence

of EL brightness: 1-(Zn0.5

-

Cd0.5

)S:Cu, F; 2-(Zn0.6

- Cd0.4

)S:Cu,

F; 3-(Zn0.7

-Cd0.3

)S:Cu, F.

3.4 Temperature dependence

The temperature dependence of EL brightness of (Zn-Cd)S: Cu, F films is shown in figure 15. It is observed

that a maximum emission is observed at a temperature of 40°C. From this observation it is clear that traps are

involved in this process, which after release of electrons at a temperature equal to 40°C give the maximum

emission. From the initial part of temperature dependent curves (Fig. 15), the plot between ln I Vs (1/T) (Fig.

16) gave the trap depth (E) as 7.9X10-4

, 3.9X10-4

, 1.54X10-4

eV for the three curves respectively.

3.5 Brightness waves

The brightness waves of EL emission for (Zn0.7-

Cd0.3

)S:Cu, F film at varying voltages (f=500 Hz , T=30°C),

frequencies (V=150 V, T=30°C) and temperatures (V=150 Volts, f=500 Hz) are shown in figure 17. It is found



that under sinusoidal excitation two primary peaks are observed during each cycle. The primary waves are also

associated with a secondary peak (hump), which under varied voltage shifts from left to right side of the

primary wave and finally disappears at higher voltages. The secondary peak may be associated to trapped

electrons and then with increase in voltage, these electrons may also find sufficient energy to be accelerated

and hence such a peak gets combined with the primary peak. This is confirmed from the fact that the difference

in peak intensities of the two primary peaks decreases with the increase in voltage. It is also observed that with

increasing frequency the secondary wave is also found to disappear which may be due to insufficient time

available at higher frequencies to hold the electrons in traps.

Fig. 16 Plots between ln I vs. (1/T): 1-

(Zn0.5

-Cd0.5

)S:Cu, F; 2 - (Zn0.6

- Cd0.4

)S:

Cu, F; 3 - (Zn0.7

-Cd0.3

)S:Cu, F.

Fig. 17 EL brightness waves as a function of (a) voltage (f=

500 Hz) (b) frequencies (V=150 Volts) & temperature (V= 150

volts & f = 500 Hz).

With increase in temperature it is found that the secondary wave, which first appears on the left side, at 40 o

C

is almost between two primary waves and finally at 50°C it appears to move on right side of primary wave. A

part of the electrons which are freed from certain centers in presence of electric field, become trapped

preferentially at the anodic side of the crystal or in the lower field region and when the external field

approaches zero these electrons have a chance to recombine with the empty luminescent centers. Thus, there is

always a superposition of the external field and polarization field such that when the external field drops to

zero there is still the polarization field. The number of such recombinations is maximum near the time when

the external field passes through zero, a secondary wave then appears clearly from the primary waves. At a

lower temperature, release of electrons from traps may be small and the secondary wave can be expected to

appear near the second primary wave. It should move to first primary wave upon increasing the temperature

since then the polarization field decays more quickly with increasing number of recombination processes.

4 Conclusions

As far as known to us the EL emission from chemically deposited films (dipping technique) has been found for

the first time. This is a very simple and cheap technique. If the emissions are improved it can provide a viable

technology. XRD, SEM and absorption spectra have been used for characterization of prepared materials.

Particle sizes are found in nano region. The emission has been associated to Cu, F combination. Brightness-

voltage behaviour shows effectiveness of acceleration-collision mechanism.

The frequency dependence shows first increase in brightness followed by saturation. Temperature

dependence shows a maximum at 40°C. Brightness-waves of EL emission show two primary peaks along with

secondary peaks during each cycle of excitation. The nature of secondary waves depends on voltage &

frequency of excitation & the ambient temperature.

Acknowledgements The authors are thankful to Dr. M. W. Y. Khan of S.O.S. in Geology, Pt. R. S. University, Raipur for

absorption spectral studies and to Dr. P. D. Sahare of Delhi University for SEM and XRD studies. One of the authors (AK)

is grateful to the Director, Raipur Institute of Technology, Raipur (C. G.) for his constant encouragement.



References

[1] R. A. Mickelson, W. S. Chen, Y. R. Hasio, and V. E. Love, IEEE Trans. Electron. Dev. 31, 542 (1984).

[2] D. B. Fraser and H. D. Cook, J. Vac. Sci. Tech. 11, 56 (1974).

[3] E. Schlam, J. Vac. Sci. Tech. 12, 891 (1975).

[4] M. Shiiki and O. Kanehisa J. Cryst. Growth 117, 1035 (1992).

[5] V. C. Chaudhari, R. H. Patil, M. G. Patil, and C. S. Shalgonkar, Mat. Chem. Phys. 59, 162 (1999).

[6] D. Sands, K. M. Brunson, C. C. Cheung, and C. B. Thomas, Semicond. Sci. Technol. 13, 816 (1988).

[7] L. Pintilie, E. Pentia, I. Pintilie, and D. Petre, Mat. Sci. Engg. B 44, 403 (1997).

[8] T. Nire, T. Watanabe, N. Tsurumaki, A. Miykoshi, and S. Tanda, Electroluminescence in: Springer Proc. In Physics

38 (1989).

[9] A. Mikami, K. Terada, K. Okibayashi, K. Tanaka, M. Yoshida, and S. Nakajima, J. Cryst. Growth 110, 381 (1991).

[10] X. T. Zhang, Y. C. Liu, Z. Z. Zhi, J. Y. Zhang, Y. M. Lu, D. Z. Shen, W. Xu, X. W. Fan, and X. G. Kong, J. Lum.

99 149 (2002).

[11] S. Bhushan and S. K. Sharma, Appl. Phys. Lett. 57, 884 (1990).

[12] S. Shrivastava and S. Bhushan, Ind. J. Pure Appl. Phys. 34, 106 (1996).

[13] S. Bhushan, M. Mukherjee, and P. Bose, J. Mat. Sci. 34, 581 (2002).

[14] S. Bhushan, M. Mukherjee, and P. Bose, Rad. Eff. Def. Sol. 153, 367 (2001).

[15] M. Mukherjee and S. Bhushan, Opt. Mat. 22, 51 (2003).

[16] M. Mukherjee and S. Bhushan, Rad. Eff. Def. Sol. 158, 491 (2003).

[17] T. Chandra and S. Bhushan, J. Mat. Sci. 39, 1 (2004).

[18] T. Chandra and S. Bhushan, J. Phys. D: Appl. Phys. 37, 2945 (2004).

[19] S. Bhushan and A. Khare, Proc. National seminar on Luminescence (NSLA-2003) (NPL, New Delhi, India, 12-14

February 2003) 220 (2003).

[20] P. K. Nair, M. T. S. Nair, A. Farnandez, and M. Ocampo, J. Phys. 22, 829 (1989).

[21] O. Mustafa and A. Necmeddin Yazici, J. Lum. 110, 31 (2004).

[22] E. C. Subba Rao, D. Chakravorty, M. F. Merriem, V. Raghavan, and L. K. Singhal, “Experiments in Materials

Science”, McGraw-Hill, 26 (1972).

[23] H. Klug and L. Alexander, X-ray diffraction procedures, John Willey and Sons, Inc. New York, 491 (1962).

[24] A. L. Dawar, P. K. Shishodia, G. Chauhan, A. Kumar, and R. C. Mathur, J. Mat. Sc. Lett. 9, 547 (1990).

[25] M. Mukherjee, P. Bose, and S. Bhushan, Ind. J. Pure Appl. Phys. 39, 804 (2001).

[26] S. Bhushan, Nuclear Tracks 10, 215 (1985).

[27] S. Bhushsn and S. K. Sharma, J. Mat. Sci. 1, 165 (1990).

[28] S. Bhushsn and S. K. Sharma, J. Phys.: Cond. Matt. 2, 1827 (1990).

[29] G. F. Alfrey and J. B. Taylor, Brit. J. Appl. Phys. Suppl. 4, 844 (1955).

G. F. Alfrey and J. B. Taylor, Proc. Phys. Soc. (London) B-68, 775 (1955).

[30] P. Zalm, G. Diemer, and H. A. Klasens, Philips Res. Repts. 10, 205 (1955).

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