The effect of irradiation with Swift (100 MeV) Ni+ 7 ions on the structural and optical properties of
Cadmium Selenide (CdSe) thin films have been investigated at different fluencies in the range of 1  1011-
1  1013 ions/cm – 2. The CdSe films on glass substrates were prepared by thermal evaporation. The structural
and optical changes with respect to increasing fluence were observed by the means of X-ray diffraction
(XRD), UV-VIS and Raman spectroscopy. After irradiating the films with Ni+ 7 ions XRD show the increased
in peak intensity and crystallite size with increasing fluence. The UV-VIS-IR spectroscopy revealed
that there is decrease in band gap energy of the films after irradiation with increasing fluencies.
Raman spectrum for as deposited and irradiated films show two peak, one at 209 cm – 1 and at 410 cm – 1
which is assigned to the longitudinal optical (LO) phonon mode

Dubey, S.K.

Jadhav, V.

Singh, Rajesh

Yadav, A.D.

English

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 7 No 3, 03002(3pp) (2015) Том 7 № 3, 03002(3cc) (2015) 
 
 
2077-6772/2015/7(3)03002(3) 03002-1  2015 Sumy State University 
Structural and Optical Studies of 100 MeV Ni+7 Irradiated Cadmium Selenide Thin Films 
 
Rajesh Singh, A.D. Yadav, V. Jadhav, S.K. Dubey 
 
Department of Physics, University of Mumbai, Vidyanagari Campus, Santacruz (E), 400098 Mumbai, India 
 
(Received 31 March 2015; published online 20 October 2015) 
 
The effect of irradiation with Swift (100 MeV) Ni+ 7 ions on the structural and optical properties of 
Cadmium Selenide (CdSe) thin films have been investigated  at different fluencies in the range of 1  1011-
1  1013 ions/cm – 2. The CdSe films on glass substrates were prepared by thermal evaporation. The struc-
tural and optical changes with respect to increasing fluence were observed by the means of X-ray diffrac-
tion (XRD), UV-VIS and Raman spectroscopy. After irradiating the films with Ni+ 7 ions XRD show the in-
creased in peak intensity and crystallite size with increasing fluence. The UV-VIS-IR spectroscopy re-
vealed that there is decrease in band gap energy of the films after irradiation with increasing fluencies. 
Raman spectrum for as deposited and irradiated films show two peak, one at 209 cm – 1 and at 410 cm – 1 
which is assigned to  the longitudinal optical (LO) phonon mode. 
 
Keywords:  CdSe thin films, Swift heavy ion irradiation, XRD, UV, Micro-Raman.  
 
 PACS numbers: 78.30.C –, 78.66. – w 
 
 
1. INTRODUCTION 
 
Cadmium Selenide (CdSe), a II-VI compound semi-
conductor has been constantly invested during recent 
years for both fundamental and practical importance [1-
3]. CdSe is a promising photovoltaic material because of 
its high absorption coefficient and nearly optimum band 
gap energy for the efficient absorption of light and con-
version into electrical power [4-5]. The synthesis of bina-
ry metal chacogenide of groups II-VI semiconductors in a 
nanoparticle form has been a rapidly growing area of 
research due to their important non-linear optical prop-
erties, luminescent properties, quantum-size effect and 
other important physical and chemical properties [6-8]. 
CdSe thin films have been prepared by using thermal 
evaporation under vacuum is a very convenient method 
for obtaining uniform films. Currently, swift heavy ion 
(SHI) irradiation of material has generated significant 
interest in the light of application of such material in 
high radiation zones [9]. SHI irradiation has been re-
ported of CdSe / FTO thin films deposited by electro dep-
osition method. After irradiating the films there is in-
crease in grain size, decrease in band gap was observed 
from structural and optical analysis [10]. In view of this, 
an effort has been made to study the structural and opti-
cal property of the SHI irradiated (100 MeV Ni+ 7 ion) 
thermally evaporation CdSe thin films using XRD, UV-
Vis and Raman spectroscopy. 
 
2. EXPERIMENTAL DETAILS 
 
CdSe thin films of thickness 200nm have been pre-
pared from 99.95 % pure CdSe powder (Alfa Aesar) in a 
vacuum evaporation unit (HHV-12A4DU) at a pressure 
of 1  10 – 6 mbar on clean glass substrate. Swift Heavy 
ion (SHI) irradiation of the as deposited CdSe films was 
done using 15 UD pelletron accelerator at Inter Uni-
versity Accelerator Center (IUAC), New Delhi, with 
100 MeV Ni+ 7 at fluences levels 1.0  1011, 1.0  1012 
and 1.0  1013 cm – 2. The beam current was maintained 
at 2 pnA (particle nanoampere) during irradiation. 
The focused ion beam was scanned over an area of 
1 cm2 using a magnetic scanner to achieve the fluence 
uniformity across the sample surface. The electronic 
and nuclear energy loss value for 100 MeV Ni+ 7 ions in 
CdSe, from the SRIM code simulation program (version 
2003.26) are estimated to be 1.88  101 eV/Å and 
3.17  10 – 2 eV/Å respectively. The structural analysis 
of films was studied by X-ray diffractometer (Model 
JEOL 8030,   0.1541 nm). The optical absorption 
spectra of CdSe thin films were obtained by a UV-VIS-
NIR spectrophotometer in the wavelength range of 250 
to 2500 nm. Micro-Raman spectroscopy was performed 
using Horiba Jobin Yvon Raman Spectrometer 
(T64000) and measurements were performed at room 
temperature with a 514.5 nm line of an Ar+ laser. 
 
3. INTERPERTATION OF EXPERIMENTAL  
RESULTS 
 
3.1 X‐ray Diffraction Studies 
 
The X-ray diffractogram of pristine and irradiated 
CdSe thin films are shown in Fig. 1, a sharp peak in 
XRD pattern is observed in all the films oriented in 
(002) plane correspond to the hexagonal phase [11]. 
After irradiation the films have the same orientation 
and it was observed that after irradiation the intensity 
of the peak increases with increasing fluence. Such 
result have been observed for the CdSe films irradiated 
by Au8 + ions with energy of 100 MeV [10]. 
The effect of irradiation with increasing fluencies is 
summarized in Table 1. The grain size (D) is calculated 
for peak at 2θ  25.40° using the Scherer formula from 
the full-width half-maximum (FWHM) (): 
 
  0.94 / cosD    , (1) 
 
where  is the wavelength of X-ray used, θ is the half 
the angle between incident and the scattered X-ray 
beam. It is observed that the grain size increases with 
the increasing fluencies which indicate improvement in 
crystallinity. 
The strain value () can be evaluated by using the 
following relation: 
 RAJESH SINGH, A.D. YADAV, V. JADHAV, S.K. DUBEY J. NANO- ELECTRON. PHYS. 7, 03002 (2015) 
 
 
03002-2 
20 30 40 50
  
(deg)
 
 
 
 
 
 
(d)
(c)
(b)
(a)
 
 
 
 
In
te
n
si
ty
, 
A
r
b
it
a
r
y
 
 
Fig. 1 – X-Ray diffractogram of pristine and SHI irradiated 
thin films of CdSe (a) Pristine (b) 1  1011 (c) 1  1012 (d) 
1  1013 cm 
 
 cos / 4    (2) 
 
The dislocation density () has been calculated by 
using the following formula 
 
 15 cos / 4aD    (3) 
 
The lattice spacing (d) is calculated from the 
Bragg’s formul 
 
 / 2sind    (4) 
 
By this study it was observed that strain and dislo-
cation density in the film decreases with the increases 
with fluencies [12]. 
 
Table 1 – Structural parameters of CdSe films irradiated at 
various fluences 
 
S
a
m
p
le
 
2
θ
 
L
a
tt
ic
e
 
sp
a
ci
n
g
 
D
 [
Å
] 
G
ra
in
 s
iz
e
 
D
 [
n
m
] 
 
[
 1
0
1
4
] 
li
n
e
s/
m
2
 
S
tr
a
in
 ε
 
[
 1
0
 –
 3
] 
h
k
l 
Pristine 25.40 3.504 27 15.34 1.737 002 
1  1011 25.37 3.508 42 12.57 1.182 002 
1  1012 25.35 3.510 56 9.43 0.753 002 
1  1013 25.32 3.513 69 7.26 0.474 002 
 
3.2 UV-VIS Spectroscopy Studies 
 
The transmission spectra of the as grown and irradi-
ated CdSe film at different fluencies was measured in the 
wavelength range 250 to 2500 nm. The absorption coeffi-
cient () was calculated from transmission spectra in or-
der to calculate the band gap (Eg). It is observed that Eg 
value decreases with increasing fluencies as shown in 
Fig. 2. Decrease in band gap energy which, in turn, de-
pends on the increase of grain size of the CdSe films with 
increasing fluencies. The decrease in band gap energy of 
high-energy irradiated sample leads to ionization of atom, 
due to which change in the local structure order of films, 
as well as it induce lattice damage and creates defect en-
ergy levels below conduction band [13]. 
 
3.3 Raman Spectroscopy Studies 
 
Fig. 3 shows the Raman spectra of as deposited and 
irradiated CdSe films at increasing fluencies. Raman 
1 2 3 4
(a)
heV
 
 
1.77eV

h

 
 
1 2 3 4
(b)
 
 
1.74eV

h


(h)eV
 
 
1 2 3 4
(c)
heV
 
 
1.7eV

h


 
 
1 2 3 4
(d)
 
 
1.67eV

h


heV
 
 
Fig. 2 – Variation of (hν)2 against (hν) for Pristine and SHI 
irradiated thin films of CdSe (a) Pristine (b) 1  1011 (c) 
1  1012, (d) 1  1013 cm – 2 
 
spectrum for as deposited and irradiated films show 
two peak, 1LO and 2LO Raman peak at 209 cm – 1 and 
416 cm – 1. Second overtone of LO phonon mode is ob-
served with decreasing intensity and also it was ob-
 STRUCTURAL AND OPTICAL STUDIES OF 100 MEV NI + 7… J. NANO- ELECTRON. PHYS. 7, 03002 (2015) 
 
 
03002-3 
served that intensity of Raman peak increases with 
increase in ion fluence. It is well known that the higher 
the intensity of the overtone, the better crystalline 
structure of the films [14]. Thus Raman spectra con-
firm formation of nanocrystalline CdSe thin films. 
 
100 150 200 250 300 350 400 450 500
0
200
400
600
800
1000
1200
1400
2
L
O
1
L
O
 
 
(d)
(c)
(b)
(a)
In
te
n
si
ty
, 
a
.u
.
Wavenumber (cm
-1
)  
 
Fig. 4 – Micro-Raman spectrograph of thin films of CdSe Pris-
tine and SHI irradiated (a) Pristine, (b) 1  1011, (c) 1  1012, 
(d) 1  1013 cm – 2 
4. CONCLUSION 
 
CdSe thin films deposited on glass substrate were ir-
radiated using Ni+ 7 ions with energy of 100MeV at dif-
ferent fluences of 1.0  1011, 1.0  1012 and 1.0  1013 cm – 2 
has been investigated using XRD analysis, UV-VIS-
Spectroscopy and Micro-Raman spectroscopy. CdSe thin 
a film exhibits a hexagonal structure highly oriented 
with (002) plane. The grain size increases with increas-
ing fluences. With the increase in fluences the average 
crystallite size increased whereas optical band gap de-
creased. Raman spectra measurements showed the 
presence of LO and 2LO phonon peaks. 
 
ACKNOWLEDGEMENTS 
 
This work is supported by Inter University Acceler-
ator Centre (IUAC), New Delhi. Authors thanks to Dr. 
Kanjilal, Dr. Fouran Singh, Inter University Accelera-
tor Centre (IUAC). New Delhi, for granting beam time 
to carry out our research work. 
 
 
 
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Structural and Optical Studies of 100 MeV Ni+7 Irradiated Cadmium Selenide Thin Films

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Structural and Optical Studies of 100 MeV Ni+7 Irradiated Cadmium Selenide Thin Films

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