Fabrication of zinc indium oxide thin films and effect of post annealing on structural, chemical and electrical properties

Article abstract of DOI:10.1016/j.jallcom.2012.03.077

In the present study, zinc indium oxide (ZIO) thin films were deposited on glass substrate with varying concentration (ZnO:In₂O₃ - 100:0, 90:10, 70:30 and 50:50 wt.%) at room temperature by flash evaporation technique. These deposite

Full text of DOI:10.1016/j.jallcom.2012.03.077

Journal of Alloys and Compounds 530 (2012) 132–137
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Journal of Alloys and Compounds
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Fabrication of zinc indium oxide thin films and effect of post annealing on
structural, chemical and electrical properties
Vipin Kumar Jaina,∗, Praveen Kumarb, Subodh Srivastavac, Y.K. Vijayc
a Institute of Engineering and Technology, JK Lakshmipat University, Jaipur 302026, India
b Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
c Thin film & Membrane Science Laboratory, University of Rajasthan, Jaipur 302004, India
a r t i c l e i n f o
a b s t r a c t
Article history:
In the present study, zinc indium oxide (ZIO) thin films were deposited on glass substrate with varying
concentration (ZnO:In2O3 – 100:0, 90:10, 70:30 and 50:50 wt.%) at room temperature by flash evapora-
tion technique. These deposited ZIO films were annealed in vacuum to study the thermal stability and
to see the effects on the structural, chemical and electrical properties. The XRD analysis indicates that
crystallization of the ZIO films strongly depends on concentration of In2O3 and post annealing where
annealed films showed polycrystalline nature. The surface morphological study of the films using scan-
ning electron microscopy (SEM) revealed the formation of nanostructured ZIO thin films. The surface
composition and oxidation state were analyzed by X-ray photoelectron spectroscopy. XPS spectra shows
that as the concentration of In2O3 increases from 10 to 50 wt%, the surface composition ratio In/Zn and
O/Zn increases for as-prepared and annealed ZIO films while the XPS valance band spectra manifest the
electronic transitions. The electrical resistivity was found to be decreased while carrier concentration
and Hall mobility increased for both types of films with increasing concentration of In2O3.
© 2012 Elsevier B.V. All rights reserved.
Received 10 January 2012
Received in revised form 13 March 2012
Accepted 17 March 2012
Available online 28 March 2012
Keywords:
ZIO thin films
XRD
SEM
XPS
Electrical resistivity
1. Introduction
organic chemical vapor deposition [14], pulsed laser deposition
(PLD) [15]. Further, it is well known that the surface plays an
Transparent conducting oxides (TCO) posses low resistiv-
ity, exhibit good adherence to many substrates and have good
transmission characteristics from the visible to near-infrared wave-
lengths enabling their wide use in many applications namely thin
film solar cells, flat-panel displays, liquid crystal displays, anti-
static coating on instrument panels, abrasion resistant coatings,
corrosion resistant coatings, Ohmic contacts to surface emitting
lasers, Ohmic contacts to light emitting diodes, Ohmic contacts to
photo detectors, Schottky contacts to photo detectors, and heat
mirrors for energy efficient windows, etc. [1–6]. At present Sn-
doped indium oxide (ITO) films are widely used for opto-electrical
devices. Other materials, such as Al, Ga and In doped ZnO, have also
been investigated with the aim of fabricating cost effective trans-
parent conducting oxide films having superior electrical, optical
and/or chemical properties [7,8]. Among these oxides, ZnO–In2O3
system has attracted much attention because of chemical and
thermal stability in addition to properties comparable to those
of ITO. Furthermore ZnO–In2O3 system has merit in minimiz-
ing use of expensive In2O3 [9–12]. ZnO–In2O3 films have been
using prepared many techniques, such as sputtering [13], metal
important role in determining the electrical properties of these
films. Thus, a detailed understanding of the surface structure and
chemical nature is essential. XPS is an important tool for studying
the electronic structure, chemical bonding and composition. It has
been reported that ZnO–In2O3 films prepared at 150 ◦C by sput-
tering showed resistivity of order of 10−4 ꢀ-cm. The resistivity of
indium oxide doped with ZnO films decreased with increase in crys-
tallinity and crystallite size due to diminishing of grain boundary
scattering [16]. The present work deals with study of structural,
chemical, and electrical properties of ZnO–In2O3 (ZIO) thin films
as a function of varying concentration of In2O3 ranging from 0 to
50 wt.%.
2. Experimental
ZIO thin films were deposited on glass substrates by flash evaporation technique
[17] using HINDHI Vacuum coating unit at a pressure of 10−6 torr. High purity ZnO
(99.99%) and In2O3 (99.9%) powders at different concentrations (100:0, 90:10, 70:30
and 50:50 wt.%) were mixed with the help of stainless steel balls at 250 rpm for 1 h
using ball milling (Retsch-TM100, Germany). Further, a mixture of the components
in powder form was fed in to a resistively heated tantalum boat by electrophon-
ically agitating the feed chute for the instantaneous evaporation of the powdered
material. The temperature of the boat was maintained at a temperature sufficiently
higher than the melting point of the evaporants. This high temperature ensures
instantaneous vaporization of the material.
∗
Corresponding author. Tel.: +91 9828117678; fax: +91 1412702457.
E-mail address: vipinjain7678@gmail.com (V.K. Jain).
0925-8388/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2012.03.077

V.K. Jain et al. / Journal of Alloys and Compounds 530 (2012) 132–137
The spacing between target, i.e. boat shaped tantalum filament and substrate
133
(a) as-prepared
was fixed at 10 cm. The thickness of the prepared films was measured by a quartz
crystal thickness monitor. Thickness of all the films was observed in the range
ZnO
In2O3
˚
1000 25 A. Substrate was kept at room temperature. Deposition rate was kept in
˚
the range of 20 2 A/s. The current and power supplied in the boat type filament
*
were in range of 4–5 ampere and 240–350 watt, respectively. Deposition conditions
were maintained carefully stable during the growth of ZIO films. The as-prepared
films were studied in terms of structural, chemical and electrical properties. The
crystalline phase of films was identified using X-ray diffractometer (Bruker AXS)
with monochromatic Cu-K␣ radiation (0.154 nm). Surface morphology of the films
was investigated by SEM (LEO-435VP scanning electron microscope). The chemical
composition and bonding states of the ZIO thin films were characterized by X-ray
photoelectron spectroscopy (Perkin Elmer-1257) using MgK␣ (1.2536 keV) radiation
at a base pressure of 5 × 10−10 torr. The electrical resistivity, carrier concentration
and Hall mobility of the films were determined by Hall measurements using the
four-probe van der Pauw technique. Further, these ZIO thin films were annealed in
vacuum at the temperature 450 ◦C for 1 h. The heating rate was kept at 10 ◦C/min.
The annealed films were also characterized by XRD, SEM, and XPS measurements.
Electrical measurements were taken with the same instruments mentioned above.
ZIO
Δ
ZIO (50:50)
*
ZIO (70:30)
ZIO (90:10)
3. Results and discussion
ZIO (100:0)
3.1. X-ray diffraction (XRD) analysis
25
30
35
40
45
50
55
60
65
Diffraction angle 2
θ
(deg.)
The as-prepared and annealed ZIO thin films were character-
ized by X-ray diffraction (XRD) to see the nature of films. Fig. 1(a)
and (b) shows the XRD patterns of as-prepared and annealed films,
respectively, with varying concentration of In2O3. Fig. 1(a) shows
that the as-prepared ZIO (100:0) or pure ZnO and ZIO (90:10) thin
films exhibit amorphous nature. Machado et al. [18] studied that
crystallization may occur with increasing In2O3 content and post
annealing process. In as-prepared ZIO (70:30) films, a peak indexed
(007) appeared near 2ꢁ angle of 27.4◦ indicating the hexagonal ZIO
structure (a = 0.315 nm and c = 2.285 nm) very close to the hexag-
onal Zn2In2O5 structure (a = 0.337 nm and c = 2.315 nm, JCPDS file
20-1442), however, peak indexed (322) observed near 36.2◦ repre-
senting the cubic In2O3 structure as well as two small peaks (101
and 102) started appearing near 2ꢁ angle of 42.3◦ and 55.8◦, indi-
cating the polycrystalline hexagonal ZnO structure (a = 0.324 nm
and c = 0.520 nm, JCPDS file 03-0888). The intensity of these ZnO
peaks was decreased and a small ZnO (002) peak along with a
sharp ZIO (101) peak was observed while peaks (007) and (322)
were disappeared, in ZIO (50:50) thin film. These new ZIO peaks
might be due to formation of compounds like (ZnO)1−x(In2O3)x,
(Zn2In2O5)1−x(ZnO)x and (Zn2In2O5)1−x(In2O3)x as also reported in
the literature [19].
(b) annealed at 450 0C
ZnO
In2O3
ZIO
*
Δ
*
ZIO (50:50)
ZIO (70:30)
*
*
ZIO (90:10)
ZIO (100:0)
20
25
30
35
40
45
50
55
60
65
Diffraction angle 2 (deg.)
θ
The amorphous phase was completely disappeared after anneal-
ing as can be seen in Fig. 1(b). The ZIO thin films became
polycrystalline where crystalline peaks of ZIO (100:0) film hav-
ing prominent orientation (101) near 42.3◦ along with small peaks
(100), (002) and (102) near 37.1◦, 39.8◦ and 55.8◦, respectively.
Intensity of ZnO peaks gradually decreased with increasing the con-
centration of In2O3 while hexagonal ZIO (007) and (101) peaks were
observed at the same position of the as-prepared ZIO films and
became stronger after annealing. Only one cubic In2O3 (532) peak
was detected near 55.5◦ in all annealed ZIO films.
It was noticeable that small addition of In2O3 into ZnO enhances
the intensity of hexagonal ZIO (007, 101 and 105) peaks. Fig. 1(a)
and (b) shows the preferential crystal growth of ZIO peak took place
towards the (101) orientation after increasing the concentration of
In2O3.
Fig. 1. XRD profile of (a) as-prepared and (b) annealed ZIO thin films.
crystal, which was 0.047◦. The grain size of as-prepared ZIO (50:50)
film was estimated to be ∼19 nm, respectively, while the estimated
grain size of the annealed ZIO films was enhanced from ∼13 nm
to ∼21 nm with the increase of In2O3 concentration from 30 to
50 wt.%. The increment in grain size can be attributed to improve-
ment of crystallinity with increasing concentration of In2O3 and
post annealing. The same tendency was observed by Changhyun
et al. [22], Joseph et al. [23], Kotlyarchuk et al. [24] Lee et al. [25]
and Paraguay et al. [26].
3.2. Scanning electron microscopy (SEM) studies
The crystallite grain size of ZIO crystallites was estimated in the
direction (101) using the Debye–Scherrer equation [20,21]
The surface morphology of the films has been studied by scan-
ning electron microscopy (SEM). Fig. 2(a) and (b) shows SEM
image of as-prepared and annealed ZIO (100:0 wt.%) films, respec-
tively, while Fig. 3(a) and (b) shows SEM image of as-prepared and
annealed ZIO (50:50 wt.%) films, respectively. The micrograph indi-
cated that films were crack-free. It was revealed from ZIO films of
both compositions that the films were composed of roughly spheri-
cal grains of varying size. Absence of apparent grains on the surface
0.9 ꢂ
D =
ˇ cos ꢁ
where D is the crystal size, ꢂ is the wavelength of the X-ray, ˇ
is the difference between measured full width at half maximum
(FWHM) of ZIO(101) peak and the unbroadened FWHM of single

134
V.K. Jain et al. / Journal of Alloys and Compounds 530 (2012) 132–137
Fig. 2. SEM image of (a) as-prepared (b) annealed ZIO (100:0 wt.%) thin films.
Table 1
of as-prepared ZIO (100:0) film can be interpreted as amorphous
nature of film. The grains were appeared in films after addition of
In2O3 and post annealing. The average grain size calculated was
30 nm for as-prepared ZIO (50:50 wt.%). Further, the average size
of grains approached to 37 nm for annealed ZIO (100:0) film and
74 nm for annealed ZIO (50:50 wt.%) film. Therefore, the grain size
increased after annealing. The higher grain sizes in annealed ZIO
films, as esteemed from SEM images, indicate that there may be
agglomeration of the particles resulting in increased size. The simi-
lar trend of improving grain size was also observed in XRD analysis.
% Composition of In, Zn and O obtained on surface of ZIO films.
% Composition
Film type
As-prepared
Annealed
at 450 ◦C
Zn
ZIO (100:0) or pure ZnO
ZIO (90:10)
ZIO (70:30)
ZIO (50:50)
ZIO (100:0) or pure ZnO
ZIO (90:10)
ZIO (70:30)
ZIO (50:50)
ZIO (100:0) or pure ZnO
ZIO (90:10)
ZIO (70:30)
40.96
34.93
29.48
18.02
0
–
38.20
35.61
26.91
–
1.54
2.41
10.22
–
In
O
1.88
2.57
12.01
59.04
63.19
67.95
69.97
3.3. X-ray photoelectron spectroscopy (XPS)
60.26
61.98
62.87
ZIO (50:50)
The XPS studies have been carried out to find the correlation
between the chemical structure and opto-electrical properties [27].
The chemical composition and bonding states of the as-deposited
and annealed ZIO thin films were characterized by XPS using MgK␣
radiation at 1.2536 keV after few monolayers sputtering of ZIO films
by using energetic 2 keV Ar+ ions. Fig. 4(a) and (b) shows the XPS
survey spectra obtained for as-prepared and annealed ZIO thin
films, respectively. The binding energies were calibrated to com-
pensate for any charge induced shifts by setting the C 1s signal
to 284.6 eV. The measured binding energies of In 3d5/2, In 3d3/2, Zn
2p3/2, Zn 2p1/2, O1s in ZIO films agree with those reported in the lit-
erature [11]. To get the quantitative analysis, survey scan was used
with the consideration of corresponding atomic sensitivity factors
for each core levels [28]. The results indicate that zinc concentra-
tions on the surface of annealed films are higher than as-prepared
ZIO films, while indium concentrations are found to be lower on
the surface of annealed films, manifests that zinc highly aggregates
in the surface phase. Because zinc is chemically active therefore it
oxidizes and finally ZnO is observed rather than pure zinc on the
surface of the ZIO thin films.
Fig. 3. SEM image of (a) as-prepared (b) annealed ZIO (50:50 wt.%) thin films.

V.K. Jain et al. / Journal of Alloys and Compounds 530 (2012) 132–137
135
(a) as-prepared
(a) as-prepared
(i) ZIO (100:0)
(ii) ZIO (90:10)
(iii) ZIO (70:30)
(iv) ZIO (50:50)
70
68
66
64
62
60
58
O
In (2p )
40
3/2In (2p1/2)
In (3d3/2)
In (3d5/2)
32
24
16
8
(iv)
Zn
In
O(KVV)
O(1s)
Zn (3p)
C1s
Zn(3s)
Zn(3d)
(iii)
(ii)
0
Zn(2p3/2)
0
10
20
30
40
50
Zn(2p )
Concentration of In2O3(wt%)
1/2
(i)
Zn(LMM)
600
Binding Energy (eV)
0
200
400
800
1000
1200
70
68
66
64
62
60
58
(b) Annealed at 4500C
O
40
32
24
16
8
(b) annealed at 4500C
(i) ZIO (100:0)
(ii) ZIO (90:10)
(iii) ZIO (70:30)
(iv) ZIO (50:50)
Zn(2p3/2
)
Zn(2p1/2
)
In (2p
)
)
3/2In (2p1/2
)
Zn
In
In (3d3/2
In (3d5/2
)
(iv)
O(KVV)
O(1s)
Zn (3p)
C1s
Zn(3s)
Zn(3d)
0
(iii)
10
20
30
40
50
Concentration of In2O3 (wt%)
(ii)
Zn(LMM)
600
Fig. 5. The variation of % composition of contents with concentration of In2O3 of (a)
as-prepared and (b) annealed ZIO thin films.
0
200
400
800
1000
1200
Binding Energy (eV)
Fig. 4. XPS survey spectra of (a) as-prepared and (b) annealed ZIO thin films.
lower binding energy with presence of some states near the Fermi
level which results the valence band maxima come near the Fermi
level at ∼1.6 eV for as-prepared ZIO (50:50) film. This indicated
the transition of films towards more conducting nature. Fig. 6(b)
shows the same trend for the reduction of the band gap with
increase in In2O3 concentration in annealed ZIO films. The gap
decreases after annealing with respect to the as-prepared samples.
The valence band maxima move toward the Fermi level (at ∼1.5 eV)
for annealed ZIO (50:50) film.
Table 1 represents the concentration of each element on the sur-
face of the as-prepared and annealed ZIO thin films. The variation in
the % composition of contents with concentration of indium oxide is
also shown in Fig. 5(a) and (b) for as-deposited and annealed films,
respectively. With high resolution XPS spectra of In 3d5/2, Zn 2p3/2
and O 1s and considering their atomic sensitivity, the atomic ratio of
In/Zn (In 3d5/2/Zn 2p3/2) and O/Zn (O 1s/Zn 2p3/2) was determined
to be increased from 0.05 to 1.50 and 1.81 to 3.88, respectively, for
as-prepared thin films and these were increased from 0.04 to 0.38
and 1.58 to 2.33, respectively, for annealed thin films when the con-
centration of In2O3 increased from 10 to 50 wt.%. These changes in
the ratio suggest the higher oxygen vacancy in the annealed sam-
ples as compared to as-prepared one and it is known that more
oxygen deficient films exhibit a lower resistivity.
Fig. 6(a) and (b) shows the XPS valence band spectra of as-
prepared and annealed films, respectively, obtained at normal
emission (0◦) in VB region (−5 eV to 10 eV). It was observed from
Fig. 6(a) that valence band maxima lies after the Fermi level at
∼1.8 eV for as-prepared ZIO (100:0) film. It was perceptible that
addition of In2O3 into ZnO shift valance band maxima towards
3.4. Electrical properties
The electrical resistivity (ꢃ), carrier concentration (n) and Hall
mobility (ꢄ) of both types of ZIO thin films (as-prepared and
annealed) deposited at different concentration of In2O3 were mea-
sured. Fig. 7(a) and (b) summarizes electrical resistivity results of
as-prepared and annealed ZIO thin films, respectively.
It can be noted from the figures that the resistivity of as-
prepared ZIO thin film decreases with the increasing concentration
of In2O3. The decrease in resistivity (ꢃ) with the increasing con-
centration of In2O3 can be attributed to the increase in the carrier

136
V.K. Jain et al. / Journal of Alloys and Compounds 530 (2012) 132–137
(b) annealed at 450 0C
VB
VB
(a) as-prepared
(iv)
ZIO (50:50)
(iii)
ZIO (70:30)
(iv)
ZIO (50:50)
(ii)
ZIO (90:10)
(iii)
ZIO (70:30)
(i)
(ii)
ZIO (100:0)
ZIO (90:10)
-4
-2
0
2
4
6
8
10
-4
-2
0
2
4
6
8
10
Binding Energy (eV)
Binding Energy (eV)
Fig. 6. XPS valance band spectra of (i) as-prepared and (ii) annealed ZIO thin films with varying concentration (ZnO:In2O3 = (a) 100:0, (b) 90:10, (c) 70:30, (d) 50:50 wt.%).
concentration and the mobility of the charge carriers. The resistivity
is given by [29]
3.0
2.8
2.6
2.4
2.2
2.0
(a) as-prepared
μ
1
ꢅ
1
qnꢄ
4.5
4.0
3.5
3.0
ρ
ꢃ =
=
-1
10
n
where ꢅ is the conductivity of the film and q is the charge of the
carriers.
In ZIO thin films, the In2O3 may diffuse into ZnO matrix. Due
to difference in their grain sizes, diffusion of In2O3 in ZnO matrix
causes an increase in free interstitial lattice spaces. The mobility
of valance electrons is increased in the free spaces and increase in
mobility causes the decreases in resistivity. In addition to this, being
less electronegative than zinc (Zn), indium (In) atoms behave as
donors and enhance the carrier concentration. Further, the oxygen
vacancies also play a very important role in the electronic proper-
ties of ZIO thin films. Oxygen vacancies like defects are the primary
source of charge carriers.
(ρ) Resistivity
(n) Carrier concentration
(μ) Mobility
0
10
20
30
40
50
Concentration of In2O3 (wt%)
The usual description of oxygen-vacancy doping in crystalline
ZIO thin film using Kreoger–Vink notation is given as
10-2
18
16
14
12
10
(b) annealed at 4500
C
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
••
x
Oo = ½O2(g) + Vo + 2e−
μ
ρ
which indicates the oxygen on the oxygen sub-lattice (Oox) is lo·s·t
as oxygen gas (O2) creates a doubly charge oxygen vacancy (Vo
)
n
and two free electrons [30,31] hence increases the concentration
of charge carriers. As number of charge carrier increases, resistivity
decreases.
After annealing in vacuum at 450 ◦C, the resistivity of ZIO film is
found to decrease remarkably as compared to as-prepared film. Its
value reaches to order of ∼10−3 ꢀ-cm. This may be due to further
increase in mobility and carrier concentration on heat treatment
given to the films. The values of so-obtained electrical resistivity of
both types of films are listed in Table 2.
(ρ) Resistivity
(n) Carrier concentration
(μ) Mobility
The annealing process causes a greater possibility of diffusion
of indium oxide from grain boundaries and interstitial lattice loca-
tions to regular ZnO lattice locations [32]. After annealing, the grain
growth results in less grain boundary and, consequently, there is
less grain-boundary scattering and thus the mobility of the charge
carriers enhanced. On vacuum annealing, oxygen vacancies further
enhances and created more free electrons and resulted in to an
increase in carrier concentration. After annealing, indium atoms
are activated and behave as effective donors. Hence, the number of
0
10
20
30
40
50
Concentration of In2O3 (wt%)
Fig. 7. The electrical resistivity, carrier concentration and Hall mobility of
(i) as-prepared and (ii) annealed ZIO thin films with varying concentration
(ZnO:In2O3 = (a) 100:0, (b) 90:10, (c) 70:30, (d) 50:50 wt.%).

V.K. Jain et al. / Journal of Alloys and Compounds 530 (2012) 132–137
137
Table 2
The electrical resistivity, carrier concentration and Hall mobility of as-prepared and annealed ZIO thin films.
Sample
As-prepared
Annealed at 450 ◦
C
ꢃ (ꢀ-cm)
n (×1019 cm−3
)
ꢄ (cm2 v−1 s−1
)
ꢃ (ꢀ-cm)
n (×1020 cm−3
)
ꢄ (cm2 v−1 s−1
)
ZIO (100:0)
ZIO (90:10)
ZIO (70:30)
ZIO (50:50)
10.4 × 10−2
9.33 × 10−2
7.42 × 10−2
4.61 × 10−2
2.07
2.16
2.21
2.83
2.9
3.1
3.8
4.8
6.41 × 10−3
3.80 × 10−3
2.27 × 10−3
1.44 × 10−3
0.95
1.2
1.9
10.2
13.7
14.5
17.3
2.5
free electrons in the annealed film increases drastically. It is evident
from the table that value of resistivity decreases with increasing
concentration of In2O3.
[3] S. Togashi, Optoelectron. Devices Technol. 7 (1992) 271.
[4] G. Kavachi, E. Kumura, Y. Wakui, N. Konishi, H. Yamamoto, Y. Matsukawa, A.
Sasano, IEEE Trans. Electron. Devices 41 (1994) 1120.
[5] J.C. Manifacier, Thin Solid Films 90 (1982) 297.
[6] R.D. Southwick, J.S. Wasylyk, G.L. Samay, J.B. Kepple, E.C. Smith, B.O. Augustsson,
Thin Solid films 77 (1981) 41.
[7] K. Tominaga, N. Umezu, I. Mori, T. Ushiro, T. Moriga, I. Nakabayashi, J. Vac. Sci.
Technol. A 16 (1998) 1213.
4. Conclusions
In the present paper, the structural, chemical and electrical
properties of cost effective ZIO thin films with varying con-
centrations have been studied. An effect of annealing has also
been studied. It was observed that crystalline nature of ZIO thin
films was improved with increasing concentration of In2O3 and
post annealing. The XRD and SEM studies ensured the formation
of nanostructured ZIO thin films. Their results are evidence for
enhancement the size of the spherical grains after annealing. XPS
evaluate the chemical nature of as prepared as well as annealed
films. XPS results show the oxygen vacancies and Zn concentra-
tion on the surface of films increase after annealing which reduce
the resistivity of the films. The XPS valance band spectra also indi-
cate the transition of films towards more conducting nature due
to reduction of band gap. A drastic decrease in electrical resistiv-
ity was observed with the increasing concentration of In2O3 and
after annealing. This may be attributed to increase in carrier con-
centration and mobility due to diffusion process, oxygen vacancy,
less grain-boundary scattering, etc.
[8] R. Wang, L.H.L. King, A.W. Sleight, J. Mater. Res. 11 (1996) 1659.
[9] V.H. Kasper, Z. Anorg. Allg. Chem. 349 (1967) 113.
[10] N. Kimizuka, M. Isobe, M. Nakamura, J. Solid State Chem. 116 (1995) 170.
[11] T. Minami, T. Kakumu, S. Tanaka, J. Vac. Sci. Technol. A 14 (1996) 1704.
[12] Y. Masuda, M. Ohta, W.S. Seo, W. Pitschke, K. Koumoto, J. Solid State Chem. 150
(2000) 221.
[13] T. Minami, H. Sonohara, T. Kazum, S. Takata, Jpn. J. Appl. Phys. 34 (1995)
971.
[14] A. Wang, J. Dai, J. Cheng, M.P. Chudzik, T.J. Marks, R.P.H. Chang, C.R. Kannewurf,
Appl. Phys. Lett. 73 (1998) 327.
[15] N. Naghavi, A. Rougier, C. Marcel, C. Guery, J.B. Leriche, J.M. Tarascon, Thin Solid
Films 360 (2000) 223.
[16] Y.R. Park, E.K. Kim, D. Jung, T.S. Park, Y.S. Kim, Appl. Surf. Sci. 254 (2008)
2250.
[17] S. Kaleemulla, A. Sivashankar Reddy, S. Uthanna, P. Sreedhara Reddy, Mater.
Lett. 61 (2007) 4309.
[18] G. Machado, D.N. Guerra, D. Leinen, J.R. Ramos-Barrado, R.E. Marotti, E.A.
Dalchiele, Thin Solid Films 490 (2005) 124.
[19] N. Naghavi, L. Dupont, C. Marcel, C. Maugy, B. Laik, A. Rougier, C. Guery, J.M.
Tarascon, Electrochim. Acta 46 (2001) 2007.
[20] B.D. Cullity, Element of X-ray Diffraction, 2nd ed., Addition-Wesley, Reading,
MA, 1978.
[21] X.W. Sun, L.D. Wang, H.S. Kwok, Thin Solid Films 360 (2000) 75.
[22] L. Changhyun, Sol. Energy Mater. Sol. Cells 43 (1996) 37.
[23] B. Joseph, Bull. Mater. Sci. 28 (2005) 487.
Acknowledgments
[24] B. Kotlyarchuk, Crys. Res. Technol. 40 (2005) 1118.
[25] C. Lee, K. Lim, J. Song, Sol. Energy Mater. Sol. Cells 43 (1996) 37.
[26] F. Paraguay, D.J. Morales, W. Estrada, L.E. Andrade, M. Miki-Yoshida, Thin Solid
Films 366 (2000) 16.
[27] Z. Wang, X. Hu, Thin Solid Films 392 (2001) 22.
[28] C.D. Wagner, W.M. Riggs, L.E. Davis, J.F. Moulder, G.E. Muilenberg, Handbook
of X-ray Photoelectron Spectroscopy, Perkin Elmer Corp., 1979.
[29] S.-Y. Lee, B.-O. Park, Thin Solid Films 484 (2005) 184.
[30] J.H.W. De Witt, J. Solid State Chem. 20 (1977) 143.
[31] G.B. Gon, Z.A. Lez, J.B. Cohen, J.H. Hwang, T.O. Mason, J. Appl. Phys. 89 (2001)
2550.
One of the author (VJ) is thankful to Mr. Pawan Kulhari, Inter
University Accelerator Centre, New Delhi (India) for his kind help in
structural experiment, Mr. Devendra Vyas, University of Rajasthan,
Jaipur (India) for providing ball milling facility and assistance.
References
[32] C.E. Benouis, A. Sanchez-Juarez, M.S. Aida, J. Appl. Sci. 7 (2) (2007) 220.
[1] H. Kawazoe, K. Ueda, J. Am. Ceram. Soc. 82 (12) (1999) 3330.
[2] J. Pla, M. Tamasi, R. Rizzoli, M. Losurdo, E. Centurioni, C. Summonte, F. Rubinelli,
Thin Solid Films 425 (2003) 185.