Structural, optical and magnetic properties of (In0.90Sn0.05Cu0.05)2O3 nanoparticles
S. Harinath Babu, S. Kaleemulla, N. Sai Krishna, N. Madhusudhana Rao, M. Kuppan, C. Krishnamoorthi, Girish
M. Joshi, R. K. Kotnala, and J. Shah
Citation: AIP Conference Proceedings 1731, 130005 (2016); doi: 10.1063/1.4948111
View online: http://dx.doi.org/10.1063/1.4948111
View Table of Contents: http://scitation.aip.org/content/aip/proceeding/aipcp/1731?ver=pdfcov
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Structural, Optical and Magnetic Properties of
(In
0.90
Sn
0.05
Cu
0.05
)
2
O
3
Nanoparticles
S. Harinath Babu
a
, S. Kaleemulla
a*
, N. Sai Krishna
a
, N. Madhusudhana Rao
a
,
M. Kuppan
a
, C. Krishnamoorthi
a
, Girish M. Joshi
a
, R.K. Kotnala
b
, J. Shah
b
a
Thin Films Laboratory, School of Advanced Sciences, VIT University, Vellore – 632 014, Tamilnadu, India
b
CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi, India
*
Email:skaleemulla@gmail.com
Abstract. This study examined structural, optical and magnetic properties of ITO (In
0.95
Sn
0.05
)
2
O
3
and Cu doped ITO
(In
0.90
Sn
0.05
Cu
0.05
)
2
O
3
nanoparticles synthesized by solid state reaction method. The synthesized nanoparticles were subjected to
structural, optical and magnetic studies. The structural properties of the nanoparticles were carried out using XRD, Raman, FT-
IR characterization techniques. Optical properties of the samples were studies using UV-Vis-NIR spectrophotometer. The
magnetic measurements were carried out using vibrating sample magnetometer. The ITO (In
0.95
Sn
0.05
)
2
O
3
nanoparticles
exhibited room temperature ferromagnetism with clear hysteresis loop. The strength of magnetization decreased in Cu doped
ITO (In
0.90
Sn
0.05
Cu
0.05
)
2
O
3
. The ITO nanoparticles were also exhibited ferromagnetism at 100 K with a magnetic moment of
0.02 emu/g.
Keywords: Nanoparticles, Cu doped ITO, solid state reaction, Ferromagnetism
PACS: 73.50.Td, 75.50.Pp, 75.47.Lx, 75.50.Dd
INTRODUCTION
Since the discovery of ferromagnetism in Mn
doped ZnO [1] with Curie temperature above room
temperature, much focus is being put on wide band
gap oxide semiconductors. Intensive research work
had been carried out on transitional metal doped
oxide semiconductors such as ZnO, TiO
2
and SnO
2
[2]. But results were quite controversial. In few
research articles it was reported that the observed
ferromagnetism was due to metal clusters/secondary
phases whereas in other research papers it was
reported that the observed ferromagnetism was
intrinsic in nature and explained by considering
different model such carrier mediated interactions
[3], double exchange interactions [4] bound poloron
magnetic (BPM) model [5]. Reports on the Cu
doped ITO nanoparticles are meagre. Hence an
attempt is made here for the synthesis and
characterization of ITO and Cu doped ITO
nanoparticles.
EXPERIMENTAL
ITO (In
0.95
Sn
0.05
)
2
O
3
and Cu doped ITO
(In
0.90
Sn
0.05
Cu
0.05
)
2
O
3
nanoparticles were prepared
by simple standard solid state reaction method. In a
typical synthesis, commercially available In
2
O
3
,
SnO
2
and Cu
2
O (Sigma–Aldrich, 99.999% pure)
powders were taken in desired ratios and mixed in
Agate mortar and ground thoroughly for 16 hours
using pestle. The ground fine stoichiometric samples
were loaded into a small one end closed quartz tube
of diameter 10 mm and length 10 cm, which was
then enclosed by a bigger quartz tube of diameter of
2.5 cm and length of 75 cm with a provision to allow
unwanted vapours to escape from the reaction
chamber and it was evacuated to a pressure of 2x10
-3
mbar using a rotary vane pump. The complete set up
was placed in horizontal tubular microprocessor
controlled furnace and heated for several hours at
different temperatures. After that the samples were
subjected to their structural and optical properties.
RESULTS AND DISCUSSION
Structural Properties
Fig.1 shows the X-ray diffraction patterns of the
Cu
2
O, In
2
O
3
, Sn doped In
2
O
3
(ITO) and Cu doped
In
2
O
3
nanoparticles, respectively. The X-ray
diffraction patterns of Cu
2
O, SnO
2
are provided here
DAE Solid State Physics Symposium 2015
AIP Conf. Proc. 1731, 130005-1–130005-3; doi: 10.1063/1.4948111
Published by AIP Publishing. 978-0-7354-1378-8/$30.00
130005-1
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to confirm that no secondary phases related to
impurities in any form are present.
0
5000
10000
0
7000
14000
20 30 40 50 60 70
0
25000
50000
Cu doped ITO
In
2
O
3
Intensity (counts)
Cu
2
O
2
T
(degrees)
FIGURE 1. X-ray diffraction patterns of Cu
2
O In
2
O
3
, Cu
doped ITO nanoparticles.
All the diffraction peaks were exactly coincided
with cubic structure of In
2
O
3
. The XRD patterns
conformed that the impurity phases were not
observed in In
2
O
3
nanoparticles. The diffraction
peaks such as (2 1 1), (2 2 2), (4 0 0), (4 1 1), (3 3 2),
(4 3 1), (5 2 1), (4 4 0), (4 3 3), (6 1 1), (5 4 1),
(6 2 2), (6 3 1), (4 4 4), (5 4 3), (6 4 0), (7 2 1), and
(6 4 2) were found in all the In
2
O
3
nanoparticles
among which (2 2 2) peak was predominant. All the
indexed peaks exactly coincided with the cubic
structure of In
2
O
3
(JCPDS No. #06-0416). Similar
diffraction peaks were also observed for ITO and Cu
doped ITO nanoparticles. The crystallite size was
calculated using Scherer’s relation and found that it
was about 30 nm.
Optical Properties
500 1000 1500 2000 2500
0
20
40
60
80
100
Reflectane (%)
Wavelength (nm)
In
2
O
3
SnO
2
ITO
Cu:ITO
FIGURE 2. Diffuse reflectance spectra of In
2
O
3
, SnO
2
,
ITO and Cu doped ITO and nanoparticles.
The absorption coefficient was calculated using
Kubelka-munk function relation [6]. Fig. 3 shows
the optical band gap of the (In
0.95-x
Sn
0.05
Ni
x
)
2
O
3
nanoparticles. The optical bang gap (E
g
) was
obtained by plotting (αhυ)
2
versus the photon energy
(hυ) and by extrapolating the linear region (α = 0).
The optical band gap was estimated using the Tauc
relation [7]. The band gap of 3.12 eV was found for
the (In
0.90
Sn
0.05
Cu
0.05
)
2
O
3
nanoparticles
.
2.0 2.5 3.0 3.5 4.0
0
50
100
150
200
250
(
D
h
Q
)
h
Q
(eV)
In
2
O
3
(In
0.90
Sn
0.05
Cu
0.05
)
2
O
3
FIGURE 3. Plots of (αhυ)
2
versus hυ of the In
2
O
3
and Cu
doped ITO nanoparticles.
Magnetic properties
-4000 -2000 0 2000 4000
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
Manetization (emu/g)
Applied Field (Gauss)
(In
0.90
Sn
0.05
Cu
0.05
)
2
O
3
(In
0.90
Sn
0.05
)
2
O
3
FIGURE 4. Magnetic hysteresis loops (M–H) of ITO and
Cu doped ITO nanoparticles at room temperature.
Fig. 4 shows the magnetic hysteresis curves of
undoped and Cu doped ITO nanoparticles at room
temperature. The In
2
O
3
and SnO
2
exhibited
diamagnetic nature at room temperature. But ITO
(In
0.95
Sn
0.05
)
2
O
3
nanoparticle exhibited
ferromagnetism at room temperature and at 100 K.
The clear hysteresis loop of the (In
0.95
Sn
0.05
)
2
O
3
nanoparticle indicates that the Curie temperature for
these nanoparticles is higher than room temperature.
The hysteresis loop shows a high coercive field (Hc)
of 683 G. The observed magnetic moment is almost
equal to that of magnetic moment observed by
Peleckis et al [8] in Ni doped In
2
O
3
nanoparticles
prepared by solid state synthesis route method.
130005-2
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Transition metal doped SnO
2
and In
2
O
3
exhibited
room temperature ferromagnetism in our earlier
studies. In the present study, tin doped In
2
O
3
(ITO)
nanoparticles also exhibited room temperature
ferromagnetism. The (In
0.90
Sn
0.05
Cu
0.05
)
2
O
3
nanoparticles also exhibited room temperature
ferromagnetism but the strength of magnetization
decreased in (In
0.90
Sn
0.05
Cu
0.05
)
2
O
3
nanoparticles.
FIGURE 5. Magnetic hysteresis loops (M–H) of ITO
nanoparticles at 100 K.
The samples exhibited the saturation magnetic
moment (M
s
) of 0.05 emu/g, coevercity(H
c
) of 683
G and retentivity (M
r
) of 0.02 emu/g, respectively.
Whereas the strength of magnetization decreased in
Cu doped ITO nanoparticles. The observed saturation
magnetic moments are better than that of saturation
magnetic moment of Co doped SnO
2
nanoparticles
prepared by co-precipitation method [9]. Fig .5
shows the M-H curve of ITO nanoparticles at 100 K.
From the figure it is clear that the saturation
magnetic moment decreased at lower temperature. it
may due to antiferromagnetic or ferrimagnetism
developed at low temperature. Room temperature
ferromagnetism was also found in nanoparticles of
nonmagnetic oxides such as CeO
2
, Al
2
O
3
, ZnO,In
2
O
3
and SnO
2
[10]; however, the corresponding bulk
samples obtained by sintering the nanoparticles at
high temperatures in air or oxygen became
diamagnetic. The origin of ferromagnetism in these
nanoscale materials is assumed to be the exchange
interactions between localized electron spin moments
resulting from the oxygen vacancies [11]. Recent
results indicated that surface ferromagnetic states and
spin polarization were realized in the presence of
vacancies on the surface of In
2
O
3
and Indium-Tin
oxide (ITO) [12]. The less magnetic moment in
polycrystalline ITO may be due to sintering of the
samples in air at different higher temperatures. In the
present study the samples were sintered in vacuum in
which oxygen vacancies can be produced easily.
However, until now, no experiments have been
performed to demonstrate the existence of surface
ferromagnetism and spin polarization on the surface
of undoped oxide. Room temperature
ferromagnetism was also observed in Fe doped ITO
thin films and concluded that the observed
ferromagnetim is due to oxygen vacancies [13].
CONCLUSION
ITO (In
0.95
Sn
0.05
)
2
O
3
and Cu doped ITO
(In
0.90
Sn
0.05
Cu
0.05
)
2
O
3
nanoparticles were prepared
using standard solid state reaction method and
studied the structural, optical and magnetic properties
systematically. The ITO and Cu doped ITO
nanoparticles exhibited ferromagnetism at room
temperature and the strength of the magnetic moment
decreased after doping Cu into ITO lattice.
ACKNOWLEDGMENTS
Authors are thankful to VIT-SIF for
providing XRD and diffused reflectance spectra
(DRS) facilities.
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