Tunable dielectric constant with transition metals doping in Zn1-x(MnTM)xO (TM = Co, Fe) nanocrystals

Article abstract of DOI:10.1016/j.jallcom.2015.04.092

We have presented dielectric studies on Zn_1-xMn_x/2Fe_x/2O and Zn_1-xMn_x/2Co_x/2O (x = doping level) semi

Full text of DOI:10.1016/j.jallcom.2015.04.092

Journal of Alloys and Compounds 642 (2015) 15–21
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jalcom
Tunable dielectric constant with transition metals doping in
Zn1 (MnTM) O (TM = Co, Fe) nanocrystals
ꢀx
x
⇑
Swati Singh, P. Dey, J.N. Roy, S.K. Mandal
Department of Physics, National Institute of Technology Agartala, Agartala, Tripura 799046, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 3 March 2015
Received in revised form 27 March 2015
Accepted 9 April 2015
Available online 21 April 2015
ꢀx 1ꢀx
We have presented dielectric studies on Zn1 Mnx/2Fex/2O and Zn Mnx/2Cox/2O (x = doping level) semi-
conducting nanoparticles (ꢁ2–40 nm). Structural analyses show the formation of single phase nanopar-
ticles. Dielectric constant ( ) is found to exhibit sensitive modulation, both with the variation of doping
element (Fe and Co) and doping level (x) in ZnMnO matrix and also with frequency (f). Enhancement of
is found to be ꢁ1500 times for Zn0.9Mn0.05Fe0.05O and ꢁ2 times for Zn0.9Mn0.05Co0.05O from that of
Zn0.9Mn0.1O nanoparticles at low frequency region. The enhancement in can be explained on the basis
e
e
e
Keywords:
Nanoparticles
Dielectric
of dielectric polarization, caused by the presence of different abundance of higher oxidation states of Fe
and Co ions in ZnMnFeO and ZnMnCoO samples. From our observation one can choose the suitable dop-
ing element, along with suitable dopant concentration to achieve the desired higher value of
e in transi-
Semiconductors
tion metal doped ZnMnO nanoparticles at room temperature. We have also estimated semiconducting
band gap of those nanoparticles using recorded absorbance spectra.
Ó 2015 Elsevier B.V. All rights reserved.
1
. Introduction
Nanomaterials have fascinated researchers in recent years
doping and unintentional formation of impurities during growth
of ZnO nanoparticles that advances in device processing tech-
niques [11]. Yang et al. reported that
on diameter of the nanowire, i.e., as the diameter of the ZnO nano-
wire decreases, also decreases [12]. In general, Some of the
research groups studied of nanoparticles, e.g., fine grained pow-
der of diamond, silicon, LiF, NaCl and have shown a strong depen-
dence of on crystal grain size [13]. Furthermore, in case of doped
sample depends on composition of doping element [14].
e of ZnO nanowire depends
because these materials exhibit unusual physical properties, such
as optical, electrical and magnetic properties, as compared to their
bulk counterpart. One of them is nanostructured zinc oxide (ZnO),
which is well known for its wide band gap of 3.34 eV and large
exciton binding energy of 60 meV. In general, ZnO is a material
of huge application in spintronics [1], sensors [2], fabric industries
e
e
e
e
[
3] etc. Recently, there is an increasing research interest in semi-
Recently, a large number of studies on different kind of transi-
tion metal (TM) doped ZnO nanoparticles have been carried out
by different research groups [15]. Many researchers are fascinated
toward diluted magnetic semiconductor (DMS), which is promis-
ing for application in spintronic devices. Moreover, some research
groups have shown that doping of TM into ZnO matrix lead to fine
tuning of band gap. This feature can find application in ultra violet
(UV) detectors and light emitters [16]. In our previous papers, we
have shown room temperature antiferromagnetic (AFM)-like
ground state for Co doped ZnO [17], ferromagnetic (FM)-like beha-
vior for Fe doped ZnO [18] and mixed ferrimagnetic-FM like beha-
vior for co – Fe and Co doped ZnO [19]. Recently, we have found
conductor nanocrystal considering the issue of size miniaturization
in semiconductor industry and surface state on nanometer scale
[
directed toward nanostructured ZnO. Also high dielectric constant
(
4]. In this attempted, a huge amount of research effort has been
e
) material also has its wide application in microelectronic devices
[
5] and memory based devices [6]. In this direction the study of
dielectric property of ZnO is gaining attention as well due to its
optical transparency and mechanical flexibility [7] and is used as
dielectric layer in device fabrication such as memory or micro-laser
[
8]. Omar reported the temperature and frequency dependent
e of
bulk ZnO [9]. Ghosh et al. reported the high frequency and static
e
e
of ZnO nanoparticle exhibiting a strong dependence on doping ele-
enhancement in e at room temperature for Fe-doped, Co-doped
ment, like Ni [10]. Recently, a review has been done on control
and Fe–Co co-doped ZnO nanoparticles, as well [20]. In this present
work, we have focussed on the dielectric study of co-doped
Zn1ꢀxMnx/2TMx/2O (Co, Fe) nanoparticles, where we have carried
out the study by keeping Mn doping fixed and tuning TM(= Co,
⇑
Corresponding author. Tel.: +91 3812348530.
E-mail address: saniitkgp2007@gmail.com (S.K. Mandal).
http://dx.doi.org/10.1016/j.jallcom.2015.04.092
925-8388/Ó 2015 Elsevier B.V. All rights reserved.
0

1
6
S. Singh et al. / Journal of Alloys and Compounds 642 (2015) 15–21
Fe) doping. In this attempt, detailed dielectric studies have been
carried out on Fe and Co doped Zn1ꢀxMnx/2TMx/2O nanoparticles
with varying dopant concentration (x) at room temperature. Here
6000
0
Zn Mn Fe O
300 C
(a)
0.8
0.1
0.1
0
400 C
0
we have shown how
ing level and choice of the doping element as well. We have also
reported a large enhancement of for both Fe and Co doped
Zn1ꢀxMnx/2TMx/2O nanoparticles, as compared to ZnMnO nanopar-
ticles at room temperature. Enhancement of for Fe doped sample
e strongly and sensitively depends on both dop-
5
00 C
4000
e
e
2000
is found to be larger as compared to Co doped ZnMnO matrix.
Particle sizes of the samples are found to be in nanometric region,
which has been confirmed from structural analysis.
Semiconducting band gap of those samples have been estimated
from absorbance spectra at room temperature.
0
0
3
4
5
00 C
6000
(b)
Zn Mn0.05Fe0.05O
0.9
0
00 C
2
. Experimental details
0
00 C
Zn1ꢀxMn
pared by low temperature chemical ‘‘pyrophoric reaction process’’ [17,18,21–23].
The required chemicals were Zn(NO for Zn, Co(NO ꢂ6H for Co,
ꢂ6H
Fe(NO O for Fe, C MnO ꢂ4H O for Mn, triethanolamine (TEA) and HNO
ꢂ9H
The requisite amount of Zn(NO O, C MnO ꢂ4H O, Fe(NO ꢂ9H O, and
ꢂ6H
Co(NO O, depending on the required doping concentration (x), were mixed
ꢂ6H
x
O, Zn1ꢀxMnx/2Cox/2O and Zn1ꢀxMnx/2Fex/2O nanoparticles were pre-
)
3 2
2
O
3
)
2
2
O
)
3 3
2
4
H
6
4
2
3
.
3000
)
3 2
2
4
H
6
4
2
)
3 3
2
3
)
2
2
with distilled water. All the nitrates were soluble in distilled water. Then the solu-
tion was heated at ꢁ190 °C with continuous stirring. After some time, TEA was
added maintaining 1:4 ratio with metal ions and TEA, with metal ions were precipi-
3
tated in the solution. At the same temperature HNO was added to dissolve the pre-
cipitation and then the clear solution was evaporated with constant stirring. After
complete dehydration, the nitrate themselves were decomposed with the evolution
0
2
0
40
60
80
of brown fumes of NO
2
leaving behind a voluminous, organic based, brownish black,
2θ (degree)
fluffy powder, i.e., precursor powder. The precursor powder, after grinding, was cal-
cined at temperatures of 300–500 °C in air for 4 h to get nanocrystalline powders.
We made circular pellets from calcined nano powders and have sintered them for
Fig. 1. (a) XRD patterns of Zn0.8Mn0.1Fe0.1O, and (b) Zn0.9 Mn0.05Fe0.05O nanopar-
ticles calcined at 300, 400 and 500 °C.
3
0–45 min. The sintering temperatures were same as that of calcination tempera-
tures of the respective nano powders. These pellets have been used for transport,
magnetic and optical studies. Details of the low temperature chemical reaction
were according to
for the same calcination temperatures are shown in
Fig. 2(a) and (b), respectively. For calcination temperature of
300 °C, XRD patterns reveal that the samples are in single phase
with ZnO wurtzite structure with the absence of any metallic
ð1 ꢀ xÞ ZnðNO
þ NðCH CH
3
Þ2 þ ðx=2Þ C
OHÞ3
4
H
6
MnO
4
ꢂ 4H
2
O þ ðx=2Þ FeðNO
3
Þ3=ðx=2Þ CoðNO Þ2
3
2
2
2
2þ
!
½Zn ꢀ NðCH
2
CH
2
OHÞ3ꢃ þ þ ½Mn ꢀ NðCH
2
CH
2
OHÞ3ꢃ
2
þ
OHÞ3ꢃ þ NOꢀ3
2þ
þ ½Fe ꢀ NðCH
2
CH
2
OHÞ3ꢃ =½Co ꢀ NðCH
2 2
CH
!
!
Oxidization in air
6000
0
(a)
Zn Mn Co O
300 C
4
5
Zn1ꢀxMn
x
O Zn1ꢀxMnx=2Fex=2O=Zn1ꢀxMnx=2Fex=2O ðnanosizedÞ þ CO
2
þ NO
2
0.8
0.1
0.1
0
00 C
þ N
2
2
þ H O:
0
00 C
Structural characterisations have been done by X-ray diffraction technique
4000
(
XRD) (Philips, PW-1729) with monochromatic Cu K radiation, Transmission elec-
a
tron microscopy (TEM) (JEOL, JEM-2100, 200 kV) and high resolution field emission
4
0
scanning electron microscopy (FE-SEM) (Carl Zeiss, SUPPRA TM ). Energy disper-
sive X-ray analysis (EDAX) has been done using Carl Zeiss, SUPPRA TM4
0
.
Thermogravimetric analysis (TG) and differential thermal analysis (DTA) have been
done in presence of air atmosphere with alumina crucible and with ramping rate of
2000
8000
1
0 °C/min, using Perkin Elmer Phyris Diamond TG-DTA. Detailed dielectric studies
have been carried out using Agilent impedance analyser (4294 A) along with a
homemade proportional–integral–derivative (PID) controlled furnace (300–
6
00 K). We have used high purity and highly conducting silver paste for the pre-
paration of electrodes on our pelletized samples. The copper wire has been used
as the connecting electrical leads for electrical connection of those samples to the
four probe cable of impedance analyser. Then the sample was kept on a flat surface
of an asbestos sheet and has been placed inside the furnace (at middle position). For
optical characterization of semiconducting nanoparticles, room temperature absor-
bance spectra were recorded using UV – visible spectrophotometer (Micro pack,
DH-2000).
(b)
Zn Mn0.05Co0.05O
0.9
0
300 C
0
6
000
400 C
0
500 C
4000
3
. Results and discussions
2000
3.1. Structural characterizations
0
Structural characterisations have been done by XRD, FE-SEM,
2
0
40
60
80
TEM and TG-DTA. XRD patterns of Zn0.8Mn0.1Fe0.1
O
and
2θ (degree)
Zn0.9Mn0.05Fe0.05O samples, calcined at temperatures of 300, 400
and 500 °C, are shown in Fig. 1(a) and (b), respectively. Similar,
XRD patterns of Zn0.8Mn0.1Co0.1O and Zn0.9Mn0.05Co0.05O samples,
Fig. 2. (a) XRD patterns of Zn0.8Mn0.1Co0.1O, and (b) Zn0.9 Mn0.05Co0.05O nanopar-
ticles calcined at 300, 400 and 500 °C.

S. Singh et al. / Journal of Alloys and Compounds 642 (2015) 15–21
17
and oxide peaks of the related doping elements, within the experi-
mental limitations. From high-resolution (HR) XRD also, we could
not detect any peak corresponding to any precipitate of doping ele-
ment. At next higher calcination temperature, the secondary phase
is found to just grow and enhance with further increasing cal-
cination temperatures. Here our motivation is to study the physical
properties of the single phase sample only. Thus, we have confined
our study on sample, calcined at 300 °C. Detailed XRD studies on
x
Zn1ꢀxMn O sample have been discussed in Ref. [17]. Low magnifi-
cation bright field TEM micrographs are shown in Fig. 3, indicate
nanometric particle size distribution in the range of ꢁ2–40 nm.
FE-SEM micrographs and EDAX spectra, shown in Figs. 4 and 5,
respectively, correspond to absence of any phase segregation and
good chemical homogeneity of these nanoparticles. Thermal analy-
ses of those samples have been carried out using TG-DTA, as shown
in Fig. 6(a) –(c). TG data show weight loss in three steps at 253, 411
and 490 °C for Zn0.9Mn0.1O nanoparticles, at 274, 327 and 428 °C
for Zn0.8Mn0.1Fe0.1O nanoparticles and at 244, 386 and 458 °C for
Zn0.8Mn0.1Co0.1O nanoparticles. All the observed peaks in TG and
DTA curves of the samples (Fig. 6) correspond to the exothermic
peaks in the measured temperature range. In case of Zn0.9Mn0.1
O
nanoparticles, the observed exothermic peaks at 253 and 411 °C
are due to dehydration and that at 490 °C is due to decomposition
of nanometric sample. In case of Zn0.8Mn0.1Fe0.1O nanoparticles,
the exothermic peaks at 274 and 327 °C are due to dehydration
and 428 °C is due to decomposition of nanometric sample. In case
Fig. 4. FE-SEM images for (a) Zn0.9Mn0.1O, (b) Zn0.8Mn0.1Fe0.1
O
and (c)
Zn0.8Mn0.1Co0.1O nanoparticles.
of Zn0.8Mn0.1Co0.1O nanoparticles the two exothermic peaks at 244
and 386 °C are due to dehydration and the peak at 458 °C is due to
decomposition of nanometric sample.
3.2. Dielectric studies
e
as a function of frequency (f) for Zn1ꢀxMn
and Zn1ꢀxMnx/2Cox/2O nanoparticles at different x are shown in
Fig. 7(a) –(c), respectively. shows usual exponential decrease
x
O, Zn1ꢀxMnx/2Fex/2O
e
with f revealing Maxwell–Wagner dispersion interfacial polariza-
tion phenomenon [24], which is in agreement with Koop’s theory
[
25]. Insets in Fig. 7(a) –(c) shows
corresponding samples at low frequency (f = 115 Hz). A maxima
in is found to appear at x = 0.1 for both Zn1ꢀxMn O and
Zn1ꢀxMnx/2Fex/2O nanoparticles, followed by decrease in with fur-
ther increase in x. Quite differently, is found to increase continu-
e as a function of x of the
e
x
e
e
ously with increase in Co content in ZnMnO matrix.
Simultaneously, we have carried out dielectric loss (tand) mea-
surement for all those corresponding samples, as shown in
Fig. 8(a)–(c), respectively. tand is found to exhibit usual exponen-
tial decrease with increase in f for x = 0 i.e., for ZnO nanoparticles.
The values of tand show slightly higher value (<4.6) at low fre-
x
quency region for Zn1ꢀxMn O, Zn1ꢀxMnx/2Fex/2O and Zn1ꢀxMnx/2Cox/2O
nanoparticles compared to ZnO nanoparticles. These entire series
of TM doped ZnMnO nanoparticles show maxima in tand in the
measured frequency range (Fig. 8).
Enhancement in
Zn1ꢀxMnx/2Fex/2O sample compared to that of Zn1ꢀxMn
Zn1ꢀxMnx/2Cox/2O sample (for x = 0.1 doping). Such enhancement
in
is found to be ꢁ1500 times for Zn0.9Mn0.05Fe0.05O and ꢁ2 times
e
from that of undoped ZnO is maximum for
x
O and
Fig. 3. Low magnification bright field TEM images for (a) Zn0.9Mn0.1O, (b)
Zn0.8Mn0.1Fe0.1O and (c) Zn0.8Mn0.1Co0.1O nanoparticles.
e

1
8
S. Singh et al. / Journal of Alloys and Compounds 642 (2015) 15–21
Fig. 5. EDAX spectra for (a) Zn0.9Mn0.1O, (b) Zn0.8Mn0.1Fe0.1O and (c) Zn0.8Mn0.1Co0.1O nanoparticles.
for Zn0.9Mn0.05Co0.05O nanoparticles from that of Zn0.9Mn0.1
O
in ZnMnO matrix, a huge enhancement in
e is observed as com-
nanoparticles at room temperature. This is clearly shown in bar
diagram in Fig. 9(a). Similar bar diagram for x = 0.2 doped samples
pared to Co doping. When TM (Fe, Co) is doped in the sub-
2+
stitutional Mn/Zn site then it has the possibility to be in Fe /
2
+
is shown in Fig. 9(b). From this bar diagram, an enhancement of
observed by ꢁ20 times for Zn0.8Mn0.1Fe0.1O and ꢁ18 times for
Zn0.8Mn0.1Co0.1O nanoparticles, compared to that of Zn0.8Mn0.2
e
is
Co ionic sate. However, it is quite possible that a large number
3
+
3+
of uncoupled Fe /Co ions are present in the sample in order to
maintain charge imbalance, created by Zn vacancies. This happens
O
2
+
3+
2+
3+
nanoparticles at room temperature. Thus, from this bar analysis
one can choose the doping element, along with dopant concentra-
by changing the ionic state from Fe M Fe /Co M Co
in
ZnMnO matrix. This changing of ionic state of the TM ions in the
system leads to effective doping of higher oxidation state of TM
ions in ZnMnO matrix. Infact, existence of such vacancy sites and
consequently the charge mixing has been found in this kind of
nanocrystalline transition metal doped ZnO DMS samples
tion to get the desired higher value of
particles at room temperature.
e in TM doped ZnMnO nano-
In our sample, doping of Fe and Co element in ZnMnO matrix
determines the extent of enhancement in . In case of Fe doping
e

S. Singh et al. / Journal of Alloys and Compounds 642 (2015) 15–21
19
6
4
3
1
0
5
0
5
0
*
(a)
Zn Mn O
1-x
3
0
x
5
4
4
.0
.5
.0
21
18
15
115 Hz
20
10
0
*
(
a)
12
*
0
.00 0.05 0.10 0.15 0.20
3
.5
.9
x
ZnO
.1
0.2
Zn 0.9Mn 0.1
O
0
4
60
40
20
0
*
(b)
4.2
3.5
2.8
8000
6000
4000
2000
0
Zn Mn Fe O
1-x x/2 x/2
4000
3000
2000
115 Hz
(b)
*
*
1000
0
ZnO
0.1
0.2
2
4
.1
.5
Zn0.8Mn 0.1Fe0.1
O
0.00 0.05 0.10 0.15 0.20
x
*
20
4.0
3.5
3.0
(c)
Zn Mn Co
O
400
300
200
100
0
1-x x/2 x/2
(
c)
*
10
0
175
1
15 Hz
140
05
*
1
70
ZnO
Zn 0.8Mn 0.1Co 0.1
O
0
.1
.2
35
0
0
1
00 200 300 400 500 600
0.00 0.05 0.10 0.15 0.20
0
x
T ( C)
Fig. 6. TG-DTA for (a) Zn0.9Mn0.1O, (b) Zn0.8Mn0.1Fe0.1O and (c) Zn0.8Mn0.1Co0.1
nanoparticles.
O
101
102
103
104
105
106
Frequency (Hz)
Fig. 7.
b) Zn1ꢀxMnx/2Fex/2O and (c) Zn1ꢀxMnx/2Cox/2O. Inset shows
level x at f = 115 Hz for corresponding samples.
e
as a function of frequency with varying doping level x for (a) Zn1ꢀxMn
x
O,
(
e
as a function of doping
[
26,27]. In this context, the formation of space charge polariza-
tion is highly possible that in turn results in this observed
enhancement of up to a certain x, as discussed in our previous
e
paper [20]. Moreover, we are working on nanoparticles samples,
as is evident from TEM micrographs. Thus the surface to volume
ratio is expected to be quite large and the surface related physi-
cal properties are supposed to be appreciably pronounced in the
system. Moreover, our samples are heavily TMs doped samples.
Thus the number of TM ions residing at the grain surface is
expected to be quite larger than its bulk region. It can be easily
understood that TM ions residing at the enhanced grain surface
are expected to be in higher and stable oxidation state [17,18].
3
.3. Optical property
To investigate the semiconducting band gap (E
g
) of those sam-
ples, we have recorded the absorbance spectra at room tempera-
ture using a UV – visible spectrophotometer. Absorbance spectra
of the Zn0.9Mn0.1O and Zn0.9Mn0.05Fe0.05O samples, as shown in
Fig. 8(a) and (b), respectively, do not show very sharp absorption
edge. This behavior may be due to broad nanometric particle size
g
distribution of those samples. In such case, E of those samples
3
+
For Fe and Co ions, the stable and higher oxidation state is Fe
can be estimated from the maximum in the first derivative curve
of each absorbance spectrum [28]. Insets in Fig. 10(a) and (b)
shows the first derivative curve of absorbance spectra for
Zn0.9Mn0.1O and Zn0.9Mn0.05Fe0.05O samples, respectively. From
the Gaussian fit of these first derivative curves, the points of inflec-
tion have been estimated. This point of inflection can be considered
to represent the absorption edge of absorbance spectra, from
which the band gap energy is estimated to be E
Zn0.9Mn0.1O and Zn0.9Mn0.05Fe0.05O samples. This value of E
equivalent to the estimated band gap energy (not shown here)
for other samples, discussed here.
3
+
and Co in ZnMnO matrix. So, there is quite possibility of the
presence of large number of uncompensated TM ions at the
enhanced grain surface of the nanoparticles. Furthermore, d-or-
bital element with half-filled subshell is the most stable. The
ground state configuration for Fe is [Ar] 3d5 and for Co is
3
+
3+
6
3+
3+
[
Ar] 3d , indicating that Fe ion is more stable than Co . As a
3+
result, we may expect a more abundance of Fe ion as compared
to Co3+ ions on the grain boundary in our samples. This, in turn
causes enhanced dielectric polarization in ZnMnFeO than
g
= 3.29 eV for
is
g
ZnMnCoO sample. Consequently, enhancement in
be much larger in Zn0.9Mn0.05Fe0.05O (ꢁ1500 times) and in
Zn0.8Mn0.1Co0.1
(ꢁ10 times) nanoparticles from that of
Zn0.9Mn0.1O nanoparticle at room temperature. Similarly, the
observed higher value of of Zn0.9Mn0.1O sample compared to
e is found to
O
4. Conclusions
e
ZnO, can be explained considering the Zn vacancy sites that in
turn induces charge imbalance in the system.
ꢀx x 1ꢀx 1ꢀx
In conclusions, Zn1 Mn O, Zn Mnx/2Fex/2O and Zn Mnx/
2Cox/2O nanoparticles were prepared through low temperature

2
0
S. Singh et al. / Journal of Alloys and Compounds 642 (2015) 15–21
4
3
2
1
0
ZnO
(a)
0.1
Zn Mn O
0.9
0.1
Zn1-xMnxO
0.2
0.42
(a)
0
.39
.36
1.0
0.5
0.0
Gaussian Fit
0
(b)
Zn Mn Fe
O
3.24 3.27 3.30 3.33
1
-x x/2 x/2
4
2
ZnO
0
.1
.2
Zn Mn Fe O
0.9 0.05 0.5
0
0.27
(b)
0.9
0.6
0.3
0
.24
.21
0
3
Gaussian Fit
(c)
Zn Mn Co
O
1
-x x/2 x/2
0
3.24 3.27 3.30 3.33
ZnO
.1
.2
3
.24
3.28
Energy (eV)
3.32
3.36
2
1
0
0
0
Fig. 10. Optical absorbance spectra for (a) Zn0.9Mn0.1O and (b) Zn0.9Mn0.05Fe0.05
nanoparticles, measured at 300 K. Insets show the derivative plot of absorbance
spectra fitted with the Gaussian function, from which the semiconducting band gap
O
g
is estimated to be E = 3.29 eV.
1
02
103
104
105
106
Frequency (Hz)
has been studied at room temperature. At low frequency range,
(
f ꢁ 115 Hz), enhancement in
e
is found to be ꢁ1500 times for
Fig. 8. tand as a function of frequency for (a) Zn1ꢀxMn
c) Zn1ꢀxMnx/2Cox/2O at 300 K with varying x.
x
O, (b) Zn1ꢀxMnx/2Fex/2O and
Zn0.9Mn0.05Fe0.05O and ꢁ10 times for Zn0.8Mn0.1Co0.1O nanoparti-
(
cles from that of Zn0.9Mn0.1O nanoparticles. Such variation in
enhancement in
e can be explained on the basis of dielectric polar-
3+
ization, induced by the presence of different abundance of Fe and
3
+
ZnMnFeO
Co ions in ZnMnFeO and ZnMnCoO nanoparticles, respectively.
From our observation, one can identify the right choice of TM
4
2
000 (a)
x = 0.1
and its doping level, x to achieve a desired enhancement of e, com-
000
mensurate with the corresponding dielectric loss, for TM doped
ZnO nanoparticles. Thus Zn0.9Mn0.05Fe0.05O sample seems to be a
promising candidate for high k-dielectric application. The semicon-
ducting band gap of those nanoparticles has been estimated using
recorded absorbance spectra at room temperature.
ZnMnCoO
ZnO
ZnMnO
2
1
0
0
0
ZnMnFeO
Acknowledgement
(
b)
3
2
00
x = 0.2
One of the authors S.K. Mandal acknowledges the DST Project
(
No. SR/FTP/PS-019/2012), India for financial support. We
25
ZnO
ZnMnCoO
acknowledge Dr. A. Nath (NIT Agartala) and IIT Kharagpur, India
for providing us some experimental facilities.
ZnMnO
1
0
0
References
[1] F. Pan, C. Song, X.J. Liu, Y.C. Yang, F. Zeng, Mater. Sci. Eng.: R: Rep. 62 (2008) 1–
35.
Fig. 9. Different value of
e
for different doping element with doping level (a) x = 0.1,
[2] R. Khan, A. Kaushik, P.R. Solanki, A.A. Ansari, M.K. Pandey, B.D. Malhotra, Anal.
Chim. Acta 616 (2008) 207–213.
(
b) x = 0.2 for f = 115 Hz at 300 K.
[
3] A. Yadav, V. Prasad, A.A. Kathe, S. Raj, D. Yadav, C. Sundaramoorthy, N.
Vigneshwaran, Bull. Mater. Sci. 29 (2006) 641–645.
[
[
[
4] G. Shan, X. Kong, X. Wang, Y. Liu, Surf. Sci. 582 (2005) 61–68.
5] A.B. Djuriši c´ , A.M.C. Ng, X.Y. Chen, Prog. Quant. Elec. 34 (2010) 191–259.
6] H. Zulkefle, L.N. Ismail, R.A. Bakar, M.H. Mamat, M. Rusop, Int. J. Appl. Phys.
Math. 2 (2012) 38–43.
chemical pyrophoric reaction process. Structural analyses reveal
the formation of single phase nanoparticles with an average parti-
cle size of ꢁ2–40 nm.
e
as function of f and doping concentration, x
[7] N.T. Salim, K.C. Aw, W. Gao, B.E. Wright, Thin Solid Films 518 (2009) 362–365.

S. Singh et al. / Journal of Alloys and Compounds 642 (2015) 15–21
21
[
[
8] M.S. Samuel, J. Koshy, A. Chandran, K.C. George, Curr. Appl. Phys. 11 (2011)
094–1099.
9] K. Omar, Modern Appl. Sci. 3 (2009) 110–116.
[19] D. Karmakar, T.V. Chandrasekhar Rao, J.V. Yakhmi, A. Yaresko, V.N. Antonov,
R.M. Kadam, S.K. Mandal, R. Adhikari, A.K. Das, T.K. Nath, N. Ganguli, I.
Dasgupta, G.P. Das, Phys. Rev. B 81 (2010) 184421-1–184421-13.
[20] S. Singh, P. Dey, J.N. Roy, S.K. Mandal, Appl. Phys. Lett. 105 (2014) 092903-1–
092903-4.
[21] S.K. Mandal, T.K. Nath, A.K. Das, D. Karmakar, J. Appl. Phys. 101 (2007) 063913-
1–063913-6.
[22] S.K. Mandal, T.K. Nath, A. Das, J. Appl. Phys. 101 (2007) 123920-1–123920-7.
[23] S.K. Mandal, A.K. Das, T.K. Nath, D. Karmakar, Appl. Phys. Lett. 89 (2006)
144105-1–144105-3.
1
[
[
[
10] C.K. Ghosh, S. Malkhandi, M.K. Mitra, K.K. Chattopadhyay, J. Phys. D Appl. Phys.
1 (2008) 1–9.
11] S.J. Pearton, D.P. Norton, K. Ip, Y.W. Heo, T. Steiner, Super Lattices Microstruct.
4 (2003) 3–32.
12] Y. Yang, W. Guo, X. Wang, Z. Wang, J. Qi, Y. Zhang, Nano Lett. 12 (2012) 1919–
922.
4
3
1
[
[
13] S.S. Batsanov, K.B. Poyarkov, S.M. Gavrilkin, Dokl. Phys. 54 (2009) 407–409.
14] A.S. Lanje, S.J. Sharma, R.S. Ningthoujam, J.-S. Ahn, R.B. Pode, Adv. Pow. Tech.
[24] K.W. Wagner, Amer. Phis. 40 (1973) 817.
2
4 (2013) 331–335.
[25] C.G. Koops, Phys. Rev. 83 (1951) 121.
[
[
15] G. Murugadoss, J. Mater. Sci. Technol. 28 (2012) 587–593.
16] S. Senthilkumar, K. Rajendran, S. Banerjee, T.K. Chini, V. Sengodan, Mater. Sci.
Semicond. Process. 11 (2008) 6–12.
[26] H.S. Hsu, J.C.A. Huang, Y.H. Huang, Y.F. Liao, M.Z. Lin, C.H. Lee, J.F. Lee, S.F. Chen,
L.Y. Lai, C.P. Liu, Appl. Phys. Lett. 88 (2006) 242507-1–242507-3.
[27] H.S. Hsu, J.C.A. Huang, S.F. Chen, C.P. Liu, Appl. Phys. Lett. 90 (2007) 102506-1–
102506-3.
[28] S. Sapra, R. Viswanatha, J. Nanda, D.D. Sarma, in: D. Bahadur, S. Vitta, O.
Prakash (Eds.), Inorganic Materials: Recent Advances, first ed., Narosa
Publishing House, New Delhi, 2004, p. 452.
[
[
17] S.K. Mandal, A.K. Das, T.K. Nath, D. Karmakar, B. Satpati, J. Appl. Phys. 100
(
2006) 104315-1–104315-8.
18] D. Karmakar, S.K. Mandal, R.M. Kadam, P.L. Paulose, A.K. Rajarajan, T.K. Nath,
A.K. Das, I. Dasgupta, G.P. Das, Phys. Rev. B 75 (2007) 144404-1–144404-14.