Junaid, Bushiri M; Saji, Chacko; Vaidyan, V K(IOP Publishing LTD, October 20, 2006)
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Abstract:
SnO2 nanocrystalline thin films were deposited on glass substrates by the
spray pyrolysis technique in air atmosphere at 375, 400, 425, 450 and
500 ◦C substrate temperatures. The obtained films were characterized by
using XRD. The room temperature photoluminescence (PL) spectra of these
films have near band edge (NBE) and deep level emission under the
excitation of 325 nm radiation. NBE PL peak intensity decreased
consistently with temperatures for samples prepared at 400, 450 and 500 ◦C,
while a sudden reduction in intensity is observed for the sample prepared at
425 ◦C. A similar effect was observed for the optical transmittance spectra.
These effects can be explained on the basis of the change in population of
oxygen vacancies as indicated by the change in a values
Anantharaman, M R; Senoy, Thomas; Sakthi Kumar, D; Joy, P A; Yasuhiko, Yoshida(IOP Publishing LTD, October 25, 2006)
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Abstract:
Composite Fe3O4–SiO2 materials were prepared by the sol–gel method with
tetraethoxysilane and aqueous-based Fe3O4 ferrofluids as precursors. The
monoliths obtained were crack free and showed both optical and magnetic
properties. The structural properties were determined by infrared
spectroscopy, x-ray diffractometry and transmission electron microscopy.
Fe3O4 particles of 20 nm size lie within the pores of the matrix without any
strong Si–O–Fe bonding. The well established silica network provides
effective confinement to these nanoparticles. The composites were
transparent in the 600–800 nm regime and the field dependent magnetization
curves suggest that the composite exhibits superparamagnetic characteristics
Sudha Kartha, C(Japan society of applied physica, November 8, 2006)
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Abstract:
Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)–acrylamide films were fabricated to improve the
storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride
concentration was optimized as 3:18 10 3 mol/l for a dye concentration of 6:2 10 4 mol/l. The gratings recorded on the
optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or
thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.
Anantharaman, M R; Senoy, Thomas; Sakthi Kumar, D; Yasuhiko, Yoshida(Springer, December 31, 2006)
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Abstract:
Sol–gel glasses with Fe3O4 nanoparticles having particle sizes laying in the range 10–20 nm were encapsulated
in the porous network of silica resulting in nanocomposites having both optical and magnetic
properties. Spectroscopic and photoluminescence studies indicated that Fe3O4 nanocrystals are embedded
in the silica matrix with no strong Si–O–Fe bonding. The composites exhibited a blue luminescence. The
optical absorption edge of the composites red shifted with increasing concentration of Fe3O4 in the silica
matrix. There is no obvious shift in the position of the luminescence peak with the concentration of Fe3O4
except that the intensity of the peak is decreased. The unique combinations of magnetic and optical
properties are appealing for magneto–optical applications.
Description:
Journal of Nanoparticle Research (2008) 10:203–206
Heterojunction diodes of n-type ZnO/p-type silicon (100) were fabricated by
12 pulsed laser deposition of ZnO films on p-Si substrates in oxygen ambient at
13 different pressures. These heterojunctions were found to be rectifying with a
14 maximum forward-to-reverse current ratio of about 1,000 in the applied
15 voltage range of -5 V to +5 V. The turn-on voltage of the heterojunctions was
16 found to depend on the ambient oxygen pressure during the growth of the ZnO
17 film. The current density–voltage characteristics and the variation of the
18 series resistance of the n-ZnO/p-Si heterojunctions were found to be in line
19 with the Anderson model and Burstein-Moss (BM) shift.
Stable, OH free zinc oxide (ZnO) nanoparticles were synthesized by hydrothermal method by varying the
growth temperature and concentration of the precursors. The formation of ZnO nanoparticles were confirmed by x-ray
diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) studies. The
average particle size have been found to be about 7-24 nm and the compositional analysis is done with inductively
coupled plasma atomic emission spectroscopy (ICP-AES). Diffuse reflectance spectroscopy (DRS) results shows that the
band gap of ZnO nanoparticles is blue shifted with decrease in particle size. Photoluminescence properties of ZnO
nanoparticles at room temperature were studied and the green photoluminescent emission from ZnO nanoparticles can
originate from the oxygen vacancy or ZnO interstitial related defects.
Sudha Kartha, C(American Institute of Physics., January 13, 2007)
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Abstract:
Poly(methyl)methacrylate was made photoconducting by molecular doping and the
photoconductivity was investigated using modulated photocurrent technique . Low-temperature
current-voltage measurements showed that the transport mechanism was thermally activated
hopping. An experimental investigation of the photoconductivity action spectrum along with
theoretical calculation enabled an estimation of the diffusion coefficient of the material. The
presence of states with a distribution of lifetimes could be understood from the frequency response
of the photocurrent . The photocurrent was due to the field-assisted dissociation of these states.
Transparent diode heterojunction on ITO coated glass substrates was fabricated using p-type AgCoO2 and n-type ZnO films by pulsed laser
deposition (PLD). The PLD of AgCoO2 thin films was carried out using the pelletized sintered target of AgCoO2 powder, which was synthesized
in-house by the hydrothermal process. The band gap of these thin films was found to be ~3.89 eV and they had transmission of~55% in the
visible spectral region. Although Hall measurements could only indicate mixed carrier type conduction but thermoelectric power measurements of
Seebeck coefficient confirmed the p-type conductivity of the grown AgCoO2 films. The PLD grown ZnO films showed a band gap of ~3.28 eV,
an average optical transmission of ~85% and n-type carrier density of~4.6×1019 cm− 3. The junction between p-AgCoO2 and n-ZnO was found
to be rectifying. The ratio of forward current to the reverse current was about 7 at 1.5 V. The diode ideality factor was much greater than 2.
Anantharaman, M R; Malini, K A; Swapna, Nair S; Joy, P A; Mathew, George(IOP Publishing LTD, March 2, 2007)
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Abstract:
Fine particles of cobalt ferrite were synthesized by the sol–gel method.
Subsequent heat treatment at different temperatures yielded cobalt ferrites
having different grain sizes. X-ray diffraction studies were carried out to
elucidate the structure of all the samples. Dielectric permittivity and ac
conductivity of all the samples were evaluated as a function of frequency,
temperature and grain size. The variation of permittivity and ac conductivity
with frequency reveals that the dispersion is due to Maxwell–Wagner type
interfacial polarization in general, with a noted variation from the expected
behaviour for the cold synthesized samples. High permittivity and
conductivity for small grains were explained on the basis of the correlated
barrier-hopping model
Anantharaman, M R; Saravanan, S; Venkatachalam, S; Avasthi, D K(Elsevier, March 26, 2007)
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Abstract:
Polyaniline thin films prepared by RF plasma polymerisation were irradiated with 92MeV Si ions for various fluences of 1 1011,
1 1012 and 1 1013 ions/cm2. FTIR and UV–vis–NIR measurements were carried out on the pristine and Si ion irradiated polyaniline
thin films for structural evaluation and optical band gap determination. The effect of swift heavy ions on the structural and optical
properties of plasma-polymerised aniline thin film is investigated. Their properties are compared with that of the pristine sample. The
FTIR spectrum indicates that the structure of the irradiated sample is altered. The optical studies show that the band gap of irradiated
thin film has been considerably modified. This has been attributed to the rearrangement in the ring structure and the formation of CRC
terminals. This results in extended conjugated structure causing reduction in optical band gap
Junaid, Bushiri M; Antony, C J; Michel, Fleck(Elsevier, May 27, 2007)
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Abstract:
The Raman and FTIR spectra of [C(NH2)3]2M(SO4)2 ·6H2O (withM= Co, Fe, Ni) were recorded and analysed. The observed spectral bands
are assigned in terms of vibrations of guanidinium ions, sulphate groups and water molecules. The analysis shows that the sulphate tetrahedra
are distorted from their free state symmetry Td to C1. This is attributed to the presence of hydrogen bonds from water molecules. The order of
distortion of the metal oxygen octahedra influenced the distortion of the sulphate tetrahedra. The appearance of 1– 3 modes of water molecules
above 3300 cm−1 indicates the presence of weak hydrogen bonds
Chitra, R Nayak; Kuriakose, V C(Elsevier, June 4, 2007)
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Abstract:
We investigate the effect of the phase difference of appliedfields on the dynamics of mutually coupledJosephsonjunctions. A phase difference between the appliedfields desynchronizes the system. It is found that though the amplitudes of the output voltage values are uncorrelated, a phase correlation is found to exist for small values of applied phase difference. The dynamics of the system is found to change from chaotic to periodic for certain values of phase difference. We report that by keeping the value of phase difference as π, the system continues to be in periodic motion for a wide range of values of system parameters. This result may find applications in devices like voltage standards, detectors, SQUIDS, etc., where chaos is least desired.
Jayaraj, M K(Electrochemical Society, July 18, 2007)
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Abstract:
ZnGa2O4:Dy3+ phosphor thin films were deposited on quartz substrates by radio frequency rf magnetron sputtering and the effect
of substrate temperature on its structural and luminescent properties was investigated. Polycrystalline film could be deposited even
at room temperature. The crystalline behavior, Zn/Ga ratio, and surface morphology of the films were found to be highly sensitive
to substrate temperature. Under UV illumination, the as-deposited films at and above 300°C gave white luminescence even
without any postdeposition treatments. The photoluminescent PL emission can be attributed to the combined effect of multicolor
emissions from the single luminescence center Dy3+ via host-sensitization. Maximum PL emission intensity was observed for the
film deposited at 600°C, and the CIE chromaticity coordinates of the emission were determined to be x,y = 0.34, 0.31 .
Anantharaman, M R; Swapna, Nair S; Francis, Xavier; Joy, P A; Kulkarni, S D(Elsevier, September 20, 2007)
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Abstract:
Ferrofluids belonging to the series NixFe1 xFe2O4 were synthesised by two different procedures—one by standard co-precipitation
techniques, the other by co-precipitation for synthesis of particles and dispersion aided by high-energy ball milling with a view to
understand the effect of strain and size anisotropy on the magneto-optical properties of ferrofluids. The birefringence measurements were
carried out using a standard ellipsometer. The birefringence signal obtained for chemically synthesised samples was satisfactorily fitted to
the standard second Langevin function. The ball-milled ferrofluids showed a deviation and their birefringence was enhanced by an order.
This large enhancement in the birefringence value cannot be attributed to the increase in grain size of the samples, considering that the
grain sizes of sample synthesised by both modes are comparable; instead, it can be attributed to the lattice strain-induced shape
anisotropy(oblation) arising from the high-energy ball-milling process. Thus magnetic-optical (MO) signals can be tuned by ball-milling
process, which can find potential applications
Description:
Journal of Magnetism and Magnetic Materials 320 (2008) 815–820
Highly conductive and transparent thin films of amorphous zinc indium tin oxide are prepared at room temperature by co-sputtering of zinc
10 oxide and indium tin oxide. Cationic contents in the films are varied by adjusting the power to the sputtering targets. Optical transmission study of
11 films showed an average transmission greater than 85% across the visible region. Maximum conductivity of 6×102 S cm−1 is obtained for Zn/In/
12 Sn atomic ratio 0.4/0.4/0.2 in the film. Hall mobility strongly depends on carrier concentration and maximum mobility obtained is 18 cm2 V−1 s−1
13 at a carrier concentration of 2.1×1020 cm−3. Optical band gap of films varied from 3.44 eV to 3 eV with the increase of zinc content in the film
14 while the refractive index of the films at 600 nm is about 2.0.
Jayaraj, M K(Electrochemical Society, December 17, 2007)
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Abstract:
Highly transparent, luminescent and biocompatible ZnO quantum dots were prepared in water, methanol, and ethanol using
liquid-phase pulsed laser ablation technique without using any surfactant. Transmission electron microscopy analysis confirmed
the formation of good crystalline ZnO quantum dots with a uniform size distribution of 7 nm. The emission wavelength could be
varied by varying the native defect chemistry of ZnO quantum dots and the laser fluence. Highly luminescent nontoxic ZnO
quantum dots have exciting application potential as florescent probes in biomedical applications.
Sol–gel glasses with Fe3O4 nanoparticles having particle sizes laying in the range 10–20 nm were encapsulated
in the porous network of silica resulting in nanocomposites having both optical and magnetic
properties. Spectroscopic and photoluminescence studies indicated that Fe3O4 nanocrystals are embedded
in the silica matrix with no strong Si–O–Fe bonding. The composites exhibited a blue luminescence. The
optical absorption edge of the composites red shifted with increasing concentration of Fe3O4 in the silica
matrix. There is no obvious shift in the position of the luminescence peak with the concentration of Fe3O4
except that the intensity of the peak is decreased. The unique combinations of magnetic and optical
properties are appealing for magneto–optical applications.