Sudha Kartha, C; Vijayakumar, K P; Poornima, N; Vimalkumar, T V(Elsevier, March 27, 2010)
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Abstract:
Effect of varying spray rate on the structure and optoelectronic properties of spray pyrolysed ZnO film
is analysed. ZnO films were characterised using different techniques such as X-ray diffraction (XRD),
photoluminescence, electrical resistivity measurement, and optical absorption. The XRD analysis proved
that, with the increase in spray rate, orientation of the grains changed from (1 0 1) plane to (0 0 2) plane.
The films exhibited luminescence in two regions—one was the ‘near band-edge’ (NBE) (∼380 nm) emission
and the other one was the ‘blue-green emission’ (∼503 nm). Intensity of the blue-green emission
decreased after orientation of grains shifted to (0 0 2) plane. Scanning electron microscope (SEM) analysis
of the films asserts that spray rate has major role in improving the crystallographic properties of
the films. Moreover resistivity of the films could be lowered to 2.4×10−2 cm without any doping or
post-deposition annealing
Sudha Kartha, C; Vijayakumar, K P; Anita, Warrier R; Sajeesh, T H(Elsevier, February 2, 2010)
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Abstract:
SnS thin films were prepared using automated chemical spray pyrolysis (CSP) technique. Single-phase, p-type,
stoichiometric, SnS films with direct band gap of 1.33 eV and having very high absorption coefficient (N105/cm)
were deposited at substrate temperature of 375 °C. The role of substrate temperature in determining the
optoelectronic and structural properties of SnS films was established and concentration ratios of anionic and
cationic precursor solutions were optimized. n-type SnS samples were also prepared using CSP technique at the
same substrate temperature of 375 °C, which facilitates sequential deposition of SnS homojunction. A
comprehensive analysis of both types of films was done using x-ray diffraction, energy dispersive x-ray analysis,
scanning electron microscopy, atomic force microscopy, optical absorption and electrical measurements.
Deposition temperatures required for growth of other binary sulfide phases of tin such as SnS2, Sn2S3 were also
determined
Sudha Kartha, C(Indian academy of science, February 24, 2003)
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Abstract:
Significant results of our experimental investigations on the dependence of pH on real time
transmission characteristics on recording media fabricated by doping PVC with complexed methylene blue
are presented. The optimum pH value for faster bleaching was found to be 4×5. In typical applications, the
illumination from one side, normal to the surface of this material, initiates a chemical sequence that records
the incident light pattern in the polymer. Thus direct imaging can be successfully done on this sample. The
recorded letters were very legible with good contrast and no scattering centres. Diffraction efficiency
measurements were also carried out on this material.
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.
Sudha Kartha, C; Vijayakumar, K P; Rajeshmon, V G; Vimalkumar, T V; Poornima, N(Hindawi Publishing Corporation, January 6, 2013)
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Abstract:
This work projects photoluminescence (PL) as an alternative technique to estimate the order of resistivity of zinc oxide (ZnO) thin
films. ZnO thin films, deposited using chemical spray pyrolysis (CSP) by varying the deposition parameters like solvent, spray rate,
pH of precursor, and so forth, have been used for this study. Variation in the deposition conditions has tremendous impact on the
luminescence properties as well as resistivity. Two emissions could be recorded for all samples—the near band edge emission (NBE)
at 380 nm and the deep level emission (DLE) at ∼500 nm which are competing in nature. It is observed that the ratio of intensities
of DLE to NBE (𝐼DLE/𝐼NBE) can be reduced by controlling oxygen incorporation in the sample. 𝐼-𝑉 measurements indicate that
restricting oxygen incorporation reduces resistivity considerably. Variation of 𝐼DLE/𝐼NBE and resistivity for samples prepared under
different deposition conditions is similar in nature. 𝐼DLE/𝐼NBE was always less than resistivity by an order for all samples.Thus from
PL measurements alone, the order of resistivity of the samples can be estimated.
Description:
International Journal of Photoenergy
Volume 2013, Article ID 105796, 9 pages
Sudha Kartha, C(Taylor and francis, March 13, 2005)
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Abstract:
A new photopolymerizable recording media is introduced based on poly
(vinyl alcohol) and vinyl acetate sensitized with methylene blue. It is observed
that this MBPVA/VAc system can be reused a number of times without
significant decrease in diffraction efficiency. The PVA-VAc ratio was optimized
at 2:1. Diffraction efficiency of 6.3% was obtained without any fixing at a dye
concentration of 9.3 10 4 mol/l at an exposure of 750 mJ/cm2. The material is
attractive on account of its reusability.
A new photopolymerizable recording media is introduced based on poly
(vinyl alcohol) and vinyl acetate sensitized with methylene blue. It is observed
that this MBPVA/VAc system can be reused a number of times without
significant decrease in diffraction efficiency. The PVA-VAc ratio was optimized
at 2:1. Diffraction efcienc4y of 6.3% was obtained without any fixing at a dye
concentration of 9.3 x 10- mol/l at an exposure of 750mJ/cm2. The material is
attractive on account of its reusability.
Sudha Kartha, C; Vijayakumar, K P; Meril, Mathew; Angel, Susan Cherian(Elsevier, September 20, 2009)
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Abstract:
Effect of chlorine doping on the opto-electronic properties of β-In2S3 thin film, deposited by spray pyrolysis
technique is studied for the first time. Chlorine was incorporated in the spray solution, using HCl. Pristine
sample prepared using In(NO3)3 and thiourea as the precursors showed very low photosensitivity. But upon
adding optimum quantity of chlorine, the photosensitivity increased by 3 orders. X-ray analysis revealed that
crystallinity was also increasing up to this optimum level of Cl concentration. It was also observed that
samples with high photosensitivity were having higher band gap. The present study proved that doping with
chlorine was beneficial as this could result in forming crystalline and photosensitive films of indium sulfide.
Sudha Kartha, C; Sreekumar, K; Rani, Joseph; Subramanyan, N V; Nimmi, K P; Pramitha, V(Optical Society of America, April 14, 2009)
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Abstract:
Incorporation of silver ions into a dye-sensitized poly(vinyl alcohol)/acrylamide photopolymer is observed
to give better performance compared to other metal-ion-doped photopolymer holographic recording
media. Plane-wave transmission gratings were recorded in the photopolymer films using a He–Ne
laser, and various holographic parameters were optimized so as to explore maximum potential of the
material for various holographic applications. Silver-doped films showed good energy sensitivity,
and gratings recorded in optimized film exhibited a diffraction efficiency of more than 75%. The
potential of the material for holographic data storage applications is also studied using peristrophic
multiplexing
Sudha Kartha, C; Vijayakumar, K P; Sreekumar, K; Maheshkumar, M V; Rajesh Menon, M R(WILEY-VCH Verlag GmbH & Co, September 22, 2011)
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Abstract:
In this paper, we report the results of investigations on the
potential of spray pyrolysis technique in depositing electron
selective layer over larger area for the fabrication of inverted
bulk-heterojunction polymer solar cells. The electron selective
layer (In2S3) was deposited using spray pyrolysis technique and
the linear heterojunction device thus fabricated exhibited good
uniformity in photovoltaic properties throughout the area of the
device. An MEH-PPV:PCBM inverted bulk-heterojunction
device with In2S3 electron selective layer (active area of
3.25 3.25 cm2) was also fabricated and tested under indoor
and outdoor conditions. Fromthe indoor measurements employing
a tungsten halogen lamp (50mW/cm2 illumination), an opencircuit
voltage of 0.41V and a short-circuit current of 5.6mA
were obtained. On the other hand, the outdoor measurements
under direct sunlight (74mW/cm2) yielded an open-circuit
voltage of 0.46V and a short-circuit current of 9.37mA