Gopal Krishna Gokhale College

Kolhāpur, India

Gopal Krishna Gokhale College

Kolhāpur, India
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Sim K.U.,Chonnam National University | Shin S.W.,Chonnam National University | Moholkar A.V.,Chonnam National University | Moholkar A.V.,Gopal Krishna Gokhale College | And 3 more authors.
Current Applied Physics | Year: 2010

The un-doped and Al, Ga, and In doped (3 wt.%) ZnO thin films have been prepared on glass substrates using RF magnetron sputtering at 350 °C. The effects of these dopants on the structural, morphological, electrical, and optical properties of deposited films have been studied. XRD study showed that all doped ZnO thin films have the polycrystalline nature with hexagonal wurtzite phase having c-axis preferred out-of-plane orientation. The cross-sectional FE-SEM micrographs showed that all the films have columnar structure. AFM images showed that doped ZnO thin films have better surface smoothness than un-doped ZnO thin films regardless of doping elements. The GZO thin film have the optimal electrical properties among all doped samples in terms of the carrier concentration (6.13 × 1023 cm-3), charge carrier mobility (28.2 cm2 V-1 s-1), and a minimum resistivity (3.61 × 10-4 Ω cm). UV-Vis spectrometer results showed that all the films are highly transparent in the visible region and the band gap energy of the films varies from 3.25 eV to 3.75 eV for the different dopants. PL spectra showed the un-doped and doped ZnO thin film exhibited a violet emission in the 390-405 nm range, with different intensities, which is due to difference in concentration of zinc vacancies. © 2010 Elsevier B.V. All rights reserved.


Babar A.R.,Shivaji University | Shinde S.S.,Shivaji University | Moholkar A.V.,Gopal Krishna Gokhale College | Bhosale C.H.,Shivaji University | And 2 more authors.
Journal of Alloys and Compounds | Year: 2011

Transparent conductive thin films of nanocrystalline Sb:SnO2 have been deposited onto preheated glass substrates by using spray pyrolysis technique. The effect of the solution molarity on structural, morphological, optoelectronic properties of Sb:SnO2 films has been investigated. XRD study reveals that films are polycrystalline with tetragonal crystal structure having average crystallite size about 20 nm. The compact and homogeneous grains are seen in FESEM images. The BEs of Sn 3d5/2 for all samples show the Sn4+ bonding state for SnO2. The BEs of Sb 3d 5/2 are in the range of 530.6-530.9 eV, indicating that all antimony detected is in a pentavalent state (Sb5+). Transparency of films in the visible region decreases with increase in precursor concentration. Photoluminescence study shows the strong violet and weak orange emission. The sensing properties of the Sb:SnO2 films for acetone, ethanol and LPG with operating temperature and gas concentration have been investigated. © 2010 Elsevier B.V. All rights reserved.


Shin S.W.,KAIST | Ra Kang S.,Chonnam National University | Ho Yun J.,Korea Institute of Energy Research | Moholkar A.V.,Chonnam National University | And 4 more authors.
Solar Energy Materials and Solar Cells | Year: 2011

The effects of different annealing conditions such as atmospheres, temperatures and times on the structural, morphological and optical properties of ZnS thin films prepared on ITO coated glass substrates by chemical bath deposition were studied. Aqueous solutions of zinc acetate and thiourea were used as precursors along with stable complexing agents, such as Na 2EDTA and Na3-citrate, in an alkaline medium. X-ray diffraction patterns showed that the as-deposited and as-annealed ZnS films had an amorphous structure or poor crystallinity below the optimized annealing conditions of 500 °C and 60 min with the exception of the films annealed in N2H2S annealing atmosphere. The ZnS thin films annealed in N2H2S atmosphere for 1 h at 500 °C showed three sharp peaks for the (1 1 1), (2 2 0) and (1 1 3) planes of polycrystalline cubic ZnS without any unwanted secondary ZnO phases. X-ray photoelectron spectroscopy revealed ZnOH and ZnS bonding in the as-deposited ZnS thin film. However, the ZnS thin films annealed at 500 °C showed ZnS bonding regardless of the annealing atmosphere. The sharp absorption edge and band gap energy of the as-deposited and as-annealed ZnS thin films varied from 295 to 310 nm and 3.5 to 3.89 eV, respectively. © 2010 Elsevier B.V. All rights reserved.


Shinde S.S.,Shivaji University | Moholkar A.V.,Gopal Krishna Gokhale College | Moholkar A.V.,Chonnam National University | Kim J.H.,Chonnam National University | Rajpure K.Y.,Shivaji University
Surface and Coatings Technology | Year: 2011

Thin films of aluminium incorporated Fe2O3, synthesized by simple chemical spray pyrolysis on to glass substrates using aqueous solutions of analytical reagent grade ferric trichloride and aluminium nitrate as precursors. The influence of aluminium doping on to morphological properties, contact angle, X-ray photoelectron spectroscopy, photoluminescence and thermal conductivity properties have been investigated. The preparative parameters have been optimized to obtain good quality thin films which are uniform and well adherent to the substrate. The FE-SEM and AFM micrographs depict the films are compact and homogeneous (spindle-shaped hematite nanostructures) with varying grain sizes (average grain size ~20-60nm). Contact angle measurement show the films are hydrophobic in nature. The chemical composition and valence states of constituent elements in Fe2O3 are analyzed by X-ray photoelectron spectroscopy. The excitonic strong violet emission has been observed in photoluminescence. The specific heat and thermal conductivity study shows the phonon conduction behavior is dominant in these polycrystalline films. We studied interparticle interactions like grains, grain boundary effects using complex impedance spectroscopy. © 2010 Elsevier B.V.


Babar A.R.,Shivaji University | Shinde S.S.,Shivaji University | Moholkar A.V.,Gopal Krishna Gokhale College | Moholkar A.V.,Chonnam National University | Rajpure K.Y.,Shivaji University
Journal of Alloys and Compounds | Year: 2010

Nanocrystalline tin oxide (SnO2) powders were synthesized by chemical co-precipitation method using stannic chloride pentahydrate (SnCl 4·5H2O) precursor in aqueous medium. The influence of sintering temperatures on the crystalline structure, morphological, electrical, dielectric and XPS properties has been studied. X-ray diffraction study reveals that sintered powder which exhibits tetragonal crystal structure and both crystallinity as well as crystal size increase with increase in temperature. The nature of species of various absorption bonds viz. Sn-O, O-Sn-O and O-H involved in sintered SnO2 samples has been studied using FTIR technique. The morphological studies reveal randomly arranged grains with compact nature and grain size increases with sintering temperature. Measurements of electrical properties show relatively lower resistivity (≈10 2-103 Ω cm) and higher dielectric constant at 400 °C than other sintering temperatures. The compositional analysis and electronic behavior of SnO2 nanoparticles is studied using X-ray photoelectron spectroscopy. The symmetric spin orbit splitting of Sn 3d 5/2 ground state and Sn 3d3/2 excited states is observed with sintering temperature while O 1s is recognized with O2- state. © 2010 Elsevier B.V.All rights reserved.


Babar A.R.,Shivaji University | Shinde S.S.,Shivaji University | Moholkar A.V.,Gopal Krishna Gokhale College | Moholkar A.V.,Chonnam National University | And 3 more authors.
Journal of Alloys and Compounds | Year: 2010

Thin films of undoped and antimony doped tin oxide (SnO2 and Sb:SnO2) prepared by spray pyrolysis technique with different antimony concentrations are found to be polycrystalline with tetragonal crystal structure, having preferential growth along the (2 1 1) and (1 1 2) planes. Randomly oriented needle-shaped polyhedron like grains are observed in the FE-SEM images owing to large scattering effect in the films. From X-ray photoelectron spectroscopy (XPS) measurement, it is observed that films are oxygen deficient. Concentration of Sb in the SnO2 films is slightly less than that of starting solution. Valence states for Sn, Sb and O, observed from the XPS measurement are Sn4+, Sb5+/Sb3+ and O22-, respectively. The direct optical band gap (Eg) has increased from 3.55 (undoped) to 3.60 eV with Sb concentration showing formation of degenerate semiconductor. The strong violet and comparatively weak red emissions have observed in room temperature photoluminescence (PL). The origin of various peaks in PL spectra can be assigned to the combined effect of oxygen vacancies, tin interstitials or dangling bonds, singly charged oxygen vacancies, interstitial oxygen and crystal defects present in the films. The films deposited with 2 at.% Sb exhibited lowest value of resistivity (1.22 × 10-3 Ω cm) and highest value of carrier concentration (5.19 × 1020 cm-3), mobility (9.83 cm2 V -1 s-1) and figure of merit (2.11 × 10-3 Ω-1). © 2010 Elsevier B.V.All rights reserved.


Moholkar A.V.,Chonnam National University | Moholkar A.V.,Gopal Krishna Gokhale College | Agawane G.L.,Shivaji University | Sim K.-U.,Chonnam National University | And 3 more authors.
Applied Surface Science | Year: 2010

This study investigated the effect of deposition temperature on the morphological, optical, electrical and opto-electrical properties of CdO:Ga films prepared by a cost effective spray pyrolysis deposition method. The substrate temperature was varied from 275 to 375 °C, in steps of 25 °C. The XRD patterns reveal that films are polycrystalline with cubic structure and are highly textured along (2 0 0) preferential orientation. The crystallinity and crystallite size increases with deposition temperature. The SEM images confirmed these results and showed larger grains and more crystallization for the higher deposition temperature. The electrical studies show degenerate, n-type semiconductor nature with minimum resistivity of 1.93 × 10 -4 Ω cm. Temperature dependence of electrical conductivity shows a semiconducting behavior with a spectrum of activation energy. The electrical conductivity of the film dependence of temperature shows the thermally activated band conduction mechanism. The optical gap varies from 2.54 to 2.74 eV. The highest figure of merit observed in the present study is 9.58 × 10-3 Ω-1 and shows improvement than our previous reports. The blue shift of absorption edge (or bandgap widening BGW) can be described by the Moss-Burstein (M-B) effect in which the optical absorption edge of a degenerate n-type semiconductor is shifted towards higher energy. © 2010 Elsevier B.V. All rights reserved.


Kang S.R.,Chonnam National University | Shin S.W.,Chonnam National University | Choi D.S.,Chonnam National University | Moholkar A.V.,Chonnam National University | And 3 more authors.
Current Applied Physics | Year: 2010

The structural, morphological, and optical properties of zinc sulfide (ZnS) thin films deposited using chemical bath deposition method are reported. These films were deposited on soda lime glass substrates using Na2EDTA as a complexing agent, in acidic medium at 80 °C. The effect of the pH ranging from 5 to 6.5 on quality of ZnS thin films is investigated. Irrespective of the pH values used for the deposition all films are polycrystalline with a wurtzite (hexagonal) structure. Field emission scanning electron microscopy (FE-SEM) characterization shows that the surface of the sample deposited with pH 5 and 5.5 is compact and uniform. However, agglomerated clusters (∼100 nm) are observed in ZnS thin films grown with pH above 6. X-ray photoelectron spectroscopy results shows the presence of only Zn-S bonding for the ZnS thin film grown at pH = 5 while those films deposited with pH > 5.5, Zn-OH as well as Zn-S bonding have been observed. The composition is almost stoichiometric for a wide range of pH values of the solution (5-6.5). The transmission spectrum of ZnS thin films having thickness from 30 to 220 nm indicates a good transmission characteristic with an average transmittance of 70-85%. The absorption coefficient depends on the pH values of the solution used and are responsible to the changes observed in absorption edges. The band gap energy values of ZnS thin films decreased from 3.91 to 3.78 eV with increasing pH values of the solution. © 2010 Elsevier B.V. All rights reserved.


Chavan H.V.,ASP College | Narale D.K.,Gopal Krishna Gokhale College
Comptes Rendus Chimie | Year: 2013

An efficient solvent-free synthesis of various 2,4,5-triaryl imidazoles and 1,2,4,5-tetraaryl imidazoles has been developed using silica chloride as a heterogeneous catalyst. The present methodology offers several advantages, such as excellent yields, shorter reaction times, economic availability, and reusability of catalyst. © 2013 Académie des sciences.


Desai S.S.,Gopal Krishna Gokhale College | Kashid D.N.,Shivaji University
International Journal of Data Mining, Modelling and Management | Year: 2015

In this article, we propose two methods for selection of meta parameter (C) in support vector regression. The proposed methods are robust because these are based on the robust statistical measures. The performance of the proposed parameter selection methods is evaluated in case of normal and non-normal distributed error variables. It is evaluated in the sense of prediction risk and mean square error of estimates of regression parameters for clean and outlier data. © Copyright 2015 Inderscience Enterprises Ltd.

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