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Investigations on the structural, optical and electronic properties of Nd doped ZnO thin films
Subramanian, M,Thakur, P,Gautam, S,Chae, K H,Tanemura, M,Hihara, T,Vijayalakshmi, S,Soga, T,Kim, S S,Asokan, K,Jayavel, R Institute of Physics [etc.] 2009 Journal of Physics. D, Applied Physics Vol.42 No.10
<P>We report the synthesis and characterization of Nd doped ZnO thin films grown on Si (1 0 0) substrates by the spray pyrolysis method. The surface morphology of these thin films was investigated by scanning electron microscopy and shows the presence of randomly distributed structures of nanorods. Grazing angle x-ray diffraction studies confirm that the doped Nd ions occupied Zn sites and these samples exhibited a wurtzite hexagonal-like crystal structure similar to that of the parent compound, ZnO. The micro-photoluminescence measurement shows a decrease in the near band edge position with Nd doping in the ZnO matrix due to the impurity levels. The near-edge x-ray absorption fine structure (NEXAFS) measurements at the O K edge clearly exhibit a pre-edge spectral feature which evolves with Nd doping, suggesting incorporation of more charge carriers in the ZnO system and the presence of strong hybridization between O 2p–Nd 5d orbitals. The Nd M<SUB>5</SUB> edge NEXAFS spectra reveal that the Nd ions are in the trivalent state.</P>
M. Ravindran,S. Senthil Kumar,N. Karuppiah,M. Asokan 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.1
Insulators flashover is one of the major problem that confronts all around the world, particularly in austere weather conditionsand highly polluted areas. Any failure in the acceptable performance of high voltage insulators result in intrerruption ofelectrical power that leads to loss of capital. Flashover voltage (FOV) is directly related to the severity of pollution on thesurface of insulator. Generally, anti-pollution flashover coating is considered as one of the most effective means to prevent andreduce flashover. This paper investigates and compares the results on application of Epoxy Resin and Room TemperatureVulcanized (RTV) Silicone Rubber for improving the performance of outdoor (near coastal thermal plant area) insulators of12 KV rating. The flash over voltage of the insulators is optimized for a polluted environment by applying the protectivecoating and tested experimentally. The experimental results are compared with simulated results using Artificial NeuralNetwork.
H.M. Mahadeva Swamy,Asokan Ramasamy,C.M. Kalleshwaraswamy,S.K. Adarsh 한국응용곤충학회 2019 Journal of Asia-Pacific Entomology Vol.22 No.3
malnad and coastal areas. White grubs are the most important pests on this crop and cause considerable yield loss. Surveys were conducted to record species that are infested with white grubs of Karnataka and Kerala states. Three species of white grubs were collected and described using morphological and molecular characters. A detailed study of male genitalial structures such as aedeagus and endophallus in three species of Leucopholis Dejean, 1833 (Coleoptera: Scarabaeidae: Melolonthinae) viz., Leucopholis lepidophora Blanchard, 1850, Leucopholis burmeisteri Brenske, 1894 and Leucopholis coneophora Burmeister, 1855 showed substantial differences. The mitochondrial cytochrome oxidase subunit I gene was sequenced for molecular identification and phylogenetic analysis in this respect. L. lepidophora, L. burmeisteri and L. coneophora species were successfully identified by employing COXI gene. Phylogenetic analyses revealed that the COXI DNA barcode fragment of Leucopholis species and out-group taxa, available in genetic databases, confirms the species identity.
M. Kovendhan,D. Paul Joseph,P. Manimuthu,A. Sendilkumar,S.N. Karthick,S. Sambasivam,K. Vijayarangamuthu,김희제,최병춘,K. Asokan,C. Venkateswaran,R. Mohan 한국물리학회 2015 Current Applied Physics Vol.15 No.5
Lithium (Li) (0-5 wt%) doped V2O5 thin films were spray deposited at 450 ℃ onto ITO substrates. Structural analysis using X-ray diffraction and Raman spectroscopy revealed orthorhombic phase of the films. In addition to the V2O5 phase, presence of VO2 peaks due to high deposition temperature is also evident from structural and optical characterization. The non-stoichiometric nature of the films due to loss of the terminal O atom was confirmed from Raman spectroscopy. The direct band gap, indirect bandgap, and phonon energies were also calculated from optical studies. Different charge states of vanadium ions present in the film were identified from X-ray photoelectron spectroscopy study. Results from cyclic voltammetry experiments reflected significant differences between the undoped and Li doped V2O5 samples. Transport properties by Hall-effect measured at room temperature indicated significant increase in conductivity, carrier concentration and mobility of V2O5 thin films on doping with Li. A Dye Sensitized Solar Cell (DSSC) was fabricated using mobility enhanced 5 wt% Li doped V2O5 film as photoanode and its efficiency was found to be 2.7%. A simple electrochromic cell is fabricated using undoped V2O5 thin film to demonstrate the colour change.
Kovendhan, M.,Paul Joseph, D.,Manimuthu, P.,Sendilkumar, A.,Karthick, S.N.,Sambasivam, S.,Vijayarangamuthu, K.,Kim, H.J.,Choi, B.C.,Asokan, K.,Venkateswaran, C.,Mohan, R. Elsevier 2015 CURRENT APPLIED PHYSICS Vol.15 No.5
Lithium (Li) (0-5 wt%) doped V<SUB>2</SUB>O<SUB>5</SUB> thin films were spray deposited at 450 <SUP>o</SUP>C onto ITO substrates. Structural analysis using X-ray diffraction and Raman spectroscopy revealed orthorhombic phase of the films. In addition to the V<SUB>2</SUB>O<SUB>5</SUB> phase, presence of VO<SUB>2</SUB> peaks due to high deposition temperature is also evident from structural and optical characterization. The non-stoichiometric nature of the films due to loss of the terminal O atom was confirmed from Raman spectroscopy. The direct band gap, indirect bandgap, and phonon energies were also calculated from optical studies. Different charge states of vanadium ions present in the film were identified from X-ray photoelectron spectroscopy study. Results from cyclic voltammetry experiments reflected significant differences between the undoped and Li doped V<SUB>2</SUB>O<SUB>5</SUB> samples. Transport properties by Hall-effect measured at room temperature indicated significant increase in conductivity, carrier concentration and mobility of V<SUB>2</SUB>O<SUB>5</SUB> thin films on doping with Li. A Dye Sensitized Solar Cell (DSSC) was fabricated using mobility enhanced 5 wt% Li doped V<SUB>2</SUB>O<SUB>5</SUB> film as photoanode and its efficiency was found to be 2.7%. A simple electrochromic cell is fabricated using undoped V<SUB>2</SUB>O<SUB>5</SUB> thin film to demonstrate the colour change.
High-energy ion induced physical and surface modifications in antimony sulphide thin films
S. Subramanian,M. Balaji,P. Chithra Lekha,K. Asokan,D. Kanjilal,Indra Sulania,Jai Prakash,D. Pathinettam Padiyan 한국물리학회 2010 Current Applied Physics Vol.10 No.4
Sb2S3 thin films prepared by electrodeposition on indium tin oxide coated glass substrate were irradiated with 150 MeV Ni11+ ions for various fluence in the range of 1011–1013 ions/㎠. The modifications in the structure, surface morphology and optical properties have been studied as a function of ion fluence. X-ray diffraction (XRD) analysis indicates a shift in the (2 4 0) peak position towards lower diffraction angle and a decrease in grain size with increase in ion fluence. Presence of microcracks due to irradiation induced grain splitting effect has been observed from the SEM micrograph at higher ion fluence. The optical absorbance spectrum revealed a shift in the fundamental absorption edge and the band gap energy increased from a value of 1.63 eV for as-deposited films to 1.80 eV for the films irradiated with 1013 ions/㎠.
R. Rathika,M. Kovendhan,D. Paul Joseph,K. Vijayarangamuthu,A. Sendil Kumar,C. Venkateswaran,K. Asokan,S. Johnson Jeyakumar 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.8
Spray deposited Molybdenum trioxide (MoO3) thin film of thickness nearly 379 nm were irradiated with 200 MeV Ag15þ ion beam at different fluences (Ø) of 5 1011,1 1012,5 1012 and 1 1013 ions/cm2. The X-ray diffraction (XRD) pattern of the pristine film confirms orthorhombic structure and the crys-tallinity decreased after irradiation with the fluence of 5 1011 ions/cm2 due to irradiation induced defects and became amorphous at higher fluence. In pristine film, Raman modes at 665, 820, 996 cm1 belong to MoeO stretching, 286 cm1 belong to MoeO bending mode and those below 200 cm1 are associated with lattice modes. Raman peak intensities decreased upon irradiation and vanished completely for the ion fluence of 5 1012 ions/cm2. The percentage of optical transmittance of pristine film was nearly 40%, while for irradiated films it decreased significantly. Red shift was observed for both the direct and indirect band gaps. The pristine film surface had densely packed rod like structures with relatively less porosity. Surface roughness decreased significantly after irradiation. The electrical trans-port properties were also studied for both the pristine and irradiated films by Hall effect. The results are discussed.
Navale Prakash M,Manamohan Maligeppagol,Asokan R.,Sharath Chandra G.,Prasad Babu K.,Latha J.,Krishna Kumar N.K.,Ellango R.,Krishna V. 한국응용곤충학회 2017 Journal of Asia-Pacific Entomology Vol.20 No.2
Helicoverpa armigera is an important pest infesting a number of crops of high commercial value leading to huge economic losses globally. RNA interference (RNAi) is a potent tool for the control of insect pests and towards this objective, transgenic tomato expressing dsRNA of Juvenile hormone acid methyl transferase (JHAMT) gene of H. armigera was developed. The H. armigera larvae fed on HaJHAMT tomato leaves led to a severe (90%) down regulation of the cognate gene expression thus adversely affected the feeding and metamorphosis. Reduction in larval and pupal weight and inability to undergo complete metamorphosis were observed that led to larval-pupal intermediates and subsequently affected the eclosion. Thus, JH down regulation is an attractive target due to specificity to insects and its important role in insect growth and development to engineer insect resistance in crops using RNAi.
Fabrication of p-n Junction Diode Using SnO/SnO2 Thin Films and Its Device Characteristics
R. Sathyamoorthy,K. M. Abhirami,B. Gokul,Sanjeev Gautam,채근화,K. Asokan 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.4
Present study demonstrates the feasibility of using oxides of Sn to fabricate the p-n junction diode and reports the device characteristics. Reactive thermal evaporation method was used to fabricate the p-type SnO and n-type SnO2 multilayer thin films. The x-ray diffraction (XRD) and Raman spectra depict the presence of both SnO and SnO2 layers. The interface of the p-n junction analyzed by cross-sectional transmission electron microscope (TEM) images and selected area electron diffraction (SAED) pattern confirmed the presence of SnO-SnO2 layers. The diode shows rectifying current-voltage characteristics with forward threshold voltage of 3.5 V.
Rathika, R.,Kovendhan, M.,Joseph, D. Paul,Pachaiappan, Rekha,Kumar, A. Sendil,Vijayarangamuthu, K.,Venkateswaran, C.,Asokan, K.,Jeyakumar, S. Johnson Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.11
Swift heavy ion (SHI) beam irradiation can generate desirable defects in materials by transferring sufficient energy to the lattice that favours huge possibilities in tailoring of materials. The effect of Ag<sup>15+</sup> ion irradiation with energy 200 MeV on spray deposited V<sub>2</sub>O<sub>5</sub> thin films of thickness 253 nm is studied at various ion doses from 5 × 10<sup>11</sup> to 1 × 10<sup>13</sup> ions/㎠. The XRD results of pristine film confirmed orthorhombic structure of V<sub>2</sub>O<sub>5</sub> and its average crystallite size was found to be 20 nm. The peak at 394 cm<sup>-1</sup> in Raman spectra confirmed O-V-O bonding of V<sub>2</sub>O<sub>5</sub>, whereas 917 cm<sup>-1</sup> arise because of distortion in stoichiometry by a loss of oxygen atoms. Raman peaks vanished completely above the ion fluence of 5 × 10<sup>12</sup> ions/㎠. Optical studies by UV-Vis spectroscopy shows decrement in transmittance with an increase in ion fluence up to 5 × 10<sup>12</sup> ions/㎠. The red shift is observed both in the direct and indirect band gaps until 5 × 10<sup>12</sup> ions/㎠. The surface topography of the pristine film revealed sheath like structure with randomly distributed spherical nano-particles. The roughness of film decreased and the density of spherical nanoparticles increased upon irradiation. Irradiation improved the conductivity significantly for fluence 5 × 10<sup>11</sup> ions/㎠ due to band gap reduction and grain growth.