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28 results on '"Vijayarangamuthu, K."'

14. A spectroscopic ellispometric study of the tunability of the optical constants and thickness of GeOx films with swift heavy ions.

Author

Vijayarangamuthu, K., Singh, Chaman, Kabiraj, D., and Rath, Shyama

Subjects
*OPTICAL constants, *GERMANIUM, *ELECTRON beam research, *HEAVY ions, *THICK films, *EVAPORATION (Chemistry)
Abstract

Sub-stoichiometric GeOx films were fabricated by electron-beam evaporation method. The films were irradiated with 100 MeV Ag7+ ions at fluences between 1 × 1012 and 1 × 1014 ions-cm-2. Spectroscopic ellipsometric measurements were performed in air at room temperature. The values of the layer thickness and refractive index were extracted from ellipsometry using a multilayer analysis and the Tauc Lorentz model. The refractive index (at 633 nm) of the as-deposited GeOx film was estimated to be 1.860 and decreased to 1.823 for films irradiated at an ion fluence of 1 × 1014 ions-cm-2. The thickness of the films also decreased after irradiation and is due to a sputtering induced by the ion beam. The change in the refractive index with ion fluence is attributed to a stoichiometric change and structural transformation represented by GeOx→ Ge + GeOy (y > x) occurring due to a thermal spike induced by ion irradiation. Swift heavy ions thus provide a scope for modulating the refractive index of GeOx films. The thickness and stoichiometric changes are supported by Rutherford backscattering measurements. [ABSTRACT FROM AUTHOR]

Published
2011
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15. Tailoring the properties of spray deposited V2O5thin films using swift heavy ion beam irradiation

Author

Rathika, R., Kovendhan, M., Joseph, D. Paul, Pachaiappan, Rekha, Kumar, A. Sendil, Vijayarangamuthu, K., Venkateswaran, C., Asokan, K., and Jeyakumar, S. Johnson

Abstract

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 Ag15+ion irradiation with energy 200 MeV on spray deposited V2O5thin films of thickness 253 nm is studied at various ion doses from 5 × 1011to 1 × 1013ions/cm2. The XRD results of pristine film confirmed orthorhombic structure of V2O5and its average crystallite size was found to be 20 nm. The peak at 394 cm−1in Raman spectra confirmed O–V–O bonding of V2O5, whereas 917 cm−1arise because of distortion in stoichiometry by a loss of oxygen atoms. Raman peaks vanished completely above the ion fluence of 5 × 1012ions/cm2. Optical studies by UV–Vis spectroscopy shows decrement in transmittance with an increase in ion fluence up to 5 × 1012ions/cm2. The red shift is observed both in the direct and indirect band gaps until 5 × 1012ions/cm2. 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 × 1011ions/cm2due to band gap reduction and grain growth.

Published
2020
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16. 200 MeV Ag15+ion beam irradiation induced modifications in spray deposited MoO3thin films by fluence variation

Author

Rathika, R., Kovendhan, M., Joseph, D. Paul, Vijayarangamuthu, K., Kumar, A. Sendil, Venkateswaran, C., Asokan, K., and Jeyakumar, S. Johnson

Abstract

Spray deposited Molybdenum trioxide (MoO3) thin film of thickness nearly 379 nm were irradiated with 200 MeV Ag15+ion beam at different fluences (Ø) of 5 × 1011, 1 × 1012, 5 × 1012and 1 × 1013ions/cm2. The X-ray diffraction (XRD) pattern of the pristine film confirms orthorhombic structure and the crystallinity decreased after irradiation with the fluence of 5 × 1011ions/cm2due to irradiation induced defects and became amorphous at higher fluence. In pristine film, Raman modes at 665, 820, 996 cm−1belong to Mo–O stretching, 286 cm−1belong to Mo–O bending mode and those below 200 cm−1are associated with lattice modes. Raman peak intensities decreased upon irradiation and vanished completely for the ion fluence of 5 × 1012ions/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 transport properties were also studied for both the pristine and irradiated films by Hall effect. The results are discussed.

Published
2019
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24. 100 MeV O7+ irradiation induced red shift in the band gaps of 3 wt% 'Li' doped Nb2O5 thin film.

Author

Kovendhan, M., Joseph, D. Paul, Manimuthu, P., Vijayarangamuthu, K., Asokan, K., Venkateswaran, C., and Mohan, R.

Subjects
REDSHIFT, IRRADIATION, BAND gaps, DOPING agents (Chemistry), NIOBIUM oxide, THIN films, POLYCRYSTALS
Abstract

Nb2O5:Li (3 wt%) thin film of thickness 353 nm spray deposited onto ITO coated glass substrate at 350 °C is irradiated with 100 MeV O7+ ion at a fluence of 5×1012 ions/cm². X-ray diffraction shows that the pristine and irradiated films are polycrystalline with a tetragonal phase. Raman peaks suppressed upon irradiation imply large surface degradation which is also seen as a decrement in transparency in visible region to one half of the pristine film. Large red shift is observed in direct and indirect band gaps upon irradiation. Hall effect reveals slight increase in carrier concentration due to irradiation induced defects. [ABSTRACT FROM AUTHOR]

Published
2014
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25. Ge nanocrystals embedded in a GeOx matrix formed by thermally annealing of Ge oxide films.

Author

Vijayarangamuthu, K., Rath, Shyama, Kabiraj, D., Avasthi, D. K., Kulriya, Pawan K., Singh, V. N., and Mehta, B. R.

Subjects
NANOCRYSTALS, GERMANIUM, ANNEALING of metals, THIN films, CRYSTALLIZATION, TEMPERATURE
Abstract

The authors investigate the formation of Ge nanocrystals by thermal annealing of substoichiometric GeOx films fabricated by electron-beam evaporation. At the same time, they also monitor the evolution of the GeOx matrix. The phase separation into semiconductor and oxide phases and the evolution of Ge nanocrystals were monitored by a combination of x-ray diffraction (XRD), Raman, and transmission electron microscopy (TEM) measurements. TEM shows spherical particles of sizes in the range of 2–9 nm. They infer that an annealing temperature of 500 °C is sufficient to generate a reasonable density of Ge nanocrystals in an amorphous GeOx matrix. Both XRD and Raman measurements suggest a simultaneous crystallization of the matrix at an annealing temperature of 600 °C. [ABSTRACT FROM AUTHOR]

Published
2009
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26. Refractive Index of Ge Nanocrystals Embedded in a GeOx Matrix.

Author

Vijayarangamuthu, K., Singh, Chaman, and Rath, Shyama

Subjects
*REFRACTIVE index, *GERMANIUM oxide films, *SEMICONDUCTOR nanocrystals, *OPTICAL properties of semiconductors, *ELLIPSOMETRY, *STOICHIOMETRY, *ANNEALING of crystals
Abstract

We investigated the optical properties of the Ge nanocrystal embedded in a GeOx matrix by spectroscopic ellipsometry. Substoichiometric films were thermally annealed to obtain embedded Ge nanocrystals. Ge nanocrystal formation is supported by XRD, Raman, and TEM studies. The refractive index increases from 1.959 for as-deposited sample to 2.167 forsample annealed at 600 °C. [ABSTRACT FROM AUTHOR]

Published
2011
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27. ‘Li’ doping induced physicochemical property modifications of MoO3 thin films.

Author

Kovendhan, M., Joseph, D. Paul, Manimuthu, P., Sambasivam, S., Karthick, S.N., Vijayarangamuthu, K., Sendilkumar, A., Asokan, K., Kim, Hee Je, Choi, Byung Chun, Venkateswaran, C., and Mohan, R.

Subjects
*LITHIUM compounds, *DOPING agents (Chemistry), *MOLYBDENUM compounds, *THIN films, *DYE-sensitized solar cells, *FABRICATION (Manufacturing)
Abstract

Highlights: [•] Undoped film was oriented along the 〈0 k 0〉 direction. [•] Mo 3d 5/2 and 3d 3/2 doublet caused by spin–orbit coupling are resolved with a splitting of 3.1eV. [•] Direct and indirect band gaps showed red shift with ‘Li’ doping compared to undoped film. [•] Intensity of the green photoluminescence emission spectra is quenched with ‘Li’ concentration. [•] Dye sensitized solar cell is fabricated using undoped MoO3 thin film as photoanode. [ABSTRACT FROM AUTHOR]

Published
2013
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28. Temporospatial Control of Graphene Wettability.

Author

Vijayarangamuthu K, Ahn S, Seo H, Yoon SH, Park CM, and Jeon KJ

Abstract

The reversible migration of adatoms along a basal plane of graphene under electrical bias is experimentally demonstrated. Single-layer graphene oxide with partial oxygen adatom coverage is utilized for this demonstration. The intensity ratio of G and G' Raman modes is used to determine the oxygen adatoms migration. Finally, reversible wettability property of graphene due to oxygen adatom migration is demonstrated., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2016
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