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629 results on '"Kabiraj D"'

18. Magnetic and Electronic Structure study of Fe/MgO/Fe/Co Multilayer Stack Deposited by E-Beam Evaporation

Author

Singh, Jitendra Pal, Gautam, Sanjeev, Singh, Braj Bhusan, Raju, M., Chaudhary, S., Kabiraj, D., Kanjilal, D., Lee, Jenn-Min, Chen, Jin-Ming, Asokan, K., and Chae, Keun Hwa

Subjects
Condensed Matter - Materials Science, Condensed Matter - Soft Condensed Matter, Condensed Matter - Strongly Correlated Electrons
Abstract

Present work investigates the magnetic and electronic structure of MgO/Fe/MgO/Fe/Co/Au multilayer stack grown on Si(100) substrates by electron beam evaporation method. X-ray diffraction study depicts polycrystalline nature of the multilayers. Results obtained from vibrating sample magnetometry (VSM) and near-edge X-ray absorption fine structure spectra (NEXAFS) at Fe & Co L- and Mg & O K-edges are applied to understand the magnetic and electronic properties of this stack and its interface properties. While the spectral features of Fe L-edge spectrum recorded by surface sensitive total electron yield (TEY) mode shows the formation of FeOx at the Fe/MgO interface, the bulk sensitive total fluorescence yield (TFY), shows Fe in metallic nature. Co L-edge spectrum reveals the presence of metallic nature of cobalt in both TEY and TFY modes. Above results are well correlated with X-ray reflectometry.

Published
2013

23. A Hybrid model for the origin of photoluminescence from Ge nanocrystals in SiO$_2$ matrix

Author

Singha, A., Roy, A., Kabiraj, D., and Kanjilal, D.

Subjects
Condensed Matter - Materials Science
Abstract

In spite of several articles, the origin of visible luminescence from germanium nanocrystals in SiO$_2$ matrix is controversial even today. Some authors attribute the luminescence to quantum confinement of charge carriers in these nanocrystals. On the other hand, surface or defect states formed during the growth process, have also been proposed as the source of luminescence in this system. We have addressed this long standing query by simultaneous photoluminescence and Raman measurements on germanium nanocrystals embedded in SiO$_2$ matrix, grown by two different techniques: (i) low energy ion-implantation and (ii) atom beam sputtering. Along with our own experimental observations, we have summarized relevant information available in the literature and proposed a \emph{Hybrid Model} to explain the visible photoluminescence from nanocrystalline germanium in SiO$_2$ matrix., Comment: 23 pages, 8 figures

Published
2006
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24. Observation of Metastable and Stable Energy Levels of EL2 in Semi-insulating GaAs

Author

Kabiraj, D. and Ghosh, Subhasis

Subjects
Condensed Matter - Materials Science
Abstract

By using combination of detailed experimental studies, we identify the metastable and stable energy levels of EL2 in semi-insulating GaAs. These results are discussed in the light of the recently proposed models for stable and metastable configurations of EL2 in GaAs.

Published
2005
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25. Energy dependent sputtering of nano-clusters from a nanodisperse target and embedding of nanoparticles into a substrate

Author

Satpati, B., Ghatak, J., Joseph, B., Satyam, P. V., Som, T., Kabiraj, D., and Dev, B. N.

Subjects
Condensed Matter - Materials Science
Abstract

Au nanoparticles, prepared by thermal evaporation under high vacuum condition on Si substrate, are irradiated with Au ions at different ion energies. During ion irradiation, embedding of nanoparticles as well as ejection of nano-clusters is observed. Ejected particles (usually smaller than those on the Si substrate) due to sputtering are collected on carbon-coated transmission electron microscopy (TEM) grids. Both the TEM grids and the ion-irradiated samples are analyzed with TEM. Unirradiated as well as irradiated samples are also analyzed by Rutherford backscattering spectrometry (RBS). In the case of low energy (32 keV) ions, where the nuclear energy loss is dominant, both sputtering and embedding are less compared to medium energy (1.5 MeV). In the high energy regime (100 MeV), where the electronic energy loss is dominant, sputtering is maximum but practically there is no embedding. Ion bombardment of surfaces at an angle with respect to the surface-normal produces enhanced embedding compared to normal-incidence bombardment. The depth of embedding increases with larger angle of incidence. Au nanoparticles after ion irradiation form embedded gold-silicide. Size distribution of the sputtered Au clusters on the TEM grids for different ion energy regimes are presented., Comment: 11 pages, 5 figures, Submitted as a contributary paper in INDO-GERMAN Workshop held at NSC, New Delhi during 20-24th Feb.,2005

Published
2005

33. Status of the development of Delhi Light Source (DLS) at IUAC

Author

Ghosh, S., Joshi, V., Urakawa, J., Terunuma, N., Aryshev, A., Fukuda, S., Fukuda, M., Sahu, B.K., Patra, P., Abhilash, S.R., Karmakar, J., Karmakar, B., Kabiraj, D., Kumar, N., Sharma, A., Chaudhari, G.K., Pandey, A., Tripathi, S., Deshpande, A., Naik, V., Roy, A., Rao, T., Bhandari, R.K., and Kanjilal, D.

Published
2017
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36. Recovery of ion-damaged 4H-SiC under thermal and ion beam-induced ultrafast thermal spike-assisted annealing.

Author

Chakravorty, Anusmita, Dufour, Ch, Singh, Budhi, Jatav, Hemant, Umapathy, G. R., Kanjilal, D., and Kabiraj, D.

Subjects
ION beams, HEAVY ions, IONS, IRRADIATION
Abstract

The recovery effect of isochronal thermal annealing and inelastic energy deposited during 100 MeV Ag swift heavy ion (SHI) irradiation is demonstrated in the case of 4H-SiC pre-damaged by elastic energy deposition of 300 keV Ar ion. The Ar-induced fractional disorder follows a nonlinear two-step damage build-up. The fractional disorder level of 0.3 displacements per atom (dpa) is established as the threshold above which the lattice rapidly enters the amorphous phase, characterized by the presence of highly photo-absorbing defects. The SHI-induced recovery suggests that the damage annealing, in the pre-damaged region (∼ 350 nm) where the S e for 100 MeV Ag is almost constant (∼ 16.21 keV/nm), is more pronounced than the damage creation by SHI. This allows the disorder values to saturate at a lower value than the present initial disorder. Furthermore, the thermal effect due to SHI irradiation of an amorphous nano-zone embedded in a crystalline host matrix has been evaluated using the 3D implementation of the thermal spike. The recovery process by SHI is ascribed to the thermal spike-induced atomic movements resulting from the melting and the resolidification of the crystalline–amorphous interface. [ABSTRACT FROM AUTHOR]

Published
2021
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41. Sub-nanosecond Thermal Spike Induced Nanostructuring of Thin Solid Films Under Swift Heavy Ion (SHI) Irradiation

Author

Ghosh, S., Kumar, H., Singh, S. P., Srivastava, P., Kabiraj, D., Avasthi, D. K., Bürger, D., Zhou, S., Mücklich, A., Schmidt, H., Stouquert, J. P., Hull, Robert, Series editor, Jagadish, Chennupati, Series editor, Osgood, Richard M., Series editor, Parisi, Jürgen, Series editor, Wang, Zhiming M., Series editor, Skorupa, Wolfgang, editor, and Schmidt, Heidemarie, editor

Published
2014
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46. Controlled generation of photoemissive defects in 4H-SiC using swift heavy ion irradiation.

Author

Chakravorty, Anusmita, Singh, Budhi, Jatav, Hemant, Meena, Ramcharan, Kanjilal, D., and Kabiraj, D.

Subjects
HEAVY ions, CARRIER density, LIGHT absorption, LUMINESCENCE
Abstract

Defects in SiC have shown tremendous capabilities for quantum technology-based applications, making it necessary to achieve on-demand, high-concentration, and uniform-density defect ensembles. Here, we utilize 100 MeV Ag swift heavy ion irradiation on n-type and semi-insulating 4H-SiC for the controlled generation of the defects that have attracted a lot of attention. Photoluminescence spectroscopy shows strong evidence of V Si emitters in semi-insulating 4H-SiC. Additionally, irradiation generates photo-absorbing centers that enhance the optical absorption, suppressing the luminescence intensity at higher fluences (ions / cm 2). In n-type 4H-SiC, irradiation drastically increases the inter-conduction band transitions, attributed to absorption from trap centers. A clear correlation is found between (i) loss in the intensity of E 2 (TO) Raman signal and the enhancement in absorbance at 532 nm and (ii) decoupling of the longitudinal optical phonon–plasmon coupled Raman mode and the reduction in carrier concentration. The optical bandgap decreases with irradiation fluence for semi-insulating 4H-SiC. This is attributed to the formation of disorder and strain-induced localized electronic states near the band edges. [ABSTRACT FROM AUTHOR]

Published
2021
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