Search

Your search keyword '"Kabiraj D"' showing total 629 results
Start Over Author "Kabiraj D"
629 results on '"Kabiraj D"'

53. Intense ionizing irradiation-induced atomic movement toward recrystallization in 4H-SiC.

Author

Chakravorty, Anusmita, Singh, Budhi, Jatav, Hemant, Ojha, Sunil, Singh, Jaspreet, Kanjilal, D., and Kabiraj, D.

Subjects
RUTHERFORD backscattering spectrometry, X-ray photoelectron spectroscopy, BACKSCATTERING, LOW temperatures, HARD X-rays, ENERGY consumption, SPACE environment
Abstract

An ultrafast thermal spike within a time interval of a few pico-seconds generated by intense ionizing energy deposited using 100 MeV Ag ions is utilized to study the atomistic details of damage recovery in 4H-SiC. Sequential single ion irradiations were performed using 300 keV Ar and 100 MeV Ag in <0001> 4H-SiC to invoke swift heavy ion (SHI) beam induced epitaxial recrystallization in samples with different degrees of pre-damaged conditions. SHI irradiation was carried out at both room temperature and a low temperature of ~80 K. Low-temperature irradiation was carried out to arrest thermal diffusion of defects and to isolate ionization-induced defect migration in 4H-SiC. Insights into the thermal spike generated by ionizing events in crystalline and amorphous regions at both the temperatures predict a SiC response to SHI. The results emphasize the role of different degrees of pre-damage induced physico-chemical conditions and irradiation temperatures against SHI-induced recrystallization as evaluated by Rutherford backscattering/channeling, Raman spectroscopy, and hard x-ray photoelectron spectroscopy. Understanding the dependence of ion-beam damage accumulation and their recovery on the inelastic to elastic energy loss ratio is important for the performance prediction of SiC intended for extreme environments such as space, defense, and nuclear radiation. We report substantial damage recovery even at a near liquid nitrogen temperature of ~80 K. The recovery gets impeded mainly by the formation of complex defects having homonuclear bonds. The results are explained in the framework of the inelastic thermal spike model, and the role of phonon in the damage recovery process is emphasized. [ABSTRACT FROM AUTHOR]

Published
2020
Full Text
View/download PDF

56. A Combinatorial Study Investigating the Growth of Ultrasmall Embedded Silver Nanoparticles upon Thermal Annealing

Author

Jatav, H., Shabaninezhad, M., Mičetić, M., Chakravorty, A., Mishra, A., Schwartzkopf, M., Chumakov, A., Roth, Stephan V., Kabiraj, D., Jatav, H., Shabaninezhad, M., Mičetić, M., Chakravorty, A., Mishra, A., Schwartzkopf, M., Chumakov, A., Roth, Stephan V., and Kabiraj, D.

Abstract

Ultrasmall nanoparticles (NPs) with a high active surface area are essential for optoelectronic and photovoltaic applications. However, the structural stability and sustainability of these ultrasmall NPs at higher temperatures remain a critical problem. Here, we have synthesized the nanocomposites (NCs) of Ag NPs inside the silica matrix using the atom beam co-sputtering technique. The post-deposition growth of the embedded Ag NPs is systematically investigated at a wide range of annealing temperatures (ATs). A novel, fast, and effective procedure, correlating the experimental (UV-vis absorption results) and theoretical (quantum mechanical modeling, QMM) results, is used to estimate the size of NPs. The QMM-based simulation, employed for this work, is found to be more accurate in reproducing the absorption spectra over the classical/modified Drude model, which fails to predict the expected shift in the LSPR for ultrasmall NPs. Unlike the classical Drude model, the QMM incorporates the intraband transition of the conduction band electrons to calculate the effective dielectric function of metallic NCs, which is the major contribution of LSPR shifts for ultrasmall NPs. In this framework, a direct comparison is made between experimentally and theoretically observed LSPR peak positions, and it is observed that the size of NPs grows from 3 to 18 nm as AT increases from room temperature to 900 °C. Further, in situ grazing-incidence small- & wide-angle X-ray scattering and transmission electron microscopy measurements are employed to comprehend the growth of Ag NPs and validate the UV + QMM results. We demonstrate that, unlike chemically grown NPs, the embedded Ag NPs ensure greater stability in size and remain in an ultrasmall regime up to 800 °C, and beyond this temperature, the size of NPs increases exponentially due to dominant Ostwald ripening. Finally, a three-stage mechanism is discussed to understand the process of nucleation and growth of the silica-embedded Ag, QC 20230602

Published
2022
Full Text
View/download PDF

96. Synthesis of confined electrically conducting carbon nanowires by heavy ion irradiation of fullerene thin film

Author

Kumar, Amit, Avasthi, D.K., Tripathi, A., Kabiraj, D., Singh, F., and Pivin, J.C.

Subjects
Dielectric films -- Chemical properties, Dielectric films -- Electric properties, Thin films -- Chemical properties, Thin films -- Electric properties, Ion bombardment -- Analysis, Physics
Abstract

The creation of conducting nanowires, parallel to each other in fullerene films by the heavy ion irradiation is described. The results have shown that the irradiation through a nanodimension mask can create a two-dimensional regular pattern of conducting nanochannels with a possibility of variety of applications.

Published
2007

Catalog

Books, media, physical & digital resources
See catalog results