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Your search keyword '"Laha, Ranjit"' showing total 102 results
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102 results on '"Laha, Ranjit"'

13. Growth and characterization of ZnO/MgZnO thin film hetero structures on p-Si for visible light detectors.

Author

Kumar, Rashmi Ranjan, Raghvendra, Laha, Ranjit, and Pandey, Saurabh Kumar

Subjects
PHOTODETECTORS, VISIBLE spectra, ZINC oxide, THIN films, ZINC oxide films, FIELD emission electron microscopy, MOLECULAR beam epitaxy, LIGHT sources
Abstract

ZnO- and MgZnO-based single- and double-layer heterostructures have been grown using an electron-beam evaporation system. Structural, morphological, optical and electrical characteristics were elaborated for all the configurations. Using x-ray diffraction, it was inferred that a hexagonal wurtzite structure is maintained for both ZnO and MgZnO with fairly good crystallinity. Field emission scanning electron microscopy (FESEM) images showed the homogeneous distribution of particles in ZnO and MgZnO throughout the films. Both atomic force microscopy and FESEM images exhibit a larger size for ZnO particles. The UV emission for ZnO at ∼371 nm and MgZnO at ∼359 nm was anticipated from photoluminescence spectra. The visible photoconductive properties of all the different configurations were studied in the dark and under the illumination of a white light source. The highest responsivities measured for the ZnO/MgZnO/Si structure were 0.242 A W−1 and 0.164 A W−1 for as deposited and annealed at 400 °C, respectively. These results show the suitability of bilayer photo detectors for visible light detection. [ABSTRACT FROM AUTHOR]

Published
2021
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25. Au concentration-dependent quenching of Raman 2D peak in graphene.

Author

Ranjan, Pranay, Tulika, Laha, Ranjit, and Balakrishnan, Jayakumar

Subjects
GRAPHENE, QUENCHING (Chemistry), RAMAN spectra, GOLD nanoparticles, SPUTTERING (Physics)
Abstract

We investigate the effect of sputtered gold nanoclusters (AuNCs) on the Raman spectra of graphene. The two prominent Raman peaks of graphene - 2D and G - show drastically different behaviour with AuNC introduction. The Raman 2D peak intensity decreases with gold coverage and finally is quenched for moderate gold nanoparticle coverage, while the G peak shows a AuNC size-dependent enhancement in peak intensity. The quenching of the 2D peak is attributed to the hybridization of graphene's 2pz orbital with the 5d orbitals of Au. The G peak enhancement is due to the surface-enhanced Raman scattering induced by the surface plasmons created in the AuNC by the incident laser beam (He-Ne laser, wavelength = 632.8 nm). The existence of surface plasmons is independently confirmed by UV-visible spectrophotometry measurements. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2017
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28. Tailoring Plasmonic Properties of Metal-Dielectric Nanocomposite Thin Films.

Author

Laha, Ranjit

Subjects
PLASMONICS, THIN films, DIELECTRIC properties, NANOCOMPOSITE materials, ELECTRIC properties of metals
Abstract

Tuning of the plasmonic properties of nanocomposite thin films made by embedding metal nanoparticles in dielectric matrices has been investigated theoretically. The working formula for localized surface plasmon resonance (LSPR) position λLSPR was derived to be λLSPR ... with λP,εd, K, f and ΧIB being respectively the plasma wavelength of Au, dielectric constant of matrix thin film, shape factor, volume fraction of AuNPs inside the matrix and real part of inter-band susceptibility. Using this formula, LSPR of nanocomposites can be varied by more than 300 nm the visible range. Analysis of the formula concludes that for a given volume fraction, changing shape has the maximum effect on shift in LSPR position. [ABSTRACT FROM AUTHOR]

Published
2017
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32. Temperature Dependent Localized Surface Plasmon Resonance Properties of Supported Gold Nanoparticles.

Author

Laha, Ranjit and Ranjan, Pranay

Subjects
*GOLD nanoparticles, *SURFACE plasmon resonance, *ELECTRIC properties of nanoparticles, *PARTICLE size distribution, *QUARTZ, *SCANNING electron microscopy, *ANNEALING of metals
Abstract

The well known localized surface plasmon resonance (LSPR) of gold nanoparticles (AuNPs) supported on a dielectric substrate depends on the particle shape, size and type of dielectric material. The particle size and shape mainly vary with the method of preparation and the parameters involved there in. In this report, we show preparation of AuNPs supported on quartz substrate by direct current sputtering followed by thermal annealing at an optimized temperature of 400 °C. The samples were characterized using optical absorption spectra, scanning electron microscopy (SEM) and the energy dispersive x-ray spectrum. The LSPR position could be tuned by varying annealing temperature. The LSPR was found to be blue shifted up to 10 nm with annealing temperature varying from 400 °C to 800 °C. The change in LSPR was ascribed to the morphology of AuNPs over quartz. [ABSTRACT FROM AUTHOR]

Published
2016
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36. Acute Cerebral Revascularization Following Cerebral Embolism.

Author

Dujovny, Manuel, Laha, Ranjit K., Barrionuevo, Pedro J., Solis, Gonzalo, and Corkill, Guy

Subjects
CAROTID artery, BLOOD vessels, CEREBROVASCULAR disease, ARTERIES, MEDICAL care, SURGERY
Abstract

The article reports that the disability and loss of life resulting from stroke continue to be significant. It has been estimated that thromboembolic cerebral infarcts will cause about 80 percent of strokes. Most emboli arise from the heart or extracranial carotid artery and lodge predominatly in the area of the middle cerebral artery. Treatment of cerebrovascular accident is both challenging and controversial. Medical treatment is largely preventive and supportive, and until recently, operative treatment was not adequately developed. Advances in microsurgical techniques, however, have generated interest in intracranial reconstructive vascular surgery.

Published
1979
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37. Dorsal longitudinal myelotomy

Author

Laha, Ranjit K, Dujovny, Manuel, and Osgood, Carroll P

Abstract

An evaluation of dorsal longitudinal myelotomy in the management of spasticity of the lower limbs has been done in 17 patients. The follow-up has varied from 1 month to over 2 years. Most patients achieved satisfactory relief from spasticity. Eight patients have died after the operation in chronic care hospitals. In all except one, the spasticity had been relieved. Eight out of the nine living patients have benefited from myelotomy. Recurrence of spasticity following the first operation occurred in four patients, two of whom improved after a repeat myelotomy. In the presence of fixed contractures of the hip and knee joints, a satisfactory clinical result may not be obtained after the myelotomy.

Published
1976
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39. Temporary Microvascular Clips

Author

Dujovny, Manuel, primary, Kossovsky, Nir, additional, Laha, Ranjit K., additional, Leff, Louis, additional, Wackenhut, Norman, additional, and Perlin, Alfred, additional

Published
1979
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41. Minimum vascular occlusive force

Author

Dujovny, Manuel, primary, Wakenhut, Norman, additional, Kossovsky, Nir, additional, Gomes, Carl W., additional, Laha, Ranjit K., additional, Leff, Louis, additional, and Nelson, Debra, additional

Published
1979
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