Browsing by Author "Govind"

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Nitrogen ion induced 2D-GaN layer formation of GaAs (001) surface
(2009) Praveen Kumar; S. Bhattacharya; Govind; B.R. Merita; S.M. Shivaprasad
This study demonstrates the formation of two-dimensional GaN on GaAs (001) surface by bombardment of nitrogen ions at room temperature. In this work the ion induced nitridation of GaAs (001) surface using nitrogen ion beam of different energies (range from 250 eV to 5 keV) has been investigated using in-situ X-ray Photoelectron Spectroscopy (XPS). A Ga rich surface produced by Ar + ion etching, promotes initial nitridation. Using nitrogen ion of different energies of constant fluence performs the nitridation. The nitridation suggests that the degree of nitridation increase as the nitrogen ion energy increases up to 3 keV and then attains saturation. The core level and valance band spectra were monitored to observe the chemical and electronic changes as a function of nitrogen ion beam energy. It is observed that Ga(3d) core level peak shifts during nitridation and N(1s) core level spectra shows that the intensity of the nitrogen peak increases and the Ga (LMM) auger peak shifts towards the higher binding energy, reveal the forming of N bonds with Ga by replacing the Ga-As bonds, forming GaN. Copyright © 2009 American Scientific Publishers.
Probing a bifunctional luminomagnetic nanophosphor for biological applications: A photoluminescence and time-resolved spectroscopic study
(2011) Bipin Kumar Gupta; Vimal Rathee; Tharangattu N. Narayanan; Palanisamy Thanikaivelan; Avishek Saha; Govind; S.P. Singh; V. Shanker; Angel A. Marti; Pulickel M. Ajayan
A bifunctional luminomagnetic 30 nm Gd1-xEuxVO 4 nanophosphor is synthesized using a facile sol-gel method. The nanophosphor is observed to produce both paramagnetic behavior and a highly efficient red emission peaking at 618 nm. Probing the luminomagnetic nanophosphor using photoluminescence, time-resolved spectroscopy, magnetization measurements, and a cytotoxicity assay reveal its suitability for biological applications, in particular, cell labeling and high-contrast imaging. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.