shreya rai | Delhi Public School International, Pushp Vihar, Saket (original) (raw)

Papers by shreya rai

Research paper thumbnail of Surface chemical reactions during electron beam irradiation of nanocrystalline CaS:Ce3+ phosphor

Journal of Applied Physics, 2010

The effects of accelerating voltage (0.5–5 keV) on the green cathodoluminescence (CL) of CaS:Ce3+... more The effects of accelerating voltage (0.5–5 keV) on the green cathodoluminescence (CL) of CaS:Ce3+ nanocrystalline powder phosphors is reported. An increase in the CL intensity was observed from the powders when the accelerating voltage was varied from 0.5 to 5 keV, ...

Research paper thumbnail of Luminescence response and CL degradation of combustion synthesized spherical SiO 2:Ce nanophosphor

Materials Research Bulletin, 2011

Research paper thumbnail of Investigations on the low voltage cathodoluminescence stability and surface chemical behaviour using Auger and X-ray photoelectron spectroscopy on LiSrBO 3:Sm 3+ phosphor

Materials Research Bulletin, 2011

Research paper thumbnail of Surface chemical changes of CaTiO 3:Pr 3+ upon electron beam irradiation

Physica B-condensed Matter

Surface chemical changes of CaTiO 3 :Pr 3 þ phosphor material and their effect on the red emissio... more Surface chemical changes of CaTiO 3 :Pr 3 þ phosphor material and their effect on the red emission intensity of the 1 D 2 -3 H 4 transition of Pr 3 þ , upon electron beam irradiation are presented. Red emission at 613 nm was obtained upon probing the surface with a 2 keV electron beam. The surface chemical changes and Pr 3 þ red emission were monitored using an Auger Electron Spectroscopy (AES) and Cathodoluminescence (CL) spectrometer, respectively. The CL intensity decreased with a decrease in O on the surface at 1 Â 10 À 8 Torr base pressure and decreased with an increase in O on the surface at 1 Â 10 À 6 Torr O 2 . The X-ray Photoelectron Spectroscopy (XPS) revealed that CL degradation at 1 Â 10 À 6 Torr O 2 is due to the formation of CaO and CaO x as well as TiO 2 /Ti 2 O 3 non-luminescent species on the surface.

Research paper thumbnail of Luminescence characterization and electron beam induced chemical changes on the surface of ZnAl 2O 4:Mn nanocrystalline phosphor

Applied Surface Science, 2011

Luminescence characteristics and surface chemical changes of nanocrystalline Mn 2+ doped ZnAl 2 O... more Luminescence characteristics and surface chemical changes of nanocrystalline Mn 2+ doped ZnAl 2 O 4 powder phosphors are presented. Stable green cathodoluminescence (CL) or photoluminescence (PL) with a maximum at ∼512 nm was observed when the powders were irradiated with a beam of high energy electrons or a monochromatic xenon lamp at room temperature. This green emission can be attributed to the 4 T 1 → 6 A 1 transitions of the Mn 2+ ion. Deconvoluted CL spectra resulted in two additional emission peaks at 539 and 573 nm that may be attributed to vibronic sideband and Mn 4+ emission, respectively. The luminescence decay of the Mn 2+ 512 nm emission under 457 nm excitation is single exponential with a lifetime of 5.20 ± 0.11 ms. Chemical changes on the surface of the ZnAl 2 O 4 :Mn 2+ phosphor during prolonged electron beam exposure were monitored using Auger electron spectroscopy. The X-ray photoelectron spectroscopy (XPS) was used to determine the chemical composition of the possible compounds formed on the surface as a result of the prolonged electron beam exposure. The XPS data suggest that the thermodynamically stable Al 2 O 3 layer was formed on the surface and is possibly contributing to the CL stability of ZnAl 2 O 4 :Mn phosphor.

Research paper thumbnail of Design and simulation of Optical Frequency Domain reflectometer for short distance fault detection in optical fibers and integrated optical devices using ptolemy-II

... Photonics and Microwave Division, School of Electrical Sciences, VIT University, Vellore - 63... more ... Photonics and Microwave Division, School of Electrical Sciences, VIT University, Vellore - 632014,Tamil Nadu, India. ... Optics Networks”, ECE Department, University of Maryland, College Park, MD [4] Rishad A. Akhtiamov, Valery F. Gusev and Renat G. Zalyalov, “Fiber Optical ...

Research paper thumbnail of Cathodoluminescent properties and surface characterization of bluish-white LiAl5O8:Tb phosphor

Journal of Applied Physics, 2011

Cathodoluminescence (CL) characteristics and electron-beam induced surface chemical changes in na... more Cathodoluminescence (CL) characteristics and electron-beam induced surface chemical changes in nanocrystalline Tb3+ doped LiAl5O8 powder phosphors are presented. Bluish-white CL with a maximum at ~543 nm was observed when the powders were irradiated with a 2 keV electron beam. The emissions in the green and the blue regions arise from the magnetic dipole 5D4-7FJ (J=6-0) and 5D3-7FJ transitions of the Tb3+ ion. The appearance of the line emissions in the blue region are discussed in terms of Tb oxidation states and their corresponding interconversion. Auger electron spectroscopy and x-ray photoelectron spectroscopy (XPS) were used to probe the chemical changes on the surface of the LiAl5O8 phosphor under electron bombardment. The XPS data suggest that the Tb ions exist both in trivalent and tetravalent oxidation states which could be the reason for the observed green as well as blue CL emissions. A thermodynamically stable Al2O3 layer formed on the surface as a result of the electron stimulated surface chemical reactions is possibly contributing to the CL stability of the LiAl5O8:Tb phosphor. The time stability of the phosphor under prolonged electron beam exposure suggests that it can be used in information displays.

Research paper thumbnail of TL and PL studies on defect-assisted green luminescence from doped strontium sulfide phosphor

Journal of Luminescence, 2008

Defect-assisted luminescence of Pr3+-doped SrS has been investigated and reported in this paper. ... more Defect-assisted luminescence of Pr3+-doped SrS has been investigated and reported in this paper. The polycrystalline sample of phosphor was prepared by conventional solid-state reaction method and checked for crystallization and phase by X-ray diffraction study. The ...

Research paper thumbnail of Low voltage electron induced cathodoluminescence degradation and surface characterization of Sr 3(PO 4) 2:Tb phosphor

Applied Surface Science, 2011

Tb3+-doped Sr3(PO4)2 phosphor was prepared by a sol–gel combustion method. A trigonal structure h... more Tb3+-doped Sr3(PO4)2 phosphor was prepared by a sol–gel combustion method. A trigonal structure having Sr and O atoms occupying two different lattice sites were obtained. Scanning Auger nanoprobe was used to analyze the morphology of the particles. Photoluminescence (PL) and cathodoluminescence (CL) properties of Sr3(PO4)2:Tb powder phosphors were evaluated and compared. In addition, the CL intensity degradation of Sr3(PO4)2:Tb was

Research paper thumbnail of Luminescence properties of Ce 3+ and Tb 3+ co-activated ZnAl 2O 4 phosphor

Cold Regions Science and Technology

In this study, a solution combustion method was used to prepare green emitting Ce 3 þ -Tb 3 þ co-... more In this study, a solution combustion method was used to prepare green emitting Ce 3 þ -Tb 3 þ co-activated ZnAl 2 O 4 phosphor. The samples were annealed at 700 1C in air or hydrogen atmosphere to improve their crystallinity and optical properties. X-ray diffraction study confirmed that both asprepared and post-preparation annealed samples crystallized in the well known cubic spinel structure of ZnAl 2 O 4 . An agglomeration of irregular platelet-like particles whose surfaces were encrusted with smaller spheroidal particles was confirmed by scanning electron microscopy (SEM). The fluorescence data collected from the annealed samples with different concentrations of Ce 3 þ and Tb 3 þ show the enhanced green emission at 543 nm associated with 5 D 4 -7 F 5 transitions of Tb 3 þ . The enhancement was attributed to energy transfer from Ce 3 þ to Tb 3 þ . Possible mechanism of energy transfer via a down conversion process is discussed. Furthermore, cathodoluminescence (CL) intensity degradation of this phosphor was also investigated and the degradation data suggest that the material was chemically stable and the CL intensity was also stable after 10 h of irradiation by a beam of high energy electrons.

Research paper thumbnail of Class VII Home Work

Research paper thumbnail of Surface chemical reactions during electron beam irradiation of nanocrystalline CaS:Ce3+ phosphor

Journal of Applied Physics, 2010

The effects of accelerating voltage (0.5–5 keV) on the green cathodoluminescence (CL) of CaS:Ce3+... more The effects of accelerating voltage (0.5–5 keV) on the green cathodoluminescence (CL) of CaS:Ce3+ nanocrystalline powder phosphors is reported. An increase in the CL intensity was observed from the powders when the accelerating voltage was varied from 0.5 to 5 keV, ...

Research paper thumbnail of Luminescence response and CL degradation of combustion synthesized spherical SiO 2:Ce nanophosphor

Materials Research Bulletin, 2011

Research paper thumbnail of Investigations on the low voltage cathodoluminescence stability and surface chemical behaviour using Auger and X-ray photoelectron spectroscopy on LiSrBO 3:Sm 3+ phosphor

Materials Research Bulletin, 2011

Research paper thumbnail of Surface chemical changes of CaTiO 3:Pr 3+ upon electron beam irradiation

Physica B-condensed Matter

Surface chemical changes of CaTiO 3 :Pr 3 þ phosphor material and their effect on the red emissio... more Surface chemical changes of CaTiO 3 :Pr 3 þ phosphor material and their effect on the red emission intensity of the 1 D 2 -3 H 4 transition of Pr 3 þ , upon electron beam irradiation are presented. Red emission at 613 nm was obtained upon probing the surface with a 2 keV electron beam. The surface chemical changes and Pr 3 þ red emission were monitored using an Auger Electron Spectroscopy (AES) and Cathodoluminescence (CL) spectrometer, respectively. The CL intensity decreased with a decrease in O on the surface at 1 Â 10 À 8 Torr base pressure and decreased with an increase in O on the surface at 1 Â 10 À 6 Torr O 2 . The X-ray Photoelectron Spectroscopy (XPS) revealed that CL degradation at 1 Â 10 À 6 Torr O 2 is due to the formation of CaO and CaO x as well as TiO 2 /Ti 2 O 3 non-luminescent species on the surface.

Research paper thumbnail of Luminescence characterization and electron beam induced chemical changes on the surface of ZnAl 2O 4:Mn nanocrystalline phosphor

Applied Surface Science, 2011

Luminescence characteristics and surface chemical changes of nanocrystalline Mn 2+ doped ZnAl 2 O... more Luminescence characteristics and surface chemical changes of nanocrystalline Mn 2+ doped ZnAl 2 O 4 powder phosphors are presented. Stable green cathodoluminescence (CL) or photoluminescence (PL) with a maximum at ∼512 nm was observed when the powders were irradiated with a beam of high energy electrons or a monochromatic xenon lamp at room temperature. This green emission can be attributed to the 4 T 1 → 6 A 1 transitions of the Mn 2+ ion. Deconvoluted CL spectra resulted in two additional emission peaks at 539 and 573 nm that may be attributed to vibronic sideband and Mn 4+ emission, respectively. The luminescence decay of the Mn 2+ 512 nm emission under 457 nm excitation is single exponential with a lifetime of 5.20 ± 0.11 ms. Chemical changes on the surface of the ZnAl 2 O 4 :Mn 2+ phosphor during prolonged electron beam exposure were monitored using Auger electron spectroscopy. The X-ray photoelectron spectroscopy (XPS) was used to determine the chemical composition of the possible compounds formed on the surface as a result of the prolonged electron beam exposure. The XPS data suggest that the thermodynamically stable Al 2 O 3 layer was formed on the surface and is possibly contributing to the CL stability of ZnAl 2 O 4 :Mn phosphor.

Research paper thumbnail of Design and simulation of Optical Frequency Domain reflectometer for short distance fault detection in optical fibers and integrated optical devices using ptolemy-II

... Photonics and Microwave Division, School of Electrical Sciences, VIT University, Vellore - 63... more ... Photonics and Microwave Division, School of Electrical Sciences, VIT University, Vellore - 632014,Tamil Nadu, India. ... Optics Networks”, ECE Department, University of Maryland, College Park, MD [4] Rishad A. Akhtiamov, Valery F. Gusev and Renat G. Zalyalov, “Fiber Optical ...

Research paper thumbnail of Cathodoluminescent properties and surface characterization of bluish-white LiAl5O8:Tb phosphor

Journal of Applied Physics, 2011

Cathodoluminescence (CL) characteristics and electron-beam induced surface chemical changes in na... more Cathodoluminescence (CL) characteristics and electron-beam induced surface chemical changes in nanocrystalline Tb3+ doped LiAl5O8 powder phosphors are presented. Bluish-white CL with a maximum at ~543 nm was observed when the powders were irradiated with a 2 keV electron beam. The emissions in the green and the blue regions arise from the magnetic dipole 5D4-7FJ (J=6-0) and 5D3-7FJ transitions of the Tb3+ ion. The appearance of the line emissions in the blue region are discussed in terms of Tb oxidation states and their corresponding interconversion. Auger electron spectroscopy and x-ray photoelectron spectroscopy (XPS) were used to probe the chemical changes on the surface of the LiAl5O8 phosphor under electron bombardment. The XPS data suggest that the Tb ions exist both in trivalent and tetravalent oxidation states which could be the reason for the observed green as well as blue CL emissions. A thermodynamically stable Al2O3 layer formed on the surface as a result of the electron stimulated surface chemical reactions is possibly contributing to the CL stability of the LiAl5O8:Tb phosphor. The time stability of the phosphor under prolonged electron beam exposure suggests that it can be used in information displays.

Research paper thumbnail of TL and PL studies on defect-assisted green luminescence from doped strontium sulfide phosphor

Journal of Luminescence, 2008

Defect-assisted luminescence of Pr3+-doped SrS has been investigated and reported in this paper. ... more Defect-assisted luminescence of Pr3+-doped SrS has been investigated and reported in this paper. The polycrystalline sample of phosphor was prepared by conventional solid-state reaction method and checked for crystallization and phase by X-ray diffraction study. The ...

Research paper thumbnail of Low voltage electron induced cathodoluminescence degradation and surface characterization of Sr 3(PO 4) 2:Tb phosphor

Applied Surface Science, 2011

Tb3+-doped Sr3(PO4)2 phosphor was prepared by a sol–gel combustion method. A trigonal structure h... more Tb3+-doped Sr3(PO4)2 phosphor was prepared by a sol–gel combustion method. A trigonal structure having Sr and O atoms occupying two different lattice sites were obtained. Scanning Auger nanoprobe was used to analyze the morphology of the particles. Photoluminescence (PL) and cathodoluminescence (CL) properties of Sr3(PO4)2:Tb powder phosphors were evaluated and compared. In addition, the CL intensity degradation of Sr3(PO4)2:Tb was

Research paper thumbnail of Luminescence properties of Ce 3+ and Tb 3+ co-activated ZnAl 2O 4 phosphor

Cold Regions Science and Technology

In this study, a solution combustion method was used to prepare green emitting Ce 3 þ -Tb 3 þ co-... more In this study, a solution combustion method was used to prepare green emitting Ce 3 þ -Tb 3 þ co-activated ZnAl 2 O 4 phosphor. The samples were annealed at 700 1C in air or hydrogen atmosphere to improve their crystallinity and optical properties. X-ray diffraction study confirmed that both asprepared and post-preparation annealed samples crystallized in the well known cubic spinel structure of ZnAl 2 O 4 . An agglomeration of irregular platelet-like particles whose surfaces were encrusted with smaller spheroidal particles was confirmed by scanning electron microscopy (SEM). The fluorescence data collected from the annealed samples with different concentrations of Ce 3 þ and Tb 3 þ show the enhanced green emission at 543 nm associated with 5 D 4 -7 F 5 transitions of Tb 3 þ . The enhancement was attributed to energy transfer from Ce 3 þ to Tb 3 þ . Possible mechanism of energy transfer via a down conversion process is discussed. Furthermore, cathodoluminescence (CL) intensity degradation of this phosphor was also investigated and the degradation data suggest that the material was chemically stable and the CL intensity was also stable after 10 h of irradiation by a beam of high energy electrons.

Research paper thumbnail of Class VII Home Work