Skip to main content

Identification of trapping and recombination levels, structure, morphology, photoluminescence and optical absorption behavior of alloyed ZnxCd1−xS quantum dots

Research Abstract
Cubic ZnxCd1−xS nanoparticles (NPs) synthesized by chemical precipitation method with average crystallite size of 2.9 ± 0.2 nm were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), high-resolution transmission electron microscope (HRTEM), UV–vis absorption, Fourier transform infrared red (FTIR), photoluminescence (PL) emission and Raman spectroscopy. XRD analysis demonstrated systematic shift of diffraction peaks to higher diffraction angles accompanied by a decrease in the lattice parameters with increasing Zn content (x); this confirmed the formation and homogeneity of ZnxCd1−xS nanoalloys. In addition, the dependence of lattice parameters and Raman shift on x showed linear behavior and good agreement with Vegard's law. TEM images of ZnxCd1−xS NPs revealed nearly spherical shape NPs, relatively narrow particle size distribution and standard deviation in the range 1.8–3.4%.; as well as HRTEM images showed well resolved diffraction crystalline planes of zinc-blende cubic type structure. Analysis of optical absorption spectra showed blue shift of both the direct optical band gap from 3.25 to 4.05 eV and excitonic absorption shoulder from 2.56 to 3.88 eV with increasing x, confirming the homogeneity of ZnxCd1−xS alloyed semiconductor NPs. At excitation wavelength 325 nm, the deconvoluted structural defects related PL emission bands are broadened and revealed stronger PL intensity than that at 370 nm. Furthermore, increasing x resulted in PL enhancement accompanied by blue shift of green emission band centered at 515 nm–445 nm. To explain composition dependent PL emission process; trapping and recombination localized levels in ZnxCd1−xS alloyed NPs were identified quantitatively and an energy band diagram was suggested.
Research Authors
M.A. Osman , A.G. Abd-Elrahim , A.A. Othman
Research Department
Research Journal
Journal of alloys and compounds
Research Pages
Pages 344-357
Research Publisher
Elsevier
Research Rank
1
Research Vol
Volume 722, 25 October 2017
Research Website
https://doi.org/10.1016/j.jallcom.2017.06.104
Research Year
2017

Identification of trapping and recombination levels, structure, morphology, photoluminescence and optical absorption behavior of alloyed ZnxCd1−xS quantum dots

Research Abstract
Cubic ZnxCd1−xS nanoparticles (NPs) synthesized by chemical precipitation method with average crystallite size of 2.9 ± 0.2 nm were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), high-resolution transmission electron microscope (HRTEM), UV–vis absorption, Fourier transform infrared red (FTIR), photoluminescence (PL) emission and Raman spectroscopy. XRD analysis demonstrated systematic shift of diffraction peaks to higher diffraction angles accompanied by a decrease in the lattice parameters with increasing Zn content (x); this confirmed the formation and homogeneity of ZnxCd1−xS nanoalloys. In addition, the dependence of lattice parameters and Raman shift on x showed linear behavior and good agreement with Vegard's law. TEM images of ZnxCd1−xS NPs revealed nearly spherical shape NPs, relatively narrow particle size distribution and standard deviation in the range 1.8–3.4%.; as well as HRTEM images showed well resolved diffraction crystalline planes of zinc-blende cubic type structure. Analysis of optical absorption spectra showed blue shift of both the direct optical band gap from 3.25 to 4.05 eV and excitonic absorption shoulder from 2.56 to 3.88 eV with increasing x, confirming the homogeneity of ZnxCd1−xS alloyed semiconductor NPs. At excitation wavelength 325 nm, the deconvoluted structural defects related PL emission bands are broadened and revealed stronger PL intensity than that at 370 nm. Furthermore, increasing x resulted in PL enhancement accompanied by blue shift of green emission band centered at 515 nm–445 nm. To explain composition dependent PL emission process; trapping and recombination localized levels in ZnxCd1−xS alloyed NPs were identified quantitatively and an energy band diagram was suggested.
Research Authors
M.A. Osman , A.G. Abd-Elrahim , A.A. Othman
Research Department
Research Journal
Journal of alloys and compounds
Research Pages
Pages 344-357
Research Publisher
Elsevier
Research Rank
1
Research Vol
Volume 722, 25 October 2017
Research Website
https://doi.org/10.1016/j.jallcom.2017.06.104
Research Year
2017

Identification of trapping and recombination levels, structure, morphology, photoluminescence and optical absorption behavior of alloyed ZnxCd1−xS quantum dots

Research Abstract
Cubic ZnxCd1−xS nanoparticles (NPs) synthesized by chemical precipitation method with average crystallite size of 2.9 ± 0.2 nm were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), high-resolution transmission electron microscope (HRTEM), UV–vis absorption, Fourier transform infrared red (FTIR), photoluminescence (PL) emission and Raman spectroscopy. XRD analysis demonstrated systematic shift of diffraction peaks to higher diffraction angles accompanied by a decrease in the lattice parameters with increasing Zn content (x); this confirmed the formation and homogeneity of ZnxCd1−xS nanoalloys. In addition, the dependence of lattice parameters and Raman shift on x showed linear behavior and good agreement with Vegard's law. TEM images of ZnxCd1−xS NPs revealed nearly spherical shape NPs, relatively narrow particle size distribution and standard deviation in the range 1.8–3.4%.; as well as HRTEM images showed well resolved diffraction crystalline planes of zinc-blende cubic type structure. Analysis of optical absorption spectra showed blue shift of both the direct optical band gap from 3.25 to 4.05 eV and excitonic absorption shoulder from 2.56 to 3.88 eV with increasing x, confirming the homogeneity of ZnxCd1−xS alloyed semiconductor NPs. At excitation wavelength 325 nm, the deconvoluted structural defects related PL emission bands are broadened and revealed stronger PL intensity than that at 370 nm. Furthermore, increasing x resulted in PL enhancement accompanied by blue shift of green emission band centered at 515 nm–445 nm. To explain composition dependent PL emission process; trapping and recombination localized levels in ZnxCd1−xS alloyed NPs were identified quantitatively and an energy band diagram was suggested.
Research Authors
M.A. Osman , A.G. Abd-Elrahim , A.A. Othman
Research Department
Research Journal
Journal of alloys and compounds
Research Pages
Pages 344-357
Research Publisher
Elsevier
Research Rank
1
Research Vol
Volume 722, 25 October 2017
Research Website
https://doi.org/10.1016/j.jallcom.2017.06.104
Research Year
2017

Mn-doped ZnO nanocrystals synthesized by sonochemical method: Structural, photoluminescence, and magnetic properties

Research Abstract
This work reports the synthesis of Mn-doped ZnO nanostructures using ice-bath assisted sonochemical technique. The impact of Mn-doping on structural, morphological, optical, and magnetic properties of ZnO nanostructures is studied. The morphological study shows that the lower doped samples possess mixtures of nanosheets and nanorods while the increase in Mn content leads to improvement of an anisotropic growth in a preferable orientation to form well-defined edge rods at Mn content of 0.04. UV–vis absorption spectra show that the exciton peak in the UV region is blue shifted due to Mn incorporation into the ZnO lattice. Doping ZnO with Mn ions leads to a reduction in the PL intensity due to a creation of more non-radiative recombination centers. The magnetic measurements show that the Mn-doped ZnO nanostructures exhibit ferromagnetic ordering at room temperature, as well as variation of the Mn content can significantly affect the ferromagnetic behavior of the samples.
Research Authors
A.A. Othman, M.A. Osman, E.M.M. Ibrahim, Manar A. Ali, A.G. Abd-Elrahim
Research Department
Research Journal
Materials Science and Engineering: B
Research Member
Research Pages
Pages 1-9
Research Publisher
Elsevier
Research Rank
1
Research Vol
Volume 219, May 2017
Research Website
https://doi.org/10.1016/j.mseb.2017.02.013
Research Year
2017

Mn-doped ZnO nanocrystals synthesized by sonochemical method: Structural, photoluminescence, and magnetic properties

Research Abstract
This work reports the synthesis of Mn-doped ZnO nanostructures using ice-bath assisted sonochemical technique. The impact of Mn-doping on structural, morphological, optical, and magnetic properties of ZnO nanostructures is studied. The morphological study shows that the lower doped samples possess mixtures of nanosheets and nanorods while the increase in Mn content leads to improvement of an anisotropic growth in a preferable orientation to form well-defined edge rods at Mn content of 0.04. UV–vis absorption spectra show that the exciton peak in the UV region is blue shifted due to Mn incorporation into the ZnO lattice. Doping ZnO with Mn ions leads to a reduction in the PL intensity due to a creation of more non-radiative recombination centers. The magnetic measurements show that the Mn-doped ZnO nanostructures exhibit ferromagnetic ordering at room temperature, as well as variation of the Mn content can significantly affect the ferromagnetic behavior of the samples.
Research Authors
A.A. Othman, M.A. Osman, E.M.M. Ibrahim, Manar A. Ali, A.G. Abd-Elrahim
Research Department
Research Journal
Materials Science and Engineering: B
Research Pages
Pages 1-9
Research Publisher
Elsevier
Research Rank
1
Research Vol
Volume 219, May 2017
Research Website
https://doi.org/10.1016/j.mseb.2017.02.013
Research Year
2017

Mn-doped ZnO nanocrystals synthesized by sonochemical method: Structural, photoluminescence, and magnetic properties

Research Abstract
This work reports the synthesis of Mn-doped ZnO nanostructures using ice-bath assisted sonochemical technique. The impact of Mn-doping on structural, morphological, optical, and magnetic properties of ZnO nanostructures is studied. The morphological study shows that the lower doped samples possess mixtures of nanosheets and nanorods while the increase in Mn content leads to improvement of an anisotropic growth in a preferable orientation to form well-defined edge rods at Mn content of 0.04. UV–vis absorption spectra show that the exciton peak in the UV region is blue shifted due to Mn incorporation into the ZnO lattice. Doping ZnO with Mn ions leads to a reduction in the PL intensity due to a creation of more non-radiative recombination centers. The magnetic measurements show that the Mn-doped ZnO nanostructures exhibit ferromagnetic ordering at room temperature, as well as variation of the Mn content can significantly affect the ferromagnetic behavior of the samples.
Research Authors
A.A. Othman, M.A. Osman, E.M.M. Ibrahim, Manar A. Ali, A.G. Abd-Elrahim
Research Department
Research Journal
Materials Science and Engineering: B
Research Pages
Pages 1-9
Research Publisher
Elsevier
Research Rank
1
Research Vol
Volume 219, May 2017
Research Website
https://doi.org/10.1016/j.mseb.2017.02.013
Research Year
2017

Mn-doped ZnO nanocrystals synthesized by sonochemical method: Structural, photoluminescence, and magnetic properties

Research Abstract
This work reports the synthesis of Mn-doped ZnO nanostructures using ice-bath assisted sonochemical technique. The impact of Mn-doping on structural, morphological, optical, and magnetic properties of ZnO nanostructures is studied. The morphological study shows that the lower doped samples possess mixtures of nanosheets and nanorods while the increase in Mn content leads to improvement of an anisotropic growth in a preferable orientation to form well-defined edge rods at Mn content of 0.04. UV–vis absorption spectra show that the exciton peak in the UV region is blue shifted due to Mn incorporation into the ZnO lattice. Doping ZnO with Mn ions leads to a reduction in the PL intensity due to a creation of more non-radiative recombination centers. The magnetic measurements show that the Mn-doped ZnO nanostructures exhibit ferromagnetic ordering at room temperature, as well as variation of the Mn content can significantly affect the ferromagnetic behavior of the samples.
Research Authors
A.A. Othman, M.A. Osman, E.M.M. Ibrahim, Manar A. Ali, A.G. Abd-Elrahim
Research Department
Research Journal
Materials Science and Engineering: B
Research Pages
Pages 1-9
Research Publisher
Elsevier
Research Rank
1
Research Vol
Volume 219, May 2017
Research Website
https://doi.org/10.1016/j.mseb.2017.02.013
Research Year
2017

Size-dependent structural phase transitions and their correlation with
photoluminescence and optical absorption behavior of annealed Zn⁠0.45Cd⁠0.55S quantum
dots

Research Abstract
In this paper, we investigate the effect of thermally induced structural phase transitions on the photoluminescence (PL) and optical absorption behaviour of Zn0.45Cd0.55S nanoparticles (NPs). Analysis of X-ray diffraction (XRD) patterns and high-resolution electron microscope (HRTEM) images reveal that the as-synthesized sample possesses zinc-blende-type cubic structure. In addition, at annealing temperature (Ta) 400 °C, the cubic structure transforms completely into the wurtzite-type hexagonal structure. Furthermore, the second phase transition of the as-synthesized sample has observed at 700 °C, where the cubic structure has transformed into mixed polycrystalline phases of hexagonal ZnO, cubic CdO, monoclinic CdSO3, and orthorhombic ZnSO4 structures. These new phases have also confirmed from the analysis of Raman and FTIR spectra. Analysis of UV–visible optical absorption spectra demonstrates that Increasing Ta results in the decrease of optical band gap due the improvement in crystallinity accompanied by the increase in the particle size. The PL emission bands at an excitation energy of 3.818 eV exhibit redshift and a decrease in the intensity with increasing Ta up to 500 °C. Meanwhile, further increase in Ta up to 700 °C results in the enhancement of green emission intensity. On the other hand, PL emission spectra at 3.354 eV and Ta 700 °C, reveal a dramatic increase in the emission intensity nearly by one-order of magnitude with respect to its value of the as-synthesized sample. This behaviour is ascribed to the incorporation of oxygen-related defects via thermal annealing in air, which act as additive radiative centers. Also, we have interpreted the observed spectral blue shift of PL emission spectrum with increasing excitation energy.
Research Authors
M. A. Osman
A. G. Abd-Elrahim
A. A. Othman
Research Department
Research Journal
Materials Characterization
Research Pages
Pages 247-263
Research Publisher
Elsevier
Research Rank
1
Research Vol
Volume 144, October 2018
Research Website
https://doi.org/10.1016/j.matchar.2018.07.020
Research Year
2018

Size-dependent structural phase transitions and their correlation with
photoluminescence and optical absorption behavior of annealed Zn⁠0.45Cd⁠0.55S quantum
dots

Research Abstract
In this paper, we investigate the effect of thermally induced structural phase transitions on the photoluminescence (PL) and optical absorption behaviour of Zn0.45Cd0.55S nanoparticles (NPs). Analysis of X-ray diffraction (XRD) patterns and high-resolution electron microscope (HRTEM) images reveal that the as-synthesized sample possesses zinc-blende-type cubic structure. In addition, at annealing temperature (Ta) 400 °C, the cubic structure transforms completely into the wurtzite-type hexagonal structure. Furthermore, the second phase transition of the as-synthesized sample has observed at 700 °C, where the cubic structure has transformed into mixed polycrystalline phases of hexagonal ZnO, cubic CdO, monoclinic CdSO3, and orthorhombic ZnSO4 structures. These new phases have also confirmed from the analysis of Raman and FTIR spectra. Analysis of UV–visible optical absorption spectra demonstrates that Increasing Ta results in the decrease of optical band gap due the improvement in crystallinity accompanied by the increase in the particle size. The PL emission bands at an excitation energy of 3.818 eV exhibit redshift and a decrease in the intensity with increasing Ta up to 500 °C. Meanwhile, further increase in Ta up to 700 °C results in the enhancement of green emission intensity. On the other hand, PL emission spectra at 3.354 eV and Ta 700 °C, reveal a dramatic increase in the emission intensity nearly by one-order of magnitude with respect to its value of the as-synthesized sample. This behaviour is ascribed to the incorporation of oxygen-related defects via thermal annealing in air, which act as additive radiative centers. Also, we have interpreted the observed spectral blue shift of PL emission spectrum with increasing excitation energy.
Research Authors
M. A. Osman
A. G. Abd-Elrahim
A. A. Othman
Research Department
Research Journal
Materials Characterization
Research Pages
Pages 247-263
Research Publisher
Elsevier
Research Rank
1
Research Vol
Volume 144, October 2018
Research Website
https://doi.org/10.1016/j.matchar.2018.07.020
Research Year
2018

Size-dependent structural phase transitions and their correlation with
photoluminescence and optical absorption behavior of annealed Zn⁠0.45Cd⁠0.55S quantum
dots

Research Abstract
In this paper, we investigate the effect of thermally induced structural phase transitions on the photoluminescence (PL) and optical absorption behaviour of Zn0.45Cd0.55S nanoparticles (NPs). Analysis of X-ray diffraction (XRD) patterns and high-resolution electron microscope (HRTEM) images reveal that the as-synthesized sample possesses zinc-blende-type cubic structure. In addition, at annealing temperature (Ta) 400 °C, the cubic structure transforms completely into the wurtzite-type hexagonal structure. Furthermore, the second phase transition of the as-synthesized sample has observed at 700 °C, where the cubic structure has transformed into mixed polycrystalline phases of hexagonal ZnO, cubic CdO, monoclinic CdSO3, and orthorhombic ZnSO4 structures. These new phases have also confirmed from the analysis of Raman and FTIR spectra. Analysis of UV–visible optical absorption spectra demonstrates that Increasing Ta results in the decrease of optical band gap due the improvement in crystallinity accompanied by the increase in the particle size. The PL emission bands at an excitation energy of 3.818 eV exhibit redshift and a decrease in the intensity with increasing Ta up to 500 °C. Meanwhile, further increase in Ta up to 700 °C results in the enhancement of green emission intensity. On the other hand, PL emission spectra at 3.354 eV and Ta 700 °C, reveal a dramatic increase in the emission intensity nearly by one-order of magnitude with respect to its value of the as-synthesized sample. This behaviour is ascribed to the incorporation of oxygen-related defects via thermal annealing in air, which act as additive radiative centers. Also, we have interpreted the observed spectral blue shift of PL emission spectrum with increasing excitation energy.
Research Authors
M. A. Osman
A. G. Abd-Elrahim
A. A. Othman
Research Department
Research Journal
Materials Characterization
Research Pages
Pages 247-263
Research Publisher
Elsevier
Research Rank
1
Research Vol
Volume 144, October 2018
Research Website
https://doi.org/10.1016/j.matchar.2018.07.020
Research Year
2018
Subscribe to