Optical properties of CdS nanoparticles upon annealing

Sivasubramanian, V.; Arora, Akhi̇lesh; Premila, M.; Sundar, C. S.; Sastry, V. Sankara

doi:10.1016/j.physe.2005.10.001

Cited by 90 publications

(64 citation statements)

References 34 publications

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“…Therefore, synthetized nanofilms contain a high density of crystalline defects. In addition, to the 1LO phonon and its phononic replicas for M65 sample, several vibrational bands are resolved at 219, 260 and 352 cm −1 suggesting that the samples have better crystalline quality [25]. The vibrational bands can be assigned to multiphonon scattering, which is consistent with reported works [26,27].…”

Section: +supporting

confidence: 88%

Rare earths (Ce, Eu) molar concentration-dependent of the structural and optical properties of CBD-CdS nanofilms

et al. 2018

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It presents the characterization of rare earths (Eu,Ce)-doped CdS nanofilms that were synthesised by the growth technique chemical bath deposition (CBD) at the reservoir temperature of 70 ± 2• C. The doping of CdS with rare earths is performed by varying the synthesis time from 60 to 135 min. The rare earths molar concentration was range from 0.0 ≤ x ≤ 3.5, which was determined by energy dispersive X-ray spectroscopy. X-ray diffraction (XRD) analysis and Raman scattering reveal that CdS nanofilms showed the zinc blende (ZB) crystalline phase. The CdS average nanocrystal size was ranged from 1.84 to 2.67 nm that was determined by the Debye-Scherrer equation from ZB (111) direction, which was confirmed by transmission electron microscopy. Raman scattering shows that the lattice dynamics is characteristic of bimodal behaviour and the multipeaks adjust of the first optical longitudinal mode for the (Eu,Ce)-doped CdS, which denotes the Raman shift of the characteristic peak about 305 cm −1 of the CdS nanocrystals. The CdS nanofilms exhibit a direct bandgap that slightly decreases with increasing doping, from 2.50 to 2.42 eV, which was obtained by room temperature transmittance. The room-temperature photoluminescence of CdS shows the band-to-band transition at 2.88 eV, which is associated to quantum confinement and a dominant radiative band at 2.37 eV that is called the optical signature of interstitial oxygen. The Eu 3+ -doped CdS photoluminescence shows the dominant radiative band at 2.15 eV, which is associated to the intra-4f radiative transition of Eu 3+ ions that corresponds to the magnetic dipole transition, ( 5 D0→ 7 F 1 ).For the Ce 3+ -doped CdS the dominant radiative transition, at 2.06 eV, is clearly redshifted, although the passivation of the CdS nanofilms byCe was approximately by a factor about 21 for the best results.Keywords: CdS; Chemical bath deposition; Rare earths; cerium; europium.Se presenta la caracterización de las nanopelículas de CdS impurificadas con tierras raras (Eu,Ce) que se sintetizaron mediante la técnica de crecimiento deposición de baño químico (CBD) a la temperatura del reservorio de 70 ± 2 • C. La impurificación de CdS con tierras raras se realizó variando el tiempo de síntesis de 60 a 135 min. La concentración molar de las tierras raras fue de 0.0 ≤ x ≤ 3.5, que se determinó mediante espectroscopia de rayos X de energía dispersiva. El análisis de difracción de rayos X (XRD) y dispersión de Raman revelan que las nanopelículas de CdS mostraron la fase cristalina de zinc blenda (ZB). El tamaño medio de los nanocristales de CdS varió de 1.84 a 2.67 nm, que se determinó mediante la ecuación de Debye-Scherrer a partir de la dirección ZB (111), que se confirmó mediante microscopía electrónica de transmisión. La dispersión Raman muestra que la dinámica de la red es característica del comportamiento bimodal y el ajuste multipicos del primer modo longitudinalóptico para el CdS impurificado con (Eu, Ce), el cual denota el desplazamiento Raman del pico característico en aproximadamente 305 ...

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Section: +supporting

confidence: 88%

Rare earths (Ce, Eu) molar concentration-dependent of the structural and optical properties of CBD-CdS nanofilms

et al. 2018

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“…Using a phenomenological model, the ratio of intensities of the overtone and the fundamental Raman spectra has been analysed, 140 and the results suggested that the electron-phonon coupling decreased as the particle size reduced. In a similar study on cubic CdS nanoparticles, synthesized using chemical precipitation in methanol, the intensity ratio I 2LO /I 1LO was found to increase as the particle size increased because of annealing at different temperatures up to 300°C 117 ( Fig. 7).…”

Section: Resonance Effectsmentioning

confidence: 75%

“…Often it has also been possible to stabilize metastable phases of compounds in the form of nanocrystalline powders 38,117 and composites. 40 Metastable monoclinic phase of selenium dispersed in a polyacrylamide host has exhibited phonon confinement effects.…”

Section: Monoatomic Systemsmentioning

confidence: 99%

Raman spectroscopy of optical phonon confinement in nanostructured materials

Arora

Rajalakshmi

Ravindran

et al. 2007

J Raman Spectroscopy

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361

294

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If the medium surrounding a nano-grain does not support the vibrational wavenumbers of a material, the optical and acoustic phonons get confined within the grain of the nanostructured material. This leads to interesting changes in the vibrational spectrum of the nanostructured material as compared to that of the bulk. Absence of periodicity beyond the particle dimension relaxes the zone-centre optical phonon selection rule, causing the Raman spectrum to have contributions also from phonons away from the Brillouin-zone centre. Theoretical models and calculations suggest that the confinement results in asymmetric broadening and shift of the optical phonon Raman line, the magnitude of which depends on the widths of the corresponding phonon dispersion curves. This has been confirmed for zinc oxide nanoparticles. Microscopic lattice dynamical calculations of the phonon amplitude and Raman spectra using the bond-polarizability model suggest a power-law dependence of the peak-shift on the particle size. This article reviews recent results on the Raman spectroscopic investigations of optical phonon confinement in several nanocrystalline semiconductor and ceramic/dielectric materials, including those in selenium, cadmium sulphide, zinc oxide, thorium oxide, and nano-diamond. Resonance Raman scattering from confined optical phonons is also discussed.

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“…The difference is that we do not distinguish between slow and fast motion of electrons in different directions. Then two subsequent transformations are applied to Hamiltonian (1) using the operators (20), (21), and after averaging over the vacuum phonon state | 0 the following Hamiltonian is obtained…”

Section: Electron-phonon Interaction In a Quasi-two-dimensional Systementioning

confidence: 99%

“…A comparative analysis is made for two AlAs/GaAs/AlAs and PbS/PbTe/PbS heterostructures. : 63.20.Kr, 79.60.Jv Recently various low-dimensional structures such as film systems [1-13], superlattices [14], quantum wires [14][15][16] and quantum dots [17][18][19][20][21][22] have been widely investigated both experimentally and theoretically. These heterosystems are of great interest mainly due to their unique physical properties which can be used in the electronic and opto-electronic devices.…”

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confidence: 99%

Polaron density of states of AlAs/GaAs/AlAs and PbS/PbTe/PbS type quantum well

Boichuk¹,

Borusevych²,

Kogoutiouk³

2007

Condens. Matter Phys.

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Polaron energy spectrum of AlAs/GaAs/AlAs and PbS/PbTe/PbS quasi two-dimensional heterostructure as a function of the wave-vector is investigated based on the adiabatic approximation and the Ritz variational technique. The electron interaction with confined, interface and half-space phonons is taken into account. A comparative analysis of the polaron energy spectrum in heterostructures with a finite and infinite breakdown of energy bands at the interface is performed by means of the Li-Lou-Pines variational method. The polaron density of states dependence as a function of energies with the values less than phonon energies is studied. The contribution of each phonon branch to the density of states is determined. A comparative analysis is made for two AlAs/GaAs/AlAs and PbS/PbTe/PbS heterostructures. : 63.20.Kr, 79.60.Jv Recently various low-dimensional structures such as film systems [1-13], superlattices [14], quantum wires [14][15][16] and quantum dots [17][18][19][20][21][22] have been widely investigated both experimentally and theoretically. These heterosystems are of great interest mainly due to their unique physical properties which can be used in the electronic and opto-electronic devices. Key words: polaron, heterostructure, quantum well, density of states PACSAlAs/GaAs/AlAs and PbS/PbTe/PbS with one-dimensional quantum well (QW) are among the most highly used low-dimensional heterostructures. The restriction of quasi-particle motion in one direction (perpendicular to the interface) causes an essential difference (in comparison with a massive crystal) not only in the energy spectrum of non-interactive quasi-particles, but also in the values of the interaction energy. Particularly, one can see the changes in the electron, phonon and polaron spectra, which, in its turn, effects the optical and kinetic properties of such structures.The theory of polaron states has been developed in many papers [3,4,23,24], where various calculation methods and heterostructure models were used. However, most investigations studied a polaron dependence of the main parameters (effective masses, dielectric permittivities, QW widths, etc.) at the minimum of the conduction band. Therefore, in performing theoretical interpretation of the experimental data it is assumed that the polaron dispersion law has a parabolic form just like the electron one. And the difference is observed only in the values of effective mass [23]. However, the electron-phonon interaction depends on the wave vector and this should effect the nature of the polaron distribution law.The object of this paper is to investigate the polaron dispersion law in AlAs/GaAs/AlAs, PbS/PbTe/PbS heterostructures for different values of QW width. A contribution of various phonon branches to the formation of the polaron dispersion law is determined. The polaron density of states dependence on the energy values is defined based on the calculations performed. *

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Optical properties of CdS nanoparticles upon annealing

Cited by 90 publications

References 34 publications

Rare earths (Ce, Eu) molar concentration-dependent of the structural and optical properties of CBD-CdS nanofilms

Rare earths (Ce, Eu) molar concentration-dependent of the structural and optical properties of CBD-CdS nanofilms

Raman spectroscopy of optical phonon confinement in nanostructured materials

Polaron density of states of AlAs/GaAs/AlAs and PbS/PbTe/PbS type quantum well

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