Raman scattering from CdSe microcrystals embedded in a germanate glass matrix

Tanaka, Akinori; Onari, Seiichiro; Arai, Toshihiro

doi:10.1103/physrevb.45.6587

Cited by 182 publications

(101 citation statements)

References 25 publications

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“…The large surface-to-volume ratio of a nanodot strongly affects the optical properties mainly due to introducing surface polarization and surface states [461]. Using a phenomenological Gaussian envelope function of phonon amplitudes, Tanaka et al [462] show that the size dependence originated from the relaxation of the q ¼ 0 selection rule based on the phonon confinement argument with negative phonon dispersion. The phonon energies for all the glasses are reduced, the values of the phonon energies of CdSe nanodots are found to be quite different for different host glasses.…”

Section: Optical Phonon Softeningmentioning

confidence: 99%

Size dependence of nanostructures: Impact of bond order deficiency

Sun

2007

Progress in Solid State Chemistry

815

717

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Section: Optical Phonon Softeningmentioning

confidence: 99%

Size dependence of nanostructures: Impact of bond order deficiency

Sun

2007

Progress in Solid State Chemistry

815

717

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“…The Raman scattering in CdSe QDs has been studied efficiently during last two decades (Alivisatos et al, 1989;Baranov et al, 2003;Dzhagan et al, 2007;Dzhagan et al, 2008;Meulenberg et al, 2004;Torchynska et al, 2007;Torchynska et al, 2008). The original CdSe QDs passivated by organic molecules reveal a Raman peak related to scattering by the longitudinal optical (LO) phonon at about 206-210 cm -1 (Meulenberg et al, 2004), which is red-shifted from its bulk value of 213 cm -1 due to phonon confinement (Meulenberg et al, 2004;Tanaka et al, 1992), as well as a weaker mode arising from the second order (2LO) appeared at 415 cm -1 (Meulenberg et al, 2004). The shift of a LO phonon Raman peak from 210 cm -1 down to 205 cm -1 and LO Raman peak softening with decreasing QD sizes from 3.0 nm to 1.6 nm was theoretically predicted in (Meulenberg et al, 2004).…”

Section: Optical Properties Of Ii-vi Semiconductor Core/shell Qdsmentioning

confidence: 99%

Semiconductor II-VI Quantum Dots with Interface States and Their Biomedical Applications

Torchynska¹,

Vorobiev²

2011

Advanced Biomedical Engineering

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“…When the materials are reduced to the nanometer scale, both size and temperature will affect the Raman redshift. The combination effect can be obtained in Eqn (7). Figure 3(d) shows both the experimental data 32 and prediction of the Raman redshift with respect to temperature for 5.1 nm nanoparticles.…”

Section: Temperature-dependent Raman Shift and Specific Heat Per Bondmentioning

confidence: 99%

“…The large surface-to-volume ratio of a nanosolid strongly affects the optical properties mainly because of the introduction of surface polarization and surface states. 27 Using a phenomenological Gaussian envelope function of phonon amplitudes, Tanaka et al 7 showed that the size dependence of the redshift of Raman optical modes originated from the relaxation of the q D 0 selection rule based on the confinement argument with negative phonon dispersion. The phonon energies for all the glasses are reduced, and the values of the phonon energies of CdSe nanosolids are found to be quite different for different host glasses because of interfacial interaction.…”

Section: Size-induced Raman Redshiftmentioning

confidence: 99%

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Atomistic origin and temperature dependence of Raman optical redshift in nanostructures: a broken bond rule

Pan

Tay

et al. 2007

J Raman Spectroscopy

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Consistent insight is presented into the atomistic origin and temperature (T) dependence of the redshift of Raman optical modes in nanostructures from INTRODUCTIONThe vibration of under-coordinated atoms at a surface and in a nanosolid is of great importance because the behavior of surface phonons influences directly the electrical, optical, and dielectric properties in semiconductor materials and devices, such as electron-phonon coupling, photoabsorption, and photoemission, as well as phonon scattering in the transport dynamics of electrons, phonons, and photons in devices. 1 -5 With miniaturization of a solid down to nanometer scales, the optical Raman modes shift toward lower wavenumbers. 6 On the other hand, when the temperature is increased, the Raman peaks also shift down to low wavenumbers monotonically yet nonlinearly at low temperatures. 7 -9 It is expected that the magnitude of vibration for a surface atom is always greater than that in the bulk. 10,11 However, the underlying mechanisms behind the size-and temperatureinduced Raman redshift of the optical modes remain ambiguous.Ł Correspondence to: Chang Q. Sun, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore. E-mail: ecqsun@ntu.edu.sg Size-induced Raman redshiftThe size-induced redshift of Raman optical modes has usually been suggested to be activated by surface disorder, 12 surface stress, 13 -15 quantum confinement, 16 -19 local heating effects, 20 -22 or surface chemical passivation. The Raman shifts of TiO 2 particles are attributed to the effects of decreasing particle size on the force constants and the amplitudes of vibration of the nearest atomic neighbors. 23 However, the effect of stress can usually be ignored for hydrogenated silicon, 24,25 in which hydrogen atoms terminate the surface dangling bonds, which reduce the bond strains and hence the residual stress. The phonon quantum confinement argument 16 attributes the redshift of the asymmetric Raman line to the relaxation of the q-vector selection rule for the excitation of the Raman active phonons due to their localization. The relaxation of the momentum conservation rule arises from the finite crystalline size and the distribution of the diameters of the nanosolid in the films. When the size is decreased, the rule of momentum conservation will be relaxed and the Raman active modes will not be limited to the center of the Brillouin zone. 13 However, Alim et al. 21,22 who have measured resonant and nonresonant Raman scattering spectra for ZnO nanocrystals with an average diameter of 20 nm, proposed that the observed phonon redshift can be attributed to the local heating effects instead of phonon Atomistic origin and temperature dependence of Raman redshift in nanostructures 781 confinement effects. A Gaussian-type phonon confinement model 17 that has been used to fit the experimental data indicates that strong phonon damping is present, whereas calculations 26 using the correlation functions of the local dielectric constant...

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Raman scattering from CdSe microcrystals embedded in a germanate glass matrix

Cited by 182 publications

References 25 publications

Size dependence of nanostructures: Impact of bond order deficiency

Size dependence of nanostructures: Impact of bond order deficiency

Semiconductor II-VI Quantum Dots with Interface States and Their Biomedical Applications

Atomistic origin and temperature dependence of Raman optical redshift in nanostructures: a broken bond rule

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