Raman study of free-standing porous silicon

Tanino, Hiroshi; Kuprin, A. P.; Deai, H.; Koshida, Nobuyoshi

doi:10.1103/physrevb.53.1937

Cited by 57 publications

(31 citation statements)

References 77 publications

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“…[3][4][5] In addition to this, Raman scattering experiments have been used in numerous studies of the vibrational properties of silicon nanostructures. [6][7][8][9][10][11][12][13][14][15][16] In many of these studies it is found that the first-order peak due to the transverse optical (TO) phonon at the point is broadened and its maximum shifted to lower energies. The phononconfinement model 6,17 attributes this behavior to the fact that in nanostructures more vibrational modes can become Raman active than in bulk crystals since the translational symmetry is broken and consequently no k = 0 selection rule applies.…”

Section: Introductionmentioning

confidence: 99%

Vibrational density of states of silicon nanoparticles

Meyer

Comtesse

2011

Phys. Rev. B

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The vibrational density of states of silicon nanoparticles in the range from 2.3 to 10.3 nm is studied with the help of molecular-dynamics simulations. From these simulations the vibrational density of states and frequencies of bulklike vibrational modes at high-symmetry points of the Brillouin zone have been derived. The results show an increase of the density of states at low frequencies and a transfer of modes from the high-frequency end of the spectrum to the intermediate range. At the same time the peak of transverse optical modes is shifted to higher frequencies. These observations are in line with previous simulation studies of metallic nanoparticles and they provide an explanation for a previously observed discrepancy between experimental and theoretical data

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Section: Introductionmentioning

confidence: 99%

Vibrational density of states of silicon nanoparticles

Meyer

Comtesse

2011

Phys. Rev. B

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“…We suggest that the 630 cm~1 line in PS is a consequence of the combination of the LO(X) and TA(X) modes. The enhancement of this mode in the PS is due to the relaxation of selection rules and surface assistance, as suggested by Tanino et al 12 However, the contribution of an bending mode to this Raman line SiH 2 should not be disregarded since we observe the SiH 2 stretching mode in the Raman spectra of the PS layer (see the inset in Fig. 5).…”

Section: Discussionmentioning

confidence: 77%

“…Many researchers have reported polarization e †ects in the Raman spectra of PS layers,10h13 but in general the results are controversial. However, the anisotropic behaviour of second-order Raman scattering in PS has not been treated in the literature except for the work of Tanino et al 12 The photoluminescence spectra of PS layers present a strong dependence on the nature of the PS substrate.9 Therefore, the PL spectra of PS should contain information regarding the structure and bonding on PS layers. Since PL and Raman spectroscopy are governed by di †erent selection rules, it is believed that a simultaneous study of the polarization e †ects on the Raman and PL spectra of PS layers can provide a better understanding of structural, bonding and anisotropic properties of this material.…”

Section: Introductionmentioning

confidence: 99%

Polarization effects on the Raman and photoluminescence spectra of porous silicon layers

Salcedo

Fernandez

Rubim

1999

J. Raman Spectrosc.

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The e †ect of di †erent polarization orientations of the excitation source on the Raman and photoluminescence (PL) spectra of a porous silicon (PS) layer within two di †erent micro-regions was investigated. Two micro-regions (2 lm) along the (100) direction were studied, close to the crystalline silicon (c-Si)-PS layer interface and the PS layer-air interface. The Raman depolarization factors obtained in the 100-1200 cm-1 phonon spectra of these two micro-regions showed that the anisotropy presented by the PS layer is similar to that presented by the c-Si (100). Large di †erences in the Raman linewidths and di †erent emission maxima in the PL spectra were observed for the two micro-regions. These results were interpreted as the PS layer being inhomogeneous along the (100) direction. These e †ects are discussed from a critical point of view by taking into account quantum conÐnement and chemical composition of the nano-crystallite surface, since the stretching mode was also observed in the Raman SiH 2 spectra. Excitation with di †erent polarizations causes a shift of the emission maxima. This shift was assigned to a polarization dichroism caused by a breakdown on the degeneracy as the nano-crystallites having a reduced symmetry in relation to c-Si. The results strongly support the hypothesis that the luminescence presented by the PS layer is due to the presence of Si-based compounds on the surface of Si nanocrystallites.

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“…10 and 11 indicate reduction of the phonon scattering rate for electrons confined in nc-Si dots. As the average diameter of nc-Si dots is about 4 nm [12], [16] the energies of a confined electron are well separated due to quantum effect. For scattering process mediated by high-frequency phonons, the discrete nature of the energy spectrum of electrons and confined optical phonons reduces the number of allowed transitions, during which the energy conservation must hold.…”

Section: A Possible Mechanism Of Suppressed Electron Energy Relamentioning

confidence: 99%

“…7(b) shows the calculated dwell time as a function of the electron energy in direction to a linear chain of quantum dots , where the total electron energy is given by the sum of and the electron energy perpendicular to a linear chain, that is, . Based on structural and optical studies of the PS diodes [12], [16] the size of the silicon dots were assumed to be 4.0 nm, and the oxide thickness and the barrier height were set 1.0 nm and 1.0 eV, respectively. The voltage across each dot was set 0.1 V, which is a typical value under device operation.…”

Section: A Possible Mechanism Of Suppressed Electron Energy Relamentioning

confidence: 99%

New insights in high-energy electron emission and underlying transport physics of nanocrystalline si

Uno

Nakazato

Yamaguchi

et al. 2003

IEEE Trans. Nanotechnology

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Abstract-This paper presents quantitative analysis of electron emission from nanocrystalline Si dots, and discusses its mechanism based on the calculations of electronic and phononic states. Analysis of emission energy distribution measured from the vacuum level shows that the energy at the peak of the distribution increases linearly with increasing voltage applied across the nanocrystalline Si system. The slope of the linear law is unity, regardless of process conditions. Increasing voltage significantly changes the shape of the distribution at the energies smaller than the peak, while it has minimal impact at the energies larger than the peak. Both the conventional field emission model and the metal-oxide-semiconductor model fail to explain those behaviors. Calculations of electronic and phononic states in a chain of the nanocrystalline Si dots indicate a possibility of strong suppression of electron energy relaxation, which may be a possible mechanism of the high-energy electron emission phenomena.

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Raman study of free-standing porous silicon

Cited by 57 publications

References 77 publications

Vibrational density of states of silicon nanoparticles

Vibrational density of states of silicon nanoparticles

Polarization effects on the Raman and photoluminescence spectra of porous silicon layers

New insights in high-energy electron emission and underlying transport physics of nanocrystalline si

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