Raman scattering of acoustical modes of silicon nanoparticles embedded in silica matrix

Ivanda, Mile; Hohl, A.; Montagna, M.; Mariotto, G.; Ferrari, M.; Orel, Zorica Crnjak; Turković, Aleksandra; Furić, Krešimir

doi:10.1002/jrs.1445

Cited by 36 publications

(37 citation statements)

References 31 publications

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“…The second peak is attributed to the l = 0, n = 0 spherical breathing mode (the dashed blue line shows the expected value). The ratio between the peak positions between these l = 0 and l = 2 mode is 1.56, similar to past experiments and theory [26][27][28] . Figure 3b shows the experimentally confirmed l = 2 peak frequencies with respect to the sizes of different polystyrene nanospheres in the trap.…”

Section: Double Nanohole Extraordinary Acoustic Raman Spectroscopysupporting

confidence: 79%

Probing the Raman-active acoustic vibrations of nanoparticles with extraordinary spectral resolution

2014

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Colloidal quantum dots, viruses, DNA and all other nanoparticles have acoustic vibrations that can act as 'fingerprints' to identify their shape, size and mechanical properties, yet high-resolution Raman spectroscopy in this low-energy range has been lacking. Here, we demonstrate extraordinary acoustic Raman (EAR) spectroscopy to measure the Raman-active vibrations of single isolated nanoparticles in the 0.1-10 cm −1 range with ∼0.05 cm −1 resolution, to resolve peak splitting from material anisotropy and to probe the low-frequency modes of biomolecules. EAR employs a nanoaperture laser tweezer that can select particles of interest and manipulate them once identified. We therefore believe that this nanotechnology will enable expanded capabilities for the study of nanoparticles in the materials and life sciences.T he interaction of light with mechanical vibrations has had great impact in two disparate regimes, which are typified by the sub-gigahertz cavity optomechanics of micrometresized structures 1 and the super-terahertz Raman spectroscopy of molecular vibrations 2 . Between these frequencies, there is a gap where new technologies are desired. This gap is crucial to nanotechnology, because it contains the acoustic regime of nanoparticles, and therefore contains valuable information about their specific size, shape and material properties. A wide range of nanoparticles have acoustic vibrations in this frequency window, including colloids 3 , quantum dots 3 , proteins 4 , DNA 5 and virions. To identify the properties of these nanoparticles, it is desirable to have an ultra-sensitive, low-frequency approach to Raman spectroscopy with high spectral resolution.To date, the spectral identification of nanoparticles using conventional Raman spectroscopy has been unfeasible due to its limited spectral resolution, which is typically 1 cm −1 in high-resolution systems. Furthermore, elastic scattering from the excitation laser source should be filtered out, which typically limits the minimum frequency of vibrations to above 10 cm −1 . For the most part, only nanoparticles smaller than 10 nm can have their acoustic vibrations probed with conventional Raman spectroscopy 6 . Yet many particles of interest, such as virions and colloidal particles, are larger than 10 nm. Moreover, smaller particles that are not as stiff, especially biomaterials such as proteins and DNA oligomers, have large-scale vibration modes around 100 GHz (ref. 7), as will be shown here. It is this region in particular that we will address in this Article-particles on the order of 10 nm, with resonances in the range of 0.7-10 cm −1 . However, the technique may be extended to a broader range of particle sizes and frequencies in a straightforward manner. Although past Raman experiments have looked at large numbers of nanoparticles simultaneously 8 , here we observe the Raman-active modes in a solution of single nanoparticles trapped by a laser tweezer. We note, however, that this is not the first demonstration of single-particle sensitivity with Raman spect...

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Section: Double Nanohole Extraordinary Acoustic Raman Spectroscopysupporting

confidence: 79%

Probing the Raman-active acoustic vibrations of nanoparticles with extraordinary spectral resolution

2014

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“…We proposed a method to accurately estimate the size distribution of such QDs from their photoluminescence (PL) spectra in previous work. 4 The size distribution of nanoparticles from low frequency Raman scattering (LFRS) has been studied [5][6][7] and in this paper high frequency Raman spectroscopy is introduced as another method to extract such information. Boron doping on Si QDs bilayers is studied by a combination of Raman and PL spectroscopies.…”

Section: Introductionmentioning

confidence: 99%

Accurate analysis of the size distribution and crystallinity of boron doped Si nanocrystals via Raman and PL spectra

et al. 2017

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A narrow size distribution of quantum dots (QDs) is needed for their application in photovoltaics but collection of such information is difficult. This paper demonstrates the application of Raman spectroscopy as a characterisation tool to extract the size distribution and crystalline fraction of Si QD samples fabricated through the sputter-anneal method. Measured Raman spectra of Si QD materials are de-convoluted into four components according to their origins and Raman scattering by Si QD cores is

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“…In fact, in some systems as silver, gold and PbF 2 , the quadrupolar vibrations dominate the Raman spectrum, in other systems, as CdS, Si, Ga 2 O 3 , and HfO 2 , the symmetric vibrations dominate. [3][4][5][6]8,9 In TiO 2 nanocrystals both modes are observed with similar intensities. 7 Different depolarization ratios for the quadrupolar vibration have been measured, ranging from about 0.3 for silver to about 0.7 for TiO 2 .…”

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confidence: 60%

Mechanism of low-frequency Raman scattering from the acoustic vibrations of dielectric nanoparticles

et al. 2006

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The depolarization ratio of the quadrupolar vibrations and the relative intensity of the symmetric l = 0 and quadrupolar l = 2 acoustic vibrations in the Raman spectra of some dielectric nanocrystals has been calculated. A dipole-induced-dipole model can account for the depolarized spectra from quadrupolar vibrations, but cannot be at the origin of the polarized peak from the symmetric vibration. Bond polarizability seems to be the main physical mechanism at the origin of Raman scattering from these modes. The study indicates that the quadrupolar modes or symmetric modes dominate the spectra when the dipole induced dipole or bond polarizability are more important, respectively. This result explains why semiconductor nanoparticles with covalent bonds show intense symmetric scattering, and fluoride crystals with ionic bond show Raman scattering from quadrupolar modes, and why in oxide crystals the two modes show comparable Raman activity. A comparison of the spectra of titania, zirconia, and hafnia nanocrystals offers further support to the model. Low-frequency Raman scattering is a widely used experimental technique for the study of the vibrational dynamics of metallic, semiconductor or dielectric nanoclusters, usually embedded in a glass. 1-9 Most theoretical approaches for the calculation of the acoustic vibrational dynamics of spheroidal clusters are based on the work of Lamb, which found the vibrations of a free homogeneous sphere. 10 The modes are classified in torsional and spheroidal, both labeled by three indices ͑lmn͒, which describe the angular ͑lm͒ and radial ͑n͒ dependence of the displacements. As shown by Duval on the basis of simple symmetry arguments, only the spheroidal symmetric ͑l =0͒ and quadrupolar ͑l =2͒ spheroidal modes are Raman active. 11 Furthermore, the l = 0 modes give a polarized Raman spectrum, whereas the l = 2 modes give depolarized spectra, allowing to distinguish the nature of the vibrations by a comparison of the VV and HV spectra. Recently, a paper appeared with the claim that the l = 0 and l = 2 spheroidal modes are not Raman active because of an odd displacement field. 12 This wrong criterium does not consider that even modes have usually odd displacements, as for example, the vibration of the oxygen molecule or the symmetric stretching of the CO 2 molecule, which are Raman active even modes, having odd displacements. In any case, the explicit calculation of the average strain starting from the potential, deriving the displacement and again deriving the strain components, shows that only the l = 0 and l = 2 spheroidal modes are Raman active. 13 There are no general rules that indicate both the relative intensity of the symmetric and quadrupolar Raman peaks, appearing in the VV spectrum, or the depolarization ratio DR 2 = I HV / I VV for the quadrupolar modes. In fact, in some systems as silver, gold and PbF 2 , the quadrupolar vibrations dominate the Raman spectrum, in other systems, as CdS, Si, Ga 2 O 3 , and HfO 2 , the symmetric vibrations dominate. [3][4][5][6]8,9 In TiO 2 ...

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Raman scattering of acoustical modes of silicon nanoparticles embedded in silica matrix

Cited by 36 publications

References 31 publications

Probing the Raman-active acoustic vibrations of nanoparticles with extraordinary spectral resolution

Probing the Raman-active acoustic vibrations of nanoparticles with extraordinary spectral resolution

Accurate analysis of the size distribution and crystallinity of boron doped Si nanocrystals via Raman and PL spectra

Mechanism of low-frequency Raman scattering from the acoustic vibrations of dielectric nanoparticles

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