Raman Spectroscopy of Ge Nanocrystals Grown by Self-Organization Processes

1996 ◽  
Vol 452 ◽  
Author(s):  
A. Stella ◽  
C. E. Bottani ◽  
P. Cheyssac ◽  
R. Kofman ◽  
P. Milani ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Size Dependence ◽  
Self Organization ◽  
Phonon Confinement ◽  
Amorphous Substrate ◽  
Crystalline Nature ◽  
Size Dispersion ◽  
Ge Nanocrystals ◽  
Confinement Model

AbstractWe report Raman spectroscopy measurements on Ge nanocrystals with average radii ranging from about 65 Å down to 10 Å (with a size dispersion lower than 20 %).Ge has been deposited by UHV evaporation on an amorphous substrate, kept at such a temperature as to produce the Ge nanodroplets nucleation in the liquid phase.A nanocrystalline size dependence of the Raman spectra has been observed and explained in the framework of a phonon confinement model. We have observed the softening of the TO Raman peak predicted by the theory when the dimensions of the particles are decreased. Moreover the observed inhomogeneous broadening of the Raman lines has been correlated with the size distribution of the particles in the samples.Our results provide a characterization of Ge nanoparticles exhibiting a good crystalline nature, down to about 10 Å, and in conditions of substantial absence of perturbations of the environment.

Modified phonon confinement model for Raman spectroscopy of nanostructured materials

2010 ◽  
Vol 82 (11) ◽  
Author(s):  
K. Roodenko ◽  
I. A. Goldthorpe ◽  
P. C. McIntyre ◽  
Y. J. Chabal
Keyword(s):  
Raman Spectroscopy ◽  
Nanostructured Materials ◽  
Phonon Confinement ◽  
Confinement Model

Formation and characterization of germanium nanoparticles

2000 ◽  
Vol 15 (11) ◽  
pp. 2400-2407 ◽  
Author(s):  
N. J. Welham
Keyword(s):  
Raman Spectroscopy ◽  
Crystallite Size ◽  
Magnesium Oxide ◽  
Phonon Confinement ◽  
X Ray Diffraction ◽  
Acid Leach ◽  
Crystallite Sizes ◽  
Crystal Core ◽  
Individual Particles

Elemental germanium was mechanically milled with magnesium oxide with the intention of forming disperse nanoparticulate germanium in a soluble matrix. The crystallite size was determined by x-ray diffraction (XRD) and Raman spectroscopy using a phonon confinement model. The crystallite size was found to decrease exponentially with milling time; however, the size determined by XRD was typically five to ten times greater than that by Raman. This was attributed to the presence of two separate crystallite sizes, which were averaged when using the Scherrer equation for the XRD data. Sonication of the powder resulted in the breakup of >20 μm aggregates into individual particles of approximately 40 nm. These particles are thought to compose a single crystal core with a crystallite size of approximately 28 nm surrounded by a layer of smaller crystallites (approximately 5 nm), which showed quantization during Raman spectroscopy. Separation of the germanium from the magnesium oxide was readily achieved using a simple acid leach, although some oxidation of germanium was evident when using an aqueous leach.

Critical Review of Raman Spectroscopy as a Diagnostic Tool for Semiconductor Microcrystals

1989 ◽  
Vol 164 ◽  
Author(s):  
P.M Fauchet ◽  
I.H. Campbell
Keyword(s):  
Raman Spectroscopy ◽  
Raman Spectrum ◽  
Raman Scattering ◽  
Diagnostic Tool ◽  
Critical Review ◽  
Size Dependence ◽  
Second Order ◽  
First Order ◽  
Surface Vibrations

AbstractRaman scattering is becoming a widely used tool for the characterization of semiconductor microcrystals due to its sensitivity to crystal sizes below a few hundred angstroms. Through detailed analysis of the first order Raman spectrum it is possible to determine the size and shape of microcrystalline grains. First order spectra must be examined with care however, since they are sensitive to other factors including: stress/strain, surface vibrations, mixed amorphous/microcrystalline phases and intragrain defects. Second order Raman spectra are more sensitive to microcrystalline effects than first order spectra. They offer the potential to measure crystal sizes greater than a few hundred angstroms but much work remains to be done to quantify the size dependence of the second order spectra.

Characterization of Ge nanocrystals embedded in SiO2by Raman spectroscopy

2003 ◽  
Vol 19 (2) ◽  
pp. 247-251 ◽  
Author(s):  
U Serincan ◽  
G Kartopu ◽  
A Guennes ◽  
T G Finstad ◽  
R Turan ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Ge Nanocrystals

scholarly journals Characterization of anatase TiO2 nanopowder by variable-temperature Raman spectroscopy

2009 ◽  
Vol 41 (1) ◽  
pp. 67-73 ◽  
Author(s):  
Maja Scepanovic ◽  
M. Grujic-Brojcin ◽  
Z.D. Dohcevic-Mitrovic ◽  
Z.V. Popovic
Keyword(s):  
Raman Spectroscopy ◽  
Grain Size ◽  
Variable Temperature ◽  
Anatase Phase ◽  
Great Influence ◽  
Tio2 Powder ◽  
Phonon Confinement ◽  
Anti Stokes ◽  
Nanosized Tio2

Raman spectroscopy has been used for characterization of commercial nanosized TiO2 powder with declared grain size of 5 nm. The Raman spectra measured in Stokes and anti-Stokes regime confirm the anatase phase of TiO2 powder in temperature range 25-1173K. It is shown that phonon-confinement (due to small grain size) and nonstoichiometry (caused by laser irradiation in vacuum) have a great influence on blueshift and broadening of the main Eg Raman mode at low temperatures, while the influence of the strong anharmonic effect becomes dominant at higher temperatures. The phonon confinement effect decreases due to the crystallite growth at temperatures above 673K.

scholarly journals Behavior of porous silicon crystallite size analized by Raman spectroscopy and phonon confinement model

2015 ◽  
Vol 34 (2) ◽  
pp. 75
Author(s):  
Miguel Angelo Do Amaral Junior ◽  
Neidenêi Gomes Ferreira ◽  
Antonio Fernando Beloto ◽  
Maurício Ribeiro Baldan
Keyword(s):  
Raman Spectroscopy ◽  
Porous Silicon ◽  
Crystallite Size ◽  
Phonon Confinement ◽  
Confinement Model

Physicochemical Characterization of Solid Dispersions of Cefdinir with PVP K-30 and PEG 4000

2010 ◽  
Vol 3 (2) ◽  
pp. 948-956
Author(s):  
Kumar P ◽  
S Kumar ◽  
A Kumar ◽  
M Chander
Keyword(s):  
Solid Dispersions ◽  
Physicochemical Characterization ◽  
Drug Carriers ◽  
Dissolution Properties ◽  
Rate Of Dissolution ◽  
Peg 4000 ◽  
Release Studies ◽  
Crystalline Nature ◽  
Physical Mixtures

The purpose of this study was to prepare and characterize solid dispersions of the antibacterial agent Cefdinir with PEG 4000 and PVP K-30 with a view to improve its dissolution properties. Investigations of the properties of the dispersions were performed using release studies, X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR). The results obtained showed that the rate of dissolution of Cefdinir was considerably improved when formulated in solid dispersions with PVP K-30 and PEG 4000 as compared with pure drug and physical mixtures. The results from XRD studies showed the transition of crystalline nature of drug to amorphous form, while FTIR studies demonstrated the absence of drug-carriers interaction.

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