The one phonon Raman spectrum in microcrystalline silicon
TL;DR: In this paper, a relaxation in the q-vector selection rule for the excitation of the Raman active optical phonons was proposed to increase the red shift and broadening of the signal from microcrystalline silicon films.
About: This article is published in Solid State Communications.The article was published on 1981-08-01. It has received 2059 citations till now. The article focuses on the topics: Raman spectroscopy & Dispersion relation.
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TL;DR: In this article, the effect of the exact shape of the microcrystal and the relationship between the width, shift and asymmetry of the Raman line is calculated and is in good agreement with available experimental data.
1,957 citations
TL;DR: The photoluminescence properties of porous silicon have attracted considerable research interest since their discovery in 1990 as discussed by the authors, which is due to excitonic recombination quantum confined in Si nanocrystals which remain after the partial electrochemical dissolution of silicon.
1,261 citations
TL;DR: In this article, the authors provide a basic understanding of the information micro-Raman Spectroscopy (mRS) may yield when applied to nanomaterials, a generic term for describing nano-sized crystals and bulk homogeneous materials with a structural disorder at the nanoscale.
905 citations
892 citations
TL;DR: In this article, the basic lattice vibrations of 2D transition metal dichalcogenide (TMD) nanosheets are discussed, including highfrequency optical phonons, interlayer shear and layer breathing phonons.
Abstract: Two-dimensional (2D) transition metal dichalcogenide (TMD) nanosheets exhibit remarkable electronic and optical properties. The 2D features, sizable bandgaps and recent advances in the synthesis, characterization and device fabrication of the representative MoS2, WS2, WSe2 and MoSe2 TMDs make TMDs very attractive in nanoelectronics and optoelectronics. Similar to graphite and graphene, the atoms within each layer in 2D TMDs are joined together by covalent bonds, while van der Waals interactions keep the layers together. This makes the physical and chemical properties of 2D TMDs layer-dependent. In this review, we discuss the basic lattice vibrations of 2D TMDs from monolayer, multilayer to bulk material, including high-frequency optical phonons, interlayer shear and layer breathing phonons, the Raman selection rule, layer-number evolution of phonons, multiple phonon replica and phonons at the edge of the Brillouin zone. The extensive capabilities of Raman spectroscopy in investigating the properties of TMDs are discussed, such as interlayer coupling, spin–orbit splitting and external perturbations. The interlayer vibrational modes are used in rapid and substrate-free characterization of the layer number of multilayer TMDs and in probing interface coupling in TMD heterostructures. The success of Raman spectroscopy in investigating TMD nanosheets paves the way for experiments on other 2D crystals and related van der Waals heterostructures.
825 citations
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TL;DR: In this article, an expression for the lifetime of an optical phonon decaying into two acoustical phonons, and its temperature dependence, was derived from perturbation theory, and the strength of the interaction was expressed in terms of the Gruneisen constant and the effect of a strain, equivalent to the instantaneous strain of a optical mode on the frequency spectrum of a linear chain with alternating force constants.
Abstract: An expression is derived from perturbation theory for the lifetime of an optical phonon decaying into two acoustical phonons, and its temperature dependence. The strength of the interaction is expressed in terms of the Gr\"uneisen constant and the effect of a strain, equivalent to the instantaneous strain of an optical mode, on the frequency spectrum of a linear chain with alternating force constants. This interaction depends on the ratio of the acoustical and optical mode frequencies at the zone boundary. Fitting the theory to silicon, the optical mode at k = 0 has a calculated half-width at 300\ifmmode^\circ\else\textdegree\fi{}K of about 1.2% of its frequency. This result is compared with experimental data.
776 citations
TL;DR: Raman scattering from single-crystal Si and Ge at 300\ifmmode^\circ\else\text degree\fi{}K was measured using an argon laser as the exciting source as discussed by the authors.
Abstract: Raman scattering from single-crystal Si and Ge at 300\ifmmode^\circ\else\textdegree\fi{}K was measured using an argon laser as the exciting source The first-order Raman spectrum yields energies for the $k\ensuremath{\approx}0$ optical modes of 5202\ifmmode\pm\else\textpm\fi{}05 ${\mathrm{cm}}^{\ensuremath{-}1}$ for Si and 3007\ifmmode\pm\else\textpm\fi{}05 ${\mathrm{cm}}^{\ensuremath{-}1}$ for Ge These values are in reasonable agreement with other determinations The full widths at half-intensity were found to be 46 ${\mathrm{cm}}^{\ensuremath{-}1}$ for Si and 53 ${\mathrm{cm}}^{\ensuremath{-}1}$ for Ge These values are compared with theoretical predictions A Raman band was observed in Si at 950 ${\mathrm{cm}}^{\ensuremath{-}1}$ which is attributed to second-order scattering and is compared with theoretical predictions
534 citations
TL;DR: In this article, an adiabatic bond charge model (BCM) for the lattice dynamics of diamond-type crystals is developed, which unifies elements of earlier models by Phillips and Martin, Keating, and Cochran.
Abstract: An adiabatic bond charge model (BCM) for the lattice dynamics of diamond-type crystals is developed. Our BCM unites elements of earlier models by Phillips and Martin, Keating, and Cochran. Four types of interactions are used: (a) central ion-ion forces, (b) Coulomb interactions of the ions and bond charges (BC's), (c) central ion-BC forces, and (d) bond-bending forces. These interactions represent the metal-like (a) and covalent (b)-(d) part of the crystal bonding. The phonon dispersion curves for Si, Ge, and $\ensuremath{\alpha}\ensuremath{-}\mathrm{Sn}$ are calculated using only four disposable parameters; for diamond, five parameters are employed. For all crystals, very good agreement with experiment is obtained. In particular, the typical flattening of the transverse acoustic phonons in the semiconducting materials is understood as a consequence of the adiabatic motion of the BC's, when the effective ion-BC coupling (b)+(c) is weak compared to the bond-bending forces (d). In an alternative representation of the BCM, the interactions (b) and (c) are replaced by central and noncentral ion-BC-ion potentials along one bond. The remaining long-range part of the Coulomb forces is unimportant; therefore, all essential interactions of the BCM are of very short range. Furthermore, the interaction parameters follow clear trends from diamond to $\ensuremath{\alpha}\ensuremath{-}\mathrm{Sn}$: type (a) increases, whereas types (b)-(d) decrease, especially the ion-BC coupling tends to vanish toward $\ensuremath{\alpha}\ensuremath{-}\mathrm{Sn}$.
510 citations
TL;DR: In this article, the authors measured the linewidth and the frequency of the q = 0 optical phonon in silicon over the temperature range of 20-770, and deduced an absolute halfwidth of 2.1
Abstract: We have measured the linewidth and the frequency of the q=0 optical phonon in silicon over the temperature range of 20-770\ifmmode^\circ\else\textdegree\fi{}K. The temperature dependence of the linewidth has been interpreted as arising from the decay of the optical phonon to two LA phonons at half the optical frequency. From the observed temperature variation, we deduce an absolute half-width $\ensuremath{\Gamma}$ of 2.1 ${\mathrm{cm}}^{\ensuremath{-}1}$ at 0\ifmmode^\circ\else\textdegree\fi{}K. This value is considerably smaller than that obtained theoretically by Cowley on the basis of numerical calculations which include decay to phonons throughout the Brillouin zone. His numerical calculations also predict a temperature dependence of the linewidth which does not agree with experiment. However, the observed change in frequency with temperature correlates very well with Cowley's theory. We have also studied the relative intensities of Stokes and anti-Stokes components of Raman spectra. The observed temperature dependence of the relative intensities is compared with that predicted on the basis of the Bose-Einstein population factor for the optical phonon.
484 citations
TL;DR: In this paper, the amorphous form of Si and several related, tetrahedrally bonded semiconductors (Ge, GaAs, GaP, InSb) were studied in the presence of Raman scattering.
Abstract: Raman scattering has been studied in the amorphous form of Si and several related, tetrahedrally bonded semiconductors (Ge, GaAs, GaP, InSb). All vibrational modes of the material can take part in the scattering process, and the Raman spectrum is a measure of the density of vibrational states. The amorphous phases are found to have vibrational spectra very similar to the corresponding crystals, reflecting the similarity in short-range order of the two phases.
306 citations