scholarly journals Micro-Raman Mapping of the Strain Field in GaAsN/GaAsN:H Planar Heterostructures: A Brief Review and Recent Evolution

2019 ◽  
Vol 9 (22) ◽  
pp. 4864
Author(s):  
Giulotto ◽  
Geddo
Keyword(s):  
Strain Field ◽  
Strain State ◽  
Phonon Frequency ◽  
Longitudinal Optical ◽  
Longitudinal Optical Phonon ◽  
Strain Behavior ◽  
Irradiation Intensity ◽  
Specific Geometry ◽  
Optical Phonon Frequency ◽  
Low Levels

Raman scattering is an effective tool for the investigation of the strain state of crystalline solids. In this brief review, we show how the analysis of the GaAs-like longitudinal optical phonon frequency allowed to map the strain behavior across interfaces in planar heterostructures consisting of GaAsN wires embedded in GaAsN:H matrices. Moreover, we recently showed how the evolution of the longitudinal optical frequency with increasing H dose strongly depends on polarization geometry. In a specific geometry, we observed a relaxation of the GaAs selection rules. We also present new results which demonstrate how laser irradiation intensity–even at low levels–may affect the line shape of the GaAs-like spectral features in GaAsN hydrogenated materials.

scholarly journals Enhancing Spectral Reflection through Controlled Phase Distribution Using Doped Polar-Dielectric Metasurfaces

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2007
Author(s):  
Mohsen Janipour ◽  
Kürşat Şendur
Keyword(s):  
Optical Properties ◽  
Doping Concentration ◽  
Phonon Frequency ◽  
Phase Distribution ◽  
Longitudinal Optical ◽  
Longitudinal Optical Phonon ◽  
Sic Nanoparticles ◽  
Polar Dielectric ◽  
Optical Phonon Frequency ◽  
The Impact

Controlling the phase distribution of wavefronts using optical metasurfaces has led to interesting optical properties and applications. Here, we explore the control of phase distribution through polar-dielectric metasurfaces composed of doped SiC nanosphere arrays. We investigate the impact of doping concentration on the optical properties of SiC nano-spheres. Our results indicate that increasing the doping of SiC nanoparticles influenced electric dipolar resonances, whereas it did not change the dipolar resonances. Using this concept, we numerically studied the extension of this idea to form metasurface arrays of single, dimer and linear trimers of the doped SiC nano-spheres. Using different doping schemes, we studied the improvement of the reflectivity at frequencies greater than the longitudinal optical phonon frequency.

Electron–Interface–Phonon Interaction and Magnetopolaronic Impurity Transitions in Quantum Wells

1997 ◽  
Vol 11 (08) ◽  
pp. 991-1008 ◽  
Author(s):  
R. Chen ◽  
D. L. Lin
Keyword(s):  
Quantum Wells ◽  
Optical Phonon ◽  
Phonon Frequency ◽  
Transition Energy ◽  
Bulk Sample ◽  
Longitudinal Optical ◽  
Longitudinal Optical Phonon ◽  
Phonon Modes ◽  
Phonon Interaction ◽  
Double Heterostructure

The polaronic effect on the hydrogenic 1s–2p+ transition energy of a donor impurity located at the quantum well center in a double heterostructure is studied theoretically in detail. The electron–optical–phonon interaction Hamiltonian is derived on the basis of eigenmodes of lattice vibrations supported by the double heterostructure. Both the confined and interface phonon modes are included in the electron–phonon coupling. The transition energy is calculated as a function of the applied magnetic field for GaAs/Al 1-x Ga x As samples of well -widths d=125 Å, 210 Å and 450 Å by the second-order perturbation. Wide transition gaps are predicted around the two-level and three-level resonances for all three cases. It is found that the transition gap narrows with the increasing well-width but remains larger than the LO and TO phonon frequency difference for d=450 Å as is observed. We also perform the same calculation by assuming that the confined electron interacts with three-dimensional and two-dimensional phonon modes. The transition energy spectra from these calculations appear to be similar to those for a bulk sample, the spectrum splits at the resonance with the longitudinal optical phonon frequency only. From comparisons of our results with these calculations as well as with experiments, it is conclusively established that the wide gap of transition energy is solely due to the interface modes.

Application of the nonuniform-field treatment to the infrared properties of LiF

1969 ◽  
Vol 47 (1) ◽  
pp. 51-64 ◽  
Author(s):  
A. J. Beaulieu
Keyword(s):  
Thin Films ◽  
Optical Phonon ◽  
Phonon Frequency ◽  
Quantitative Agreement ◽  
Longitudinal Optical ◽  
Optical Frequency ◽  
Nonuniform Field ◽  
Optical Phonon Frequency ◽  
Experimental Values ◽  
Comparison Of The Results

The "nonuniform-field treatment" developed earlier for infinitely thick crystals is applied to the LiF crystal. Comparison with experimental results both at 45° and at small angles of incidence gives good quantitative agreement only when the ratio of the longitudinal optical frequency to the transverse optical frequency is assumed to be 1.7 instead of 2.2 as predicted by the Lyddane–Sach–Teller relation. An extension of the treatment to thin films is presented and the comparison of the results with Berreman's experimental values indicates that the asymmetry and the amplitude of the features which could not be explained before can be predicted in terms of the nonuniform-field treatment, again provided the optical phonon frequency ratio is 1.7.

Strain Shift Coefficients for Phonons in Si-Ge Heterostructures

1991 ◽  
Vol 239 ◽  
Author(s):  
J.-M. Baribeau ◽  
D. J. Lockwood
Keyword(s):  
Molecular Beam ◽  
Composition Dependence ◽  
Vibration Mode ◽  
Phonon Frequency ◽  
Longitudinal Optical ◽  
Stress Factor ◽  
Double Crystal ◽  
Raman Scattering Spectroscopy ◽  
X Ray ◽  
Shift Coefficient

ABSTRACTStrain shift coefficient measurements for longitudinal optical phonons in molecular beam epitaxy grown metastable pseudomorphic Si1−xGex layers on (100) Si (0 < x < 0.35) and Ge (0.80 < x < 1) are reported. Strain in partially relaxed annealed specimens was obtained by double-crystal x-ray diffractometry and the corresponding strain phonon shift was measured by Raman scattering spectroscopy. For epilayers grown on Si it was found that the epilayer Si-Si phonon frequency varies linearly with strain. The magnitude of the strain shift coefficient b however showed a small composition dependence varying from b ≈ -700 cm-1 at x = 0 to b ≈ -950 cm-1 at x = 0.35, corresponding to a stress factor τ = 0.40 + 0.57x: + 0.13x2 cm-1/kbar. For the Ge-Ge vibration mode in epilayers grown on Ge, b decreased from ∼-425 cm-1 at x = 1 to ∼-500 cm-1 at x = 0.8, corresponding to a stress factor τ ≈ 0.52 – 0.14x - 0.08x2 cm-1/kbar.

Reducing exciton–longitudinal optical phonon coupling with increasing Mg incorporation in MgZnO powders

2007 ◽  
Vol 102 (12) ◽  
pp. 123504 ◽  
Author(s):  
Ching-Ju Pan ◽  
Kuo-Feng Lin ◽  
Wei-Tse Hsu ◽  
Wen-Feng Hsieh
Keyword(s):  
Optical Phonon ◽  
Longitudinal Optical ◽  
Longitudinal Optical Phonon ◽  
Phonon Coupling

The effect of low temperature coating and annealing on structural and optical properties of CdSe/CdS core/shell QDs

2016 ◽  
Vol 55 (4) ◽  
Author(s):  
Maya Isarov ◽  
N. Grumbach ◽  
Georgy I. Maikov ◽  
Jenya Tilchin ◽  
Youngjin Jang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Interface Layer ◽  
Longitudinal Optical ◽  
Band Gap Energy ◽  
Longitudinal Optical Phonon ◽  
Core Shell ◽  
Temperature Dependent ◽  
Structural And Optical Properties ◽  
Wide Range ◽  
Temperature Dependent Properties

This paper presents the optical temperature dependent properties, over a wide range of temperatures from 4 to 300 K, of new CdSe/CdS core/shell colloidal quantum dots (QDs) with varying shell thickness coated and annealed at low temperature. It was demonstrated that low temperature coating and annealing processes enhanced the photoluminescence (PL) quantum yield accompanied by variation in the QDs structure, formation of an alloyed interface layer, suppression of the number of defects at the CdSe/CdS interface, band gap energy red-shift, narrowing of CdS longitudinal optical phonon band, and decrease of the PL inhomogeneous broadening parameter.

scholarly journals Depth Profiling of Ion-Implanted 4H–SiC Using Confocal Raman Spectroscopy

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 131
Author(s):  
Ying Song ◽  
Zongwei Xu ◽  
Tao Liu ◽  
Mathias Rommel ◽  
Hong Wang ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Epitaxial Layer ◽  
Depth Profiling ◽  
Longitudinal Optical ◽  
Longitudinal Optical Phonon ◽  
Objective Lens ◽  
Substrate Layer ◽  
Depth Analysis ◽  
Confocal Raman ◽  
Ion Implanted

For silicon carbide (SiC) processed by ion-implantation, dedicated test structure fabrication or destructive sample processing on test wafers are usually required to obtain depth profiles of electrical characteristics such as carrier concentration. In this study, a rapid and non-destructive approach for depth profiling is presented that uses confocal Raman microscopy. As an example, a 4H–SiC substrate with an epitaxial layer of several micrometers thick and top layer in nanoscale that was modified by ion-implantation was characterized. From the Raman depth profiling, longitudinal optical (LO) mode from the epitaxial layer and longitudinal optical phonon-plasmon coupled (LOPC) mode from the substrate layer can be sensitively distinguished at the interface. The position profile of the LOPC peak intensity in the depth direction was found to be effective in estimating the thickness of the epitaxial layer. For three kinds of epitaxial layer with thicknesses of 5.3 μm, 6 μm, and 7.5 μm, the average deviations of the Raman depth analysis were −1.7 μm, −1.2 μm, and −1.4 μm, respectively. Moreover, when moving the focal plane from the heavily doped sample (~1018 cm−3) to the epitaxial layer (~1016 cm−3), the LOPC peak showed a blue shift. The twice travel of the photon (excitation and collection) through the ion-implanted layer with doping concentrations higher than 1 × 1018 cm−3 led to a difference in the LOPC peak position for samples with the same epitaxial layer and substrate layer. Furthermore, the influences of the setup in terms of pinhole size and numerical aperture of objective lens on the depth profiling results were studied. Different from other research on Raman depth profiling, the 50× long working distance objective lens (50L× lens) was found more suitable than the 100× lens for the depth analysis 4H–SiC with a multi-layer structure.

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