Optical Properties

Cerdeira, F.

doi:10.1016/s0080-8784(08)62583-1

Cited by 4 publications

(4 citation statements)

References 102 publications

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“…The study of the interaction between electromagnetic radiation and any materials can be interpreted from the optical properties. It is crucial for industrial as well as scientific applications in the fields of laser technology, mirror production, optical windows, photovoltaic devices, and many more. − In the current work, to examine the optical properties of Na 2 GeO 3 , we have calculated the optical dielectric constant (ϵ), absorption coefficient (α), and refractive index (η) under different compressive pressures. Since the observed results are most prominent along the x -axis, interpretation and analysis are done for the x -axis in this work.…”

Section: Resultsmentioning

confidence: 99%

A Thorough Investigation of Electronic, Optical, Mechanical, and Thermodynamic Properties of Stable Glasslike Sodium Germanate under Compressive Hydrostatic Pressure: Ab Initio Study

et al. 2023

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In this paper, we have tried to elucidate the variation of structural, electronic, and thermodynamic properties of glasslike Na 2 GeO 3 under compressive isotropic pressure within a framework of density functional theory (DFT). The result shows stable structural (orthorhombic → tetragonal) and electronic (indirect → direct) phase transitions at P ∼ 20 GPa. The electronic band gap transition plays a key role in the enhancement of optical properties. The results of the thermodynamic properties have shown that Na 2 GeO 3 follows Debye's lowtemperature specific heat law and the classical thermodynamic of the Dulong−Petit law at high temperature. The pressure sensitivity of the electronic properties led us to compute the piezoelectric tensor (both in relaxed and clamped ions). We have observed significant electric responses in the form of a piezoelectric coefficient under applied pressure. This property suggested that Na 2 GeO 3 could be a potential material for energy harvest in future energy-efficient devices. As expected, Na 2 GeO 3 becomes harder and harder under compressive pressure up to the phase transition pressure (∼20 GPa) which can be read from Pugh's ratio (k H ) > 1.75, however, at pressures above 20 GPa k H < 1.75, which may be due to the formation of fractures at high pressure.

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Section: Resultsmentioning

confidence: 99%

A Thorough Investigation of Electronic, Optical, Mechanical, and Thermodynamic Properties of Stable Glasslike Sodium Germanate under Compressive Hydrostatic Pressure: Ab Initio Study

et al. 2023

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“…The first strong peak corresponds to the so-called no-phonon recombination line, which is placed at 1.10-1.11 eV, and is originated from the silicon substrate. 16 The second ͑phonon-assisted͒ line at 1.05-1.08 eV is caused by the transverse optical/acoustical phonon replica from the Si bandgap line in the Si 1−x Ge x layers. 17,18 The studied samples also exhibit PL peaks at around 0.82 and 0.85 eV ͑Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Changes in distribution of defect states in bandgap of the Si 0.7 Ge 0.3 layers are expected to be the main reason for the observed variation in the PL line strengths. In particular, intensity of these PL lines from Si 1−x Ge x layers normally increases with the density of the relatively deep dislocation-related N͑E͒ peaks [15][16][17][18] but could be suppressed by nonradiative recombination via hole and electron traps.…”

Section: Methodsmentioning

confidence: 99%

“…The most probable origin of the lines with E PL = 1.10-1.11 and E PL = 1.05-1.08 eV is electron transitions ͑direct of phonon-assisted͒ between delocalized states just above the conduction band bottom ͑E c ͒ of the silicon, and localized states in the vicinity of its valence band top, E v . 16 The D 2 line is likely caused by the radiative electron recombination within the Si 0.7 Ge 0.3 layers. In such a case, all the above-mentioned dislocation-related states at E−E v Х 0.35, 0.51, and 0.63 eV ͑see the previous section͒ could be the terminal states for the electron transition, and the intensity of the D 2 line is expected to be roughly proportional to the intensity of a dislocation-related peak.…”

Section: Methodsmentioning

confidence: 99%

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Morphology, Defect Spectrum, and Photoluminescence of Thin Si[sub 0.7]Ge[sub 0.3] Layers

Ligatchev

Wong

2005

J. Electrochem. Soc.

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Results of experimental investigations of atomic structure and morphology of thin ͑8-30 nm͒ ͗100͘-oriented undoped and borondoped Si 0.7 Ge 0.3 layers, deposited by atmospheric pressure chemical vapor deposition at 650°C on silicon wafers, were presented in the first part of this paper. The second part is devoted to studies of influence of structural and morphological features of these films on their spectra of defect states N͑E͒ and photoluminescence ͑PL͒. The N͑E͒ distribution in the bandgap of our layers has been investigated with deep-level transient spectroscopy technique. The standard D1-D3 and dislocation-related defect levels were observed in the samples. The N͑E͒ spectrum is not notably dependent on morphological features of the undoped layers, but defect density reduces significantly in the whole studied range of their energy at the layers doping with boron. The PL was excited with an argon ion ͑Ar + ͒ laser at the sample temperature of about 5 K. Two PL peaks with energies of 1.10 and 1.08 eV, as well as PL lines at 0.82-0.85 eV ͑D 2 ͒, are detected in all studied samples. These PL features are originated from the no-phonon line of the Si substrate, as well as from phonon-assisted lines and dislocation-related defects of the Si 0.7 Ge 0.3 layers, respectively. The intensities of the observed PL lines are influenced by the layer thickness, morphology, and doping. Possible mechanisms of interrelations between the films morphology, defect spectrum N͑E͒, and the PL line strengths are discussed.

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Influence of surface roughness and internal strain on defect spectrum and intensity of low-temperature photoluminescence of thin Si1−xGex layers

Ligatchev

Wong

Yoon

2004

Journal of Applied Physics

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Microstructure, surface roughness, morphology, defect spectrum, and low-temperature photoluminescence of thin (10–125 nm) strained Si1−xGex layers (0.1⩽x⩽0.3), deposited by chemical vapor deposition (CVD) at 650 °C on silicon wafers have been studied. Nominally undoped layers with crystalline orientations of 〈100〉 and 〈111〉 have been investigated. Local strain within the layers was estimated from x-ray diffraction data. It decreases with the layer thickness in the 〈100〉-oriented samples, but rises in the 〈111〉-oriented ones. Nanoscale (∼10–30 nm) and microscale (∼0.2–1 μm) morphologies have been found on the surface of the Si1−xGex layers by atomic-force microscopy. The lateral sizes of the morphologies and surface roughness depend on the thickness, germanium concentration x, and crystalline orientation of the layers. The spectrum of defect states N(E) in the band gap of these samples has been experimentally studied by the deep-level-transient-spectroscopy (DLTS) technique. The standard D1(P1), D2, P3, and P4 defect peaks were observed. The N(E) spectrum is strongly influenced by germanium concentration, crystalline orientation, and surface roughness of the films (especially at Ec−E<0.4 eV). Photoluminescence (PL) was excited with argon ion (Ar+) laser at a sample temperature of about 5 K. Both “no-phonon” and phonon-assisted PL peaks around 1.1 eV, as well as a strong peak at 0.80 eV were observed. These peaks originated, respectively, from the no-phonon line from the Si substrate, transverse optical/acoustical phonon replica and dislocation-related Si1−xGex band, D1. Intensities of these PL peaks are influenced by the layer thickness, internal strain, surface roughness, and germanium concentration x. Possible mechanisms of relationship between the local strain, film roughness, the defect spectrum N(E), and the D1 line strength are discussed.

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Optical Properties

Cited by 4 publications

References 102 publications

A Thorough Investigation of Electronic, Optical, Mechanical, and Thermodynamic Properties of Stable Glasslike Sodium Germanate under Compressive Hydrostatic Pressure: Ab Initio Study

A Thorough Investigation of Electronic, Optical, Mechanical, and Thermodynamic Properties of Stable Glasslike Sodium Germanate under Compressive Hydrostatic Pressure: Ab Initio Study

Morphology, Defect Spectrum, and Photoluminescence of Thin Si[sub 0.7]Ge[sub 0.3] Layers

Influence of surface roughness and internal strain on defect spectrum and intensity of low-temperature photoluminescence of thin Si1−xGex layers

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