scholarly journals Thickness-dependent in-plane anisotropy of GaTe phonons

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nguyen The Hoang ◽  
Je-Ho Lee ◽  
Thi Hoa Vu ◽  
Sunglae Cho ◽  
Maeng-Je Seong
Keyword(s):  
Monoclinic Crystal ◽  
Monoclinic Crystal Structure ◽  
Gallium Telluride ◽  
Plane Anisotropy ◽  
Parallel Polarization ◽  
Potential Applications ◽  
Raman Modes ◽  
G 12 ◽  
Polarized Raman ◽  
Different Thickness

AbstractGallium Telluride (GaTe), a layered material with monoclinic crystal structure, has recently attracted a lot of attention due to its unique physical properties and potential applications for angle-resolved photonics and electronics, where optical anisotropies are important. Despite a few reports on the in-plane anisotropies of GaTe, a comprehensive understanding of them remained unsatisfactory to date. In this work, we investigated thickness-dependent in-plane anisotropies of the 13 Raman-active modes and one Raman-inactive mode of GaTe by using angle-resolved polarized Raman spectroscopy, under both parallel and perpendicular polarization configurations in the spectral range from 20 to 300 cm−1. Raman modes of GaTe revealed distinctly different thickness-dependent anisotropies in parallel polarization configuration while nearly unchanged for the perpendicular configuration. Especially, three Ag modes at 40.2 ($${\text{A}}_{\text{g}}^{1}$$ A g 1 ), 152.5 ($${\text{A}}_{\text{g}}^{7}$$ A g 7 ), and 283.8 ($${\text{A}}_{\text{g}}^{12}$$ A g 12 ) cm−1 exhibited an evident variation in anisotropic behavior as decreasing thickness down to 9 nm. The observed anisotropies were thoroughly explained by adopting the calculated interference effect and the semiclassical complex Raman tensor analysis.

scholarly journals Hydrothermal Synthesis and Optical Properties of Magneto-Optical Na3FeF6:Tb3+ Octahedral Particles

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 320
Author(s):  
Zhiguo Zhao ◽  
Xue Li
Keyword(s):  
Light Emission ◽  
Red Light ◽  
Hydrothermal Process ◽  
Functional Materials ◽  
Rare Earth Ions ◽  
Monoclinic Crystal ◽  
One Pot ◽  
Monoclinic Crystal Structure ◽  
Micro Particles ◽  
Potential Applications

Sodium iron hexafluoride (Na3FeF6), as a colorless iron fluoride, is expected to be an ideal host for rare earth ions to realize magneto-optical bi-functionality. Herein, monodispersed terbium ions (Tb3+) doped Na3FeF6 particles are successfully synthesized by a facile one-pot hydrothermal process. X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM) reveal that the Tb3+ doped Na3FeF6 micro-particles with regular octahedral shape can be assigned to a monoclinic crystal structure (space group P21/c). Under ultraviolet light excitation, the Na3FeF6:Tb3+ octahedral particles given orange-red light emission originated from the 5D4→7FJ transitions of the Tb3+ ions. In addition, the magnetism measurement indicates that Na3FeF6:Tb3+ octahedral particles are paramagnetic with high magnetization at room temperature. Therefore, the Na3FeF6:Tb3+ powders may find potential applications in the biomedical field as magnetic-optical bi-functional materials.

scholarly journals Broadband terahertz absorber based on dispersion-engineered catenary coupling in dual metasurface

Nanophotonics ◽  
2018 ◽  
Vol 8 (1) ◽  
pp. 117-125 ◽  
Author(s):  
Ming Zhang ◽  
Fei Zhang ◽  
Yi Ou ◽  
Jixiang Cai ◽  
Honglin Yu
Keyword(s):  
Optical Model ◽  
Dispersion Management ◽  
Bandwidth Extension ◽  
Limited Bandwidth ◽  
Terahertz Absorber ◽  
Simple Strategy ◽  
Management Ability ◽  
Potential Applications ◽  
Resolution Imaging ◽  
Different Thickness

AbstractTerahertz (THz) absorbers have attracted considerable attention due to their potential applications in high-resolution imaging systems, sensing, and imaging. However, the limited bandwidth of THz absorbers limits their further applications. Recently, the dispersion management of metasurfaces has become a simple strategy for the bandwidth extension of THz devices. In this paper, we used the capability of dispersion management to extend the bandwidth of THz absorbers. As a proof-of-concept, a dual metasurface-based reflective device was proposed for broadband near-unity THz absorber, which was composed of two polarization-independent metasurfaces separated from a metallic ground by dielectric layers with different thickness. Benefiting from the fully released dispersion management ability in adjusting the dimensions of the metasurfaces, we obtained an absorbance above 90% in the frequency range from 0.52 to 4.4 THz and the total thickness for the bandwidth approaching the theoretical Rozanov limit. The experimental results verified the ability of dispersion management in designing broadband absorbers and the performance of the designed absorber. The underlying physical mechanism of dispersion management was interpreted in the general equivalent circuit theory and transmission line model. In addition, the catenary optical model was used to further interpret the physics behind this dual metasurface. Moreover, we found that the alignment deviations between the dual metasurface had little impact on the performance of the designed absorber, which indicates that the dual-metasurface does not require center alignment and is easy to be fabricated. The results of this work could broaden the application areas of THz absorbers.

scholarly journals Ultralong free-standing single crystal perovskite microwires with extremely low dark current

2021 ◽  
Author(s):  
Xiangshun Geng ◽  
Qi-Xin Feng ◽  
He Tian ◽  
Weijian Chen ◽  
Xiaoming Wen ◽  
...  
Keyword(s):  
Single Crystal ◽  
Dark Current ◽  
Near Infrared ◽  
Carrier Lifetime ◽  
Low Loss ◽  
Free Standing ◽  
Monoclinic Crystal ◽  
Monoclinic Crystal Structure ◽  
Integrated Optical ◽  
Integrated Optical Waveguide

Abstract Super long perovskite microwires (PMWs) are in a great demand in many fields such as low-loss microcables and integrated optical waveguide. Despite decades of research into PMWs, single crystal PMWs with several centimeters long have not been obtained. Here, ultralong (up to 7.6 centimeters) monoclinic crystal structure CH3NH3PbI3·DMF PMWs have been synthesized. The high-quality microwire exhibits long carrier lifetime of 1775.7 ns. The as-prepared free-standing PMWs can be integrated to any arbitrary substrate and 808 nm near-infrared photodetectors have been successfully demonstrated. The fabricated device shows a high light on/off ratio of 1.79×106 and an extremely low dark current of 2.5 fA at 1 V bias. This work provides a strategy for the solution growth of ultralong microwires.

scholarly journals Characterization of CuO/n-Si heterojunction solar cells produced by thermal evaporation

2018 ◽  
Vol 36 (4) ◽  
pp. 668-674 ◽  
Author(s):  
Reşit Özmenteş ◽  
Cabir Temirci ◽  
Abdullah Özkartal ◽  
Kadir Ejderha ◽  
Nezir Yildirim
Keyword(s):  
Solar Cells ◽  
Band Gap ◽  
Thermal Evaporation ◽  
Front Surface ◽  
Band Gap Energy ◽  
Monoclinic Crystal ◽  
Photovoltaic Properties ◽  
X Ray ◽  
Heterojunction Solar Cells ◽  
Monoclinic Crystal Structure

AbstractCopper(II) oxide (CuO) in powder form was evaporated thermally on the front surface of an n-Si (1 0 0) single crystal using a vacuum coating unit. Structural investigation of the deposited CuO film was made using X-ray difraction (XRD) and energy dispersive X-ray analysis (EDX) techniques. It was determined from the obtained results that the copper oxide films exhibited single-phase CuO properties in a monoclinic crystal structure. Transmittance measurement of the CuO film was performed by a UV-Vis spectrophotometer. Band gap energy of the film was determined as 1.74 eV under indirect band gap assumption. Current-voltage (I-V) measurements of the CuO/n-Si heterojunctions were performed under illumination and in the dark to reveal the photovoltaic and electrical properties of the produced samples. From the I-V measurements, it was revealed that the CuO/n-Si heterojunctions produced by thermal evaporation exibit excellent rectifying properties in dark and photovoltaic properties under illumination. Conversion efficiencies of the CuO/n-Si solar cells are comparable to those of CuO/n-Si produced by other methods described in the literature.

Preparation, Crystal Structure, and Properties of the Lanthanoid Carbides Ln4C7 with Ln = Ho, Er, Tm, and Lu

1996 ◽  
Vol 51 (5) ◽  
pp. 646-654 ◽  
Author(s):  
Ralf Czekalla ◽  
Wolfgang Jeitschko ◽  
Rolf-Dieter Hoffmann ◽  
Helmut Rabeneck
Keyword(s):  
Crystal Structure ◽  
Rietveld Method ◽  
Magnetic Ordering ◽  
Monoclinic Crystal ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Monoclinic Crystal Structure ◽  
Arc Melting ◽  
Structure Factors ◽  
Hydrolysis Of

The isotypic carbides Ln4C7 (Ln = Ho, Er, Tm, Lu) were prepared by arc-melting of the elemental components, followed by annealing at 1300 °C. The positions of the metal and of some carbon atoms of the monoclinic crystal structure of LU4C7 were determined from X-ray powder data, and the last carbon positions were found and refined from neutron powder diffraction data: P21/c, a = 360.4(1), b = 1351.4(3), c = 629.0(2) pm, β = 104.97(2)°, Z = 2, R = 0.026 for 429 structure factors and 15 positional parameters. The structure contains isolated carbon atoms with octahedral lutetium coordination and linear C3-units, with C-C bond lengths of 132(1) and 135(1) pm. This carbide may therefore be considered as derived from methane and propadiene. The hydrolysis of LU4C7 with distilled water yields mainly methane and propine, while the hydrolyses of the corresponding holmium and erbium carbides resulted in relatively large amounts of saturated and unsaturated C2-hydrocarbons in addition to the expected products methane and propine. The structure comprises two-dimensionally infinite NaCl-type building elements, which are separated by the C3-units. It may be described as a stacking variant of a previously reported structure of HO4C7, now designated as the a-modification. The Lu4C7-type β -modification was obtained at higher temperatures. Its structure was refined by the Rietveld method from X-ray powder data to a residual R = 0.037 for 320 F values and 15 positional parameters. Lu4C7 is Pauli paramagnetic; β -HO4C7 and Er4C7 show Curie-Weiss behavior with magnetic ordering temperatures of less than 20 K.

trans-Bis(O-ethylxanthato)bis(triphenylphosphine)ruthenium(III) hexafluorophosphate monohydrate

2006 ◽  
Vol 62 (5) ◽  
pp. m1077-m1078
Author(s):  
Yuko Ohuchi ◽  
Kyoko Noda ◽  
Takayoshi Suzuki ◽  
Kazuo Kashiwabara ◽  
Hideo D. Takagi
Keyword(s):  
Crystal Structure ◽  
Title Compound ◽  
Complex Cation ◽  
Orthorhombic Crystal ◽  
Monoclinic Crystal ◽  
Monoclinic Crystal Structure

In the monoclinic crystal structure of the title compound, trans-[Ru(C3H5OS2)2(C18H15P)2]PF6·H2O, the structure of the RuIII complex cation is very similar to that in the orthorhombic crystal of the nonhydrated complex [Noda, Ohuchi, Hashimoto, Fujiki, Itoh, Iwatsuki, Noda, Suzuki, Kashiwabara & Takagi (2006), Inorg. Chem. 45, 1349–1355]. In the present crystal structure, the P—Ru—P bond axes of the complex cations are aligned parallel to the [101] direction.

About the crystalline structure of vanadates Ca1.5±0.1Mn0.5±0.1V2O7 and Ca1.5Cd0.5V2O7

2018 ◽  
Vol 33 (3) ◽  
pp. 246-255
Author(s):  
V.D. Zhuravlev ◽  
A.P. Tyutyunnik ◽  
A.Yu. Chufarov ◽  
N.I. Lobachevskaja ◽  
Yu. A. Velikodnyi ◽  
...  
Keyword(s):  
Homogeneity Region ◽  
Powder Diffraction Data ◽  
Compound I ◽  
Monoclinic Crystal ◽  
Conventional Solid State Reaction ◽  
Space Group ◽  
X Ray ◽  
Triclinic System ◽  
Monoclinic Crystal Structure ◽  
Calcium Cations

The crystal structures of Ca1.5Mn0.5V2O7 (I) and Ca1.5Cd0.5V2O7 (II) synthesized by the citrate method and by a conventional solid-state reaction, respectively, were determined using X-ray powder diffraction data. It was found that the compound I has a monoclinic crystal structure a = 4.88563(9) Å, b = 11.21279(22) Å, c = 5.69643(11 Å), β = 96.376(7)°, V = 310.132(10) Å3 (space group P21/c), Z = 2). Compound I has a narrow homogeneity region Ca1.5±0.1Mn0.5±0.1V2O7. The vanadate Ca1.5Cd0.5V2O7 crystallizes in the triclinic system with the parameters a = 6.66139(6) Å, b = 6.93019(7) Å, c = 7.02211(6) Å, α = 85.4404(9)°, β = 63.7505(7)°, γ = 82.5515(10)° и V = 288.201(5) Å3 (space group P$\bar 1$, Z = 2). It is one of the formulations of the primary solid solution, formed as a result of the substitution of part of the calcium cations for cadmium cations in Ca2V2O7.

scholarly journals Orientation Identification of the Black Phosphorus with Different Thickness Based on B2g Mode Using a Micro-Raman Spectroscope under a Nonanalyzer Configuration

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5572
Author(s):  
Rubing Li ◽  
Yongchao Shang ◽  
Huadan Xing ◽  
Xiaojie Wang ◽  
Mingyuan Sun ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Research Field ◽  
Black Phosphorus ◽  
New Method ◽  
Important Condition ◽  
Crystalline Orientation ◽  
Parallel Polarization ◽  
Good Consistency ◽  
Non Destructive ◽  
Different Thickness

As an anisotropic material, the unique optoelectronic properties of black phosphorus are obviously anisotropic. Therefore, non-destructive and fast identification of its crystalline orientation is an important condition for its application in optoelectronics research field. Identifying the crystalline orientation of black phosphorus through Ag1 and Ag2 modes under the parallel polarization has high requirements on the Raman system, while in the nonanalyzer configuration, the crystalline orientation of the thick black phosphorus may not be identified through Ag1 and Ag2 modes. This work proposes a new method to identify the crystalline orientation of black phosphorus of different thicknesses. This method is conducted under the nonanalyzer configuration by B2g mode. The results show that B2g mode has a good consistency in the identification of crystalline orientations. In this paper, a theoretical model is established to study the angle-resolved Raman results of B2g mode. The new method can accurately identify the crystalline orientation with different layers of black phosphorus without misidentification.

scholarly journals Growth and Characterizations of Organic NLO Imidazolium L-Tartrate (IMLT) Single Crystal

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Hiral Raval ◽  
B. B. Parekh ◽  
K. D. Parikh ◽  
M. J. Joshi
Keyword(s):  
Second Harmonic ◽  
Structural Parameters ◽  
Diffraction Method ◽  
Nir Spectroscopy ◽  
Optical Parameters ◽  
Dielectric Study ◽  
X Ray Diffraction ◽  
Monoclinic Crystal ◽  
Monoclinic Crystal Structure ◽  
Evaporation Technique

Good quality single crystals of organic imidazolium L-Tartrate (IMLT) are grown up from aqueous solution by slow solvent evaporation technique. Various structural parameters and monoclinic crystal structure have been confirmed using powder X-ray diffraction method. The presence of various functional groups has been identified by ATR-FTIR. UV-Vis-NIR spectroscopy has shown more than 60% of optical transparency with the lower UV cutoff at 245nm. The optical band gap value of the material is evaluated to be 4.8 eV. Other optical parameters such as refractive index, optical and electrical conductivity, Urbach energy, extinction coefficient, and optical and electrical susceptibility have been evaluated from transmission spectrum data. The above essential parameters manifest appropriate usage of IMLT as an NLO material. The thermogravimetric analysis indicates high thermal stability of material up to 214°C. Apart from that, the dielectric study at various temperatures confirms decrement of dielectric constant and dielectric loss at higher frequencies. The efficiency of Second Harmonic Generation (SHG) is found to be 3.5 times that of the KDP crystals. A range of analysis suggests suitability and potentiality of IMLT crystal for various optoelectronic applications.

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