Independence verification and decoupling measurement of Raman shift coefficients with coexisting temperature and stress

2022 ◽  
Vol 184 ◽  
pp. 122279
Author(s):  
Yupu Li ◽  
Aoran Fan ◽  
Yufeng Zhang ◽  
Xing Zhang
Keyword(s):  
Raman Shift

scholarly journals Ultrafast carbothermal reduction of silica to silicon using a CO2 laser beam

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Seok-Ho Maeng ◽  
Hakju Lee ◽  
Min Soo Park ◽  
Suhyun Park ◽  
Jaeki Jeong ◽  
...  
Keyword(s):  
Carbon Black ◽  
Laser Beam ◽  
Carbothermal Reduction ◽  
Gas Flow ◽  
Crystalline Silicon ◽  
Reduction Process ◽  
Reaction Chamber ◽  
Raman Shift ◽  
Influence Of Process Parameters ◽  
Laser Beam Intensity

AbstractWe report the extraction of silicon via a carbothermal reduction process using a CO2 laser beam as a heat source. The surface of a mixture of silica and carbon black powder became brown after laser beam irradiation for a few tens of seconds, and clear peaks of crystalline silicon were observed by Raman shift measurements, confirming the successful carbothermal reduction of silica. The influence of process parameters, including the laser beam intensity, radiation time, nitrogen gas flow in a reaction chamber, and the molar ratios of silica/carbon black of the mixture, on the carbothermal reduction process is explained in detail.

scholarly journals Transport Properties and High Temperature Raman Features of Heavily Gd-Doped Ceria

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4148 ◽  
Author(s):  
Cristina Artini ◽  
Sabrina Presto ◽  
Sara Massardo ◽  
Marcella Pani ◽  
Maria Maddalena Carnasciali ◽  
...  
Keyword(s):  
Solid Oxide Fuel Cells ◽  
Oxygen Vacancies ◽  
Arrhenius Plot ◽  
Solid Oxide ◽  
Raman Shift ◽  
Threshold Temperature ◽  
Doped Ceria ◽  
Lower Activation ◽  
Slope Change ◽  
Heavily Doped

Transport and structural properties of heavily doped ceria can reveal subtle details of the interplay between conductivity and defects aggregation in this material, widely studied as solid electrolyte in solid oxide fuel cells. The ionic conductivity of heavily Gd-doped ceria samples (Ce1−xGdxO2−x/2 with x ranging between 0.31 and 0.49) was investigated by impedance spectroscopy in the 600–1000 K temperature range. A slope change was found in the Arrhenius plot at ~723 K for samples with x = 0.31 and 0.34, namely close to the compositional boundary of the CeO2-based solid solution. The described discontinuity, giving rise to two different activation energies, points at the existence of a threshold temperature, below which oxygen vacancies are blocked, and above which they become free to move through the lattice. This conclusion is well supported by Raman spectroscopy, due to the discontinuity revealed in the Raman shift trend versus temperature of the signal related to defects aggregates which hinder the vacancies movement. This evidence, observable in samples with x = 0.31 and 0.34 above ~750 K, accounts for a weakening of Gd–O bonds within blocking microdomains, which is compatible with the existence of a lower activation energy above the threshold temperature.

Molecular Vibration Theoretical Analysis of Two-Dimensional Photoelectric Conversion Material WSe2

2018 ◽  
Vol 765 ◽  
pp. 16-23
Author(s):  
Rui Zhang ◽  
Hong Bo Li ◽  
Guo Qiang Hao ◽  
Wen Bo Liu ◽  
Xiao Jun Ye ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Density Functional ◽  
Molecular Vibration ◽  
Raman Shift ◽  
Vibration Modes ◽  
Photoelectric Conversion ◽  
Functional Theory ◽  
Conversion Materials ◽  
Direct Band ◽  
New Generation

Monolayer WSe2is flexible, nearly transparent and direct band-gap semiconductor with the potential to be new generation thin film photoelectric conversion materials. The molecule vibration modes of monolayer and bulk WSe2was analyzed by factor group and the phonons dispersion and vibration frequency was calculated by first-principles based on density functional theory. Furthermore, the comparison between the above calculations and experiment values of Raman shift of monolayer and bulk WSe2was made to verify the accuracy of theoretical analysis and theoretically explain the differences of monolayer and bulk WSe2materials in Raman spectra.

Residual Stress Measurement and Simulation of 3C-SiC Single and Poly Crystal Cantilevers

2010 ◽  
Vol 645-648 ◽  
pp. 865-868 ◽  
Author(s):  
Ruggero Anzalone ◽  
Massimo Camarda ◽  
Daniel Alquier ◽  
M. Italia ◽  
Andrea Severino ◽  
...  
Keyword(s):  
Experimental Data ◽  
Theoretical Study ◽  
Stress Measurement ◽  
Bulk Material ◽  
Raman Shift ◽  
Silicon Substrates ◽  
Free Standing ◽  
Element Analysis ◽  
Micro Fabrication ◽  
Sic Films

The fabrication of SiC MEMS-based sensors requires new processes able to realize microstructures on either bulk material or on the SiC surface. The hetero-epitaxial growth of 3C-SiC on silicon substrates allows one to overcome the traditional limitations of SiC micro-fabrication. In this work a comparison between single crystal and poly crystal 3C-SiC micro-machined structures will be presented. The free-standing structures realized (cantilevers and membrane) are also a suitable method for residual field stress investigation in 3C-SiC films. Measurement of the Raman shift indicates that the mono and poly-crystal 3C-SiC structures release the stress in different ways. Finite element analysis was performed to determine the stress field inside the films and provided a good fit to the experimental data. A comprehensive experimental and theoretical study of 3C-SiC MEMS structures has been performed and is presented.

Bond Nature of Raman Shift in CdSexS1–x Nanocrystals: A Bond-by-Bond Approach

2019 ◽  
Vol 123 (35) ◽  
pp. 21751-21756
Author(s):  
Yukun Gao ◽  
Penggang Yin
Keyword(s):  
Raman Shift

Compact and Efficient HFCVD for Electronic Grade Diamond and Related Materials

2009 ◽  
Vol 1203 ◽  
Author(s):  
R. Vispute ◽  
Andrew Seiser ◽  
Geun Lee ◽  
Jaurette Dozier ◽  
Jeremy Feldman ◽  
...  
Keyword(s):  
Diamond Film ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Deposition Efficiency ◽  
Raman Shift ◽  
Compositional Variation ◽  
Force Microscopy ◽  
Substrate Rotation ◽  
Sample Rotation ◽  
Hot Filament

AbstractA compact and efficient hot filament chemical vapor deposition system has been designed for growing electronic-grade diamond and related materials. We report here the effect of substrate rotation on quality and uniformity of HFCVD diamond films on 2” wafers, using two to three filaments with power ranging from 500 to 600 Watt. Diamond films have been characterized using x-ray diffraction, Raman Spectroscopy, scanning electron microscopy and atomic force microscopy. Our results indicate that substrate rotation not only yields uniform films across the wafer, but crystallites grow larger than without sample rotation. Well-faceted microcrystals are observed for wafers rotated at 10 rpm. We also find that the Raman spectrum taken from various locations indicate no compositional variation in the diamond film and no significant Raman shift associated with intrinsic stresses. Results are discussed in the context of growth uniformity of diamond film to improve deposition efficiency for wafer-based electronic applications.

scholarly journals Rare earths (Ce, Eu) molar concentration-dependent of the structural and optical properties of CBD-CdS nanofilms

2018 ◽  
Vol 64 (3) ◽  
pp. 240 ◽  
Author(s):  
Joel Diaz-Reyes ◽  
Jorge Indalecio Contreras-Rascón ◽  
Mariana Enelia Linares-Avilés ◽  
José Francisco Sánchez-Ramírez ◽  
José Eladio Flores-Mena ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Rare Earths ◽  
Room Temperature ◽  
Longitudinal Mode ◽  
Radiative Transition ◽  
Molar Concentration ◽  
Raman Shift ◽  
Interstitial Oxygen ◽  
Synthesis Time ◽  
X Ray

It presents the characterization of rare earths (Eu,Ce)-doped CdS nanofilms that were synthesised by the growth technique chemical bath deposition (CBD) at the reservoir temperature of 70±2°C. The doping of CdS with rare earths is performed by varying the synthesis time from 60 to 135 min. The rare earths molar concentration was range from 0.0≤x≤3.5, which was determined by energy dispersive X-ray spectroscopy. X-ray diffraction (XRD) analysis and Raman scattering reveal that CdS nanofilms showed the zinc blende (ZB) crystalline phase. The CdS average nanocrystal size was ranged from 1.84 to 2.67 nm that was determined by the Debye–Scherrer equation from ZB (111) direction, which was confirmed by transmission electron microscopy. Raman scattering shows that the lattice dynamics is characteristic of bimodal behaviour and the multipeaks adjust of the first optical longitudinal mode for the (Eu,Ce)-doped CdS, which denotes the Raman shift of the characteristic peak about 305 cm−1 of the CdS nanocrystals. The CdS nanofilms exhibit a direct bandgap that slightly decreases with increasing doping, from 2.50 to 2.42 eV, which was obtained by room temperature transmittance. The room-temperature photoluminescence of CdS shows the band-to-band transition at 2.88 eV, which is associated to quantum confinement and a dominant radiative band at 2.37 eV that is called the optical signature of interstitial oxygen. The Eu3+-doped CdS photoluminescence shows the dominant radiative band at 2.15 eV, which is associated to the intra-4f radiative transition of Eu3+ ions that corresponds to the magnetic dipole transition, (5D0→7F1). For the Ce3+-doped CdS the dominant radiative transition, at 2.06 eV, is clearly redshifted, although the passivation of the CdS nanofilms by Ce was approximately by a factor about 21 for the best results.

scholarly journals Analytical solution for residual stress and strain preserved in anisotropic inclusion entrapped in an isotropic host

Solid Earth ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 817-833
Author(s):  
Xin Zhong ◽  
Marcin Dabrowski ◽  
Bjørn Jamtveit
Keyword(s):  
Residual Stress ◽  
Aspect Ratio ◽  
Analytical Solution ◽  
Strain State ◽  
Spherical Inclusion ◽  
Raman Shift ◽  
Stress And Strain ◽  
Wide Range ◽  
Inclusion Shape ◽  
Diamond Inclusions

Abstract. Raman elastic thermobarometry has recently been applied in many petrological studies to recover the pressure and temperature (P–T) conditions of mineral inclusion entrapment. Existing modelling methods in petrology either adopt an assumption of a spherical, isotropic inclusion embedded in an isotropic, infinite host or use numerical techniques such as the finite-element method to simulate the residual stress and strain state preserved in the non-spherical anisotropic inclusions. Here, we use the Eshelby solution to develop an analytical framework for calculating the residual stress and strain state of an elastically anisotropic, ellipsoidal inclusion in an infinite, isotropic host. The analytical solution is applicable to any class of inclusion symmetry and an arbitrary inclusion aspect ratio. Explicit expressions are derived for some symmetry classes, including tetragonal, hexagonal, and trigonal. The effect of changing the aspect ratio on residual stress is investigated, including quartz, zircon, rutile, apatite, and diamond inclusions in garnet host. Quartz is demonstrated to be the least affected, while rutile is the most affected. For prolate quartz inclusion (c axis longer than a axis), the effect of varying the aspect ratio on Raman shift is demonstrated to be insignificant. When c/a=5, only ca. 0.3 cm−1 wavenumber variation is induced as compared to the spherical inclusion shape. For oblate quartz inclusions, the effect is more significant, when c/a=0.5, ca. 0.8 cm−1 wavenumber variation for the 464 cm−1 band is induced compared to the reference spherical inclusion case. We also show that it is possible to fit an effective ellipsoid to obtain a proxy for the averaged residual stress or strain within a faceted inclusion. The difference between the volumetrically averaged stress of a faceted inclusion and the analytically calculated stress from the best-fitted effective ellipsoid is calculated to obtain the root-mean-square deviation (RMSD) for quartz, zircon, rutile, apatite, and diamond inclusions in garnet host. Based on the results of 500 randomly generated (a wide range of aspect ratio and random crystallographic orientation) faceted inclusions, we show that the volumetrically averaged stress serves as an excellent stress measure and the associated RMSD is less than 2 %, except for diamond, which has a systematically higher RMSD (ca. 8 %). This expands the applicability of the analytical solution for any arbitrary inclusion shape in practical Raman measurements.

Stress Evaluation on Hetero-Epitaxial 3C-SiC Film on (100) Si Substrates

2012 ◽  
Vol 717-720 ◽  
pp. 521-524 ◽  
Author(s):  
Ruggero Anzalone ◽  
M. Camarda ◽  
C. Locke ◽  
J. Carballo ◽  
N. Piluso ◽  
...  
Keyword(s):  
Growth Rate ◽  
Growth Process ◽  
Film Growth ◽  
Raman Shift ◽  
Fundamental Parameter ◽  
Free Standing ◽  
Si Substrates ◽  
Shift Analysis ◽  
Hydrogen Carrier ◽  
The Impact

SiC is a candidate material for micro- and nano-electromechanical systems (MEMS and NEMS). In order to understand the impact that the growth rate has on the residual stress of CVD-grown 3C-SiC hetero-epitaxial films on Si substrates, growth experiments were performed and the resulting stress was evaluated. Film growth was performed using a two-step growth process with propane and silane as the C and Si precursors in hydrogen carrier gas. The film thickness was held constant at ~2.5 µm independent of the growth rate so as to allow for direct films comparison as a function of the growth rate. Supported by profilometry, Raman and micro-machined free-standing structures, this study shows that the growth rate is a fundamental parameter for low-defect and low-stress hetero-epitaxial growth process of 3C-SiC on Si substrates. Stress analysis performed by modify Stoney’s equation trough optical curvature measurement, Raman shift analysis and micro-machining of free-standing structures that shows apparent disagreement about the nature of the stress. These odds between the experimental data can be explained assuming a strong stress field located in the substrate and related to defects generated in the silicon during the growth process.

Measurement of Concentration and Temperature Gradients at Binary Mixture Boiling Bubbles

2010 ◽  
Author(s):  
Oliver S. Knauer ◽  
Andreas Braeuer ◽  
Matthias C. Lang ◽  
Alfred Leipertz
Keyword(s):  
Heat Transfer ◽  
Hydrogen Bonds ◽  
Binary Mixture ◽  
Scattered Light ◽  
Volatile Component ◽  
Nucleate Boiling ◽  
Temperature Gradients ◽  
Raman Shift ◽  
High Heat Flux ◽  
Linear Superposition

Due to the high heat flux available, nucleate boiling is one of the most utilized processes for the transfer of large amounts of heat in chemical or power engineering applications. Nevertheless, the basic physical phenomena of this kind of heat transfer are physically not well understood, especially for multi-component mixtures in which the heat transfer coefficient is a function of the mixture composition. To apprehend the binary mixture boiling phenomena, the knowledge of the composition and temperature field surrounding a boiling bubble near the heater surface is of great impact. These quantities are measured at individual boiling bubbles by means of laser-optical methods without disturbing the system and with high spatial resolution. An optical accessible and temperature adjustable boiling chamber for the generation of single bubbles of acetone-isopropanol mixtures was constructed. As the vapor-liquid equilibriums (VLE) of these mixtures show a large gap between the saturated liquid and vapor line, significant composition alterations occur during the phase transition. Concentration and temperature gradients have been measured along a line by linear Raman spectroscopy. Due to the species specific Raman shift and the linear superposition of the inelastic scattered light intensities, qualitative and quantitative composition information can be achieved. In alcohols, e.g. isopropanol, the molecules can develop hydrogen bonds, which have an impact on the shape of the O-H bind signal in the Raman spectrum. As the ratio of molecules with and without hydrogen bonds changes with temperature, the temperature of the liquid phase can be derived from the spectra as well. The results show an enhancement of isopropanol, the less volatile component, near the phase boundary due to preferential evaporation of acetone. Furthermore, a not expected depletion of isopropanol approximately 0.75 mm away from the bubble was measured. The detected temperature increases near the boiling bubble, indicating a heat transfer from the gas phase to the surrounding liquid. The temperature distribution also has a minimum at the same position as the isopropanol distribution. A species conservation calculation with simplified assumptions was carried out and validated the measured composition distribution in the liquid surrounding a boiling bubble.

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