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The manifestation of mechanical phenomena in quantum materials at the macroscopic level is intricately linked to pronounced electron‐electron interactions within their lattices, a relationship that becomes especially evident in low‐dimensional materials. Violet phosphorous (VP), a nascent 2D material distinguished by its unique vertically aligned tubular structures, has garnered considerable attention owing to its layer‐dependent electronic bandgap, exceptional carrier mobility, and robust air stability. Herein, a comprehensive exploration of the phonon modes exhibited by few‐layer VP through an integrated experimental‐theoretical approach, focusing on the modulation of their Raman response under the uniaxial strain along a‐axis, b‐axis, and tube direction, respectively, is undertaken. Density functional theory calculations highlight when strain is applied along the a‐ or b‐axis direction, the strain is predominantly mitigated through tube rotational adaptations instead of the change of bond length and bond angle, culminating in a pronounced anisotropic Raman response. Moreover, the strain engineering can effectively optimize the photoelectric response performance of VP, including increase the responsivity ≈2500% and elevate the anisotropic ratio from 2.26 to 3.38. This investigation not only confirms the superior stretchability and impact resistance properties of cross‐structured VP but also establishes the groundwork for exploring the strain‐induced anisotropic optoelectric properties to VP. [ABSTRACT FROM AUTHOR]

The current work,A series of rare earth Sm3+ ion substituted Cr-Mg-Bi ferrites Cr0.7Mg0.2Bi0.1SmxFe2-xO4 (x = 0.00, 0.02, 0.04, and 0.06) have beensynthesized by thesol-gel auto-combustion method. The XRD, FESEM, HRTEM,UV–Vis, FTIR, Raman spectroscopy, Photo Luminesce and Magnetic Properties analysis have been used to investigate structural, morphological, optical, Raman spectroscopy, Photo Luminesce and Magnetic Properties. Every sample contains a single-phase spinel structure, as confirmed by XRD.The substitution of Sm3+ ions is found to increase the lattice parameter from 8.258 to 8.248 Å.A monotone diffraction peak (311) is visible near small angles of degrees (35.33–35.13). The Debye-Scherrer equation, the nanoparticles' crystallite size ranges from 35.357 to 54.778 nm.FE-SEMs reveal a spherical grain that groups and has a porous form, with particles 38.13–53.28 nmin size.HR-TEM micrographs illustrate spherical morphology and their average particle size decreases from 55.32 to 65.42 nm. The selected area electron diffraction (SAED) pattern confirms the crystal planes which were revealed from XRD calculations.The spinel structure was confirmed by FTIR spectroscopy, which found 414 cm−1 and 516 cm−1 vibrational band at the octahedral and tetrahedral sites.As the concentration of Sm3+ rises, the direct and indirect band gap energy values determined from UV–Vis show an increase and decrease.The generated NPs' semiconducting nature is confirmed by the strong correlation between the g-value and particle size change.Photoluminescence (PL) investigation shows that all processed samples have four bands.(i) peak centered at 412 nm, which is near-band edge emission and corresponds to the ultraviolet (UV) band,(ii) The violet band has a high-intensity peak at 434 nm,(iii) The blue band is related to a low-intensity, sharp peak located at 466 nm, and (iv) A broad peak at 502 nm with a very low intensity distinguishes the green band.The Raman spectroscopy investigation revealed that the CMBSF nanoparticles had a mixed spinel structure. The magnetic investigation shows that when the Sm content of ferrites increases, saturation magnetization drops from 39.86 to 33.16 emu/g.The sample's coercivity (Hc) increases from 16.06 to 21.90 KOe with Sm substitution.

This research study proposes a unique photonic crystal fiber (PCF) consisting of a solid core and a hexa-spiral shape, using tellurite as the background material. The proposed PCF exhibits numerous significant optical guiding properties, such as nonlinearity, dispersion, effective index, effective mode area, etc. Simulated findings from COMSOL Multiphysics v5.5 confirm that the PCF can achieve high nonlinearity and zero-dispersion at 1650 nm. The base material is tellurite, which has a significant nonlinear refractive index (RI) of 5.11 × 10−19 m2 W−1. The resultant wave has a bandwidth of 562.65 nm when pumped at a wavelength of 1650 nm. Additionally, a continuum can be produced by pumping at 1500 and 1550 nm. The designed PCF can generate a broad spectrum of supercontinuum with a pulse duration of 200 fs and 10 kW input power. Here is also performed measurements and inspections on the impact of higher-order Taylor series dispersion coefficients, pulse width, input power, etc. The proposed PCF has many potential applications, including nonlinear optics, high dispersion characteristics, infinitely single-mode fibers, high wattage beam transmission, particle trapping, and sensing. To address these applications, here is used COMSOL Multiphysics to generate data, such as propagation constants, attenuations, effective area, and fields, which were used by Optisystem. To the best of our knowledge, this is the first investigation to verify the performance of our designed PCF in Optisystem, for modeling signal transmission for supercontinuum generation and Raman shift.

In this work, an efficient method is reported for creating a metal nanoparticle (silver) / Si composite structure consisting of a vertical array of silicon nanowires (SiNWs) decorated with silver metal nanoparticles. A two-stage metal-assisted etching method is employed to obtain SiNWs and Silver (Ag) metal nanoparticles are decorated on the SiNWs using the electroless deposition method. It allows the good coverage of silver metal nanoparticles over SiNWs. Scanning Electron Microscopy (SEM) analysis revealed that Ag was covered with SiNWs. High-work function metal nanoparticles such as Ag nanoparticles on SiNWs have been utilized in different applications such as photovoltaics and sensors. The size of SiNWs is determined through the Raman shift. The silicon optical phonon peak showed an increase in redshift and a decrease of full-width at half maxima with a decrease in diameter due to the quantum confinement. The Electron Field Emission (EFE) characteristics of the Ag-decorated SiNW films were studied based on the current-voltage measurements and analyzed using the Fowler-Nordheim (F-N) equation. The low turn-on field is obtained through the Ag metal nanoparticles which have wider applications in low-power operational devices. [ABSTRACT FROM AUTHOR]

This research study proposes a unique photonic crystal fiber (PCF) consisting of a solid core and a hexa-spiral shape, using tellurite as the background material. The proposed PCF exhibits numerous significant optical guiding properties, such as nonlinearity, dispersion, effective index, effective mode area, etc. Simulated findings from COMSOL Multiphysics v5.5 confirm that the PCF can achieve high nonlinearity and zero-dispersion at 1650 nm. The base material is tellurite, which has a significant nonlinear refractive index (RI) of 5.11 × 10−19 m2 W−1. The resultant wave has a bandwidth of 562.65 nm when pumped at a wavelength of 1650 nm. Additionally, a continuum can be produced by pumping at 1500 and 1550 nm. The designed PCF can generate a broad spectrum of supercontinuum with a pulse duration of 200 fs and 10 kW input power. Here is also performed measurements and inspections on the impact of higher-order Taylor series dispersion coefficients, pulse width, input power, etc. The proposed PCF has many potential applications, including nonlinear optics, high dispersion characteristics, infinitely single-mode fibers, high wattage beam transmission, particle trapping, and sensing. To address these applications, here is used COMSOL Multiphysics to generate data, such as propagation constants, attenuations, effective area, and fields, which were used by Optisystem. To the best of our knowledge, this is the first investigation to verify the performance of our designed PCF in Optisystem, for modeling signal transmission for supercontinuum generation and Raman shift. [ABSTRACT FROM AUTHOR]

With a motivation to unravel the effect of cation (Mn) doping-induced modifications in structure, charge transfer resistance, and Li-ion diffusion in V 2 O 5 a systematic study using X-ray diffraction (XRD), Raman Spectroscopy and electrochemical impedance spectroscopy (EIS) has been employed using three electrodes configuration. Structural investigations using XRD suggest the selective diffusion of Mn ion towards the c-axis at a low doping percentage. Raman spectroscopy suggests the shift in 994 cm-1 modes which substantiates the uniaxial diffusion of Mn ions. Nyquist plots show that interfacial charge transfer resistance is highest for the lowest doping i.e., 1% Mn-doped V 2 O 5 and exhibits the lowest diffusion coefficient as compared to other doped V 2 O 5 samples. Specific capacitance calculated from cyclic voltammetry is found to be highest for the 4% Mn-doped V 2 O 5 sample. Moreover, diffusion of Lithium ions improves with an increase in doping concentration due to higher concentration of defects as evident from Δd/d and Nelson–Riley factor (NRF) for pure V 2 O 5 and Mn-doped V 2 O 5. [ABSTRACT FROM AUTHOR]

The present research work is a systematic study to know the influence of Mn doping on structural, electronic, and optical properties of ZnTe nanoclusters (NCs). The calculations are performed on 4-atom, 6-atom, 8-atom, and 14-atom molecules of pure and Mn-doped ZnTe using Generalized Gradient Approximation (GGA) in the framework of density functional theory implemented in Amsterdam Density Functional (ADF). It has been found that 6-atom (Zn3Te3) has hexagon while 8-atom (Zn4Te4) Zinc-blende structure with TD symmetry and the smallest units of ZnTe NCs. The Raman and IR spectra are also studied, which are comparable to the reported theoretical results. Different modes such as symmetric, Asymmetric, scissoring, rocking, wagging, and twisting are identified. Due to quantum size affecting the wavelengths of the calculated absorption peaks gradually shift to red in order of 4- atom, 6-atom, 8-atom, and 14-atom. [ABSTRACT FROM AUTHOR]

Due to its ubiquitous occurrence in igneous, metamorphic, and sedimentary rocks and its wide application in geochronology and geochemistry, zircon has become the most widely used accessory mineral in the geological community. Nevertheless, the decay of U and Th causes radiation damage to the zircon structure, resulting in various degrees of metamictization, which can affect the accuracy of U–Pb dates and Hf and O isotope results. If the degree of zircon radiation damage can be quantified, the influence on geochemical analyses can be evaluated, and the results can be corrected more precisely. In this paper, synthetic and natural zircon crystals with different crystallization ages were selected for Raman spectroscopy analysis, cathodoluminescence imaging, and determination of the U and Th concentrations. The results show that Raman FWHM (full width at half band-maximum) and Raman shift correlate with alpha dose (Dα) of zircons following these equations, FWHM = 44.36 (± 2.32) × [1 − exp(− 2.74 × Dα)] + 1.7 (± 0.19), Raman Shift = − 6.53 × Dα + 1007.69. Analysis of synthetic zircon crystals shows that doped REEs (rare earth elements and P) can also lead to an increase in the FWHM. However, this effect can be ignored for natural zircon samples with REE contents at a normal level of hundreds to a few thousand ppm. The FWHM and Raman shift can be used as proxies to measure the degree of zircon radiation damage. Using the updated equations to calculate the latest age when zircon began to accumulate radiation damage, a more accurate and more meaningful "radiation damage age" can be obtained. [ABSTRACT FROM AUTHOR]

All-carbon nano-heterostructure photodetectors based on different carbon allotropes demonstrate excellent photoelectric performance due to their ultrahigh carrier mobility, excellent optoelectronic properties, and strong interfacial coupling effects. However, the further improvement of device performance is still limited by the interfacial charge transfer and the large dark current of graphene. Herein, asymmetric all-carbon nano-heterostructures have been designed as active channels to fabricate C60/graphene/single-walled carbon nanotube (SWCNT) heterojunction photodetectors. With an optimal C60 thickness of 35 nm, the asymmetric C60/graphene/SWCNT photodetector exhibits excellent broadband photoelectric response from the visible to NIR range (405–1064 nm) with a high responsivity of 4568 A W–1 @ 940 nm, an ultrahigh detectivity of 3.56 × 1014 Jones @ 940 nm, and a fast response time of 2.57 ms. Importantly, the interfacial charge transfer mechanism has been for the first time investigated by combining Raman shift statistics, absorption spectra, and fluorescence lifetime with photoluminescence spectra at room temperature. Our results demonstrate that the asymmetric channel structure effectively promotes the separation and transfer efficiency of photogenerated carriers, thus enhancing the photoelectric performance of photodetectors. This work not only gives a method to characterize the interfacial charge transfer in carbon-based heterostructures but also provides a strategy to design and fabricate high-performance all-carbon nano-heterostructure photodetectors. [ABSTRACT FROM AUTHOR]

Hydrogels have been widely studied as promising materials in several applications, such as wearable devices, electronic skin, soft robot, artificial muscle and articular cartilage, due to their numerous prominent performances. However, the inferior mechanical property, especially difficult for hydrogels to simultaneously obtain high tensile strength and elongation, limits their further clinical application. Thus, here we used the multilayer and single layer graphene (MG and SG) as reinforcement fillers to improve the mechanical performances of neat polyvinyl alcohol (PVA) hydrogels. Our results showed that the high tensile strength and fracture elongation were simultaneously obtained from PVA/0.20wt%MG hydrogel, which were higher than those of PVA/SG hydrogel. Further, the elastic modulus of PVA/graphene composites was measured by calculating the effective modulus of SG and MG within PVA matrix from the Raman shift of D peak for the PVA/SG and PVA/MG composite hydrogel, respectively. The findings demonstrate the possibility of in situ exfoliation of MG in hydrogels under large tensile strain. [ABSTRACT FROM AUTHOR]

Cubic boron nitride (c-BN) has the same structure as diamond, and it shows very inert reaction activity in different chemical environments, even under high-pressure (P) and high-temperature (T) conditions. Furthermore, the P- and T-dependent Raman shift of c-BN (e.g., TO mode) can be distinguished from that of the diamond anvil (c-BN at ~1054 cm–1 vs. diamond at ~1331 cm–1 at ambient conditions), making c-BN a potential P-T sensor for diamond-anvil cell (DAC) experiments. However, the Raman shift of c-BN has not been well studied at high P-T conditions, especially at temperatures above 700 K. In this study, we systematically calibrated the Raman shift of the TO mode (νTO) for synthetic c-BN grains at high-P and high-T conditions up to 15 GPa and 1300 K. Both ruby (Mao et al. 1986) and Sm2+:SrB4O7 (Datchi et al. 2007) were used as internally consistent standards for calibration of c-BN P-T sensor. Our results show that the Raman shift of c-BN is negatively correlated with temperature [∂νTO/∂T = –0.02206(71)] but positively correlated with pressure [∂νTO/∂P = –3.35(2)]. More importantly, we found that the P-T cross derivative for the Raman shift of c-BN [∂2νTO/∂P∂T = 0.00105(7)] cannot be ignored, as it was assumed in previous studies. Finally, we calibrated a Raman shift P-T sensor of c-BN up to 15 GPa and 1300 K as follows: P = A T − A T 2 + 0.2194 B T , Δ ν 0.1097 where A(T) = 3.47(6) + 0.00105(7)T, B(T, ΔνTO) = 2.81(51) – 0.0053(16)T – 1.78(11) × 10–5T2 – ΔνTO. The c-BN Raman shift P-T sensor in this study fills the P-T gap ranging from previously performed externally resistance-heated to laser-heated DAC experiments. The effect of c-BN grain size and Raman system laser power on the calibration were also tested for the P-T sensor. In addition, we conducted three sets of high-P-T experiments to test the practicability of c-BN P-T sensor for water-rock interaction experiments in DAC. Testing experiments showed c-BN has very stable chemical activity in water and clear Raman signal at high-P-T conditions in comparison with other P-T sensors (e.g., ruby, Sm2+:SrB4O7, and quartz). Hence, the Raman shifts of c-BN may serve as an ideal P-T sensor for studying water-rock interactions in a DAC, especially at high-P and high-T conditions relevant to subduction zones. [ABSTRACT FROM AUTHOR]

The growing interest in improving optoelectronic devices requires continuous research of the materials and processes involved in manufacturing. From a chemical point of view, the study of this sector is crucial to optimize existing manufacturing processes or create new ones. This work focusses on the experimental evaluation of residual stresses on samples that are intended to simulate part of the structure of an optoelectronic device. It represents an important starting point for the development of optoelectronic devices with characteristics suitable for future industrial production. Silicon chips, with a thickness of 120 μm, were soldered onto copper and alumina substrates, using different assembly parameters in terms of temperature and pressure. Using Raman spectroscopy, the stress evaluation was estimated in a wide temperature range, from −50 to 180 °C. Silicon chips soldered with AuSn alloy on copper substrates demonstrated at 22 °C a compressive stress, developed in the center of the assembly with a maximum value of −600 MPa, which reached −1 GPa at low temperatures. They present a stress distribution with a symmetric profile with respect to the central area of the chip. The silicon chip assembled on a ceramic substrate without pressure turned out to be extremely interesting. Even in the absence of pressure, the sample did not show a large shift in the Raman position, indicating a low stress. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rietveld refinement analysis confirmed a rhombohedral perovskite structure (space group R3c) for the nanoparticles. • Saturation magnetization (Ms) increased from 8.12 emu/g for x = y = 0.05 to 18.67 emu/g for x = y = 0.20. Remanent magnetization (Mr) improved from 1.49 emu/g to 5.63 emu/g. • Polarization values showed a significant increase with doping, with the polarization at 50 Hz rising from 0.79 µC/cm2 for x = y = 0.05 to 2.02 µC/cm2 for x = y = 0.20. • The degradation rate constant for methylene blue (MB) dye increased from 4.8 × 10−3 for BNCFO (0.05) to 10.23 × 10−3 min−1 for BNCFO (0.20). • The highest hydrogen production rate achieved was 8.88 µmol/g after 1.0 h of visible-light irradiation for Bi 0.80 Nd 0.20 Fe 0.80 Co 0.20 O 3. This study investigates the structural, magnetic, ferroelectric, and photocatalytic properties of bismuth ferrite ceramics co-doped with Nd and Co. The ceramics were synthesized using a combination of solid-state and mechanical milling techniques, and their compositions were varied within the range of Bi 1−x Nd x Fe 1−y Co y O 3 , with x and y ranging from 0.05 to 0.20. The materials were characterized using XRD (Rietveld refinement), WDXRF, Raman spectroscopy, and impedance analysis. Magnetic measurements revealed that the saturation magnetization (Ms) and remanent magnetization (Mr) significantly increased as the concentrations of Nd and Co increased. The magnetic properties showed an improvement, with the Ms value increasing from 8.12 emu/g for x = y = 0.05 to 18.67 emu/g for x = y = 0.20. Similarly, the magnetic response increased from 1.49 emu/g to 5.63 emu/g. The ferroelectric properties also exhibited improvement, with polarization values increasing from 0.79 µC/cm2 to 2.02 µC/cm2 at a frequency of 50 Hz. Photocatalytic activity was evaluated by measuring the degradation of organic dyes under visible light exposure, which showed a notable increase of up to 70 % when the doping concentrations were at their highest. These results suggest that Bi 1−x Nd x Fe 1−y Co y O 3 ceramics have a wide range of applications, making them promising materials for advanced devices and environmental cleanup. By doping with Nd and Co, the materials' properties are enhanced, leading to significant improvements in their ability to convert light into energy. [ABSTRACT FROM AUTHOR]

ZnO nanoparticles with the size ∼ 20 nm to 40 nm were prepared by dual doping of Ag+ and Al3+ ions using a microwave-assisted chemical synthesis technique. The composition of Ag is fixed as 2 at.% and Al is varied from 0 to 6 at.%. The prepared ZnO nanoparticles were characterized using XRD, HRTEM, FESEM, EDS, XPS, FT-IR, Raman spectra, UV- visible spectra and photocatalytic studies. XRD results confirmed the crystallinity and hexagonal wurtzite structure of Ag+ and Al3+-doped ZnO nanoparticles. It is observed that the increase of the Al dopant ratio reduced the crystallite size. EDS and FT-IR data supported the purity of samples. The optical band gap values showed a blue shift (3.54 eV to 3.89 eV) as the Al doping ratio increased. The blue shift is discussed in terms of the doping process and induced some transitions on inter bands. The photocatalytic activity of synthesized samples was monitored using Methylene Blue dye. The low absorbance and high degradation efficiency were obtained for the high-doping concentration of Al on all irradiation times. The leaching study shows no catalyst leaching into the reaction medium.

One of the most important parameters in Raman spectroscopy is the wavenumber (Raman shift), which is calculated from the difference between the excitation and Raman scattering absolute wavenumbers. Because the observed wavenumbers are strongly dependent on the spectrometer and measurement conditions, it is essential to calibrate the system by using a well‐characterised material. We therefore reliably estimated the wavenumbers and evaluated their uncertainty for the peaks of benzonitrile and cyclohexane by using a HeNe laser and Raman‐scattered light calibrated with Ne/Ar emission lines. We considered the uncertainties originating from the fitting and repeatability of both the Ne/Ar emission lines and the Rayleigh/Raman‐scattered lights, as well as the unstabilised HeNe laser, and the pixel and spectral resolutions. We also considered the uncertainty originating from the differences in results among the grades and manufacturers (four for benzonitrile and seven for cyclohexane). The estimated wavenumbers of 12 peaks for benzonitrile and 11 peaks for cyclohexane were comparable with those described in ASTM E1840 with an expanded uncertainty from 1.3 to 1.6 cm−1 (k = 2, coverage factor). It was also confirmed that the wavenumbers at 10°C and 35°C were within the expanded uncertainty; thus, these values should be widely useful for the calibration of Raman systems. [ABSTRACT FROM AUTHOR]

Optimising the performance of materials requires, among other things, the characterisation of residual stresses during the design stage. Raman spectroscopy offers access to these residual stresses at the micrometre scale when this inelastic light scattering is active in these materials. In this case, the relationship between the Raman mode shift and the pressure must be known. High-pressure cells with diamond anvils or bending instruments coupled to Raman spectrometers are habitually used to determine this relationship. In this article, we propose a new method that involves a Hertzian contact to obtain this relationship. A device that compresses an alumina ball against a transparent glass plane is connected to a Raman spectrometer. Under these conditions, the contact pressure can be as high as 1.5 GPa. The contact between the glass plane and the ball is observed through a diaphragm. Several hundred Raman spectra are recorded depending on the contact diameter. The spectral profiles obtained represent the shift in the Raman modes of alumina and glass along the contact diameter. Hertz's theory accurately describes the pressure profile as a function of position for elastic materials. Therefore, the contact diameter can be measured by fitting the spectral profile with a function identical to the Hertz profile. We then deduce the maximum pressure. Next, the calculated pressure profile along the contact diameter is correlated with the spectral profile. We obtain a pressure dependence of the Raman mode with a coefficient equal to 2.07 cm − 1 /GPa for the Eg modes of alumina at 417 cm − 1 , which is in good agreement with the literature. In the case of glass, we refine the measurement of the Q3 mode shift at 1096 cm − 1 in the studied pressure range compared to the literature. We find a coefficient of 4.31 cm − 1 /GPa. This work on static contacts opens up promising prospects for investigations into dynamic contacts in tribology. [ABSTRACT FROM AUTHOR]

This paper aims to improve the machining efficiency of silicon carbide (SiC), reduce residual surface stress, inhibit surface cracks, and reduce surface damage. Single-point diamond scratch experiments were performed on SiC samples after hydrogen ions implantation to study the macro-scale machining performance. The improvement mechanism by which ion implantation reduces surface cracks and machining defects in 4H–SiC samples under different loading forces was comparatively studied. Scale-like cracks and brittle fracture fragments in the scratched area of the ion-implanted samples were reduced significantly. Acoustic emission sensors were used to detect the acoustic signal of brittle fracture. The lower intensity of the acoustic emission signal in the ion-implanted sample indicates that less brittle fracture was generated during scratching. Variation of the contour line in the scratch area with loading force was measured using laser scanning confocal microscopy. The depths of the smooth contours in the scratched area of the samples without and with ion implantation were 96 nm and 360 nm, respectively. The scratch area was scanned by a Raman spectrometer to quantitatively study the effect of ion implantation on micro-level defects. Formulas illustrating the relationship between residual stresses and Raman shift displacement were derived by integrating Raman shift and a secular equation. The results show a reduction in defects at microscale, an enhancement of machinability, and a reduction in residual stresses on the surface of the ion-implanted sample. Ion implantation assisted machining technology can effectively improve the machining quality and efficiency of SiC wafers. [ABSTRACT FROM AUTHOR]

In this paper, the edge strain relaxation of InGaN/GaN MQW micro-pillars is studied. Micro-pillar arrays with a diameter of 3–20 μm were prepared on a blue GaN LED wafer by inductively coupled plasma (ICP) etching. The peak wavelength shift caused by edge strain relaxation was tested using micro-LED pillar array room temperature photoluminescence (PL) spectrum measurements. The results show that there is a nearly 3 nm peak wavelength shift between the micro-pillar arrays, caused by a high range of the strain relaxation region in the small size LED pillar. Furthermore, a 19 μm micro-LED pillar's Raman spectrum was employed to observe the pillar strain relaxation. It was found that the Raman E2H mode at the edge of the micro-LED pillar moved to high frequency, which verified an edge strain relaxation of = 0.1%. Then, the exact strain and peak wavelength distribution of the InGaN quantum wells were simulated by the finite element method, which provides effective verification of our PL and Raman strain relaxation analysis. The results and methods in this paper provide good references for the design and analysis of small-size micro-LED devices. [ABSTRACT FROM AUTHOR]

ReX2 (X=S, Se) have attracted great attention due to weak interlayer coupling and excellent properties. Herein, we put forward a theoretical model to pursue the joint effect of layer numbers and temperature on band gap and Raman shifts from the perspective of atomistic origin. Clearly, the band gap of ReX2 can be modulated in a wide range by layer numbers and temperature. Furthermore, the different Raman modes of ReX2 have opposite shift with layers owing to weak interlayer coupling and distortional symmetry, but both possesses a redshift with increasing temperature. It is demonstrated that both layer numbers and temperature can be measured as useful methods to realize the desirable properties, providing helpful guidance for application of ReX2 in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Water content and oxygen isotopes in zircon provide crucial constraints on magma source and process, yet they can be significantly modified by zircon metamictization, which causes secondary water absorption into the zircon crystal and the concomitant oxygen isotope changes. Therefore, it is imperative to develop a screening scheme to select the least-metamict zircons for the analyses. We propose a screening scheme based on our study on the Suzhou A-type granite (South China) through integrating Raman spectroscopy, water and trace element measurements, and oxygen isotope analysis. The results show that the primary water content is retained in zircon when the full-width at half maximum (FWHM) is <8 cm−1 or the Raman shift is >1007 cm−1 of v3(SiO4) vibration band, while the primary δ18O is preserved at <10 cm−1 FWHM or >1005.5 cm−1 Raman shift. Changes in trace element concentrations in Suzhou zircons are different from previous observations in metamict zircons but most likely related to magma evolution, which implies that trace elements are insensitive to metamictization. Primary δ18O in Suzhou zircons (4.5–6.0‰) fall into the mantle range, indicating a dominant mantle contribution to Suzhou granites. Primary water content was estimated at ca. 650–1400 ppm, significantly higher than those of typical I-type granite (400–736 ppm) and upper mantle-derived zircons (81–177 ppm). The high primary zircon water content was not controlled by the sub-solidus process, temperature, pressure, and cation charge balance but considered to reflect the high-water content in melts. This suggests a hydrous origin for the Suzhou A-type granite, which challenges the conventional view of anhydrous petrogenesis for A-type granites. [ABSTRACT FROM AUTHOR]

Because carbon nanotube (CNT) films have high photothermal conversion efficiency (PTCE), they have been widely used in bolometric and photothermoelectric photodetectors, seawater desalination, and cancer therapy. Here, we present a simple, quick, and non-destructive method to measure the PTCE of CNT films. According to the linear relationship between the Raman shift of the G+ peak and the temperature of a CNT, the offset of the G+ peak under varying excitation light power can characterize the changed temperature. Combining the simulation of the temperature distribution, the final value of the PTCE can be obtained. Finally, a CNT film with a high PTCE was chosen to be fabricated as a bolometric photodetector; a quite high responsivity (2 A W−1 at 532 nm) of this device demonstrated the effectiveness of our method. [ABSTRACT FROM AUTHOR]

The growing interest in improving optoelectronic devices requires continuous research of the materials and processes involved in manufacturing. From a chemical point of view, the study of this sector is crucial to optimize existing manufacturing processes or create new ones. This work focusses on the experimental evaluation of residual stresses on samples that are intended to simulate part of the structure of an optoelectronic device. It represents an important starting point for the development of optoelectronic devices with characteristics suitable for future industrial production. Silicon chips, with a thickness of 120 μm, were soldered onto copper and alumina substrates, using different assembly parameters in terms of temperature and pressure. Using Raman spectroscopy, the stress evaluation was estimated in a wide temperature range, from −50 to 180 °C. Silicon chips soldered with AuSn alloy on copper substrates demonstrated at 22 °C a compressive stress, developed in the center of the assembly with a maximum value of −600 MPa, which reached −1 GPa at low temperatures. They present a stress distribution with a symmetric profile with respect to the central area of the chip. The silicon chip assembled on a ceramic substrate without pressure turned out to be extremely interesting. Even in the absence of pressure, the sample did not show a large shift in the Raman position, indicating a low stress.

Herein, we fabricated nanoscale 2D CeO 2 sheet structure to develop a stable resistive gas sensor for detection of low concentration (ppm) level formaldehyde vapors. The fabricated CeO 2 nanosheets (NSs) showed an optical band gap of 3.53 eV and cubic fluorite crystal structure with enriched defect states. The formation of 2D NSs with well crystalline phases is clearly observed from high-resolution transmission electron microscope (HRTEM) images. The NSs have been shown tremendous blue-green emission related to large oxygen defects. A VOC sensing device based on fabricated two-dimensional NSs has been developed for the sensing of different VOCs. The device showed better sensing for formaldehyde compared with other VOCs (2-propanol, methanol, ethanol, and toluene). The response was found to be 4.35, with the response and recovery time of 71 s and 310 s, respectively. The device showed an increment of the recovery time (71 s to 100 s) with the decrement of the formaldehyde ppm (100 ppm to 20 ppm). Theoretical fittings provided the detection limit of formaldehyde ≈8.86 ± 0.45 ppm with sensitivity of 0.56 ± 0.05 ppm -1 . The sensor device showed good reproducibility with excellent stability over the study period of 135 d, with a deviation of 1.8% for 100 ppm formaldehyde. The average size of the NSs (≈24 nm) calculated from HRTEM observation showed lower value than the calculated Debye length (≈44 nm) of the charge accumulation during VOCs sensing. Different defect states, interstitial and surface states in the CeO 2 NSs as observed from the Raman spectrum and emission spectrum are responsible for the formaldehyde sensing. This work offers an insight into 2D semiconductor-based oxide material for highly sensitive and stable formaldehyde sensors., (© 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.)

• Appearance of Raman active modes due to A 1g , E 1g and E 2g symmetry. • Collapse of the magnetic collinearity due to magnetic dilution and spin canting. • High spin state of Fe3+ ions due to occurrence of the five sexets. • Octahedrally coordinated Fe3+ ions at the 12k, 4f 2 and 2a sites. Investigations were conducted on the cation distribution and magnetic characteristics of M-type strontium hexaferrites substituted with Pr3 + and Co2+. The Raman modes that have been observed are typical modes of M-type hexaferrites in single phase. Raman modes corresponding to vibration of the entire spinel block, trigonal bi-pyramidal[2b (↑)], tetrahedral [4f 1 (↓)] as well as octahedral [12k (↑), 2a (↑), and 4f 2 (↓)] crystallographic sites as a result of A 1g , E 1g and E 2g symmetry are revealed by the analysis of the Raman spectra. The preference of Co2+ ions for the site where they replace Fe3+ was identified as the cause of the variation in the magnetic parameters. Since each sample has a squareness ratio value greater than0.5, it can be concluded that they possess a single magnetic domain structure. The Mössbauer analysis suggests that the high spin state of the Fe3+ ions is responsible for all five sexes, as indicated by the range of δ values (0.05 to 0.5 mm/s) for Fe3+. When Pr3+-Co2+ doping increases, the relative area values of the 2b site decrease, suggesting that Co2+ prefers to occupy the 2b site. The magnetic properties of the M-type hexagonal structure have been tuned as a result of the doping of Pr3+ and Co2+ cations on the structure. The produced samples have potential applications as permanent magnets and in magnetic recording media. [ABSTRACT FROM AUTHOR]

In this contribution, we reported our findings on NdFeO3–PbTiO3 composite system synthesized by conventional solid-state reaction route. The cell parameters, density and bond lengths (Fe-OI, Fe-OII) are determined by Rietveld refinement of X-ray diffraction data. Phase purity of the system was further confirmed through Fourier transform infrared (FTIR) and Raman spectroscopy techniques. The FTIR spectra reflected two important absorption bands around 656–505 cm−1 and 486–412 cm−1, corresponding to stretching (ν1) and bending (ν2) vibrational modes. The stretching vibrational mode (ν1) represents the absorbed IR energy in metal oxide (M–O) bonds. If the Raman spectra are related to two different symmetries, this includes the presence of two different phases in the sample. Thus, the phase purity is absent. The blue shift of Raman active mode at 720 cm−1 in pristine sample suggests that the increase in PbTiO3 concentration enhances the structural distortion in the system. The particle sizes as estimated using SEM micrographs were found to be in the range 147–250 nm. The ferroelectric behavior of NdFeO3 has been improved drastically with increase in PbTiO3 concentration. The P-E loops fitted by ferroelectric capacitor model established a good agreement between experimental and simulated data. The thermal properties of the powder samples were analyzed in a wide temperature range (300–900 K). The room temperature dielectric permittivity (ε′) and loss tangent (tanδ) for all the samples were analyzed in a broad frequency range (75 kHz–5 MHz). The behavior of dielectric permittivity in low-frequency region followed Maxwell–Wagner interfacial model, while in the high-frequency region, the composite system exhibited capacitive nature. The Néel temperature of the composite system decreased as compared to that of NdFeO3. The energy bandgap as determined with the help of Tauc's plots exhibits a slight decrease for composite samples in respect of pristine NdFeO3. [ABSTRACT FROM AUTHOR]

In this paper, the edge strain relaxation of InGaN/GaN MQW micro-pillars is studied. Micro-pillar arrays with a diameter of 3–20 μm were prepared on a blue GaN LED wafer by inductively coupled plasma (ICP) etching. The peak wavelength shift caused by edge strain relaxation was tested using micro-LED pillar array room temperature photoluminescence (PL) spectrum measurements. The results show that there is a nearly 3 nm peak wavelength shift between the micro-pillar arrays, caused by a high range of the strain relaxation region in the small size LED pillar. Furthermore, a 19 μm micro-LED pillar’s Raman spectrum was employed to observe the pillar strain relaxation. It was found that the Raman E2H mode at the edge of the micro-LED pillar moved to high frequency, which verified an edge strain relaxation of = 0.1%. Then, the exact strain and peak wavelength distribution of the InGaN quantum wells were simulated by the finite element method, which provides effective verification of our PL and Raman strain relaxation analysis. The results and methods in this paper provide good references for the design and analysis of small-size micro-LED devices.

Low‐pressure (below 2 GPa) Raman spectra of benzofuroxan are investigated using a gasketed Mao–Bell‐type sapphire anvil cell and Raman spectrometer to clarify the pressure‐induced structural change and molecular vibration behavior. The first‐principle calculations are performed to compare with the experimental data and to analyze the phase transition and trigger mechanism of initial reaction. Variations of pressure‐induced Raman band width, shift, and intensity are examined. The results show that the benzofuroxan molecule will become nonplanar with increasing pressure. A phase transition occurs because of an abrupt redshift in shift–pressure relationship and reduction of the cell volume, appearing of a new vibration band above 0.13 GPa. Several active vibration modes are found, and the effects of the active mode vibrations on the initial decomposition of benzofuroxan are analyzed using the relaxed scan method for the main change in bond length, bond angle, or dihedral angle to obtain the optimal reaction channel leading to initial decomposition. The results demonstrate that the initial decomposition is the open‐loop reaction in N(O)–O position, which is originated from the increase of dihedral angle O‐C‐N(O)‐O from the out‐of‐plane torsional vibration of furoxan ring (518 cm−1). The scanning energy barrier related to dihedral angle O‐C‐N(O)‐O is about 22.6 kcal/mol, which is consistent with the calculated activation barrier (18.1 kcal/mol) of open‐loop reaction. This proves the reliability of our conclusions. [ABSTRACT FROM AUTHOR]

The progress in the fabrication of carbon-nanotube-based structures has made it possible to use Raman spectroscopy to measure the deformation states of carbon nanotubes and abutting materials. In this work, we investigate the effects of laser power and surrounding materials on the Raman shift of carbon-nanotube (CNT) papers for the laser intensity in a range of 0.071 to 1.415 kW/mm2 without action of mechanical loading. Two different configurations of the CNT papers are used in the Raman measurement; one uses a suspended CNT paper, and the other places a CNT paper on a glass or aluminum substrate. The experimental results reveal that there exist combinational effects of the laser power and abutting materials on the changes of the wavenumbers of the D, G and G′ bands of the CNT papers. We derive an analytical relation between the strain components, temperature and the change of the wavenumber of the Raman peak, which yields a proportional relationship between the change of the wavenumber of the Raman peak and the laser power. Such a relationship is supported by the experimental results.

Because carbon nanotube (CNT) films have high photothermal conversion efficiency (PTCE), they have been widely used in bolometric and photothermoelectric photodetectors, seawater desalination, and cancer therapy. Here, we present a simple, quick, and non-destructive method to measure the PTCE of CNT films. According to the linear relationship between the Raman shift of the G+ peak and the temperature of a CNT, the offset of the G+ peak under varying excitation light power can characterize the changed temperature. Combining the simulation of the temperature distribution, the final value of the PTCE can be obtained. Finally, a CNT film with a high PTCE was chosen to be fabricated as a bolometric photodetector; a quite high responsivity (2 A W−1 at 532 nm) of this device demonstrated the effectiveness of our method.

Raman shift is one of the most important parameters in Raman spectroscopy and is theoretically calculated from the difference in the wavenumbers of excitation and Raman scattering. At present, there are no standard procedures available to reliably estimate the Raman shift and evaluate its uncertainty from experimental results. In this study, we reliably estimated the Raman shift and evaluated its uncertainty for a non‐doped crystalline Si substrate (NMIJ CRM5606‐a) using a He‐Ne laser and its plasma lines (Ne emission lines). The Raman scattering wavenumber of NMIJ CRM 5606‐a was estimated by the bracket calibration method using the wavenumbers of the closest Ne emission lines. The Raman shift was determined from the differences in the theoretical wavenumbers of a He‐Ne laser and the observed Raman scattering. To evaluate the combined standard uncertainty, we considered the uncertainty originating from the He‐Ne laser and the Ne emission lines, the repeatability of experimental results, inhomogeneity of measuring points and spectral dispersion. The estimated Raman shift was 520.45 cm−1 ± 0.28 cm−1 (coverage factor k = 2). The Raman shift was validated by the other estimated Raman shifts obtained with other two Raman spectrometers. [ABSTRACT FROM AUTHOR]

The results of the research of a composite based on multi-walled carbon nanotubes (MWCNTs) decorated with CuO/Cu2O/Cu nanoparticles deposited by the cupric formate pyrolysis are discussed. The study used a complementary set of methods, including scanning and transmission electron microscopy, X-ray diffractometry, Raman, and ultrasoft X-ray spectroscopy. The investigation results show the good adhesion between the copper nanoparticles coating and the MWCNT surface through the oxygen atom bridge formation between the carbon atoms of the MWCNT outer graphene layer and the oxygen atoms of CuO and Cu2O oxides. The formation of the Cu–O–C bond between the coating layer and the outer nanotube surface is clearly confirmed by the results of the O 1s near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS) of the Cu/MWCNTs nanocomposite. The XPS measurements were performed using a laboratory spectrometer with sample charge compensation, and the NEXAFS studies were carried out using the synchrotron radiation of the Russian–German dipole beamline at BESSY-II (Berlin, Germany) and the NanoPES station at the Kurchatov Center for Synchrotron Radiation and Nanotechnology (Moscow, Russia).

The thermal conductivity of isotropic graphite was investigated using Raman spectroscopy technique. In this method, the Raman laser acted simultaneously as an excitation source and a heating source. The dependences of the Raman peak position on temperature and laser power for the isotropic graphite were analyzed to establish Raman thermometry. Meanwhile, the local temperature rise induced by the laser irradiation was also theoretically described using a three‐dimensional heating model, which can be related to the thermal conductivity. The laser absorptivity, the spot size, and the probing volume of Raman spectra were discussed, respectively. Besides, simulations of the localized temperature distribution were performed. On the basis of the Raman thermometry and the three‐dimensional heating model, the thermal conductivity of 55 W/m K for the isotropic graphite was estimated, which was comparable with the value (60 W/m K) obtained by the laser flash technique. [ABSTRACT FROM AUTHOR]

WS _2 is two-dimensional layered material which the electronic band gap is dependent on the number of layers. From application point of view, the WS _2 few layers are good candidate for nano scale flexible electronics . In this study, the WS _2 number of layers is modified using liquid phase exfoliation method. The blue shift of WS _2 supernatant absorption peaks suggested the change of layer thickness compare to the non-exfoliated one. This supernatant is further deposited on Polyethylene terephthalate (PET) to create a flexible multilayer WS _2 thin films. The morphology and the content of the thin film are confirmed by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS), respectively. The Raman and photoluminescence spectroscopy show typical characteristics of WS _2 multilayers which are dominated by W-S vibrations, exciton contributions, as well as the local defect and strain effects. Furthermore, the electrical characterization reveals the robustness of the WS _2 electronic properties again the mechanical stretching. This study highlights the abundant optical and electrical characterization of WS _2 multilayer which are applicable for flexible electronic devices.

Abstract Amorphous diamond-like carbon coating (DLC) of 2 μm in thickness was deposited over the aluminum alloy substrate using magnetron sputtering deposition technique. In order to understand the efficacy of coating deposition, coated specimens were subjected to rotating bending fatigue in air and methanol environments respectively. Raman spectroscopy was used in conjunction with grazing incidence X-diffraction technique to obtain depth-resolved residual stress gradients of coated-aluminum substrate. The residual stress generated due to coating deposition was calculated using Raman spectroscopy and it was −1.13 ± 0.16 GPa (compressive in nature). Furthermore, Raman spectroscopy was utilized for the quantification of stress relaxation upon fatigue loading in air and methanol environments. It was observed that the irrespective of the testing environment, good correlation exists between the stress relaxation magnitude and number of cycles endured before failure. Graphical abstract Unlabelled Image Highlights • Diamond-like amorphous carbon was coated over the aluminum alloy substrate using magnetron sputtering technique. • Residual stress profile of coated substrates up to 3 μm in depth measured using non-destructive techniques. • Role of chemical environment revealed through poor fatigue performances of specimens tested in methanol environment. • Good correlations exist between residual stress relaxation upon fatigue loading and the fatigue properties of the material. [ABSTRACT FROM AUTHOR]

A real-time comparative measurement method is proposed to enhance the measurement accuracy of Raman shifts. Several experimental configurations are presented and demonstrated. The error sources in Raman shifts are also analyzed. The method is tested on a Raman spectrometer by measuring a sample of monocrystalline silicon and a sample of polystyrene. Experimental results indicate that the accuracy limit of the method is 0.07 cm-1. The measurement uncertainty of the Raman shift of the silicon is 0.2 cm-1 (k = 2), and the measurement uncertainty of the polystyrene is also improved. It is shown that the real-time comparative measurement method can remarkably enhance the measurement accuracy of Raman shift, and it applies to Raman spectrometers regardless of whether their exact laser wavelengths are known or not. [ABSTRACT FROM AUTHOR]

Abstract The diamond films were deposited on a Si substrate with chemical vapor deposition MCVD using methane-hydrogen gas. Raman active phonon and sp2/sp3 ratio in diamond/Si(100) films were investigated by Raman spectra in the difference scattering configurations. Furthermore, the Raman scattering spectrum of diamond/Si(100) hetero-junction was measured with different thickness to investigate the spin dynamics of nitrogen vacancy spins. The Fluorescence scanning microscopy indicated that nitrogen vacancy center electron spin was coupled to the host nitrogen nuclear spin by the electron spin resonance. The strong peak of 1332 cm−1 displayed the F 2g symmetry of diamond, while the broad E 2g mode peak of 1550 cm−1 was a broad band G mode, and 1150 cm−1 peak corresponded to the nano-diamond and disordered graphitic carbon form with disordered SP2 hybridization. The Raman spectra of the diamond films were observed as a function of the residual stress, crystal size and their orientation. The peaks of 1132 cm−1 and 1480 cm−1 were associated with hydrogen bonding. The transport of diamond exhibited sp3 spin related effect. The diamond/Si(100) PDOS is the results of spin-related couple of sp3, p and d orbital hybridization. The spin dynamics was achieved by the orbital competition, strong crystal field and charge order. [ABSTRACT FROM AUTHOR]

In this work, modification in structural and electrical properties of zirconium nitride (ZrN) thin films induced by silicon-ion irradiation is studied. ZrN thin films are grown on glass substrate over Zirconium (Zr) layer using cathodic arc evaporation method. The samples of the film are irradiated with silicon ions of energy 2.08 MeV at different fluences ranging from 5 × 1 0 1 3 ions/cm − 2 to 5 × 1 0 1 5 ions/cm − 2 . The structural and electrical properties of the prepared films are investigated using X-ray diffraction (XRD), Raman spectroscopy and four-point probe method. XRD analysis shows significant shift in the peak corresponding to (111) crystallographic plane of ZrN at low fluence (5 × 1 0 1 3 ions/cm − 2 ) while modest peak shift at high fluence rate (5 × 1 0 1 5 ions/cm − 2 ) is observed. Under the electrical properties point of view, it is observed that the decrease in resistivity is small at high ion fluence as compared to that at low ion fluence. At highest fluence of 5 × 1 0 1 5 ions/cm − 2 , resistivity of the irradiated sample approaches the resistivity of the un-irradiated sample indicating very small changes in structure at very high dose irradiance. [ABSTRACT FROM AUTHOR]

We formulated the composition and temperature dependence of the Si and Si1–xGex Raman shift from the perspectives of bond order–length–strength correlation and local bond average approach. It is verified that the Raman shift Δω varies in the form of Δω ∝ zE1/2/d, with inclusion of bond length d and energy E changing with temperature and composition. Numerical reproduction of the thermally induced Si1–xGex phonon softening indicates that bond thermal expansion and energy loss dictate the frequency redshift, which resulted in quantitative information on the bond energy and the reference frequencies from which the Raman shifts proceed. Observations not only gain deeper insight into the mechanism of the Raman shift but also demonstrate the revealing power of Raman technique for the bonding thermodynamics. [ABSTRACT FROM AUTHOR]

Abstract: Changes are investigated in the positions, half‐widths, and intensities of the Q‐branches of the main ethane Raman bands (ν3, 2ν6, 2ν2, 2ν8, and ν1) in the methane/ethane mixture depending on methane concentration at the fixed pressure of 25 bar. It was found that with increasing methane fraction, the above‐mentioned ethane Raman bands, with the exception of ν3, are shifted to the high wavenumbers, and the bands of 2ν8/ν1 Fermi doublet demonstrate a violation of the linear dependence of the intensity on the concentration. The data obtained will be useful for diagnostics of natural gas composition using Raman spectroscopy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Eu3+-doped LnF 3 NPs prepared via a low-temperature thermal decomposition process. • Thermal stability, surface chemistry, and optical absorption studies. • Comparative Raman active modes were discussed. • The influence of host lattice on luminescence properties was investigated. The thermal co-precipitation approach was employed for the synthesis of the Eu3+-ion doped YF 3 , LaF 3, and GdF 3 nanoparticles (NPs) and compared their photophysical properties. Ammonium fluorite was used as a fluorine source for the synthesis of metal fluorides at lower temperatures. Luminescent lanthanide fluoride (LnF 3) NPs were characterized by different techniques containing X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), FT-Raman, UV/Visible absorption spectra, and photoluminescence spectroscopic procedures to investigate the crystal structural, thermal, Raman effect, surface, optical, and luminescent properties. XRD study shows two types of crystal phase orthorhombic in YF 3 :Eu & GdF 3 :Eu and hexagonal in LaF 3 :Eu NPs. TGA, FTIR, and absorption spectra studies show the exterior adsorbed –OH molecules, which assist in the development of colloidal solution in aqueous media. Raman vibrations were strongly affected which were correlated with the XRD reflection planes. In comparative photo-physical properties, the excitation and emission spectra exhibited remarkable intensities of the Eu3+-ion transitions. Similarly, the emission spectra of all three samples exhibited the highest emission efficiency of the magnetically-dipole(5D 0 →7F 2) transition in comparison to the electric-dipole 5D 0 →7F 1 transition, which reflected the transformation of the crystal symmetry. Comparative analysis was presented to investigate the role of the host lattice on crystallinity, thermal stability, and luminescent properties. These findings are highly fruitful in designing photonic-based applications including optical biosensors, fingermark detection, security systems, etc. [ABSTRACT FROM AUTHOR]

We revised the calibration of a water vapor Raman lidar by co-located radiosoundings for a site in the high European Arctic. For this purpose, we defined robust criteria for a valid calibration. One of these criteria is the logarithm of the water vapor mixing ratio between the sonde and the lidar. With an error analysis, we showed that for our site correlations smaller than 0.95 could be explained neither by noise in the lidar nor by wrong assumptions concerning the aerosol or Rayleigh extinction. However, highly variable correlation coefficients between sonde and consecutive lidar profiles were found, suggesting that small scale variability of the humidity was our largest source of error. Therefore, not all co-located radiosoundings are useful for lidar calibration. As we assumed these changes to be non-systematic, averaging over several independent measurements increased the calibration’s quality. The calibration of the water vapor measurements from the lidar for individual profiles varied by less than ±5%. The seasonal median, used for calibration in this study, was stable and reliable (confidence ±1% for the season with most calibration profiles). Thus, the water vapor mixing ratio profiles from the Koldewey Aerosol Raman Lidar (KARL) are very accurate. They show high temporal variability up to 4 km altitude and, therefore, provide additional, independent information to the radiosonde.

Raman imaging eliminates the need for staining procedures, providing label-free imaging to study biological samples. Recent developments in stimulated Raman scattering (SRS) have achieved fast acquisition speed and hyperspectral imaging. However, there has been a problem of lack of detectors suitable for MHz modulation rate parallel detection, detecting multiple small SRS signals while eliminating extremely strong offset due to direct laser light. In this paper, we present a complementary metal-oxide semiconductor (CMOS) image sensor using high-speed lock-in pixels for stimulated Raman scattering that is capable of obtaining the difference of Stokes-on and Stokes-off signal at modulation frequency of 20 MHz in the pixel before reading out. The generated small SRS signal is extracted and amplified in a pixel using a high-speed and large area lateral electric field charge modulator (LEFM) employing two-step ion implantation and an in-pixel pair of low-pass filter, a sample and hold circuit and a switched capacitor integrator using a fully differential amplifier. A prototype chip is fabricated using 0.11 μm CMOS image sensor technology process. SRS spectra and images of stearic acid and 3T3-L1 samples are successfully obtained. The outcomes suggest that hyperspectral and multi-focus SRS imaging at video rate is viable after slight modifications to the pixel architecture and the acquisition system. [ABSTRACT FROM AUTHOR]

The optical properties of Si-doped metamorphic InGaAs layers with electron concentration in the range of 3 × 1016 to 6 × 1018 cm−3 are investigated in detail. The 10 K photoluminescence spectrum of lightly doped metamorphic In0.81Ga0.19As showed a narrow sharp peak at 546 meV with a full width at half maximum of 17.1 meV, comparable to that of InP-lattice-matched In0.53Ga0.47As, which is an evidence of the good crystalline quality. In the temperature range of 10-300 K, only band-to-band transition was observed in both lightly Si-doped In0.53Ga0.47As and In0.81Ga0.19As, while the band-to-band emission was overlapped by multiple transitions in heavily Si-doped In0.81Ga0.19As. A marked blueshift and significant increase in the linewidth of photoluminescence at high doping level were observed due to the enhanced band filling as well as many body effects in the heavily Si-doped high indium content material. The alloy disorder, caused by heavy Si doping, seriously degrades the crystalline quality and immensely reduces the possibilities of radiative recombination in In0.81Ga0.19As. [ABSTRACT FROM AUTHOR]

In this study, a Raman spectrum of TNT was characterized through experiments and simulated using 22 hybrid density functional theory (DFT) methods. Among the different hybrid DFT methods, it was found that the most accurate simulation results of the Raman shift frequency were calculated by the O3LYP method. However, the deviations of the calculated Raman frequencies from the experimental value showed no dependency on the abilities of the DFT methods in recovering the correlation energy. The accuracies of the DFT methods in predicting the Raman bands are probably determined by the numerical grid and convergence criteria for optimizations of each DFT method. It was also decided that the prominent Raman shift 1362 cm −1 is mainly caused by symmetric stretching of the 4-nitro groups. Findings of this study can facilitate futuristic development of more effective surface enhanced Raman spectroscopy/scattering (SERS) substrates for explosive characterization and detection. [ABSTRACT FROM AUTHOR]