X-ray Diffraction Peak Positions Research Articles

Effect of arsenate and phosphate substitution on hydroxyl group in libethenite Cu2PO4OH - olivenite Cu2AsO4OH solid solution series

Libethenite and olivenite have been regarded as intriguing photocatalysts because of their singular structures. Copper hydroxy-phosphates and -arsenates exhibit distinctive properties: they incorporate bridging hydroxyl (OH) groups shared by neighboring copper atoms. In materials employed for photoelectrochemical applications, the significance of surface OH groups and OH-related defects frequently varies and is contingent upon the specific material system and the reaction under consideration. Hydroxyl groups can enhance photocatalytic performance by generating OH radicals or serving as crucial agents in catalytic reactions. Therefore, the presence of an OH group within the crystal structure of the material can give rise to potentially interesting behaviors. Seven compounds within the solid solution series of libethenite Cu2PO4OH and olivenite Cu2AsO4OH with stoichiometric ratio (Cu2(Px,As1- xO4)OH, x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1 were synthesized at 70 °C via aqueous solutions, and their properties were examined using X-ray diffraction (XRD), Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy. The effect of substituting (PO4)3– ions with (AsO4)3– ions on the alteration of the lattice parameters and spectral characteristics was elucidated by analyzing the correlation between the chemical composition and X-Ray diffraction peak positions. The substitution process leads to modifications in the unit cell parameters and volume. These isomorphic substitutions can be also discerned through alterations in the infrared and Raman spectra, which exhibit variations in the position and intensity of the bands corresponding to phosphates, arsenates, and hydroxyl ions. The incorporation of As into the solid solution resulted in altered bond lengths and geometries, which is consistent with the symmetry transition from orthorhombic libethenite to monoclinic olivenite. The variations in the unit cell parameters and the shifts in the peak position exhibited non-linear trends, and a discernible step was observed between the Cu2(P0·3As0.7)O4OH and Cu2(P0·5As0.5)O4OH intermediate phases. The findings of this study will prove beneficial in evaluating the feasibility of the libethenite-olivenite isometric series as a photocatalysts.

Lattice variation as a function of concentration and grain size in MgO–NiO solid solution system

The study aimed to understand how changes in crystal's size affect the lattice parameters and crystal structure of Mg1-xNixO solid solution for six X values ranging from x = 0 to x = 1. Mg1-xNixO was synthesized via two different wet-chemical techniques: the sol-gel and the microwave hydrothermal method, both followed by calcination at different temperatures of 673, 873, 1073, 1273 and 1473 K. As annealing caused grain growth, the varied temperature range allowed to examine a wide range of grain sizes. The lattice parameters and x values were determined from XRD (X-ray diffraction) peak positions and intensities respectively. The grain size was evaluated by XRD line profile analysis and supported by SEM (scanning electron microscope) observations. At the temperatures of 673 and 873 K grain size was in the nanometric range and from 1073 K and above grain size was in the micrometric range. A non-monotonic lattice variation versus grain size was found for each concentration. When grain size decreased there was a slight contraction, however for grain size in the nanometric range there was a severe lattice expansion. Both lattice parameter changes were explained by two effects acting together: contraction due to surface stress and expansion due to weakening of the ionic bonding at nanocrystalline particles. In this current research study, the lattice parameter was mapped in two dimensions: concentration and grain size. The findings of this study provided valuable insights into the lattice variation in the MgO–NiO solid solution system.

Mineralogical differences between seam and prism material in loess‐derived fragipans in western Kentucky

AbstractFragipan horizons are common diagnostic subsurface features typically identified by their dense, brittle nature under field conditions. Fragipan horizons are often hypothesized to contain various silicate bonding agents, including phyllosilicates, amorphous aluminosilicates/silica, and silica sorbed to iron oxyhydroxides. However, the association of silica (Si) with other minerals in these horizons remains uncertain. To fill this knowledge gap, we sampled the prism and seam material of four loess‐derived fragipan horizons in western Kentucky. We characterized and compared the clay mineral composition of the prism and seam material using X‐ray diffraction (XRD), selective extractions, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Fragipan prism and seam material exhibited a mixed clay mineralogy comprised of vermiculite, mixed layer minerals (hydroxyl‐interlayered vermiculite), illite, kaolinite, and quartz. We identified goethite in fragipan prisms in much greater quantities when compared to seam material, confirmed by both XRD and DRIFTS and corroborated by higher dithionite‐extractable iron in prisms. DRIFT spectra showed a peak near 3180 cm−1 assigned to OH‐stretching mode of goethite, which was prominent in prism materials. Goethite 110 XRD peak positions were negatively correlated to dithionite‐extractable aluminum (Al) and Si content of the prism material, which may suggest greater Si sorbed to the surfaces of Al‐substituted goethite. These results demonstrate the potential importance of Al‐substituted goethite in fragipan prisms and provide insight about possible associations with Si.

Influences of hydrogen ions doping on the lattice structure of AlN thin films for temperature interpretation application

In this paper, hydrogen ions doping is used to construct lattice defects in AlN thin films. Effects of hydrogen ions doping on the lattice structure, components, and defects of AlN thin films were analyzed. SIMS results show several main types of point defects formed in hydrogen ions doped AlN thin films. XPS spectra find many nitrogen-vacancy defects on the surface of AlN thin films. These point defects make Raman scattered photons fall, thus weakening Raman scattering intensity. High-resolution TEM image shows abundant dislocation defects. Lattice defects produced by hydrogen ions doping make the lattice structure of AlN thin films stretched along the c-axis. The X-ray diffraction peak of the (002) crystal plane of the AlN thin films shifts to the left seriously. The lattice defects caused by hydrogen ions doping are repaired at high temperatures, and then the lattice of the AlN thin films shrinks, which leads to the recovery of the X-ray diffraction peak position. The X-ray diffraction angle increases linearly with temperature and time. The linear variation relationship can be used for temperature interpretation.

Carbonate content control in carbonate apatite coatings of biodegradable magnesium

Carbonate apatite (CAp) coating has been developed as a bioabsorbable corrosion-control coating for biodegradable Mg alloys. Carbonate content in the CAp coatings can be utilized to control the bioabsorbability and corrosion rate of CAp-coated Mg alloys. In this study, the carbonate content in the CAp coatings of pure Mg was varied by NaHCO3 concentration of the coating solution from 0.25 to 1.0 mol/L, and hydroxyapatite (HAp) was formed without NaHCO3. The CAp and HAp coatings were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The carbonate content in the apatite coatings formed with 0, 0.25, 0.5 and 1.0 mol/L NaHCO3 was determined to be 2, 12, 15 and 18 wt%, respectively, from the apatite 002 plane XRD peak position using the existing conversion constant as well as from the coating composition obtained by the XPS analysis. The values of carbonate content obtained by each method were in good accordance, indicating that the carbonate content can be determined simply by XRD measurements. Two types of carbonate group were present in the CAp coatings, CO32− and HCO3-, and the relative content of HCO3- to CO32− increased with an increase in the carbonate content.

Effect of indium doping on the optoelectronic properties of ZnSe films

Polycrystalline In:ZnSe films were prepared by the thermal co-evaporation method, where high purity ZnSe and In2Se3 powders are taken as source materials. Orderly change in the X-ray diffraction peak position and red shift in the optical absorption edge have confirmed the incorporation of the dopant in the system. Photoluminescence spectra showed that the doped system has a Zn vacancy, which is in line with energy dispersive spectroscopy measurements. The chemical state of the doped films i.e., Zn2+, In3+ and Se2− was analysed by Raman and X-ray photoelectron spectroscopy (XPS); XPS has also indicated the incorporation of oxygen in small fractions which improves the conductivity of the films. The electrical investigation has revealed that electrical properties altered by doping and majority charge carriers are electrons and carrier density is in the order of 1015 cm−3. Films with 15 at. % In exhibited good photoresponse in the visible range and suitable for photodetector applications.

Structural phase transition and negative thermal expansion in Cu 1.8 Zn0.2V2–x P x O7 solid solutions

Negative thermal expansion (NTE) is exhibited over the entire x range for Cu1.8Zn0.2V2–x P x O7. In particular, dilatometric measurements using epoxy resin matrix composites containing the spray-dried powder demonstrated that the thermal expansion suppressive capability was almost unchanged for x ≤ 1.0. With increasing x, the X-ray diffraction peak position moves systematically, but some peaks are extremely broad and/or asymmetric, suggesting disorder in the internal structure. The crystallographic analysis confirmed NTE enhancement by microstructural effects at least for x = 0.2. Preliminary measurements suggest higher resistivity and lower dielectric constant than that of pure vanadate, which is suitable for application to electronic devices.

Effect of Lanthanum doping on the thermoelectric power factor of CaMnO3

The present work describes the effect of Lanthanum substitution on the thermoelectric properties of Calcium Manganate. The n-type LaxCa1-xMnO3 (0 ≤ x ≤ 0.1) perovskite ceramics were synthesized by Solid State Reaction method. The variation in the cell parameters, electrical conductivity and thermoelectric power factor with the increase of La concentration in Calcium Manganate was investigated. The incorporation of La in the A-site was found to shift the X-Ray Diffraction peak position to lower angles indicating an increase in unit cell volume. The lowest value of resistivity was obtained for x = 0.10, which is several orders lower than that of pure/ undoped Calcium Manganate ceramics. However, due to the inverse dependence of the Seebeck coefficient on carrier concentration, the value of Seebeck coefficient was found to be low for x = 0.10 samples. The highest value of the power factor was about 225 μW m-1 K-2at 1075 K in La substituted samples which is about two orders higher than the undoped Calcium Manganate samples.

In Situ Bulk Observations and Ab Initio Calculations Revealing the Temperature Dependence of Stacking Fault Energy in Fe\u2013Cr\u2013Ni Alloys

The dependence of stacking fault energy ({gamma }_{text{SFE}}) on temperature in austenitic Fe–Cr–Ni alloy powders was investigated by in situ high energy synchrotron X-ray diffraction and ab initio calculations in the temperature range from − 45 °C to 450 °C. The X-ray diffraction peak positions were used to determine the stacking fault probability and subsequently the temperature dependence of γSFE. The effect of temperature on the diffraction peak positions was found to be mainly reversible; however, recovery of dislocations occurred above about 200 °C, which also gave an irreversible contribution. Two different ab initio-based models were evaluated with respect to the experimental data. The different predictions of the models can be explained by their respective treatment of the magnetic moments for Cr and Ni, which is critical for the alloy compositions investigated. Ab initio calculations, taking longitudinal spin fluctuations (LSF) into consideration within the quasi-classical phenomenological model, predict a temperature dependence of {gamma }_{rm SFE} in good agreement with the experimentally evaluated trend of increasing γSFE with increasing temperature: left|Updelta {gamma }_{rm SFE}/Updelta Tright|=0.05 {text{mJ}} {text{m}}^{-2}/{text{K}}. The temperature effect on γSFE is similar for all three investigated alloys: Fe–18Cr–15Ni, Fe–18Cr–17Ni, Fe–21Cr–16Ni (wt pct), while their room temperature {gamma }_{rm SFE} are evaluated to be 22, 25, 20 mJ m−2, respectively.

The Effect of Severe Plastic Deformation on the Corrosion Resistance of AISI Type 304L Stainless Steel

The AISI type 304L stainless steel (SS) was solution annealed at 1050 °C and cryo-rolled at liquid nitrogen (L-N2) temperature (77 K) under severe plastic deformation (SPD). The thickness reduction through cryo-rolling plastic deformation was carried out up to 90% (designated as CR-90) of initial thickness. The cryo-rolling during rolling at liquid N2 temperature (77 K), resulted in transformation induced plastic deformation of the austenite γ-phase into α’- martensite phase. The phase transformation was characterized by x-ray diffraction (XRD) and saturation magnetization (Ms) measurement. The microstructure was measured by using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD peak positions confirmed the martensite (α’) phase formation. Saturation magnetization (Ms) value of the cryo-rolled specimens shows increasing linearity with cryo-rolling, and transformed to bct martensite (α’). The measured corrosion rate of the cryo-rolled specimens as per ASTM A-262 practice-C test (Huey test) ranges from 6.6 mpy or 0.167 mm/yr (CR 0) to 12.9 mpy or 0.328 mm/yr (CR 90), indicating the effects of severe deformation of strain-induced martensite with the cryo-rolling. Further, the role of severe deformation of strain-induced martensite with the cryo-rolling on AISI type 304L SS and also influence on the corrosion resistance are investigated in detail. The deformation microstructure roles, i.e., the phases and volume percentage induced by the different percentage of the cryo-rolling that influences the corrosion resistance properties and corresponding corrosion resistance in nitric acid have been investigated.

Fabrication of Al-TiO₂ Thin Film Electrode by Spray Pyrolysis Technique for Urea Sensing.

A simple cost effective Al-TiO₂ thin film electrode was fabricated for urea sensing. Urea is the key end product of nitrogen metabolism in humans. Increased level of urea leads to loss of kidney function. Thus determination of urea is important in analysis of kidney diseases. Al-TiO₂ thin films were deposited with different concentration of Al by Spray pyrolysis technique. The X-ray diffraction (XRD) pattern reveals the anatase phase of the Al-TiO₂ thin films with tetragonal structure. A shift is observed in the XRD peak position compared to as prepared TiO₂ thin film indicates the incorporation of Al ions into Ti ions. The UV-Vis spectroscopy study shows that the absorption increases and the absorption peak shifts towards the visible region for Al-TiO₂ thin films compared with that of the as prepared TiO₂ thin film. The optical band gap values changes with the change in the Al concentration in TiO₂ thin films. The electrochemical analysis for optimized Al-TiO₂ thin film electrode was carried out by cyclic voltammetry (CV) method. CV studies of Al-TiO₂ thin film electrode show the good stability and linearity which is essential to fabricate biosensor. The sensor response to urea is linear with correlation coefficient of 0.944 and the sensitivity is 3.17 μA mM-1 cm-2.

Phase transformation in MOCVD growth of (AlxGa1−x)2O3 thin films

This paper investigated the growth of (AlxGa1−x)2O3 thin films on semi-insulating (010) Ga2O3 substrates over the entire Al composition range (0% < x ≤ 100%) via metalorganic chemical vapor deposition (MOCVD). For the Al composition x < 27%, high quality single phase β-(AlxGa1−x)2O3 was achieved. A mixture of β and γ phases existed in (AlxGa1−x)2O3 when Al composition ranged between 27% and 40%, whereas a single γ-phase was observed for the films with Al composition x > 40%. The transition from the β to γ phase in AlGaO alloys was observed from x-ray diffraction spectra. The growth of γ-phase AlGaO with higher Al content was further confirmed via atomic resolution scanning transmission electron microscopy imaging and nanodiffraction. Compositional and statistical analyses performed on data acquired from atom probe tomography provided insight on the local compositional homogeneity in AlGaO films with different Al compositions. For AlGaO with pure β or γ phases, the Al composition distribution showed homogeneity with similar Al composition values as extracted from the x-ray diffraction peak positions. For AlGaO films with mixed β and γ phases, inhomogeneity in the Al composition distribution became more obvious in the nm scale. A mechanism was proposed for the observed phase transformation between β and γ phases in MOCVD growth of AlGaO films.

Reducing the Crystallite Size of Spherulites in PEO-Based Polymer Nanocomposites Mediated by Carbon Nanodots and Ag Nanoparticles.

The PEO-based polymer nanocomposites were prepared by solution cast method. Green approaches were used for synthesis of carbon nanodots (CNDs) and silver nanoparticles (Ag NPs). It was found that the crystallite size of spherulites of PEO was greatly scarified upon incorporation of CNDs and Ag NPs. In the present work, in opposition to other studies, broadening of surface plasmon resonance (SPR) peak of metallic Ag NPs in PEO-based polymer composites was observed rather than peak tuning. Various techniques, such as powder X-ray diffraction (XRD), SEM, UV–Vis spectroscopy, and photoluminescence (PL), were used to characterize the structural, morphological, and optical properties of the samples. Increase of amorphous phase for the PEO doped with CND particles was shown from the results of XRD analyses. Upon the addition of suspended Ag NPs to the PEO:CNDs composites, significant change of XRD peak position was seen. A field-emission scanning electron microscope (FESEM) was used to investigate the surface morphology of the samples. In the SEM, a significant change in the crystalline structure was seen. The size of PEO spherulites in the PEO nanocomposite samples became smaller and the percentage of amorphous portion became larger, owing to the distribution of CNDs and Ag NPs. The UV–Vis absorption spectra of the PEO-based polymer were found to improve and shift to higher wavelengths upon incorporation of CNDs and Ag NPs into the PEO matrix. The SPR peak broadening in the UV–Vis spectra was observed in the PEO:CNDs composites due to the Ag NPs. The absorption edge value of PEO was found to shift toward lower photon energy as the CNDs and Ag NPs are introduced. The photoluminescence (PL) spectra were also observed for the PEO:CNDs and PEO:CNDs:Ag samples and found to be more intense in the PEO:CNDs system than in the PEO:CNDs:Ag system. Lastly, the optical band gap of the samples was further studied in detail using of Tauc’s model and optical dielectric loss parameter. The types of electron transition were specified.

Williamson-Hall analysis in evaluation of lattice strain and the density of lattice dislocation for nanometer scaled ZnSe and ZnSe:Cu particles

Abstract Undoped and Cu-doped ZnSe nanoparticle (NPs) were prepared and grown hydrothermally in aqueous media assisted by microwave irradiation (MWIR) at different synthesis conditions of pH and MWIR times. In the mentioned process, sodium hydroxide (NaBH4), used for preparing selenium ions source with dissolving it and selenium powder in deionized water. To investigate the structural aspects and nanoparticles morphology, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used. According to the results of XRD, no displacement was seen in the position of XRD peaks of ZnSe nanoparticles by altering the pH and microwave irradiation time. XRD analysis demonstrated cubic zinc blende NPs and TEM images indicated round shape morphology of them. Depending to the microwave irradiation time, upon the XRD outputs, the size of the synthesized NPs were in the range of 1.54–2.18 nm. In this research, for samples synthesized at different pHs (= 8, 10.2, 11.2 and 12.2), at two microwave irradiation time of 0 and 6 min, and also at the presence of Cu-dopant (with the contents of 0, 0.1,0.75 and 1.5%), structural characteristics such as dislocation density(δ), lattice strain(e), size of nanoparticles (D) and full width at half maximum (FWHM:βhkl) have been evaluated upon the Scherrer and Williamson-Hall methods, in which undoped and ZnSe:Cu 0.1% synthesized at pH = 11.2 have the best crystalline quality; such results for the optimum samples, introduce them as promising materials in optoelectronic devices. The results of structural features obtained from Scherrer and Williamson-Hall approaches are highly intercorrelated and show the same trends with the variation of synthesis conditions.

Band-edge emission, defects, morphology and structure of in-doped ZnO nanocrystal films

In-doped ZnO films grown by ultrasonic spray pyrolysis have been studied by means of the scanning electron microscopy (SEM), energy dispersive X ray spectroscopy (EDS) and X ray diffraction (XRD) methods. The photoluminescence (PL), transmittance and absorbance have been controlled as well. It was shown that the ZnO optical band gap demonstrates the blue high energy shift to 3.31 eV at 300 K and the PL intensity of near band edge (NBE) emission enlarges at In doping 0.5–2.5 at%. Simultaneously, the positions of XRD peaks and their intensities vary insignificantly owing to the difference in the In3+and Zn2+ ionic radii. Meanwhile, intensity decreasing the green PL band confirms the occupation of the zinc vacancies by In ions with the formation of substitutional InZn defects and ZnO crystal quality improving.At higher In contents the new PL band (3.034eV) appears in PL spectra and its peak shifts to lower energy with In content increasing. This PL band was attributed to the emission via the complex defects, formed by Ini interstitial atoms. Simultaneously, the PL intensity and ZnO film crystallinity falling down, the ZnO crystal lattice parameters increase and the ZnO optical band gap demonstrates the red low energy shift. To reveal a nature of the optical transition responsible for the new PL band, PL spectra have been studied in the temperature range 11–290 K. The dependence of the Ini complex defect formation versus In contents in ZnO NC films is analyzed and discussed. The optimal In concentration range to fabricate the ZnO films with high optical parameters has been estimated.

Synthesis of Li+-ion activated NaYF4: Er3+/Yb3+ phosphors via a modified solid-state process for latent fingerprint detection

Li+-ion codoped NaYF4: Er3+/Yb3+ phosphors (β-NaYF4) with a hexagonal structure were synthesized via a modified solid-state route. High-speed planetary ball milling and solid-liquid mixing were simultaneously used to overcome the drawbacks of high synthesis temperatures in conventional routes. A pure β-NaYF4 phase was obtained through calcination at 600 °C for 3 h. Increases in the codoping content of Li+ ion caused a slight shift in X-ray diffraction peak positions toward high angles owing to the distortion of the local crystal field. Field emission scanning electron microscope images showed agglomerated spherical particles of approximately 0.7 µm with narrow size distribution. The upconversion properties of β-NaYF4 codoped with Li+-ion were explored. Two emission bands in the green regions (520 nm and 545 nm) and one emission band in the red region (615 nm) were observed owing to the 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 transitions of Er3+, respectively. Codoping with 6 mol% Li+ increased the upconversion intensity by three times, which was explained using the energy level diagram. The present phosphors with improved upconversion properties were utilized for latent fingerprint detection on smooth surfaces of regularly used polymer sheets, glass substrates, and compact discs. Using the present phosphors, the base elements with three-level features, such as sharp ridges, valleys, ridge flow, bifurcation, ridge shapes, and dots, were observed on all hydrophilic and hydrophobic surfaces. The prepared phosphors exhibited promising characteristics to detect the features of fingerprint impression for individual identification in forensic applications.

Lattice dynamics, phase transition, and tunable fundamental band gap of photovoltaic (K,Ba)(Ni,Nb) O3−δ ceramics from spectral measurements and first-principles calculations

Ferroelectrics have long been recognized as one of the candidate class of materials for applications in photovoltaic devices. Recently, ferroelectric perovskite $(\text{K},\text{Ba})(\text{Ni},\text{Nb}){\mathrm{O}}_{3\ensuremath{-}\ensuremath{\delta}}$ has been successfully synthesized and demonstrated to have a near-optimal band gap (1.39 eV), exhibiting good photovoltaic performance. However, the connection between the structural order-disorder transformation, electronic structure, bulk photovoltaic, and photocatalytic properties remains not well understood. Here, we investigate the phase transition evolutions of lead-free ${[{\mathrm{KNbO}}_{3}]}_{1\ensuremath{-}x}{[{\mathrm{BaNi}}_{1/2}{\mathrm{Nb}}_{1/2}{\mathrm{O}}_{3\ensuremath{-}\ensuremath{\delta}}]}_{x}$ ($\mathrm{KBNNO}x$, $x=0--0.5$) ceramics via x-ray diffraction (XRD), Raman scattering, and computational evidences. The lattice dynamics and the origin of the successive rhombohedral$\ensuremath{\rightarrow}$orthorhombic$\ensuremath{\rightarrow}$tetragonal$\ensuremath{\rightarrow}$cubic phase transitions have been systemically explored based on temperature-dependent XRD peak positions and phonon modes under different geometries. Moreover, the differences in the phase transition temperature and interior structure between the solid solution $x=0.2$ and the end member $x=0$ highlight local and nonlocal characteristics, which are helpful for understanding the photovoltaic mechanisms. Additionally, the robust photocatalytic decoloration effect on methylene blue can further confirm the photon-generated carrier behavior in the partly structural disordered orthorhombic phase. This identification of structural phases, combined with the ability to perform photocatalytic decoloration, give some insights on promising oxide applications as semiconducting ferroelectric absorbers and carrier-separating layers in photocatalytic or photovoltaic devices.

Improved Absorbance and Near-Infrared Dispersion of AuGe Nanoparticles over Au Nanoparticles Prepared with Similar Thermal Annealing Environment

The difficulty in patterning the structures at sub-wavelength range leads to employ the bottom-up approach to form nanostructures of metals as well as dielectric components that disperse them in host media. The optical properties of nanoparticles are studied with UV-Vis 750 (lambda) NIR spectroscopy and fit with empirical relations. The refractive index is about the volume fraction of particles. The AuGe nanoparticles demonstrate improved absorbance, lower refractive index, and higher extinction than Au nanoparticles formed with similar thermal process. Surface plasmon resonance (SPR) phenomena are highly sensitive to the bonding between atoms, atomic structure, and the electronic configuration in atoms of the given material. If one takes into account the structure of materials, then the literature on eutectic alloys predicts that alloying gold with germanium (AuGe) with varying compositions will also change the x-ray diffraction peak positions of gold itself. The peak shift can be interpreted as the change in grain size or shift in grain boundaries implying a corresponding change in material’s atomic arrangement within lattice structure. As a result, there will be a change in the charge distribution of free electron cloud in original gold ultimately affecting a change in the plasmon resonance frequency and thereby modulating the various optical phenomena such as absorbance, reflectance, and refractive index. This alloying also brings a change in the dielectric constant of the material such that the plasmonic behavior may shift among different regions (UV, visible, NIR, MWIR, and LWIR). Metal semiconductor eutectic alloy which is widely popular as a soldering material would have scope in futuristic photonic applications due to its tuneable optical properties. In this work, we study the effects of Au and AuGe nanoparticle deposition on GaAs films grown by molecular beam epitaxy (MBE). Au and AuGe thin films (12-nm thick) were annealed in the temperature ranges of 400–800 and 300–700 °C, respectively, to form Au and AuGe nanoparticles. The formation of these nanoparticles was confirmed by scanning electron microscopy (SEM) measurements. Optical absorption spectroscopy measurements showed plasmon resonance peaks at around 670 and 535 nm for the AuGe-deposited 300 °C-annealed sample and Au-deposited 600 °C-annealed sample on sapphire, respectively, thereby confirming the plasmonic effect. Correlation of Raman spectroscopy measurement results with X-ray diffraction measurement results reveal that the transverse optical mode intensity and full width at half maximum of the GaAs (400) peak increased with an increase in annealing temperature, indicating degradation of the crystalline properties of GaAs film at higher annealing temperatures. The highest increments of the photoluminescence (PL) intensities in comparison to that of the bare GaAs film were observed to be 37 and 77% for the Au-deposited 600 °C-annealed and AuGe-deposited 300 °C-annealed samples, respectively. These enhancements of PL spectra are an indication of the significant scattering of photons by Au and AuGe nanoparticles, and they are attributed mainly to the contribution of the local surface plasmon resonance of these nanoparticles. A comparative analysis of PL enhancements revealed that AuGe nanoparticles induced a greater enhancement than Au nanoparticles. The calculated activation energies of the Au-deposited 600 °C-annealed sample, AuGe-deposited 300 °C-annealed sample, and bare GaAs sample were around 18, 24, and 33 meV, respectively. We found one-order increment in peak responsivity of AuGe plasmonic-based trilayer InAs quantum dot detector in comparison to as-grown detector at 80 K. Therefore, this study is expected to be very useful in the realization of high-performance plasmonic-based optoelectronic and sensing devices.

Structure, Elastic Constants and XRD Spectra of Extended Solids under High Pressure

ABSTRACTWe present results of evolutionary simulations based on density functional calculations of a potentially new type of energetic materials called extended solids: P-N and N-H. High-density structures with covalent bonds generated using variable and fixed concentration methods were analysed in terms of thermo-dynamical stability and agreement with experimental X-ray diffraction (XRD) spectra. X-ray diffraction spectra were calculated using a virtual diffraction algorithm that computes kinematic diffraction intensity in three-dimensional reciprocal space before being reduced to a two-theta line profile. Calculated XRD patterns were used to search for the structure of extended solids present at experimental pressures by optimizing data according to experimental XRD peak position, peak intensity and theoretically calculated enthalpy. Elastic constants has been calculated for thermodynamically stable structures of P-N system.

Role of Ga particulates on the structure and optical properties of Y3(Al,Ga)5O12:Tb thin films prepared by PLD

Y3(Al,Ga)5O12:Tb thin films (70nm) have been prepared by pulsed laser deposition on a Si (100) substrate at the substrate temperature of 300°C. The effect of annealing time on the structural, morphological and luminescence properties of Y3(Al,Ga)5O12:Tb thin films at 800°C were studied. The crystal structure of the samples was studied by X- ray diffraction (XRD) and showed shifts in the peak positions to lower diffraction angles for the annealed film compared to the XRD peak positions of the commercial Y3(Al,Ga)5O12:Tb powder. A new excitation band different from the original Y3(Al,Ga)5O12:Tb powder was also observed for the annealed films. The shift in the XRD pattern and the new excitation band for the annealed film suggested that the films were enriched with Ga after annealing.