Varying Doping Levels Research Articles

Significant phonon localization and suppressed transport in silicon-doped gallium oxide: A study using a unified neural network interatomic potential

Monoclinic gallium oxide (β-Ga2O3) is a fourth-generation semiconductor with great application potential in high-power microelectronics. Recent studies indicate that the electrical conductivity of β-Ga₂O₃ can be substantially enhanced through silicon (Si) doping. However, the effects on thermal transport, especially by considering the practical nanostructures within the crystal, have not yet been explored. To address this gap, we have developed a unified neural network potential for investigating the unexplored phonon transport of the β-(SixGa1–x)2O3 with varying doping levels. Our atomistic simulations showed that compared to intrinsic β-Ga2O3, the room-temperature thermal conductivities respectively decreased by 36.5%, 33.5%, and 38.8% along the a, b, and c axes in β-SiGa511O768, and by 79.6%, 74.9%, and 77.8% in β-SiGa7O12. The significant degradation in phonon transport is attributed to increased lattice anharmonicity, reduced sound velocity, and most importantly, induced phonon localization due to Si substitutions. A quantitative analysis reveals that the localization primarily occurs in phonons with frequencies exceeding 2.5 THz. The vibration is confined to a region around the Si atom, extending only to its second-nearest neighbors.

Structural and phonon anomalies in the superconducting with varying doping level at high pressures

We examined the effect of the lattice compression on the crystal structure of the Bi2Sr2CaCu2 superconductor with nearly optimally doped and overdoped composition using X-ray diffraction technique. Our studies show that at high pressures (up to 30 GPa ) the doping level does not affect the crystal structure of this superconductor. Along with this, structural anomalies in ratio appear at a pressure that corresponds to that at which T c begins to decrease. This fact indicates a close connection between the observed anomalies and superconductivity. We also studied the effect of doping and pressure on the T c (P) and on the Raman active lattice modes of the Bi2Sr2CaCu2 superconductors. We find universal suppression of the T c by the pressure starting from the critical pressure P c in the range from 9 to 16 GPa, depending on the doping level of the Bi2Sr2CaCu2 samples. Concomitantly, we observe phonon anomalies around 10 to 20 GPa, which indicate possible pressure-induced charge redistribution in BiO layers. These newly detected anomalies may be related to the changes in the electronic structure which compete with the superconductivity.

Delineating Dy3+ and Sm3+ in thermally stable strontium silicate apatites for multifunctional applications

The structural, optical and temperature dependent luminescence properties of a series of Sr2Y8-xREx(SiO4)6O2 (RE=Dy and Sm) silicate phosphors are investigated for their multifunctional applications. The phosphors were synthesized using the solid-state reaction route with varying doping levels and characterized for phase purity. X-ray Diffraction analysis revealed the hexagonal crystal structure of (Sr2RE2)(RE6)(SiO4)6O2, indicating the incorporation of rare earth (RE) ions into two distinct crystallographic sites, thereby augmenting the luminescence properties. Dy3+ doped compounds exhibit intense yellow emission, promising white light generation when paired with InGaN blue LED chips. Sm3+ doped samples show orange-red emission around 601 nm, attributed to multipole-multipole interactions, with rapid decay curves suitable for high-speed response LEDs. Correlated Color Temperature (CCT) values were computed to assess the commercial viability of these phosphors in luminescence applications and the role of lighting in the growth of indoor plants and office spaces is discussed. The Sr2Y7.8Dy0.2(SiO4)6O2 phosphor with remarkable quantum yield of 63.56% demonstrated a thermal stability of 0.27 eV with enhanced sensitivity of about 0.39% K−1 and Sr2Y7.8Sm0.2(SiO4)6O2 with stability around 0.31eV with sensitivity of 1.11% K⁻¹ at 100K reveals them as potential candidates for optical temperature sensing. These results declare the competence of synthesized novel silicate apatites in solid-state lighting and optical thermometry.

An Unprecedented Metal Distribution in Silica Nanoparticles Determined by Single-Particle Inductively Coupled Plasma Mass Spectrometry.

Metal-containing nanoparticles are now common in applications ranging from catalysts to biomarkers. However, little research has focused on per-particle metal content in multicomponent nanoparticles. In this work, we used single-particle inductively coupled plasma mass spectrometry (ICP-MS) to determine the per-particle metal content of silica nanoparticles doped with tris(2,2'-bipyridyl)ruthenium(II). Monodispersed silica nanoparticles with varied Ru doping levels were prepared using a water-in-oil microemulsion method. These nanoparticles were characterized using common bulk-sample methods such as absorbance spectroscopy and conventional ICP-MS, and also with single-particle ICP-MS. The results showed that averaged concentrations of metal dopant measured per-particle by single-particle ICP-MS were consistent with the bulk-sample methods over a wide range of dopant levels. However, the per-particle amount of metal varied greatly and did not adhere to the usual Gaussian distribution encountered with one-component nanoparticles, such as gold or silver. Instead, the amount of metal dopant per silica particle showed an unexpected geometric distribution regardless of the prepared doping levels. The results indicate that an unusual metal dispersal mechanism is taking place during the microemulsion synthesis, and they challenge a common assumption that doped silica nanoparticles have the same metal content as the average measured by bulk-sample methods.

Investigating the physicochemical characteristics of monovalent metal-doped nickel oxide thin films

The effect of Ag doping on the optical, structural, and electrical properties of deposited Ni1-xAgxO thin films deposited on glass substrates by spray pyrolysis has been studied. This work aims to investigate the optical and physical characteristics variations of Ni1- xAgxO thin films fabricated into semiconductors with varying doping levels x. The values of 0 at.%, 2 at.%, 4 at.%, 6 at.%, and 8 at.% are these levels. The transmission spectra demonstrate the good optical transparency of the Ni1-xAgxO thin films in the visible range of 70% to 85%. The thin films of Ni1-xAgxO exhibited optical gap energies ranging from 3.63 to 3.71eV. Between 329 and 430meV was the range of the Urbach energy. Nonetheless, numerous flaws with the highest Urbach energy are observed in Ni0.92Ag0.08O thin films. The lowest optical gap energy is found in Ni0.92Ag0.08O thin sheets. A maximum of 0.024(Ω.cm)-1 electrical conductivity was observed in the Ni0.92Ag0.08O thin films. Our films have an average electrical conductivity of approximately 0.0176(Ω.cm)-1 . The Ni1- xAgxO thin film XRD patterns show that the films have a cubic structure and are polycrystalline.

Design and performance study of ultra-high temperature CaMnO3/polysilylaryl-enyne absorbing material

This work describes the preparation and properties of a novel category of thermosetting microwave absorbing composite materials. The composites were prepared by a simple solution casting process, employing high temperature resistant polysilylaryl-enyne (abbreviated as PSAE) resin as matrix and perovskite CaMnO3 (abbreviated as CMO) ceramic filler as absorbent filler. The microstructure, electromagnetic, wave absorbing and thermal properties of the CMO-PSAE composites were all examined. The results showed that the increasing fraction of CaMnO3 filler not only densified the microstructure of the composites, but also greatly improved their temperature resistance, thermal conductivity and wave absorption properties. The CMO-PSAE composite doped with 50 vol% CaMnO3 ceramic filler showed the strongest ability to absorb electromagnetic waves, with an effective absorption bandwidth (EAB) of 4.16 GHz and a minimum reflection loss is −53.01 dB. Besides, the thermal conductivity of the composite reached 1.106 W/(m·K). Furthermore, this composite material has exceptional thermal resistance, with the highest Td5 reaching 650 °C. Composites with varying doping levels can be used for specific performance needs in practical scenarios. Thus, such novel CMO-PSAE composites exhibit potential applications in the electromagnetic countermeasure field under high-temperature environments.

Insight to structure-activity relationship of non-stoichiometric CuMgAl spinel catalysts for CO hydrogenation to dimethyl ether: Effect of MgO doping amount

Understanding the structure-activity relationship of catalysis is of critical importance for the design and modulation of catalysts. Herein, Cu-Al spinel catalysts with varied Mg doping levels were synthesized and investigated for CO hydrogenation to dimethyl ether (DME). The results revealed that the coordination distribution of cations in catalysts was effectively regulated by controlling Mg content. Increasing the Mg content facilitated the migration of Cu2+ ions in catalysts from tetrahedral to octahedral sites, enhancing the sustained release performance of copper, and further promoting the stabilization role of Cu nanoparticles by spinel. Importantly, suitable Mg content enhanced the synergistic effect between Cu nanoparticles and spinel active sites, which was conducive to improving DME selectivity. However, excessive Mg doping suppressed the reduction of copper species, and also adversely generated excessive strong base sites. Consequently, an optimal Mg/(Mg+Cu) mole ratio of 0.15 over the C0.85M0.15A2 catalyst exhibited superior selectivity to DME at 64.2 % (at 48 h) and excellent stability during the continuous testing for 120 h. The In-situ DRIFTS experiment confirmed that this reaction involved CH3O* intermediates, and the pathway was elucidated as the hydrogenation of CH3O* to form CH3OH and further dehydration to generate CH3OCH3.

Effect of ratio gold nanoparticles on the properties and efficiency photovoltaic of thin films of amorphous tungsten trioxide

At a substrate temperature of 320 o C, a chemical spray pyrolysis approach was applied. to create tungsten oxide thin films on glass substrates with varying Au nanoparticle doping concentrations (0, 0.04 and 0.08 M) that have a thickness of roughly 250 nm. Investigated were the structural and optical characteristics. The films were amorphous to the pure films at the substrate temperature (320 °C), according to X-ray diffraction and remain so even after adding GNPs, because the WO3 structure is amorphous in all samples, whereas the cubic structure of the gold nanoparticles. The morphology of the films was examined using atomic force microscopy (AFM), which showed a decrease in the grain size of the films doped with gold compared to the thin films before the doping process. a UV-Vis spectrophotometer was used to examine the membranes' optical characteristics between the wavelengths of (300-1000) nm. was the optical energy gap of the films (3.23) eV for tungsten oxide film and decreased after adding nanoscale gold to (3.04, 2.95) eV for films doped with different proportions of Au NPs (0.04, 0.08 M), respectively. Hall testing confirms that with 8 (mM) Gold (Au) doping, WO3 material of the n type was obtained with a maximum carrier mobility of 219.92(cm2 /Vs) and conductivity of 6.52 (Ω.cm)-1 . The I-V characteristics of the photovoltaic formed under illumination were determined by measuring the incident power density (100 mW/cm2 ) at varied Au doping levels.

Understanding the Physical Properties of Pr-Gd Co-Doped Ceria and Its Role As the Interlayer in Solid Oxide Cells

In solid oxide cells, a doped ceria interlayer is widely applied between the state-of-the-art yttrium-stabilized zirconia electrolyte and the oxygen electrode to mitigate thermal expansion mismatch and chemical interactions for extended durability. The conventional gadolinium doped ceria is usually a pure ionic conductor and blocks electronic currents under oxidative atmosphere. Adding electronic conduction to the interlayer may increase triple phase boundary areas, thus decrease charge transfer resistance and improve electrode stability. The addition of Pr in Gd-doped ceria results in unique physical properties such as an oxygen partial pressure (pO2) dependent ionic conductivity and electronic conduction in a wide range of pO2. In this study, Pr/Gd co-doped ceria (PGCO) is prepared with varying doping levels and its physical properties such as ionic and electronic conductivities are measured under different oxygen partial pressures and temperatures. PGCO with varying Pr/Gd doping is investigated as interlayer for solid oxide cell applications.

Three-Dimensional-Printed Photocatalytic Sponges Decorated with Mn-Doped ZnO Nanoparticles.

The present work reports on the fabrication of high-density polyethylene sponges, decorated with Mn-doped ZnO nanostructures. The sponges were developed utilizing three-dimensional printing technology, while Mn-doped ZnO nanostructures, with varying doping levels, were grown at mild temperatures. The nanostructures were fully characterized by means of scanning electron microscopy, X-ray diffraction, and Raman spectroscopy, revealing the existence of Mn doping. Moreover, their photocatalytic properties were investigated using the degradation/decolorization of a commercially available liquid laundry detergent, based on synthetic, less foaming ingredients, under UV irradiation. The Mn-doped ZnO nanostructures show better photocatalytic activity at higher doping levels. This study demonstrates that it is possible to achieve the adequate degradation of a typical detergent solution in water by means of low-cost and environmentally friendly approaches, while Mn-doped ZnO/HDPE nanostructures are good candidates for real environmental applications.

Structure and spectroscopic properties of Er3+ doped LiNbO3 thin film grown by e-beam evaporation

Er3+ doped LiNbO3 (Er: LN) single crystal films with varied doping levels of Er3+ were grown on z-cut LiTaO3 bulk single crystals by using e-beam evaporation method. The crystallographic orientation, fluorescence properties, ions valence states, Er3+ concentration and Li2O content of films were studied. The main phase of the obtained films is determined to be LN from X-ray diffraction and Raman scattering studies, and the films are found to be orienting along (006). Enhancement in the visible and near-infrared luminescence is observed as the doping concentration of Er3+ is increased. The Li2O content of films is determined using the optical birefringence method and found to be at a constant value of 48.8 mol%, which is consistent with the Raman results. XPS results show that the Er concentration in the films is lower than that in the polycrystalline powder since e-beam evaporation has a low efficiency for heavier Er3+. Fluorescence intensity ratios estimated at different measurement temperatures suggest that the Er: LN films have excellent temperature sensitivity, which shows the potential of the films for optical thermometry applications.

Recent advances in modified boron-doped diamond electrodes: A review

This review presents recent developments in the modification of boron-doped diamond electrodes (BDDEs) and their application in biosensing, electroanalysis, electrosynthesis, fuel cell construction, and CO2 reduction. The various modification procedures are also described. In addition to the outstanding properties of unmodified BDDEs, they have recently become a highly functional substrate for various modifications. The modifications of BDDEs by metals or metal oxides were aimed at increasing the surface area and promoting electron transfer kinetics or electrocatalytic activity for CO2 reduction, sensing of oxygen, or stripping voltammetry. Modification by polymers such as Nafion, polypyrrole, or polyaniline was used mostly to fine-tune the specificity of voltammetric analyses and interference suppression. DNA, enzymes, or other biomolecules were used to obtain specific sensing capabilities. These chemical modifications are critically compared to the other strategies used for BDDEs, including varied boron doping levels, the ratio of sp2 to sp3 carbon, and BDDE surface pre-treatment.

Accelerated dissolution of doped UO2-based model systems as analogues for modern spent nuclear fuel under repository conditions

Systematic single-effect dissolution studies were carried out on the dissolution behaviour of pure and Cr- or Nd-doped UO2 reference pellets as model materials for spent nuclear fuel with varying doping levels, densities, and grain sizes as well as of industrially produced Cr- and Cr/Nd-doped UO2 pellets. The results were obtained from accelerated static batch dissolution experiments performed under strictly controlled conditions using H2O2 as simulant for radiolytic oxidants formed due to the alpha-irradiation of water. The results indicate that the addition of Cr and the consequential modification of the fuel matrix does not lead to a significant change of the dissolution behaviour of these model materials compared to pure UO2 reference materials. Contrarily, the dissolution rates of Nd-doped pellets are significantly lower than those of pure and Cr-doped pellets. These results provide additional insights into the influence of doping on the dissolution behaviour of modern spent light water reactor fuels under the post-closure conditions expected in a deep geological repository.Graphical abstract

Quadratic electro-optic effect in the nonconjugated conductive polymer iodine-doped polyethylene terephthalate

Quadratic electro-optic effect has been measured in the nonconjugated conductive polymer iodine-doped polyethylene terephthalate (PET). Films of PET were doped with iodine in the vapor phase using standard procedure. The optical absorption and FTIR spectroscopic results show that iodine doping causes a charge-transfer from the terephthalic ring to iodine, thus forming a metallic quantum dot of subnanometer dimension. Nonlinear optical measurements were performed on the iodine-doped PET samples using field-induced birefringence method at 633 nm with lock-in detection. The magnitude of the Kerr coefficient for varying doping levels was determined. The magnitudes were shown to increase with doping level. For an iodine molar concentration of 0.28, a Kerr coefficient of ∼1.5 × 10−11 m/V2 was measured. For a molar concentration of iodine of 0.83, the measured Kerr coefficient was ∼5 × 10−11 m/V2. These magnitudes are comparable to (slightly smaller than) the Kerr coefficients measured in other iodine-doped nonconjugated conductive polymers representing metallic quantum dots of subnanometer dimensions.

Deep ultraviolet spontaneous emission enhanced by layer dependent black phosphorus plasmonics.

Although graphene has been the primary material of interest recently for spontaneous emission engineering through the Purcell effect, it features isotropic and thickness-independent optical properties. In contrast, the optical properties of black Phosphorus (BP) are in-plane anisotropic; which supports plasmonic modes and are thickness-dependent, offering an additional degree of freedom for control. Here we investigate how the anisotropy and thickness of BP affect spontaneous emission from a Hydrogenic emitter. We find that the spontaneous emission enhancement rate i.e. Purcell factor (PF) depends on emitter orientation, and PF at a particular frequency and distance can be controlled by BP thickness. At lower frequencies, PF increases with increasing thickness due to infrared (IR) plasmons, which then enhances visible and UV far-field spectra, even at energies greater than 10 eV. By leveraging the thickness and distance-dependent PF, deep UV emission can be switched between 103 nm or 122 nm wavelength from a Hydrogenic emitter. Additionally, we find that doping can significantly tune the PF near BP and this alteration depends on the thickness of the BP. Our work shows that BP is a promising platform for studying strong plasmon-induced light-matter interactions tunable by varying doping levels, emitter orientation, and thickness.

Optical and spin inhomogeneous linewidths in 171Yb[formula omitted]:Y[formula omitted]SiO5

Single crystals of 171Yb3+:Y2SiO5 are promising systems for quantum technologies as an efficient optical to spin interface. This is due to the long optical and spin coherence lifetimes, or narrow homogeneous linewidths, observed in this material at zero magnetic field. Inhomogeneous linewidths are also of importance since they affect peak absorption, available bandwidth or spin–spin interactions. In this work, we investigate inhomogeneous linewidths in a series of 171Yb3+:Y2SiO5 single crystals grown by the Czochralski method with the purpose of identifying the broadening mechanisms in the regime of ultra-low doping, i.e. in the ppm range. In a series of samples obtained with varying doping level, growth atmosphere, and cut at different locations in a crystal boule, optical inhomogeneous linewidths between 0.6 and 1.3 GHz are observed. This study suggests that these variations are due to changes in dislocation densities. Spin inhomogeneous linewidths, recorded using electron paramagnetic resonance, did not show the differences between samples observed in the optical domain. They were otherwise found to vary as a function of magnetic field orientation, enabling determination of directions that minimize e.g. detrimental spin–spin interactions. These results suggest ways to reduce optical inhomogeneous linewidths in 171Yb3+:Y2SiO5, which is of interest for high efficiency quantum memories and optical to microwave quantum transducers.

High performance low-bandgap (0.8 eV) single junction GaInNAsSb solar cells incorporating Au-based back surface reflectors

Low-bandgap GaInNAsSb single junction solar cells incorporating a planar Au back surface reflector for enhancing the photocurrent generation are reported. In particular, a 700 nm thick GaInNAsSb junction with a bandgap of 0.78 eV (corresponding to 6.2% N) incorporating the back reflector exhibited a short-circuit current density of 15.2 mA/cm2 for AM1.5D (1000 W/m2) illumination, when placed underneath a GaAs-filter mimicking the operation of a multijunction architecture. The corresponding external quantum efficiency represents the highest external quantum efficiency reported so far for dilute nitride solar cells with bandgaps below 0.8 eV. Electrical simulations reveal that the relatively high value of the quantum efficiency is attributed to a low p-type carrier concentration and partially to the varying doping level in the GaInNAsSb region. Moreover, the absorption coefficients for low-bandgap GaInNAsSb materials are estimated and used in a comprehensive optical analysis to understand the photon harvesting performance of the solar cells with reflector. The analysis reveals incomplete absorption in the GaInNAsSb layers for the double-pass configuration enabled by the planar back reflector pointing to the need for deploying more advanced structured reflectors. However, the structures exhibited high collection efficiencies laying the foundation for further improvements of the quantum efficiency values. Moreover, the low-bandgap dilute nitride solar cells show potential to meet the current-matching requirements in next-generation multijunction devices with five or more junctions, thus being a prospective alternative for replacing Ge as the bottom junction.

Direct fabrication and characterization of vertically stacked Graphene/h-BN/Graphene tunnel junctions

We have used a lithography free technique for the direct fabrication of vertically stacked two-dimensional (2D) material-based tunnel junctions and characterized by Raman, AFM, XPS. We fabricated Graphene/h-BN/Graphene devices by direct deposition of graphene (bottom layer), h-BN (insulating barrier) and graphene (top layer) sequentially using a plasma enhanced chemical vapor deposition on Si/SiO2 substrates. The thickness of the h-BN insulating layer was varied by tuning the plasma power and the deposition time. Samples were characterized by Raman, AFM, and XPS. The I-V data follows the barrier thickness dependent quantum tunneling behavior for equally doped graphene layers. The resonant tunneling behavior was observed at room temperature for oppositely doped graphene layers where hydrazine and ammonia were used for n-doping of one of the graphene layers. The resonance with negative differential conductance occurs when the band structures of the two electrodes are aligned. The doping effect of the resonant peak is observed for varying doping levels. The results are explained according to the Bardeen tunneling model.

Size-Dependent Doping Synergy and Dual-Color Emission in CsPb1-xMnxCl3 Nanocrystals

The doping of atomic impurities into colloidal semiconductor nanocrystals (NCs) is a powerful way to tune optical and electronic properties. Manganese (Mn)-doped CsPbCl3 NCs in particular show dual exciton/dopant emission in the visible spectrum, making them materials of current interest for optoelectronic applications. Here, we examine the impact of Mn doping on the photophysics of CsPbCl3 NCs from a different perspective. Using ultracentrifugation, we extract size-resolved fractions from a series of parent NC suspensions prepared at varied doping levels, and we measure the photoresponse as a function of NC size. Our results reveal synergistic radiative effects, with large enhancements in both blue (exciton) and red (dopant) quantum yield (QY) over a narrow range of Mn concentration. We ascribe the first effect to defect passivation and the latter to efficient exciton–dopant charge transfer near a critical point in the number of Mn per NC where the dopant spacing coincides with the Bohr exciton radius. Advanced computational techniques applied to Mn-doped CsPbCl3 reproduce emission colors and concentration trends, with a drop in QY at higher doping levels. Our results offer additional insight into the photophysical interplay of doping, quantum confinement, and radiative relaxation in lead-halide perovskites, while clarifying the complexity of the underlying kinetics and highlighting the critical role of the dopant number per NC at the nanoscale.

Roles of oxygen-containing functional groups of O-doped g-C3N4 in catalytic ozonation: Quantitative relationship and first-principles investigation

Graphitic carbon nitride (g-C3N4) with varied oxygen doping levels was fabricated to investigate the quantitative relationship between oxygen-containing groups and activity of catalytic ozonation employing atrazine as a model pollutant. The regulation on both the types and the amounts of different oxygen-containing groups (CO/CO/COOH) were achieved by simply varying the dosage of the oxalate precursor. The regression analysis showed that the increase of CO/CO groups within appropriate range promoted the catalytic activity for ozonation, while the presence of carboxyl groups induced by excessive oxygen doping exhibited adverse effect. Moreover, the corresponding quantitative structure-activity relationships were established. The electron-rich O centers of oxygen doped g-C3N4 (CO/CO) were identified as the active sites for catalytic ozonation, and the enhanced adsorption of ozone on the active sites were substantiated by DFT calculations. This study is believed to shed light upon the roles of different oxygen-containing functional groups in catalytic ozonation by carbonaceous catalysts.