Doping Concentration Research Articles

Atomic Structure Simulation and Properties’ Prediction using Machine Learning on Neodymium Oxide Nanoparticles Zinc Tellurite Glasses Aided by FTIR and TEM Analysis

The optical, structural, and physical characteristics of zinc tellurite glasses doped with neodymium oxide nanoparticles, which are produced by the melt-quenching method, were examined in this work. The amorphous character of the glasses was verified by XRD analysis. Using the Pair Distribution Function (PDF) and Monte Carlo simulations and visualisation for precise molecule distribution representation, an intuitive Python interface was created to emphasize these features. The density increased with increasing Nd2O3 concentrations, from 5346 to 5606 kg/cm2. Density data was used to infer the molar volume. The best projected density was achieved by the Gradient Boosting Regressor model, with a R2 of 0.9988 and an RMSE of 0.0032; the best predicted molar volume was achieved by linear regression, with a R2 of 1 and an RMSE of 2.67e-15. These models successfully represent the correlations between dopant concentration and glass properties, advancing our knowledge of the optical properties for further glass technology research.

Efficient Near-Infrared Quantum Cutting in Y2O3 co-doped with Ho3+, Yb3+ Phosphor for the Application in Solar Cell

Abstract: An efficient Near-Infrared Quantum Cutting has been demonstrated in Ho3+ and Yb3+ co-activated Y2O3 sample, synthesized by a complex based precursor solution method. The phosphors have been characterized by X-ray diffraction (XRD), Crystal structure photoluminescence (PL) and CIE Chromaticity analysis. The phosphor materials give efficient emission in the green region both through UC and PL, while efficient NIR emission is observed through the QC process. The Photoluminescence emission (PL) spectra of Y2O3 doped 1% Ho3+ x% Yb3+ (x= 0, 5, 10, 20, 30, and 50) samples, The cooperative energy transfers from one Ho3+ to two Yb3+, an intense NIR emission around 549 nm of Yb3+ 2F5/2 - 2F7/2 transition was obtained under 449 nm excitation. Near infrared photons (wavelength range 549 nm) emitted by an Yb3+ ion pair. The Properties of Y2O3 doped with Ho3+ and Yb3+ quantum-cutting phosphors are dependent on various factors such as dopant concentration, crystallinity, homogeneity, particle size. Effective control of the above parameters the quantum-cutting ability of the phosphor material. Small particle size of the quantum-cutting phosphor Y2O3:Ho3+, Yb3+ make it a suitable candidate for its application in solar cells.

Photocatalytic Degradation of Transition Metal (Ni) Doped ZnS Nanoparticles Synthesized via Simple Solvothermal Route

Ni doped ZnS nanoparticles were obtained using the simple Solvothermal Microwave Irradiation (SMI) method in this research. This technique is cost-effective and results in a high level of uniformity in particle size. The sample's structural characteristics were examined utilizing XRD Technique, FESEM image, Elemental analysis of the as prepared sample obtained from EDX spectrum and their optical characteristics analysed by using UV-Visible absorption study. The XRD pattern of Ni doped ZnS nanoparticles were to obtain their crystallite size (D), lattice constant (a), and volume of the unit cell (V). As the concentration of Ni dopant increased (0, 2.5, 5.0) M %, the values of the lattice constant decreased, leading to an overall decrease in the volume of the unit cell. FESEM images reveals the sample have uniform surface morphology and EDX analysis give evidence for element Zn, Ni, S presents in the sample. Ni doped ZnS nanoparticle dimension strongly influences their optical characteristics. The optical bandgap, as obtained from UV-Vis measurements, ranges from 3.54 eV to 3.50 eV with doping concentrations varying from 0 M% to 5.0 M% .This adjustment in optical properties suggests that Ni-doped ZnS nanoparticles have diverse applications in optoelectronics, sensors, UV detectors, and as an efficient photocatalyst for degrading pollutants in water. The efficiency of the degradation of Methylene Blue dye by Ni doped ZnS nanoparticles was found to be 75.19%.

Self‐Assembled Biconvex Microlens Array Using Chiral Ferroelectric Nematic Liquid Crystals

AbstractRecently, it is shown (Popov et al, Sci. Rep, 2017, 7, 1603) that chiral nematic liquid crystal films adopt biconvex lens shapes underwater, which may explain the formation of insect eyes, but restrict their practical application. Here it is demonstrated that chiral ferroelectric nematic liquid crystals, where the ferroelectric polarization aligns parallel to the air interface, can spontaneously form biconvex lens arrays in air when suspended in submillimeter‐size grids. Using Digital Holographic Microscopy, it is shown that the lens has a paraboloid shape and the curvature radius at the center decreases with increasing chiral dopant concentration, i.e., with decreasing helical pitch. Simultaneous measurements of the imaging properties of the lenses show the focal length depends on the pitch, thus offering tunability. The physical mechanism of formation of the self‐assembled ferroelectric nematic microlenses is also discussed.

A novel high-brightness red phosphor Ca4Nb2O9: Eu3+ for WLEDs

In this study, new phosphors Ca4Nb2O9 doped with Europium (Eu3+) ions were created using a high-temperature solid-state method. Characterizations with X-ray diffraction (XRD), Rietveld refinement, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS) and elemental mapping revealed successful doping and uniform elemental distribution. The band gap is 4.17 eV for Ca4Nb2O9 and 3.73 eV for Ca3.7Nb2O9: 0.3Eu3+, which is shown that the band gap decreases with increasing concentration. Subsequently, the samples underwent photoluminescence (PL) spectra testing, revealing that the Ca4Nb2O9: Eu3+ phosphors exhibited intense red emission when excited at 395 and 465 nm. Meanwhile, the principal emission peak resided at 613 nm, and the ideal doping concentration of Eu3+ was determined to be x = 0.3. In addition, at 420 K, the luminous intensity of Ca3.7Nb2O9: 0.3Eu3+ under 395 and 465 nm excitation is 60 % as well as 82 % of its strength at 300 K, respectively, indicating excellent thermal stability. Furthermore, the phosphor exhibits a relatively high quantum efficiency, reaching 45.47 % when excited with 395 nm light and 58.17 % when excited with 465 nm light. Finally, a white light-emitting diode (WLED) device with a Ra value of 86.3 and correlated color temperature (CCT) of 4450 K was fabricated. The results suggest that the prepared phosphor, in combination with a near-ultraviolet (NUV) light-emitting diode (LED) chip, has the potential for application in white light-emitting diodes.

OPTIMIZING THE INFLUENCE OF DOPING AND TEMPERATURE ON THE ELECTROPHYSICAL FEATURES OF P-N AND P-I-N JUNCTION STRUCTURES

In this paper, we investigate the effects of doping and temperature (at 300 K and 400 K) on the characteristics of Silicon (Si) and Gallium Arsenide (GaAs) p-n and p-i-n homojunction structures, utilizing doping concentrations of p+= n+=2∙1017 and p=n=1016 cm-3 through numerical calculation and modeling. Furthermore, we have analyzed three different cases: A) p-n, B) p+-n, and C) p-n+, to examine their influence on the distributions of space charge, potential, electric field, minority charge carriers, and the I-U curve at 300 K. It can be seen from the results that in case A, the recombination process is not observed at a lower voltage in the symmetrical p-n junction compared to than case B and C asymmetrical p-n junction. The voltage-temperature characteristics of the prepared samples were then measured at a temperature of 300K. I-U curve at 300 K. Calibration of the Si p-n homojunction structures is performed using experimental data to validate the proposed model. With the help of this constructed complex model, the influence of various geometrical changes, such as the radial p-n transition, on electrophysical properties will be examined in our next work.

Electronic vs phononic thermal transport in Cr-doped V2O3 thin films across the Mott transition

Understanding the thermal conductivity of chromium-doped V2O3 is crucial for optimizing the design of selectors for memory and neuromorphic devices. We utilized the time-domain thermoreflectance technique to measure the thermal conductivity of chromium-doped V2O3 across varying concentrations, spanning the doping-induced metal–insulator transition. In addition, different oxygen stoichiometries and film thicknesses were investigated in their crystalline and amorphous phases. Chromium doping concentration (0%–30%) and the degree of crystallinity emerged as the predominant factors influencing the thermal properties, while the effect of oxygen flow (600–1400 ppm) during deposition proved to be negligible. Our observations indicate that even in the metallic phase of V2O3, the lattice contribution is the dominant factor in thermal transport with no observable impact from the electrons on heat transport. Finally, the thermal conductivity of both amorphous and crystalline V2O3 was measured at cryogenic temperatures (80–450 K). Our thermal conductivity measurements as a function of temperature reveal that both phases exhibit behavior similar to amorphous materials, indicating pronounced phonon scattering effects in the crystalline phase of V2O3.

White emitting Sr3Ga2Ge4O14: Dy3+ phosphors with high purity and good thermal stability

A series of white emitting phosphors Sr3Ga2Ge4O14: xDy3+ (x = 1, 3, 5, 7, 9 and 11 %) were synthesized by a high-temperature solid-phase method. All samples exhibit two emission peaks at 478 nm and 571 nm, corresponding to the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions of Dy3+ ions, respectively. The optimal doping concentration of Sr3Ga2Ge4O14: xDy3+ phosphors was determined as 7 % mol, and the concentration quenching mechanism is confirmed as a dipole–dipole interaction. Finally, the temperature dependent luminescence spectra indicate that the synthesized Sr3Ga2Ge4O14: 7 % Dy3+ phosphors had good thermal stability.

Rare earth samarium substituted barium-calcium hexaferrites: Insight into structure, dielectric and magnetic aspects

This study presents the synthesis of samarium-substituted Ba-Ca hexaferrites (Ba0.5Ca0.5Fe12-xSmxO19) utilizing the sol–gel method. X-ray diffraction (XRD) analysis is performed to evaluate the structure of fabricated materials. The lattice shows an expansion up to a doping concentration of x = 0.12, and minor contraction at x = 0.16. Both X-ray density and bulk density exhibit an upward trend with increasing doping levels, while porosity reduces and dislocation density shows an increase. Scanning electron microscopy (SEM) confirms the homogeneity and uniformity of the doped samples. The dielectric properties displays the interaction of the materials with an external electric field, revealing that the dielectric constant (ε′), dielectric loss (ε″), and dissipation factor progressively increases with samarium concentration. Magnetic characterizations demonstrate a significant enhancement in saturation magnetization and coercivity, attaining peak values of 33.19 emu/g and 1.805 kOe, respectively. Moreover, the anisotropy field (Ha) and anisotropy constant (K) shows an increase with higher doping concentrations confirming the prepared material as an alternative for electric and magnetic industry applications.

Low-power ternary inverter using vertical tunnel field-effect transistor with pocket

ABSTRACT This paper proposes a vertical tunnel FET with pocket (VP-TFET)-based standard ternary inverter (T-inverter) model for low-power applications. Using TCAD Sentaurus tool and mixed-mode simulations, it is verified that the device can exhibit T-inverter voltage transfer characteristics (VTCs) with three steady output voltage levels when the doping length and concentration of the pocket are optimized The device’s T-inverter characteristics are achieved by employing channel-channel and source-channel tunnelling mechanisms. Current matching is crucial for n-/p–type devices to produce a steady third output voltage state. The proposed ternary inverter’s static noise margin (SNM) and static and dynamic power dissipations are computed to be 220 mV, 4.8 × 10−12 W, and 4 × 10−12 W, respectively, which assures better noise immunity and low power consumption compared to other models.

Influence of Wrinkle Structure on Properties of Na-doped ZnO Films

Un-doped ZnO and Na-doped ZnO (NZO) thin films with various Na doping concentrations were successfully fabricated on glass substrates by a sol-gel process. The effect of Na ions at concentrations of 0, 1, 2, 3, 4, and 5% on the crystalline structure, surface morphology, and optoelectronic properties of ZnO films was studied using appropriate measurement techniques. XRD analysis revealed a polycrystalline hexagonal wurtzite structure in the NZO films. The NZO films' average crystal size ranged from 17.7 nm to 19.6 nm. SEM micrographs showed that wrinkle network appeared in the pure and doped ZnO films due to solvent evaporation during the thermal annealing process. UV-Vis spectroscopy pointed out that the average transmittance of NZO films is as large as ca. 78%. The optical bandgap of the films varied slightly between 3.235 eV for the pure ZnO and 3.246 eV for the Na 5% doped NZO film. When Na ions were doped into the NZO films, the electrical conductivity improved. Moreover, the absorption figure of merit exhibited the largest value of 0.981 Ω-1cm-1 for the fabricated NZO films, which enables the use of these films for solar cells and for other optoelectronic applications.

Impact of Lattice Strain on the Electronic and Thermoelectric Properties of CoAs3 Skutterudite Material

Using density functional theory (DFT) combined with semi‐classical Boltzmann transport theory, the electronic and thermoelectric properties of binary skutterudite CoAs3 material are investigated up to 30 GPa. Elastic properties calculations confirm the mechanical stability at 0 GPa and under varying hydrostatic pressures, with ductility influenced by pressure. To ensure dynamical stability, the phonon dispersion frequencies are computed at both 0 and 30 GPa. Electronic band structure calculations, using the GGA + TB‐mBJ approximation, indicate that CoAs3 initially exhibits a direct band gap at its equilibrium lattice constant, which shifts to become indirect under increasing pressure. To assess the impact of pressure on the thermoelectric properties of CoAs3, the Seebeck coefficient, thermal conductivities, and figure of merit (ZT) are calculated at pressures of 5, 10, 20, and 30 GPa for various temperatures (300, 600, 900, and 1200 K). These computations provide valuable insights into how varying pressures influence the material's thermoelectric performance. The optimal thermoelectric properties in CoAs3 material are achieved at 5 GPa and 1200 K for n‐doping (20 GPa and 600 K for p‐doping), with an ideal doping concentration of 1.5 × 1021 cm−3 (5.5 × 1018 cm−3). Under these conditions, the material reaches a high figure of merit (ZT) value of 0.52 for n‐doping and 0.49 for p‐doping. These findings underscore CoAs3 as a promising candidate for applications in energy harvesting and optoelectronic systems, showcasing its robust thermoelectric performance under precise pressure and temperature conditions.

Preparation and properties of GdPO4:Dy3+ phosphors and ceramics with high thermal stability

In this work, Gd1-xPO4:xDy3+ powders were synthesized by calcining the mixed raw materials at 1273 K and the optimal doping concentration was determined. Then the optimized composition powders were fabricated as ceramics after granulation, pressing and sintering. Meanwhile, the luminescent properties of the phosphors and ceramics, especially the thermal stability, were discussed. The results revealed that Gd1-xPO4:xDy3+ exhibited two strong emission peaks of blue light and yellow light under the excitation of 349 nm, ascribed to the energy level transition from 4F9/2 to 6H15/2 and 6H13/2 of the electrons of Dy3+, and the color coordinates were located in the white light region. The optimal doping concentration of Dy3+ was found as 0.1, and the electronic dipole-dipole interaction contributed to the concentration quenching. It was noted that the phosphors had good thermal stability. Specifically, the thermal stability was further improved after the ceramics was formed and the relative intensity between the blue and yellow changed the opposite, indicating different occupation sites of Dy3+.

Reconfigurable Multilevel Storage and Neuromorphic Computing Based on Multilayer Phase-Change Memory.

In the era of big data, the amount of global data is increasing exponentially, and the storage and processing of massive data put forward higher requirements for memory. To deal with this challenge, high-density memory and neuromorphic computing have been widely investigated. Here, a gradient-doped multilayer phase-change memory with two-level states, four-level states, and linear conductance evolution using different pulse operations is proposed. The mechanism of multilevel states is revealed through high-resolution transmission electron microscopy (HRTEM) and finite-element analysis (FEA), which show that the sequential phase change among different sublayers is realized due to the different physical properties of the sublayers with different doping concentrations. Taking advantage of the devices' linear conductance evolution characteristic, a handwritten digit (28 × 28 pixel) recognition task is implemented with a high learning accuracy of 93.46% by building a simulated artificial neural network made up of this gradient-doped multilayer phase-change memory. It is proved that this gradient-doped multilayer phase-change memory is capable of both binary multilevel digital storage and brain-inspired analog in-memory computing in the same device, enabling reconfigurable applications in the future.

Design strategies and systematic analysis of GaN vertical MPS diodes with T-shaped shielding rings

Abstract We report gallium nitride (GaN) vertical merged pn-Schottky (MPS) diodes with T-shaped p-GaN shielding rings (SRs). The embedded T-shaped SR features an overlapped depletion region by the lateral and vertical p n junctions under reverse bias condition, which can effectively enhance the charge coupling effect and homogenize the 2-D electric field distribution. In the meantime, the incorporation of the T-shaped SRs can minimize unnecessary depletion of the vertical conduction channel and guarantee a decent current spreading through the drift region. The impact of the key design parameters on the reverse breakdown and forward conduction performance are investigated systematically. We found that the doping concentration and the geomatical shape of the T-shaped p-GaN SRs are closed related to the electric field distribution and forward current conduction behavior, which determines the reverse breakdown and forward conduction performance. With optimum design parameters of the T-shaped SRs, the breakdown voltage of the MPS diodes features a dramatic improvement to 2749 V from 1123 V in conventional MPS diodes. The results can provide a design strategy for high performance vertical GaN power diodes towards high-power and high-frequency applications.

Ab initio study of iron-doped zinc oxide for efficient dye degradation

First principle calculations were performed on iron doped zinc oxide (Fe-ZO) to reduce its bandgap to optimize its visible light absorption. The doping of iron in the ZO is done via supercells of Zn1-xFexO. The doped systems are analyzed using generalized gradient approximation plane wave pseudopotential on density functional theory, or local density approximation and LDA + U with PBE. The computational analysis reveals that the bandgap reduced with increasing dopant concentration. Furthermore, a robust absorption is observed toward the visible region of the spectrum. This enhances its ability as a photochemical material to increase degradation rates of industrial grade dyes.

Engineering ceria oxide with nickel doping and rich oxygen vacancies for enhanced electrocatalytic degradation of aromatic organics

Aromatic dyes are widely applicable in the textile, leather, and ink industries yet receive serious contamination issues to water bodies, soil, and even air. Herein, we develop an efficient electrocatalytic oxidation method for degrading aromatic dyes via developing supportive CeO2-based electrode materials decorating with highly dispersive Ni and rich oxygen vacancies. The decorating Ni species are in situ converted from a composite of CeO2 nanocrystals and formamide-derived polyaminoimidazole (PAI)-coordinated Ni to ensure the high dispersion of Ni species. The decomposition of PAI ligands also helps to create the localized reductive atmosphere for the generation of rich surface oxygen vacancies, which further benefits the enhancement of electronic conductivity and charge transport ability. The effects of Ni doping concentrations, Rhodamine B (RhB, as a simulating aromatic dye) concentrations, pH of RhB solution, types and concentrations of electrolytes, and working current densities on the degradation performance are comprehensively investigated. Electrocatalytic measurements reveal that the CeO2 catalyst with optimal Ni concentration and fine single-crystal sizes of 5.5 ± 0.03 nm (termed as Ni0.025-CeO2-x) exhibits very promising degradation efficiency (96.9 %) and structural durability (repeated use for 5 cycles with limited activity decrease).

Exploring the potential of epoxy nanocomposites infused with Alq3 for UV sensing applications

This research explores the morphological, molecular, and photoluminescent properties of epoxy-based nanocomposite sheets containing Alq3, as well as their response to UV irradiation. By analyzing the surface morphology via SEM, it is observed that the pristine epoxy sheets exhibit uniformity, while the nanocomposites display dispersed nanoparticles, influenced by the concentrations of dopants. Raman spectroscopy reveals changes in molecular structures and vibrational modes, with broadened peaks indicating potential interactions between the additives and epoxy matrix. The photoluminescence (PL) emission spectra show enhancements in intensity and shifts in peak wavelengths toward the green emission region, significantly influenced by the dopants. UV irradiation causes changes in both Raman and PL signals, with varying effects on different nanocomposite configurations. Linear regression analysis demonstrates strong correlations between signal changes and irradiation time, particularly pronounced in epoxy/Alq3 nanocomposite sheets, with marginal errors from Raman and PL signal-induced changes of 5% and 2%, respectively. Additionally, stability and reproducibility assessments reveal consistent signal trends over prolonged UV exposure and high reproducibility with minimal error of less than 5%. Overall, these epoxy nanocomposite sheets display promising results for UV sensing applications due to their sensitivity, linearity, stability, and reproducibility.

Atomistic study of selenium doping effects on the mechanical properties of zinc-blende and wurtzite CdTe nanowires

CdSexTe1–x semiconductor materials, having potential to be used to design dependable and reproducible nanowire devices, require an extensive study of their mechanical behaviors. The uniaxial tensile deformation mechanism of CdSexTe1–x nanowires (NWs) with different Se dopant concentration are yet to be explored. By integrating theoretical analysis with computational simulation, this research demonstrated that Se doping in CdTe NWs influences the mechanical response and failure modes. Ultimate tensile strength (UTS) and elastic modulus (EM) were studied for both zinc-blende (ZB) and wurtzite (WZ) structures with different crystal orientations. The findings revealed that these mechanical properties increase linearly with increasing Se concentration in all cases. In addition, the WZ structures exhibited similar mechanical properties under both zigzag and armchair loadings, unlike the ZB structures, which exhibited a strong dependence on the crystal orientation. The [111]-oriented ZB structures showed the highest EM and UTS whereas [100]-oriented ZB structures showed lowest EM and UTS. The failure mechanism was explored for CdSe50Te50 to underscore the influence of the dopant on the NWs failure for tensile loading. In both the cases of WZ structure, the failure planes were perpendicular to the loading direction. Furthermore, the failure plane varied with the Se content in ZB CdSexTe1–x. Atomic coordination and bond length affected by doping defined the alterations of mechanical properties and the preferred modes of failure. The significance of the interaction between doping elements and nanowire structures offers insights that unite material science and mechanics, contributing to the scientific understanding of solid materials’ behavior.

Understanding Spin-Orbit-Coupling-Induced Reverse Intersystem Crossing in DMAC-TRZ-Doped Organic Light-Emitting Diodes via Magnetic-Field-Effect Measurement.

An efficient reverse intersystem crossing (RISC) process in thermally activated delayed fluorescence (TADF) material is a common way to obtain high-performance organic light-emitting diodes (OLEDs), but the physical mechanism for the spin flipping of the RISC remains vague. Here, using magneto-electroluminescence (MEL) as an effective tool, we found that the RISC (CT3 → CT1) from a triplet charge transfer (CT3) to the singlet charge transfer (CT1) state is decided by spin-orbit coupling (SOC) in metal-free OLEDs based on a typical TADF emitter DMAC-TRZ. By fitting and analyzing the current and concentration-dependent MEL data, it is found that the characteristic magnetic field of the SOC-induced RISC process is approximately 65-85 mT, which is obviously larger than that (several mT) of the hyperfine-interaction-induced RISC process. Simultaneously, the dissociation effect of the electric field on the CT3 state causes the SOC-induced RISC process to decrease with increasing bias current. The different formation methods of excited states lead to the nonmonotonic change of SOC-induced RISC process with the increase of dopant concentration. Furthermore, considering the orbital polarization of dipoles, the SOC mechanism is further verified by the measurement of magneto-photoluminescence to be the responsible for achieving the spin flipping in TADF molecules. Therefore, this work clarifies the underlying dynamic mechanism of the RISC process in TADF-OLEDs.