Effect Of Doping Concentration Research Articles

Role of Dysprosium Doping on Structural, Optical, Magnetic and Electrical Properties of ZnO Nanorods

Well-defined Dy-doped ZnO rods were synthesized by hydrothermal route. Various studies were carried out on the synthesized rods like x-ray diffraction to confirm their hexagonal wurtzite structure; TEM, HRTEM and selected area electron diffraction to establish their rodlike structure; energy-dispersive x-ray spectroscopy analysis confirming appropriate substitution of dopant; UV-Vis spectra, which showed decrease in band gap with dopant concentration and photoluminescence study furnishing information regarding the presence of various types of defects. Further, magnetic studies were done using VSM to confirm roomtemperature ferromagnetic behaviour of both for undoped and doped ZnO rods and, the electrical studies were performed using four probe method, which confirmed that the ‘variation in resistivity with dopant concentration’ was related to crystallinity of the samples. UV-Vis spectra showed effect of dopant concentration on band gap and photoluminescence study confirms induced ferromagnetic behaviour due to Dy doping.

Influence of Al Doping Concentration and Annealing Parameters on TiAl Based Ohmic Contacts on 4H-SiC

TLM structures on Al-implanted regions with different implanted Al concentrations and different annealing temperatures were processed and characterized by electrical measurements in order to determine the influence of these parameters on the ohmic resistivity. Based on these results, a TCAD model was developed that considers the carrier concentration of the implanted region, the effective density of states for holes and the hole tunneling mass at the Ti3SiC2-SiC interface. It could be shown that Ti3SiC2 allows to form ohmic contacts on Al implanted samples with an effective doping concentration down to 3·1017 cm-3. Furthermore the effective density of states for holes in Ti3SiC2 was determined to 8.5·1018 cm-3 and the hole tunneling mass in SiC and Ti3SiC2 in the range of 2·10-34 kg to 6·10-33 kg depending on the sample.

Self-cleaning lanthanum doped cadmium sulfide thin films and linear/nonlinear optical properties

A high quality lanthanum (La) doped cadmium sulfide (CdS) thin films were synthesized onto a glass substrates by chemical bath deposition. The effects of lanthanum doping concentration on the composition, structural and optical properties of CdS thin films have been studied. The transmittance of CdS thin film is 80% and gradually decreased as the La content was increased. Analysis of the optical absorption coefficient of CdS and La doped CdS thin films revealed that a presence of direct optical transition and the optical direct band gap of the films apparently decreased from 2.45 to 2.09 eV when the lanthanum content was increased from 0 to 12 wt %. The values of optical and electrical conductivity of CdS and La doped CdS thin films have been increases with increasing the lanthanum content. The self cleaning test shows that 12% La doped CdS thin films have excellent photocatalytic activity.

Concentration Dependence of Dopant Electronic Structure in Bottom-up Graphene Nanoribbons.

Bottom-up fabrication techniques enable atomically precise integration of dopant atoms into the structure of graphene nanoribbons (GNRs). Such dopants exhibit perfect alignment within GNRs and behave differently from bulk semiconductor dopants. The effect of dopant concentration on the electronic structure of GNRs, however, remains unclear despite its importance in future electronics applications. Here we use scanning tunneling microscopy and first-principles calculations to investigate the electronic structure of bottom-up synthesized N = 7 armchair GNRs featuring varying concentrations of boron dopants. First-principles calculations of freestanding GNRs predict that the inclusion of boron atoms into a GNR backbone should induce two sharp dopant states whose energy splitting varies with dopant concentration. Scanning tunneling spectroscopy experiments, however, reveal two broad dopant states with an energy splitting greater than expected. This anomalous behavior results from an unusual hybridization between the dopant states and the Au(111) surface, with the dopant-surface interaction strength dictated by the dopant orbital symmetry.

From Transparent Conducting Material to Gas-Sensing Application of SnO2:Sb Thin Films

Transparent conductive thin films of nanocrystalline tin oxide:antimony (SnO2:Sb) were deposited on a preheated glass substrate at 400°C via spray pyrolysis technique. The effects of Sb doping concentration on morphological, structural and optical properties of the films were investigated by ultraviolet (UV)-visible absorption, x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The XRD study revealed that all the films had a polycrystalline nature, which increased with the Sb doping up to 4 wt.% and then decreased with further Sb doping. Similarly, the SEM images highlighted that the grain size of the SnO2:Sb thin films increased with Sb doping from 2 wt.% to 4 wt.% and then decreased for 6 wt.%. UV–visible study demonstrated that the average transmission in the visible region was found to vary from 35% to 75% depending on the Sb doping concentration. As a proof of concept, we implemented the SnO2:Sb thin films with different Sb doping for gas-sensing applications. To measure the selectivity of the SnO2:Sb thin films, the Sb-doped and -undoped films were exposed to different types of gases with varied concentration. The results of this work demonstrated that the SnO2:Sb thin film-based gas sensor had a high potential for NH3 at a low temperature (100°C). In addition, long-term stability of the SnO2:Sb thin film-based sensor was measured at 100 ppm NH3 for 90 days.

Thermoluminescence behavior of Sm3+ activated ZnB2O4 phosphors synthesized using low temperature chemical synthesis method

Abstract This study is mainly centered on thermoluminescence (TL) behavior under beta excitation at room temperature (RT) of Sm3+ activated ZnB2O4 phosphors synthesized by low temperature chemical synthesis method. The prepared phosphors were characterized by the X-ray powder diffraction (XRD) method. The effects of dopant concentration, beta radiation dose (0.115–69 Gy) and heating rate (0.5–10 °C/s) on TL intensity of Sm3+ doped ZnB2O4 phosphors and reproducibility are investigated using a lexsyg smart TL/OSL reader system. The activation energy values, E obtained from the analysis of the TL glow curve were calculated with initial rise (IR) method and peak shape (PS) method over the deconvoluted glow curves. The Ea–Tstop and CGCD methods indicated that the glow curve of this phosphor is the superposition of at least six components, which were called to as P1–P6, in the temperature range between RT and 400 °C. The results reveal that 2% Sm3+ doped ZnB2O4 gives optimum TL response, the relative intensity of the glow peak increases linearly with increase of beta dose and, the peaks of TL glow curves shift towards the higher temperature side with increase in heating rate as the total area under the glow peak remains the same. The maximum variation of reproducibility for ten successive irradiation cycles of 20.7 Gy is less than 3% from the average value and the sample doped 2% Sm3+ shows a good stability for the reusability. Additionally, the results obtained from IR and PS methods indicates that the complex glow curve is composed of six distinguishable peaks.

Investigation on structural, morphology and photoluminescence properties of lanthanum doped zinc oxide nanostructure for optical application by co-precipitation method

The doping of semiconductor by rare earth metal nanoparticles is an effective way for increasing photo catalytic activity. The preparation of ZnO particles with different concentrations of La doping (0, 3, 5 and 7 at.%) via co-precipitation method, and the effects of lanthanum doping concentration on the structures, morphologies and photoluminescence properties were investigated by XRD, FESEM, EDAX and PL. The XRD results indicated that the synthesized La-doped ZnO nanoparticles had the pure wurtzite structure. The crystallite size calculated by Debye–Scherrer’s formula is in the range of 36–28 nm. In addition, increasing the doping concentration of La ions in ZnO increase the defects in ZnO lattice and hence resulting in UV emission, which indicate the presence of narrow band-gap in doped nanoparticles.

Study of visible light emission under UV excitation in Y2O3:Er3+-Gd3+ and Y2O3:Eu3+-Gd3+ nanocrystals

In this work, we study the Y2O3:Er3+-Gd3+ and Y2O3:Eu3+-Gd3+ nanocrystals using statistical tools in order to quantify the effect of dopant concentration, crystallite size, induced strain, and lattice parameters on luminescent parameters such as intensity and color emission. Samples were synthesized using the sol–gel method. In the case of emission properties of Y2O3:Er3+-Gd3+, the most important factor is Erbium concentration, while the energy transfer between Gadolinium-Erbium is statistically insignificant, compared to the dynamics between Erbium–Erbium ions. On the other hand, the Y2O3:Eu3+-Gd3+ emission intensity depends on the dopant concentration: an increase of Gadolinium ions increases the emission intensity, and the quadratic effect of the Eu3+ ions reduce the emission intensity. However, the color coordinate is not so influenced by the dopant concentration; in the case of Y2O3:Er3+-Gd3+ samples, the color coordinate depends only on Er3+ concentration.

A New Physical Insight for the 3-D-Layout-Induced Cylindrical Breakdown in Lateral Power Devices on SOI Substrate

The layout-induced cylindrical breakdown may occur as a result of the multifinger or circular layout-induced 3-D curvature effect resulting in the breakdown voltage reduction of the power device significantly. In this paper, by using effective doping concentration (EDC) concept, the inherent 3-D problem is simplified as a 1-D problem. Based on the EDC concept, a 1-D analytical model is presented to qualitatively and quantitatively explore the impact of curvature effect on the breakdown mechanism of SOI lateral double diffused MOS. The analytical solutions are found out to be consistent with the simulation results well obtained from MEDICI, a commercial technology computer-aided design tool. To the best of our knowledge, the proposed model is the first 1-D model which can accurately describe the 3-D curvature effect.

Role of copper/vanadium on the optoelectronic properties of reactive RF magnetron sputtered NiO thin films

In this study, pristine nickel oxide (NiO), copper-doped NiO (Cu–NiO) and vanadium-doped NiO (V–NiO) thin films were deposited using reactive RF magnetron co-sputtering as a function of dopant sputtering power. Cu (0–8 at%) and V (0–1 at%) were doped into the NiO lattice by varying the sputtering power of Cu and V in the range of 5–15 W. The effect of dopant concentration on optoelectronic behavior is investigated by UV–Vis–NIR spectrophotometer and Hall measurements. XRD analysis showed that the preferred orientation of the cubic phase for undoped NiO changes from (200) to (111) plane when the sputtering parameters are varied. The observed changes in the lattice parameters and bonding states of the doped NiO indicate the substitution of Ni ions by monovalent Cu and trivalent V ions. The optical bandgap of pristine NiO, Cu–NiO, and V–NiO was found to be 3.6, 3.45, and 3.05 eV, respectively, with decreased transmittance and resistivity. Further analysis using SEM and AFM described the morphological behavior of doped NiO thin films and Raman spectroscopy indicated the structural changes on doping. These findings would be helpful in fabricating solid-state solar cells using doped NiO as efficient hole transporting material.

Shape‐Tunable Selective Synthesis of Bismuth Fluoride Nanostructures for Versatile Applications

AbstractA facile approach for shape‐tunable synthesis of bismuth fluoride nanoparticles is reported. The approach is based on the homogeneous precipitation of precursor materials in mixed solvents (H2O and ethylene glycol) and only ethylene glycol. The influencing factors on the morphology of the particles, i.e., solvent ratio, F/Bi ratio, and ethylenediaminetetraacetic acid, are studied in detail, and are schematically illustrated. The morphology, crystallinity, structure, and optical properties of the prepared samples are characterized by using a field‐emission scanning electron microscope, transmission electron microscope, X‐ray diffractometer, Fourier transform infrared spectrometer, and spectrofluorometer, respectively. The hollow sphere‐shaped nanoparticle doped with Eu3+ ions exhibit reddish orange emission under ultraviolet illumination due to the symmetric environment around the dopant ions. Subsequently, the effect of dopant concentration on the optical properties is also evaluated. The temperature‐dependent photoluminescence emission spectra reveal good thermal stability. The obtained results provide an efficient strategy for synthesizing the shape‐tunable nanoparticles with excellent optical properties.

Effect of Dopant Concentration on Structural, Optical and Magnetic Properties of Zn1-xNixO Nanocomposites

Effect of Dopant Concentration on Structural, Optical and Magnetic Properties of Zn1-xNixO Nanocomposites

Research on formation mechanism of nano spherical mix-phase TiO2

Grain size control has been a research field of great importance as it requires the exploration of material formation mechanism, a major decisive factor in obtaining material’s ideal size and structure. The purpose of this experiment was to analyse the effect of cerium ion doping concentration on the transformation of TiO2. Mixed-phase anatase and rutile were prepared for this experiment, providing means to examine the specific transformation relationships at different temperatures for a specific phase, and vice versa. The results of this experiment clearly also deduced the formation mechanism based on the third L. Pauling Principle and Ostward’s rule, and found grain effect of cerium doping on the transition of TiO2.

Cobalt-Assisted Morphology and Assembly Control of Co-Doped ZnO Nanoparticles.

The morphology of metal oxide nanostructures influences the response of the materials in a given application. In addition to changing the composition, doping can also modify the morphology of a host nanomaterial. Herein, we determine the effect of dopant concentration, reaction temperature, and reaction time on the morphology and assembly of CoxZn1−xO nanoparticles synthesized through non-aqueous sol-gel in benzyl alcohol. With the increase of the atom % of cobalt incorporated from 0 to 15, the shape of the nanoparticles changes from near spherical, to irregular, and finally to triangular. The tendency of the particles to assemble increases in the same direction, with Co0.05Zn0.95O consisting of non-assembled particles, whereas Co0.15Zn0.85O consists of triangular nanoparticles forming spherical structures. The morphology and assembly process are also sensitive to the reaction temperature. The assembly process is found to occur during the nucleation or the early stages of particle growth. The cobalt ions promote the change in the shape during the growth stage of the nanoparticles.

Study of Undoped and Indium Doped ZnO Thin Films Deposited by Sol Gel Method

In this paper, we report the effects of Indium doping concentrations (from 0 to 10wt%) on the structural, morphological, and optical properties of deposited In doped ZnO (IZO) thin films prepared by the sol–gel method through the dip coating technique. X-ray diffraction (XRD) analysis indicates that all ZnO thin films have a polycrystalline nature with a hexagonal wurtzite phase with (002) as a preferential orientation. XRD results demonstrate that the particle size of ZnO decreased with the increase in Indium concentrations. Raman scattering spectra confirmed the wurtzite phase and the presence of intrinsic defects in our samples. Energy dispersive spectroscopy (EDS) and the X-ray photoelectron spectroscopy (XPS) measurements, confirmed the presence of zinc, oxygen and indium elements which is in agreement with XPS results. The photoluminescence (PL) spectra of the films exhibit defects-related visible emission peaks, with intensities differing owing to different concentrations of zinc vacancies. UV–Vis spectrometer measurements show that all the films are highly transparent in the visible wavelength region (≥ 70%) and presented two different absorption edges at about 3.21 eV and 3.7 eV, these may be correspond to the band gap of zinc oxide and indium oxide respectively.

Effect of Low Doped Calcium on the Magnetic Properties of La0.7Ba0.297Ca0.003MnO3 for Magnetocaloric Application

Effect of low doped calcium concentration to the magnetic properties of La0.7Ba0.3MnO3 material has been reported in this paper. This compound was chosen because it has high potential to be applied in electronic devices. The most intensive research in the last decade is about magnetocaloric effect (MCE). Magnetic refrigeration will replace Freon R12 that is used in conventional refrigeration with magnetic material which has MCE properties. It is due to conventional refrigeration produce chlorofluorocarbons (CFC) and hydrochlorofluorocarbons (HCFCs) gases which causes ozone depletion. The magnetic measurement was performed by using Vibrating Sample Magnetometer in the range of temperature between 300-400 K under external magnetic field until 20 kOe. By using derivative of magnetization as a function of temperature of the material’s result, Curie temperature (Tc ) of the material is 332.7 K. By using equation (5) for calculating magnetic field dependence of magnetization at various temperature result, magnetic entropy change value (ΔSM ) of the material can be obtained. The ΔSM of the material is -2.928 Jkg-1K-1. The material has highest magnetic entropy change value around its Tc . It is due to there is strong lattice spin coupling around its Tc and would be weak at below and above its Tc .

Orange-red emitting Gd2Zr2O7:Sm3+: Structure-property correlation, optical properties and defect spectroscopy

Local structure analysis of dopant ion, understanding host to dopant energy transfer dynamics and defects characterization in a doped material which plays an important role in the designing a highly efficient opto-electronic material. In this connection a new Sm3+ doped Gd2Zr2O7 pyrochlore material was synthesized using gel-combustion technique and was characterized systematically using X-ray diffraction (XRD), time resolved photoluminescence spectroscopy (TRPLS), positron annihilation lifetime spectroscopy (PALS) and density functional theory (DFT) based ab-initio calculation. Based on DFT site selective energetics calculation and luminescence decay measurement, it was observed that the Sm3+ was distributed at both Gd3+ and Zr4+ site with higher Sm3+ fraction at the Gd3+ site. PALS was used to probe the presence of defects in the phosphor. In this work intense orange-red emission is realized through manipulating the energy transfer from host defect emission (oxygen vacancies) to Sm3+ which allows color emission from green in undoped to orange-red in doped samples. Effect of dopant concentration and annealing temperature was probed using TRPLS and PALS. These all information is highly important for researcher looking to achieve pyrochlore based phosphor materials with high quantum yield.

Structural and optical properties of Na-doped ZnO films

Zn1-xNaxO (x = 0.0–0.05) solutions have been synthesized by the sol-gel technique using Zinc acetate dihydrate and Sodium acetate which were dissolved into solvent and chelating agent. Na-doped ZnO nanoparticles were obtained from solutions to find phase and crystal structure. Na-doped ZnO films have been deposited onto glass substrate by using sol-gel dip coating system. The effects of dopant concentration on the structure, morphology, and optical properties of Na-doped ZnO thin films deposited on glass substrate are investigated. Characterization of Zn1-xNaxO nanoparticles and thin films are examined using differential thermal analysis (DTA)/thermogravimetric analysis (TGA), Scanning electron microscope (SEM) and X-Ray diffractometer (XRD). Optical properties of Zn1-xNaxO thin films were obtained by using PG Instruments UV–Vis–NIR spectrophotometer in 190–1100 nm range. The structure, morphology, and optical properties of thin films are presented.

Effective Doping Concentration Theory: A New Physical Insight for the Double-RESURF Lateral Power Devices on SOI Substrate

Double-reduced surface field (D-RESURF) technique aims to increase the doping concentration of drift regions and maintain a high breakdown voltage. However, conventional 2-D models are too complicated and unable to elaborate its physical meaning. Hence, the D-RESURF effective doping concentration (EDC) theory is proposed in this paper to explore the physical insight of the D-RESURF effect by equating the sophisticated 2-D structure to a simple 1-D RESURF model with segmented-doped p-n junction. The EDC indicates that an NPNP structure may exist because of the influence of the P-top region. Thus, two electric field valleys and one electric field peak can be formed on the surface. Based on the theory, a 1-D analytical model is presented to qualitatively and quantitatively explore the impact of D-RESURF effect on breakdown mechanism of silicon on insulator lateral double diffusion MOS. The results obtained by the proposed model are found to be sufficiently accurate comparing with TCAD simulation results.

TG–DTA analysis, structural, optical and magnetic properties of PbS thin films doped with Co2+ ions

Cobalt-doped PbS (PbS:Co) thin films were grown on glass substrates via a cost effective spray technique using perfume atomizer. The effect of Co doping concentration on the thermal behavior, structural, optical and magnetic properties of PbS thin films was investigated and the results are reported in this paper. TG–DTA studies confirm that the thermal behavior of pure PbS is strongly influenced with Co doping. X-ray diffraction patterns reveal that both the undoped and doped PbS thin films exhibit face-centered cubic crystal structure with a strong (2 0 0) preferential growth texture. The increase of Co doping concentration tends to increase the band gap of pure PbS from 2.24 to 2.46 eV which may be attributed to quantum confinement effect. Undoped PbS thin film exhibit paramagnetic behavior at room temperature which becomes ferromagnetic with Co doping. From the results obtained it is observed that the PbS thin films doped with 3 wt% Co concentration exhibit better magnetic properties.