Function Of Dopant Concentration Research Articles

Preparation and characterization of pure and copper-doped PVC films

Abstract Pure and Cu2+-doped polyvinyl chloride (PVC) polymer films were prepared using the solution cast technique. Investigations were conducted using DSC, TGA, XRD, FT-IR, UV–Vis, SEM and EPR. Differential scanning calorimetry studies suggested that the Cu2+ samples have higher values of the glass transition (T g) temperature, and thermo gravimetric studies show that weight loss of polymer film indicates the improved thermal stability of the polymer film. The features of the complexation of the polymer films were studied by X-ray diffraction. FT-IR spectra exhibits the bands in three regions, which are attributed to C–Cl, C–C and numerous CH groups of stretching and bending vibrations. The absorption spectra have been recorded in the wavelength range 200–900 nm. The absorption edge, direct bandgap, indirect bandgap and urbach energy have been evaluated. Film morphology was examined by scanning electron microscopy. XRD, DSC and SEM reveal the amorphous nature and surface morphology of polymer films, respectively. Electron paramagnetic resonance studies were used to calculate the number of spins and paramagnetic susceptibility as a function of dopant concentration, all the Cu2+-doped PVC samples exhibit signal with g values g ⊥=2.176 and g ||=2.254. The observed variation in the EPR signal intensity is due to variation in the dopant concentration.

Boron doped ZnO embedded into reduced graphene oxide for electrochemical supercapacitors

In this work, reduced graphene oxide/boron doped zinc oxide (RGO/ZnO:B) composites were fabricated by a hydrothermal process and their electrochemical properties were investigated as a function of dopant concentration. First, boron doped ZnO (ZnO:B) particles was fabricated with different boron concentrations (5, 10, 15 and 20wt%) and then ZnO:B particles were embedded into RGO sheets. The physical properties of sensitized composites were characterized by XRD and SEM. Characterization indicated that the ZnO:B particles with plate-like structure in the composite were dispersed on graphene sheets. The electrochemical properties of the RGO/ZnO:B composite were investigated through cyclic voltammetry, galvanostatic charge/discharge measurements in a 6M KOH electrolyte. Electrochemical measurements show that the specific capacitance values of RGO/ZnO:B electrodes increase with increasing boron concentration. RGO/ZnO:B composite electrodes (20wt% B) display the specific capacitance as high as 230.50F/g at 5mV/s, which is almost five times higher than that of RGO/ZnO (52.71F/g).

Functional data analysis techniques for the study of structural parameters in polymer composites

This article presents a novel method, based on functional data analysis, to analyse measurements of structural parameters of polymers and polymer composites. The method is demonstrated using newly developed biodegradable conducting polymer composites prepared via a solution casting technique. The measurements of the macro- and microstructural parameters that are used in the characterization of these films are obtained using X-ray diffraction, an impedance analyser and a UV–vis spectrometer. A functional representation of the measured values of the parameters at different dopant concentrations is adopted by viewing them as realizations of a continuous-time stochastic process observed with measurement error. This allows one to estimate the mean functional relationship between a parameter and the dopant concentration. A functional version of principal component analysis is performed, by which the major modes of variation are discovered and the correlations of parameter values at different concentrations are estimated. This provides insight into local and global features of the relationship between these parameters. Some comments are made on how the parameters vary as a function of dopant concentration.

Effect of isovalent dopants on photodegradation ability of ZnS nanoparticles

Isovalent (Mn, Cd, Cu, Co)-doped-ZnS nanoparticles having size vary in between 2 to 5nm are synthesized by co-precipitation route. Their photocatalytic activity for decoloration of Cango Red and Malachite Green dyes is tested in visible radiation under natural conditions. Structural and morphological features of the samples are investigated by X-ray diffraction, Raman spectroscopy, Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and UVVis spectrometer. Single phase zinc blende structure of as-synthesized undoped and doped-ZnS is confirmed by XRD and revealed by Rietveld fitting. SEM and TEM images show ultrafine nanoparticles having size in the range of 2 to 5nm. UV–Vis absorption spectra exhibit blue shift in absorption edge of undoped and doped ZnS as compared to bulk counterpart. The photocatalytic activity as a function of dopant concentration and irradiation time is systematically studied. The rate of de-coloration of dyes is detected by UVVis absorption spectroscopy and organic dye mineralization is confirmed by table of carbon (TOC) study. The photocatalytic activity of Mn-doped ZnS is highest amongst all dopants; however Co as a dopant is found to reduce photocatalytic activity than pure ZnS.

Comparative study of sputter‐deposited SnO2 films doped with antimony or tantalum

AbstractSnO2 films doped with antimony or tantalum were sputter‐deposited for comparison, using an identical set of parameters. The influence of dopant concentration and choice of deposition parameters such as substrate temperature on the optoelectronic properties, especially film resistivity, were determined. Comparative analysis shows that tantalum doping yields lower film resistivity, probably due to an increased inhibiting influence of grain boundary scattering in the case of antimony doping. Sputter‐deposited tantalum‐doped films with lower than previously achieved resistivity , carrier density , and mobility are reported, while maintaining optical transmittance above 85% at a film thickness 400 nm. Ta/Sb co‐doped thin films were synthesized for the first time, achieving similar results.Comparison of resistivity values achievable by doping sputter‐deposited tin oxide films with antimony (blue) or tantalum (red) as a function of dopant concentration.

Lattice contraction and lattice deformation of UO2 and ThO2 doped with Gd2O3

The lattice deformations in two doped fluorite systems, (U1−xGdx)O2.00 and (Th1−xGdx)O2−x/2, have been reassessed by precise X-ray and electron diffraction investigations and the results were interpreted using the Bond Valence Sum (BVS) approach. For the (U1−xGdx)O2.00 system, the experimental findings and theoretical assessment confirm earlier work: the lattice keeps its fluorite structure with a unit cell parameter that contracts linearly with dopant concentration. The lattice contraction in the (Th1−xGdx)O2−x/2 system has for the first time been analyzed up to the solubility limit. Similar as for (U1−xGdx)O2.00, the (Th1−xGdx)O2−x/2 solid solution contracts linearly as a function of dopant concentration but additionally, it develops a superstructure which is closely related to the parent fluorite structure. An excess anion bixbyite trial model is proposed to describe this superstructure.

Effect of particle morphology and coating thickness on fluorescent behavior of Ce doped yttrium aluminium garnet phosphor screens

Cerium activated yttrium aluminium garnet (Y3Al5O12; YAG) powder was synthesized by co-precipitation method using aluminium nitrate, yttrium nitrate and cerium nitrate as starting materials and ammonium carbonate as precipitant. The concentration of cerium (Ce) was varied from 0.02 to 0.1 mol. The precursor of Ce doped YAG was calcined at 1250 °C for 1–12 h for achieving different morphology of particles. X-ray diffraction analysis was carried out to confirm the formation of YAG phase. Electrophoretic deposition was used for uniform coating of synthesized YAG:Ce powder on glass substrate. The deposition time was varied from 1 to 9 min for achieving different thickness of coating. Photoluminescence property of coating was investigated as a function of dopant concentration, particle morphology and coating thickness. The excitation wavelength used in this investigation was 430 nm. YAG:Ce showed peak emission at ~530 nm. The maximum emission intensity was achieved at Ce content of 0.04 mol in YAG with spherical morphology of particles having 300 nm particle size and 11 μm coating thickness.

Characterizations of Indium-Doped Cu<sub>2</sub>SnSe<sub>3</sub> Bulks Made by Reactive Sintering at 550 °C

Indium-doped Cu2SnSe3 bulk materials with the Cu2(Sn1-xInx)Se3 (In-x-CTSe) formula at x = 0, 0.05, 0.1, 0.15, and 0.2 were prepared at 550 °C for 2 h with soluble sintering aids of Sb2S3 and Te. Defect chemistry was studied by measuring structural and electrical properties of In-x-Cu2SnSe3 as a function of dopant concentration. In-x-CTSe pellets show p-type at x = 0, 0.05 and 0.1 and n-type at x = 0.15 and 0.2. The low hole concentration of 4.56×1017 cm-3 and high mobility of 410 cm2 V-1 s-1 were obtained for Cu2(Sn1-xInx)Se3 bulks at x= 0.1 (10% In). The explanation based upon the In-to-Cu antisite defect for the changes in electrical property was declared.

Structural and electrical properties of Si- and Ti-doped Cu2SnSe3 bulks

Silicon-doped (Cu2(Sn1−xSix)Se3 and titanium-doped (Cu2(Sn1−xTix)Se3 at x=0, 0.05, 0.1, 0.15, and 0.2 were prepared at 550°C for 2h with soluble sintering aids of volatile Sb2S3 and Te. Defect chemistry was studied by measuring structural and electrical properties of Si-doped and Ti-doped Cu2SnSe3 (CTSe) as a function of dopant concentration. Si-doped CTSe pellets show p-type at x=0 and 0.05 and n-type at x=0.1, 0.15, and 0.2, whereas Ti-doped CTSe pellets show p-type at x=0, 0.05 and 0.1 and n-type at x=0.15 and 0.2. The lowest hole concentration of 3.6×1017cm−3 and the highest mobility of 1525cm2V−1s−1 were obtained for the Si-doped (Cu2(Sn1−xSix)Se3 bulks at x=0.1 (10% Si), while they were 3.1×1017cm−3 and 813cm2V−1s−1 for the Ti-doped CTSe bulks at x=0.15 (15% Ti), as compared to 1.1×1018cm−3 and 209cm2V−1s−1 for undoped one. The explanations based upon antisite defects of Si-to-Sn, Ti-to-Sn, Cu-to-Sn, and Sn-to-Cu for the changes in electrical property were declared. The study in bulk Si-doped and Ti-doped CTSe is based upon defect state and is consistent and supported by the data of electrical property and lattice parameter.

Photoluminescence and structural properties of Eu3+ doped SrZnV2O7 nanocrystals

Novel SrZn1−xEuxV2O7 nanoparticles were synthesized employing urea assisted solution combustion process. The Rietveld refinement technique was used to study the effect of Eu3+ doping on the crystal structure of the host lattice. It was found to crystallize in monoclinic lattice with the P121/c1 (14) space group. The photoluminescent spectral analysis showed that upon excitation in the near UV region, these nanophosphors can emit very intense red luminescence (616nm) corresponding to the hypersensitive 5D0→7F2 transition of Eu3+ ions. X-ray diffraction studies revealed the low symmetrical co-ordinative environment of the activator ion (trigonal bipyramidal) with no inversion center in the SrZnV2O7 host lattice. The optimum concentration of Eu3+ ion in SrZnV2O7 for better luminescence was found to be 4mol% The critical distance for energy transfer (24.1602Å) imparted the initial idea of intensity variation as a function of dopant concentration. Dipole–dipole (d–d) interactions were successfully accounted for the concentration quenching arising from the over-doping of the activator ions. These near UV light absorbers (395nm) can be thrivingly used in white LEDs using lnGaN chip system, plasma display panels (PDPs) and solid state laser.

Microstructures and Electrical Properties of HPMC/PVP Polymer Blend Films Complex with Ferric Chloride (FeCl3)

Microstructural studies on FeCl3 doped Hydroxypropyl methyl cellulose (HPMC)/Poly vinyl pyrrolidone (PVP) blend films were carried out using X-Ray diffraction studies. The XRD data revealed that the crystalline regions of the HPMC/PVP blend film decreases up to a certain percentage of FeCl3 and then increases. Electrical conductivity studies on these doped films suggest complex formation due to doping which affects microstructure and also ac conductivity of polymer films. All these results were analyzed and explained on the basis of micro structural modification of HPMC/PVP blends as function of dopant concentration.

Imaging of morphological changes and phase segregation in doped polymeric semiconductors

The electrical conductivity and morphological characteristics of two conjugated polymers, P3HT and PCPDTBT, p-doped with the strong electron acceptor tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) are studied as a function of dopant concentration. By combining scanning and transmission electron microscopy, SEM and TEM, with electrical characterization, we observe a correlation between the saturation in electrical conductivity and the formation of dopant rich clusters. We demonstrate that SEM is a useful technique to observe imaging contrast for locating doped regions in thin polymer films, while in parallel monitoring the surface morphology. The results are relevant for the understanding of structure property relationships in doped conjugated polymers.

Optical, mechanical and TEM assessment of titania-doped Bi2V1−x Ti x O5⋅5−δ bismuth vanadate oxides

Optical, mechanical and structural behaviors have been studied for titania-doped Bi2V1−x Ti x O5⋅5−δ which are used as electrolytes for intermediate temperature fuel cells. Parameters like band gap (E g), Urbach energy (E u), refractive index, hardness (H) and fracture strength (K) have been calculated as a function of dopant concentration, i.e. 0⋅05 ≤ x ≤ 0⋅2. Furthermore, analysis of transmission electron microscopy (TEM) images for all the oxides was conducted along with line spectra of planes. Results are discussed in light of correlation of these optical and mechanical parameters to their structural properties. Band gap has also been correlated to the conductivity of these oxides. Good correlation has been obtained between them.

Suppression of optical damage at 532 nm in Holmium doped congruent lithium niobate.

Optical damage experiments were carried out in a series of Holmium doped congruent lithium niobate (Ho:cLN) crystals as a function of dopant concentration and laser intensity. The light induced beam distortion was recorded with a camera and a detector under the pseudo-Z-scan configuration. At 532 nm, strong suppression of the optical damage was observed for the 0.94 mol. % doped crystal. Increased resistance to optical damage was also observed at 488 nm. The suppression of the optical damage is predominantly attributed to the reduction of the Nb antisites due to the holmium doping.

Calotropis procera mediated combustion synthesis of ZnAl2O4:Cr3+ nanophosphors: Structural and luminescence studies

ZnAl2O4:Cr3+ nanophosphors were synthesized for the first time by a simple and environment friendly route using Calotropis procera milk latex as fuel. The structural and surface morphological studies were carried out using powder X-ray diffraction (PXRD), scanning electron microscopy and transmission electron microscopy techniques. The photoluminescence (PL) properties of ZnAl2O4:Cr3+ as a function of dopant concentration and calcination temperature was studied in detail. The PXRD patterns and Rietveld confinement confirmed the cubic crystal system with space group Fd-3m. The crystallite size estimated from Scherrer’s and W–H plots was found to be in the range of 16–26nm. The PL spectrum shows an intense peak at ∼688 and ∼699nm assigned to spin – forbidden 2Eg→4A2g transition of Cr3+ ions. The PL measurements for two excitations (∼410 and 527nm) and with respect to calcination temperature indicated no significant change in the shape and position of emission peak except PL intensity. The CIE chromaticity coordinates lies well within the white region. Thermoluminescence (TL) studies revealed well resolved glow peak at ∼212°C with a small shoulder at 188 and 233°C. The glow peak intensity at ∼212°C increases linearly with γ-dose which suggest ZnAl2O4:Cr3+ is suitable candidate for radiation dosimetric applications. The activation energy (E in eV), order of kinetics (b) and Frequency factor (s) were estimated using glow peak shape method.

Atomistic Origin of the Enhanced Crystallization Speed and n‐Type Conductivity in Bi‐doped Ge‐Sb‐Te Phase‐Change Materials

Phase‐change alloys are the functional materials at the heart of an emerging digital‐storage technology. The GeTe‐Sb2Te3pseudo‐binary systems, in particular the composition Ge2Sb2Te5(GST), are one of a handful of materials which meet the unique requirements of a stable amorphous phase, rapid amorphous‐to‐crystalline phase transition, and significant contrasts in optical and electrical properties between material states. The properties of GST can be optimized by doping with p‐block elements, of which Bi has interesting effects on the crystallization kinetics and electrical properties. A comprehensive simulational study of Bi‐doped GST is carried out, looking at trends in behavior and properties as a function of dopant concentration. The results reveal how Bi integrates into the host matrix, and provide insight into its enhancement of the crystallization speed. A straightforward explanation is proposed for the reversal of the charge‐carrier sign beyond a critical doping threshold. The effect of Bi on the optical properties of GST is also investigated. The microscopic insight from this study may assist in the future selection of dopants to optimize the phase‐change properties of GST, and also of other PCMs, and the general methods employed in this work should be applicable to the study of related materials, for example, doped chalcogenide glasses.

Cd1-xZnxS/ZnS core/shell quantum dot ferroelectric liquid crystal composite system: analysis of faster optical response and lower operating voltage

Cd1−xZnxS/ZnS core/shell-structured quantum dot (QD)-doped ferroelectric liquid crystal (FLC) Felix 17/000 has been investigated in the present study. In the SmC* phase, the effect of QD on the dielectric and electro-optical properties of FLC has been studied as a function of dopant concentration. A substantial change in the different parameters like tilt angle, spontaneous polarisation, response time and relative permittivity has been observed for the composite system. Nearly two times faster response of the composite system with lower operating voltage is one of the promising results of the present study. The faster optical response along with the decreased value of spontaneous polarisation can be utilised in low power consumption liquid crystal displays.

Surface ionisation of molecular H2 and atomic H Rydberg states at doped silicon surfaces

The detection of ions or electrons from the surface ionisation of molecular H2 and atomic H Rydberg states incident at doped Si surfaces is investigated experimentally to analyse the effect of the dopant charge distribution on the surface-ionisation processes. In both experimental studies, the molecular H2 and atomic H Rydberg states are generated via two-colour vacuum ultraviolet--ultraviolet (VUV–UV) resonant excitation. For H2, various Stark states of the N+ = 2, n = 17 manifold are populated in the presence of an electric field. The variation of the observed surface-ionisation signal with surface dopant concentration and type, shows similar characteristics for all the Stark states. A comparison is made between these ion-detected surface-ionisation profiles and those obtained via electron detection. Different trends as a function of dopant concentration and type are observed for the two cases, explained by the greater effect of surface charges on the post-ionisation ion trajectory compared to the electron trajectory. For the atomic-H Rydberg states with principal quantum number populated in the absence of a Stark field, the observed behaviour is similar to the interaction of molecular H2 Rydberg states at the same surfaces, and these measurements confirm that the observed effects are attributable to the nature of the target surface rather than the specific atomic or molecular Rydberg species.

Ferromagnetic Effects in Cr-Doped Fe<sub>2</sub>O<sub>3</sub> Thin Films

Among various phases of iron oxide, hematite (Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) has attracted world attraction owing to its stability, oxidation, and corrosion resistance. Undoped and Cr-doped Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> thin films were prepared using sol-gel spin coating method. XRD results indicate that incorporation of chromium causes contraction in the unit cell, which, according to Bragg's law, leads to shift of peak positions to higher diffraction angles. Contraction in unit cell is because of the smaller ionic radius of Cr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> as compared with iron cation. M-H curves of Cr-doped Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> thin films show transition from weak ferromagnetic to strong ferromagnetic behavior as a function of dopant concentration. The change in magnetic properties has been correlated to the change in energies and structures of hematite with incorporation of chromium.

Europium doped zinc sulfide: a correlation between experimental and theoretical calculations.

This paper presents the correlation among electronic and optical property effects induced by the addition of different concentrations of europium (Eu3+) in zinc sulfide (ZnS) by microwave-assisted solvothermal (MAS) method. A shift of the photoluminescence (PL) emission was observed with the increase of Eu3+. The periodic DFT calculations with the B3LYP hybrid functional were performed using the CRYSTAL computer code. The UV-vis spectra and theoretical results indicate a decrease in behavior of the energy gap as a function of dopant concentration. Therefore, new localized states are generated in the forbidden band gap region, the new states increase the probability of less energy transitions which may be responsible for a red shift in the PL bands spectrum.