Conductivity Type Research Articles

Negative dielectric constant and multi-visible photolumenses emissions of Cd(1-x)CoxO nanocomposites with (0.00 ≤ x ≤ 1.00)

We report the photolumenses (PL) and dielectric measurements of Cd(1-x)CoxO nanocomposites with (0.00 ≤ x ≤ 1.00). It is found that an increase in x correlates with a significant change in crystallite size, particle size, porosity, Debye temperature, Young's modulus, q-factor, binding energy, impedance of grains and their boundaries. The samples with x = 0.50 or 0.60 show an adverse change in the behavior of these parameters. We could not evaluate any shift in the wave length of PL emissions, although they are different in intensities. The samples of x = 0.40 and 1.00 show more visible emission colors at 640, 678, 716, and 791 nm. The x = 0.00 sample shows a negative dielectric constant (ε\\), but it crossovers to positive for the other values of x. ε\\ was gradually decreased as frequency increased up to 10 KHz, after which it nearly saturated except x = 0.80, in which it linearly decreased and never saturated. The ac conductivity decreased gradually against x such that the type of conduction is dependent on the chosen x. The Cole-Cole plot shows a straight line for x = 0.00 and arcs for x = 0.20 and 0.60, and a complete semicircular for x = 0.40, 0.50, 0.80 and 1.00. Furthermore, the effective capacitance was 9260 μF for x = 0.00, but it drops to 0.013 μF for x = 0.40, whereas the vice is true for bulk resistance. These results lend a reasonable certainty to the assertion that Co substitutes for Cd and make them potential prospects for devices such as diodes that emit light, cathode-luminescence displays, integrated circuits, Li-battery and supercapacitors.

The influence of the volume concentration of hydrogen on the fine structure of the IR absorption spectra and conductivity features in congruent LiTaO3 crystals

A new method for changing the volume concentration of hydrogen in congruent LiTaO3 (lithium tantalate, LT) crystals has been studied. It has been established that pre-treatment of the sample in adipic acid significantly increases the volumetric concentration of hydrogen in the sample during subsequent annealing in a humid atmosphere at a relatively low annealing temperature. First of all, this preserves the LT single crystal in a single-domain state. In contrast to known methods for increasing the volumetric concentration of hydrogen, the proposed method affects the absorption coefficient of the sample in the optical range less than for a congruent LiNbO3 crystal. It has been shown that the type of IR absorption spectrum of OH− groups and the defect structure of the LT crystal significantly depend on the volume concentration of hydrogen in the sample. The study also analyzed the reasons for this effect. The temperature dependences of the electrical conductivity of LT samples with different hydrogen concentrations have been studied. It has been shown that the type of electronic conductivity of LT samples changes when the concentration of OH groups in the crystal increases significantly.

Influence of the substrate conductivity type on the electroluminescence properties of PP+IN and PIN+N diodes based on amorphous silicon carbide (a-Si1-xCx:H) / crystalline silicon (c-Si) heterostructures

The study of the conduction and light emission mechanisms of PIN diodes based on amorphous silicon-carbide (a-Si1-xCx:H) thin film and crystalline silicon (c-Si) substrates is reported in this work. Using the same low-temperature process (200 °C), PP+IN and PIN+N structures were fabricated on p-type and n-type silicon (Si) substrates, respectively. The plasma enhanced chemical vapor deposition (PECVD) technique was employed for the active layers deposition where two different CH4/SiH4 flow rates ratios of 30 sccm/6 sccm and 30 sccm/1 sccm were used. All structures show red-orange light emission in forward bias (FB). The structures with the active layer deposited with a lower SiH4 flow rate, display light emission with a higher intensity at a lower voltage bias.In addition, we related the current-voltage measurements with different conduction models and the dominant charge transport mechanisms in the PIN structures were proposed. The highest Si content structures were related to Fowler-Nordheim (F-N) tunneling, because of its active layer with lower barrier height. On the other hand, the lowest Si content structures were associated with the Poole-Frenkel (P-F) emission, due to a higher density of defects in localized tail states. The results showed the same conduction and emission mechanisms for the PP+IN and PIN+N diodes with the same active layer, regardless of the conduction type of substrate, proving that it is feasible to use the same process for developing light emission devices on p-type and n-type Si substrates.

Dislocation density as a factor compensating the polarization doping effect in graded p-AlGaN contact layers

One of the approaches to improve p-doping properties in (Al)GaN-based materials is using a method called polarization doping. In this study, the graded p-AlGaN contact layers were deposited using plasma-assisted molecular beam epitaxy with different III/N ratios. To study the influence of Ga flux on the structural and electrical properties of the grown graded p-AlGaN structures, the samples were investigated using reflection high-energy electron diffraction, atomic force microscopy, secondary ion mass spectrometry, X-ray diffraction, and Hall effect measurements. The electronic structure of the samples was investigated by X-ray absorption near edge spectroscopy, while the polarity of the layers was analyzed by means of transmission electron microscopy. Our study reveals that growing with a higher Ga flux increases Mg incorporation and changes its distribution in the graded layer. However, it was shown that the main factor drastically affecting the magnitude and the type of conductivity in the graded p-AlGaN structures is the dislocation density. The highest hole concentration of ∼3.0×1018 cm−3 was observed for sample grown with a low Ga flux.

Risk to pollution of aquifers associated with productive activities and environmental management of water resources: bibliometric analysis and trends

Its analyzed the evolution and trends of the concept, and studies the models used to know the vulnerability and risk of aquifers and strategies for their management. The methodological process starts from questions guiding the knowledge of research trends, authors among others to proceed to carry out the analyses from the databases of Scopus, Web of Science and Dimensions. VOSviewer and Bibliometric (Rstudio) software were used. Among the most representative results, it was found that most of the research to determine the risk of aquifer contamination is focused on different models such as improved flux prototypes for NO2 emission from agriculture (IPNOA), pollutant origin surcharge hydraulically (POSH), intrinsic vulnerability methods ground water occurrence, overall aquifer class, depth to groundwater (GOD), depth recharge, aquifer, soil, topography, impact, hydraulic conductivity (DRASTIC), substance, infiltration, not saturated, type of coverage, topographic surface, conductivity (SINTACS) and chlorofluorocarbons (CFC) among others. Different models have been used that integrate both hydrological and hydro-geological aspects as well as social aspects including fundamental rights, other models such as the diffuse model, which has had better results in its application, the gaps in the research, are especially focused on conducting holistic research when assessing the risk of these dynamical systems.

Box–Behnken experimental design for optimization of chitosan foam materials reinforced with cellulose and zeolite

AbstractFoam materials produced from biopolymers stand out as a more environmentally friendly insulation material solution. This study presents a comprehensive investigation into the development and optimization of chitosan‐based foam materials using a Box–Behnken design. The foams were engineered using varying proportions of chitosan (0.5–3%), cellulose (0.5–3%), and zeolite (0.5–3%), targeting their application as thermal insulators. The physical and thermal properties of the foams that were produced were affected by the type and ratios of components, with density and thermal conductivity ranging from 0.0853 to 0.1915 g cm−3 and 0.0324 to 0.0921 W mK−1, respectively. Higher chitosan content improved insulation properties and mechanical strength whereas zeolite increments increased density and thermal conductivity. Using statistical analysis through the Box–Behnken design, we optimized the foam formulations, achieving minimum thermal conductivity and maximum compression strength at an averaged density, suggesting a strong potential for environmental sustainability applications. The recommended optimal chitosan:cellulose:zeolite composition ratio of 3:3:0.88 provides a valuable insight for tailored foam material formulation. This study shows the relationships between the composition of a composite material and its resultant properties, optimizing its preparation for industrial applicability in an environmentally conscious way within the context of insulation and construction. This investigation contributes to the field of material science by highlighting the versatility and potential of biopolymers but also aligns with the increasing need for green building materials.

Influence of Electrode Potential on Oxygen Mobility Probed by Polarized Isotopic Exchange in Solid Oxide Electrolyser Cells: Insights for Electro‐Assisted Oxidation Reactions

AbstractOxygen mobility was studied by oxygen isotopic exchange on three electrodes used in Solid Oxide Electrolyser Cells under polarization (La0.8Sr0.2MnO3 (LSM), La0.6Sr0.4Co0.2Fe0.8O3‐δ (LSCF) and La2NiO4+δ (LNO)). The rate of the surface and the bulk mechanisms for oxygen mobility is depending on the type of conductivity (electronic conduction or mixed ionic and electronic conductivity). It is shown that a one oxygen atom exchange is dominant for the surface path whereas a two oxygen atoms mechanism dominates for the bulk path. The rate constant for the bulk path is much higher than the one for the surface path by two orders of magnitude. Additionally, polarized oxygen isotopic exchange revealed that electrode overvoltage increases significantly the rate constant for the surface path, whereas its impact on the bulk path is negligible.

Study on deterioration of mechanical properties and voltage-strength theoretical model of CFRP/ conductive ECC composites under coupling effect of anode polarization, load and erosion environment

This study aims to systematically investigate the deterioration of tensile properties, voltage variation, and voltage-strength theoretical model of CFRP/ conductive ECC composites under coupling effect of anode polarization, load and erosion environment. The effects of testing parameters including conductive ECC mixture type, electric current density, polarization time, tensile stress value, sulfate soak time, and sulfate attack-wet and dry cycle time were synthetically investigated. The experimental results indicated that the voltage increases approximately linearly with the increase of degradation time in the voltage-deterioration time curves. The stress-strain curve can be divided into three stages: the stress-strain linear increase stage, the strain hardening characteristic stage, and the decline stage during failure. The conductive ECC mixture type, polarization time, current density, tensile stress value, sulfate soak time, and sulfate attack-wet and dry cycle time all have significant effects the deterioration of tensile strength and the voltage change ratio of CFRP/ conductive ECC composite. More importantly, an innovative voltage-strength theoretical model was proposed, which can predict the relationship between voltage and material deterioration strength. The theoretical model is in good agreement not only with the experimental results of this study, but also with the results of other studies. The model proposed can be used to predict deterioration degree of materials in real time, which has very important guiding significance for impressed current cathodic protection-structural strengthening technology (ICCP-SS) technology. This study is expected to promote a more comprehensive understanding of the deterioration of mechanical properties and voltage-strength theoretical model of CFRP/conductive ECC composites for ICCP-SS technology.

Thermoelectric properties of sintered Ba2AgSi3 crystals and search for impurities to control conductivity type by first-principles calculation

In this study, the basic properties of Ba2AgSi3 were investigated in detail from both experimental and computational viewpoints. Polycrystalline Ba2AgSi3 formed by an arc-melting apparatus under an argon atmosphere was ground into powders, and then powder samples were sintered using the spark plasma sintering method. Both n-type and p-type samples were obtained. This may be due to a slight deviation from the stoichiometric composition. The energy bandgap of Ba2AgSi3 was measured to be around 0.17 eV from the temperature dependence of electrical conductivity and was in agreement with that by first-principles calculations. Sintered samples exhibited a high Seebeck coefficient of −273 μV K−1 and a high power factor of 0.38 mW m−1 K−2 at 307 K for n-type samples. They were 217 μV K−1 and 0.23 mW m−1 K−2, respectively, at 320 K for p-type samples. The electronic structures of impurity-doped Ba2AgSi3 were also discussed using first-principles calculations to investigate the insertion site of impurity atoms. The calculations suggest that the substitution of B (P) at any Si site shifts the Fermi level and transforms it into p-type (n-type) semiconductors. On the other hand, substitution of Ba or Ag sites with B or P is unlikely to occur in terms of formation energy.

Tunable 2D Electron- and 2D Hole States Observed at Fe/SrTiO3 Interfaces.

Oxide electronics provide the key concepts and materials for enhancing silicon-based semiconductor technologies with novel functionalities. However, a basic but key property of semiconductor devices still needs to be unveiled in its oxidic counterparts: the ability to set or even switch between two types of carriers-either negatively (n) charged electrons or positively (p) charged holes. Here, direct evidence for individually emerging n- or p-type 2D band dispersions in STO-based heterostructures is provided using resonant photoelectron spectroscopy. The key to tuning the carrier character is the oxidation state of an adjacent Fe-based interface layer: For Fe and FeO, hole bands emerge in the empty bandgap region of STO due to hybridization of Ti- and Fe- derived states across the interface, while for Fe3O4 overlayers, an 2D electron system is formed. Unexpected oxygen vacancy characteristics arise for the hole-type interfaces, which as of yet hadbeen exclusively assigned to the emergence of 2DESs. In general, this finding opens up the possibility to straightforwardly switch the type of conductivity at STO interfaces by the oxidation state of a redox overlayer. This will extend the spectrum of phenomena in oxide electronics, including the realization of combined n/p-type all-oxide transistors or logicgates.

Layered carbon nitride films deposited under an oxygen-containing atmosphere and their electronic properties

Layered carbon nitride (g-C3N4) is a novel semiconducting and functional material for optoelectronic applications. The physical and chemical properties of g-C3N4 films differ depending on the preparation atmosphere. Herein, we deposited g-C3N4 films under a mixed oxygen (O2)-nitrogen (N2) gas atmosphere and studied their effects on the carrier transport properties. Although no significant change in the film orientation was observed, the deposition rate decreased as the O2 gas ratio in the mixed N2/O2 atmosphere increased. Despite their thinness, the luminescence intensity of g-C3N4 films deposited under an O2-containing atmosphere increased by 3.5–5.0 times compared to that deposited under an N2 atmosphere. With respect to voltage application, carrier transport owing to the thermionic emission and/or direct tunneling initially followed ohmic conduction, followed by insufficient trap-filled conduction. As the applied voltage increased further, fully trap-filled conduction was confirmed owing to Fowler–Nordheim tunneling. Moreover, the conductivity type could be changed to p-type and n-type using N2 gas and mixed N2/O2 gas atmospheres, respectively, during film deposition. In addition to the intrinsic transport properties, the intentionally formed Schottky barrier also affected the carrier transport; therefore, the diode-like rectifying behavior of the current density was achieved.

Hysteresis and Its Correlation to Ionic Defects in Perovskite Solar Cells.

Ion migration has been reported to be one of the main reasons for hysteresis in the current-voltage (J-V) characteristics of perovskite solar cells. We investigate the interplay between ionic conduction and hysteresis types by studying Cs0.05(FA0.83MA0.17)0.95Pb(I0.9Br0.1)3 triple-cation perovskite solar cells through a combination of impedance spectroscopy (IS) and sweep-rate-dependent J-V curves. By comparing polycrystalline devices to single-crystal MAPbI3 devices, we separate two defects, β and γ, both originating from long-range ionic conduction in the bulk. Defect β is associated with a dielectric relaxation, while the migration of γ is influenced by the perovskite/hole transport layer interface. These conduction types are the causes of different types of hysteresis in J-V curves. The accumulation of ionic defects at the transport layer is the dominant cause for observing tunnel-diode-like characteristics in the J-V curves. By comparing devices with interface modifications at the electron and hole transport layers, we discuss the species and polarity of involved defects.

Effect of Sb modification on dielectric and electrical properties of lithium bismuth titanate

Sb-modified alkali bismuth titanate Li0.5Bi0.5− x Sb x TiO3 (x = 0 and 0.1) compounds are prepared using the method of solid-state-reaction route. The XRD exploration in environmental conditions confirms the development of new compounds having single-phase orthorhombic crystal structures. Non-uniformly distributed grains are noticed in SEM micrographs for both compounds. The electric & dielectric behavior is analyzed by use of an impedance analyzer. The exploration of the dielectric behaviors of both compounds in a wide frequency range (100 Hz–1 MHz) & temperature range (30–500 °C) suggests that these characteristics are strongly dependent on frequency & temperature. Activation energy assessed from temperature variation of ac-conductivity in various zones recommends that the electric transport phenomenon obeys the Arrhenius equation and shows a mixed type of conductivity.

Time-dependent dielectric breakdown of SiC-CMOS technology for harsh environments

To estimate the failure time of silicon carbide (SiC) integrated circuits in harsh environments, the activation energy (Ea) and field acceleration factor of SiC n-channel MOS (nMOS) and p-channel MOS (pMOS) were measured using time-dependent dielectric breakdown testing at constant voltage stress in the range of 25–350 °C. Ea around 300 °C was 0.7 eV for nMOS and 0.66 eV for pMOS, which was about twice as high as that below 150 °C and did not differ greatly depending on the conductivity type. The gate dielectric breakdown mechanism shifted from the 1/E model to the E model as the temperature rose, and this is thought to have caused the Ea to change. The field acceleration factor in the E model at 300 °C was 2.7 and 2.3 cm/MV for nMOS and pMOS, respectively. The maximum operating electric fields of nMOS and pMOS for a 100-year lifetime are 6.8 and −7.2 MV/cm, which are over 25% lower than the fields at room temperature, mainly due to a shift in the dominant breakdown model. A more conservative failure time design will be required for SiC-ICs exposed to high temperatures.

Electron and hole bipolar injection in magnesium oxide films

It is assumed that the reliability and functionality of nonvolatile memory elements based on MgO are determined by the charge transport in MgO. In the present study, the type of MgO conductivity is established using experiments on the injection of minority charge-carriers in the n(p)-Si/MgO/Mg structures. It is shown that electrons and holes contribute to the MgO conductivity, causing bipolar charge transport. Using ab initio simulations, it was found that native point defects in MgO can provide both electron and hole conductivity.

Growth and Characterization of p-Type and n-Type Sb2Se3 for Use in Thin-Film Photovoltaic Solar Cell Devices

In this study, a two-electrode electrodeposition technique was employed to grow thin films of antimony selenide (Sb2Se3) on glass/fluorine-doped tin oxide (FTO) substrates. The highest quality thin films were consistently obtained within the range of 1600 mV to 1950 mV. Subsequent electrodeposition experiments were conducted at discrete voltages to produce various layers of thin films. Photoelectrochemical cell (PEC) measurements were performed to characterize the semiconductor material layers, leading to the identification of both p-Type and n-Type conductivity types. Optical absorption spectroscopic analysis revealed energy bandgap values ranging from 1.10 eV to 1.90 eV for AD-deposited Sb2Se3 samples and 1.08 eV to 1.68 eV for heat-treated Sb2Se3 samples, confirming the semiconducting nature of the Sb2Se3 material. Additionally, other characterization techniques, including X-ray diffraction analysis, reveal that the AD-deposited layers are almost amorphous, and heat treatment shows that the material is within the orthorhombic crystalline system. Heat-treated layers grown at ~1740 mV showed highly crystalline material with a bandgap nearing the bulk bandgap of Sb2Se3. Raman spectroscopy identified vibrational modes specific to the Sb2Se3 phase, further confirming its crystallinity. To explore the thin-film morphology, Scanning Electron Microscopy (SEM) was employed, revealing uniformly deposited material composed of grains of varying sizes at different voltages. Energy Dispersive X-ray analysis (EDX) confirmed the presence of antimony and selenium in the material layers.

Interlayer Charge Transfer Induced Electrical Behavior Transition in 1D AgI@sSWCNT van der Waals Heterostructures.

The emergence of one-dimensional van der Waals heterostructures (1D vdWHs) opens up potential fields with unique properties, but precise synthesis remains a challenge. The utilization of mixed conductive types of carbon nanotubes as templates has imposed restrictions on the investigation of the electrical behavior and interlayer interaction of 1D vdWHs. In this study, we efficiently encapsulated silver iodide in high-purity semiconducting single-walled carbon nanotubes (sSWCNTs), forming 1D AgI@sSWCNT vdWHs. We characterized the semiconductor-metal transition and increased the carrier concentration of individual AgI@sSWCNTs via sensitive dielectric force microscopy and confirmed the results through electrical device tests. The electrical behavior transition was attributed to an interlayer charge transfer, as demonstrated by Kelvin probe force microscopy. Furthermore, we showed that this method of synthesizing 1D heterostructures can be extended to other metal halides. This work opens the door for the further exploration of the electrical properties of 1D vdWHs.

Effect of Cu doping on the electronic structure, magnetic and optical properties of GaN/ZnS heterojunctions: a first-principles study

In this paper, the generalized gradient approximation method in density functional theory is adopted to calculate the GaN/ZnS heterojunction system with coexistence of Cu doping and point defects. The electronic structure, magnetic coupling mechanism and optical properties of each system are analyzed. It is shown by the research results that broader band gap width tuning (0.26–2.92 eV) can be achieved in the interface region of the Cu-doped GaN/ZnS heterojunction system. The magnetic sources of the system have two aspects, on the one hand, unpaired electrons are induced by cation vacancies to undergo spin polarization, thereby magnetic moments are contributed to the system, on the other hand, The GaN/ZnS heterojunction is induced by Cu doping to generate bound magnetic polarons, causing a magnetic phase transition in the system, and the total magnetic moment of the system is restricted by the concentration of bound magnetic polarons. In terms of optical properties, deep energy levels are introduced and hole-electron recombination centers are formed in the Cu-doped heterojunction system containing Ga vacancies. Compared with the non-magnetic heterojunction system, the magnetic heterojunction system exhibits a higher absorption intensity for visible light, and the redshift of its absorption spectrum is more pronounced. Furthermore, when the Cu-doped GaN/ZnS heterojunction system contains different vacancy defects, different conductive types can be achieved.

Easily scalable and highly flexible machine knitted resistive pressure sensor for smart textile applications

This study presents textile based resistive pressure sensor that incorporates off-the-shelf PES/stainless steel conductive yarn and nonconductive acrylic yarn. The fabrication process involves integrating the resistive pressure sensors directly into the base fabric during one knitting operation through computerized machine knitting technology with little human involvement. This work also explores opportunities for manufacturing of soft, highly flexible, and easily controllable double-layered out-of-plane sensors in an easily scalable way. A custom resistance measuring circuit was built to characterize the sensors and the resulting equivalent resistance under various loads, i.e., (0 g–900 g). Reproducibility was confirmed by developing and testing several sensors with the same structural characteristics. The results obtained from the experiments showed that the conductive yarn types and the design parameters significantly affect the sensing properties of knitted sensors. It has been found that sensor types 2, 5, and 6 show better stability, repeatability, high response and recovery time, dynamic ranges, and sensitivity when subjected to various loadings, compared to other developed sensors in this work. As a proof of concept, this sensor demonstrates various smart textile applications, including interactive sleeves for wearable user interface, soft controllable switch, and human movement detection.

Исследование структур на основе GaP методом электрохимического вольт-фарадного профилирования

Gallium phosphide substrate structures with different crystallographic orientation and degree of doping have been studied by means of electrochemical capacitance-voltage (ECV) profiling. A brief description of the ECV profiling as well as its advantages over the conventional capacitance-voltage technique are given. The ECV measurement modes for GaP structures has been worked out, and the necessary electrolyte meets the requirement of polishing character during etching the samples has been selected. During the experiment, the current-voltage and capacitance-voltage characteristics were measured, by which the type of conductivity for each of the samples was determined. Depth distribution profiles of majority charge carrier concentration were obtained. The doping uniformity of samples with p- and n-type impurities is shown up to a depth of 1 μm.