Changes In Electrical Properties Research Articles

Al3+ doping induced changes of structural, morphology, photoluminescence, optical and electrical properties of SnO2 thin films as alternative TCO for optoelectronic applications

Highly transparent and conductive pure (SnO2) and aluminum doped tin oxide (Al:SnO2) thin films were deposited on glass substrates by the sol-gel spin-coating method. The structural, morphological, optical and electrical properties of the prepared thin films at different doping rates have been studied. X-ray diffraction results revealed that all the films were polycrystalline in nature with a tetragonal rutile structure. SEM images of the analyzed films showed a homogeneous surface morphology, composed of nanocrystalline grains. The EDS results confirmed the presence of Sn and O elements in pure SnO2 and Sn, O, Al in doped SnO2 thin films. The optical results revealed a high transmittance greater than 85% in the visible and near infrared and a band gap varying between 3.82 and 3.89 eV. PL spectra at room temperature showed that the most dominant defects correspond to oxygen vacancies. A low resistivity of order varying between 10−3 and 10−4 Ω cm and a high figure of merits ranging between 10−3 and 10−2 Ω−1 in the visible range were obtained. The best performances were obtained for samples containing 2 at. % Al, which could be used as an alternative TCO layer for future optoelectronic devices.

Non-destructive, Contactless and Real-Time Capable Determination of the α’-Martensite Content in Modified Subsurfaces of AISI 304

Cryogenic turning can be used to produce deformation-induced martensite in metastable austenitic steels. Martensite exhibits a higher hardness than austenite and increases the wear resistance of the workpiece. In order to reliably induce a desired martensite content in the subsurface zone during the turning process, a non-destructive, contactless and real-time testing method is necessary. Eddy current testing is an electromagnetic method that is non-destructive, non-contact and real-time capable. Furthermore, eddy current testing has been integrated into production processes many times. Eddy current testing can be used to detect the transformation of paramagnetic austenite to ferromagnetic α′-martensite based on the change in magnetic and electrical properties. Thus, the newly formed subsurface can be characterized and the manufacturing process can be monitored. The objective of this study was to understand the correlation of eddy current testing signals with newly formed α′-martensite in the subsurface of AISI 304 and to quantify the amount formed. The measurements were performed within a machining center. Several methods for reference measurement of martensite content are known in the literature. However, depending on the method used, large discrepancies may occur between the determined contents. Therefore, different analytical methods were used for reference measurements to determine the total martensite content in the subsurface. Metallographic sections, magnetic etching, Mössbauer spectroscopy, and X-ray diffraction with two different analytical methods were employed. Based on the correlation between the eddy current testing signals and the α′-martensite content in the subsurface, process control of the manufacturing process can be achieved in the future.

One-Step Hydrothermal Synthesis, Thermochromic and Infrared Camouflage Properties of Vanadium Dioxide Nanorods.

Vanadium dioxide (VO2) has attracted interest from researchers because it undergoes a metal–insulator phase transition (MIT), which is accompanied by a reversible and remarkable change in both electrical and optical properties. VO2 exhibits numerous polymorphs and thus it is essential to control the growth of specific monoclinic VO2 (M) and rutile VO2 (R) phases. In this study, we developed a cost-effective and facile method for preparing VO2 nanorods with a highly crystalline monoclinic phase by one-step hydrothermal synthesis, in which only V2O5 and H2C2O4 are used as raw materials. The phase evolution of VO2 during the hydrothermal process was studied. The obtained VO2 nanorods were thoroughly mixed with fluorocarbon resin and homogeneous emulsifier in an ethanol solution to obtain a VO2 dispersion. To prepare VO2 films, screen printing was performed with a stainless steel screen mesh mask on glasses or fabric substrate. The VO2 coating had good thermochromic performance; the infrared transmittance change was greater than 20% @1.5 μm whilst keeping the visible transmittance greater than 50%. Meanwhile, the polyester base coating on the fabric had an emissivity change of up to 22%, which provides a solution for adaptive IR camouflage.

Acute afterload leads to increased electrophysiological heterogeneity after myocardial infarction

Abstract Background Myocardial infarction (MI) results in altered mechanical loading and changes in the cardiac electrical properties. The infarct border zone is pro-arrhythmic but the exact role of mechano-electrical coupling remains unclear. Objective We studied spatial electrical heterogeneity in MI animals during acute afterload increase using a novel E-field methodology for high resolution mapping of local activation-repolarization intervals (ARI) in vivo. Methods Anterior-septal MI was induced in five domestic pigs by 120-minute occlusion of the left anterior descending artery followed by reperfusion. This led to an infarct size of 17.7±2.1% of the left ventricle. After 1 month, electro-anatomical mapping was performed before and during an acute afterload challenge induced by partially inflating a balloon in the descending aorta. A non-contact recording of a 64-electrode array was translated to 2048 non-contact electrograms distributed over the left ventricle. The non-contact electrograms were processed to determine the ARIs using a custom-made algorithm, previously validated against monophasic action potential recordings. Based on the contact map we defined border zone (BZ, voltage 0.5 to 1.5 mV) and remote (>1.5mV) regions. Heterogeneity was defined as the interquartile range (IQR) of ARIs in fixed neighborhoods of 1cm radius (figure 1A) and analyzed in 10 segments (5 BZ and 5 remote) of a modified version of the AHA model (49 segments by dividing the 16 non-apical segments). Other segments were discarded due to artefacts mainly caused by the array touching the septal and apical wall. Results Acute afterload challenge resulted in an increase of the systolic left ventricular pressure of 41.7±5.4% and increased left ventricular repolarization heterogeneity (IQR 4.03±1.23ms baseline to 4.85±1.38ms during inflation, p=0.004). There was a significant increase in heterogeneity in both BZ (4.78±1.60ms to 5.64±1.66ms, p=0.020) and remote (2.24±0.17ms to 3.00±0.86ms, p=0.034) regions (figure 1B). The IQR in the infarct BZ was higher compared to the remote zone at rest (4.78±1.60ms vs 2.24±0.17ms, p=0.010) as well as during inflation (5.64±1.66ms vs 3.00±0.86ms, p=0.008) (figure 1B). Both BZ and remote regions responded equally to acute afterload (p for interaction = 0.803). Conclusion Increased afterload leads to increased repolarization heterogeneity. This heterogeneity is higher in the infarct BZ. These alterations could provide a functional substrate for reentry. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): KU Leuven - C1 funding

Enhancing the electrical properties of graphite nanoflake through gamma-ray irradiation

Understanding changes in material properties through external stimuli is critical to validating the expected performance of materials as well as engineering material properties in a controlled manner. Here, we investigate a change in the c-axis electrical properties of graphite nanoflakes (GnFs) induced by gamma-ray irradiation, using conductive probe atomic force microscopy (CP-AFM). The fundamentals behind the change in their electrical properties are elucidated by analyzing the interlayer spacing, graphitization, and morphology. An increase in gamma-ray irradiation dose for GnFs leads to an exponential increase in the electrical conductance and a gradual decrease in the interlayer spacing, while accompanying indistinguishable changes in their morphology. Our experimental results suggest that the c-axis electrical conductance enhancement of GnFs with gamma-ray irradiation might be attributed to a reduction in interlayer spacing, though the created defects may also play a role. This study demonstrates that gamma-ray irradiation can be a promising route to tailor the electrical properties of GnFs.

Effect of Biaxial Bending Strains on the Electrical Characteristics of Flexible Low-Temperature Polysilicon Thin-Film Transistors

The change of electrical properties of flexible low-temperature polysilicon (LTPS) thin-film transistors (TFTs) under biaxial bending strains was studied. Biaxial strains were applied using a ring-on-ring bending test rig. The magnitude of the strain was determined by theoretical calculations and finite-element simulations. With an increase in strain, the transfer curve shifted to a negative bias. At a biaxial strain level of 12%, the threshold voltage decreased by 27%, the field-effect mobility decreased by 13%, and the subthreshold slope increased by 25%. It had a more significant effect on the property changes than the uniaxial strain; this difference may be attributed to additional trap states generated by the biaxial strain. The analysis showed that the trap density increased when the strain level increased. The contributions of the increases in the grain-boundary trap state density and the interface trap state density to the degradation in the electrical properties were derived to be 10% and 90%, respectively. After removal of the biaxial bending strains, the electrical performance showed recovery behavior, but the performance could not return fully to its original state.

Experimental study of gas flow rate influence on a dielectric barrier discharge in helium

A systematic study was performed to investigate the influence of gas flow rate on a helium dielectric barrier discharge. A closed-chamber barrier discharge with plane electrodes was examined through electrical and spectroscopic measurements for a set of gas flow rates varying from 0.05 l min−1 to 5 l min−1. The work was concentrated on the presumed connection between the gas flow rate and the impurity level, and consequential change of the discharge operation. A method was developed for estimation of impurities from the emission spectrum and applied in our discharge. The obtained results showed a strongly non-linear decrease of impurities concentration with increasing flow rate of the working gas. Experimental results showed a significant change of electrical properties, like breakdown voltage and current density with the gas flow. The measured electric field distribution did not show important change. The increase of the gas electrical capacitance with gas flow rate was detected, due to the rise of the transferred charge. The intensity of atomic and molecular emissions, along with space time development of certain emissions indicated the change in excitation mechanism with the variation of the gas flow. Analysis shows that the main mechanism of the changes in the discharge is the decrease of impurities, which leads to reduction of helium metastable quenching which, in turn, increases the density of helium metastables important for ionization and excitation processes. The obtained results mostly agree with the models of the discharge behavior with change of impurity level.

Multimodal imaging shows fibrosis architecture and action potential dispersion are predictors of arrhythmic risk in spontaneous hypertensive rats.

Hypertensive heart disease (HHD) increases risk of ventricular tachycardia (VT) and ventricular fibrillation (VF). The roles of structural vs. electrophysiological remodelling and age vs. disease progression are not fully understood. This cross‐sectional study of cardiac alterations through HHD investigates mechanistic contributions to VT/VF risk. Risk was electrically assessed in Langendorff‐perfused, spontaneously hypertensive rat hearts at 6, 12 and 18 months, and paced optical membrane voltage maps were acquired from the left ventricular (LV) free wall epicardium. Distributions of LV patchy fibrosis and 3D cellular architecture in representative anterior LV mid‐wall regions were quantified from macroscopic and microscopic fluorescence images of optically cleared tissue. Imaging showed increased fibrosis from 6 months, particularly in the inner LV free wall. Myocyte cross‐section increased at 12 months, while inter‐myocyte connections reduced markedly with fibrosis. Conduction velocity decreased from 12 months, especially transverse to the myofibre direction, with rate‐dependent anisotropy at 12 and 18 months, but not earlier. Action potential duration (APD) increased when clustered by age, as did APD dispersion at 12 and 18 months. Among 10 structural, functional and age variables, the most reliably linked were VT/VF risk, general LV fibrosis, a measure quantifying patchy fibrosis, and non‐age clustered APD dispersion. VT/VF risk related to a quantified measure of patchy fibrosis, but age did not factor strongly. The findings are consistent with the notion that VT/VF risk is associated with rate‐dependent repolarization heterogeneity caused by structural remodelling and reduced lateral electrical coupling between LV myocytes, providing a substrate for heterogeneous intramural activation as HHD progresses. Key points There is heightened arrhythmic risk with progression of hypertensive heart disease.Risk is related to increasing left ventricular fibrosis, but the nature of this relationship has not been quantified.This study is a novel systematic characterization of changes in active electrical properties and fibrotic remodelling during progression of hypertensive heart disease in a well‐established animal disease model.Arrhythmic risk is predicted by several left ventricular measures, in particular fibrosis quantity and structure, and epicardial action potential duration dispersion.Age alone is not a good predictor of risk.An improved understanding of links between arrhythmic risk and fibrotic architectures in progressive hypertensive heart disease aids better interpretation of late gadolinium‐enhanced cardiac magnetic resonance imaging and electrical mapping signals.

Changes of cross-linked network and DC electrical properties of nanocomposite silicone rubber under thermal aging

Nano dielectrics have brought hope for solving the problem of cable insulation at high voltage levels. In this paper, nano Al2O3 and MgO are doped to silicone rubber and the nanocomposites are aged at 200 °C for 0-80 days. The electrical conductivity and DC breakdown characteristics of aged materials are investigated. The microscopic and elemental properties are also analysis. It is found that with the increase of thermal aging time, electrical conductivity of all sets decreases first and then increases, while the DC breakdown voltage experiences a process of first increasing and then decreasing. During the initial aging process, secondary vulcanization of silicone rubber occurs, however, the cross-linked network degrades with further aging, which could explain the changes in electrical properties. The introduction of metal oxides could react with exfoliated radicals to form s table compounds, thus, the performance of Al2O3 and MgO doped materials have better electrical properties under thermal aging.

Electrical conductivity of semiconducting nanoparticles

A simple and comprehensive theoretical model has been presented for the computation of the electrical conductivity for nanosolids, considering the size, the shape, the relaxation factor and the packing fraction dependent cohesive energy. The computational results for the electrical conductivity obtained through the present model, for CdSe, Bi2S3, Si and Ge semiconducting nanosolids in different shapes demonstrate that the electrical conductivity lowers down as the size of particle decreases. It is also observed that the electrical conductivity of spherical nanoparticle shifts towards tetrahedral shape which indicates that the structure of the nanomaterials also changes at its lower range and hence their electrical property changes accordingly. Our computed results show good agreement with the available experimental findings which authenticates the present comprehensive picture. The present model for electrical conductivity of nano-solids can be applied for the materials in the nano-range which have not been investigated experimentally.

Impact of copper ions on physical, structural, spectroscopic, and dielectric properties of Bi2O3–CaO–P2O5–B2O3 glasses

The objective of the present study is to investigate the physical, structural, spectroscopic and dielectric studies on the multi component 3Bi2O3–10CaO–20P2O5-(67-x)B2O3: xCuO (0 ≤ x ≤ 0.9 mol%) glass network. The specimens were fabricated by the melt quenching and heat treatment method. X-ray diffraction (XRD) approves the amorphous temperament of glasses. To prove the existence of copper ions and their valence states, the optical absorption and electron spin resonance (ESR) spectra of the glasses were investigated. Optical absorption spectra exhibited a dominant band virtually at 850 nm as a result of copper ions. Optical band gap energy (Eo) and Urbach energy (ΔE) of specimens were estimated. It is observed that Eo exhibited a decreasing tendency with an increase in the concentration of CuO but the values of ΔE showed a reverse trend. These outcomes promoted the intensification of dopant ions in the specimens. Investigations on electron spin resonance (ESR) spectra authenticated occupancy of copper ions in work-pieces. Amplification in intensity of signal indicates magnification of Cu2+ ions. The spin-Hamilton parameters (SHP) of samples were determined. Fourier transform infrared (FTIR) studies reveal the structural variations in the glasses. The presence of conventional bismuth, phosphate and borate bands was displayed by the FTIR curves of the specimens. The dielectric studies indicate the change in electrical properties of the glasses. The dielectric properties of the glasses were analyzed in a substantial range of frequencies (1–103 kHz) and temperatures (30–300 °C). All outcomes are in favor of decrease in the rigidity of glasses with an increase in the concentration of CuO.

Microstructural and electrical behavior of NiCr/Al nanomultilayered films prepared by magnetron sputtering

The NiCr/Al nanomultilayered films with different Al thicknesses (tAl) were prepared by magnetron sputtering. The structural evolution of the Al nanolayer with the increase in tAl was investigated. When the Al layer thickness changed from 1.2 nm to 2.4 nm, the Al layer could keep the co-epitaxial growth with the adjacent NiCr layer. Accordingly, the crystallization degree improved. When the Al layer thickness changed from 2.4 nm to 3.0 nm, the transformation from the coherent to incoherent interfaces took place between the NiCr and Al layers. Meanwhile, the co-epitaxial growth with the adjacent NiCr nanocrystallites was destroyed, the crystallinity and the grain size decreased, leading to the increase of the resistivity under the combined effects of the grain boundary scattering and interface scattering. The interfacial evolution of NiCr/Al nanomultilayered films was closely related to the changes of electrical properties. When the Al layer thickness changed from 3.0 nm to 3.6 nm, the surface quality of the film was improved, which effectively reduced the scattering of defects and vacancies during the electron transport, resulting in the decrease of the resistivity of the NiCr/Al nanomultilayered film.

Changes of Morphological, Optical, and Electrical Properties Induced by Hydrogen Plasma on (0001) ZnO Surface

Changes of Morphological, Optical, and Electrical Properties Induced by Hydrogen Plasma on (0001) ZnO Surface

Effect of Irradiation (SRFE) on MSM Photodetectors Device

This paper presents the effect of high energy irradiation expose on metal-semiconductor-metal (MSM) photodetectors device. High energy radiation may impact to lattice structure of semiconductor device. The most impact of radiation on MSM device had been studied base on polycrystalline silicon. Based on our research in SRFE process exposed on P-N power device, radiation will interact with device mechanism and structure that change electrical properties of device. However, MSM device show electrical properties change after irradiation exposure process by photocurrent increased around 4 times when compare with non-irradiated.

Fiber electric double-layer platform for a phase shifter based on the Pockels effect of liquid molecules.

The electric double layer (EDL) was formed at the interface of the electrode and liquid and has been widely used in a series of applications, ranging from batteries to biosensors, based on the electrical property changes. In this paper, we demonstrate a simple microfiber phase shifter based on the Pockels effect of liquid in the electric double layer. By constructing an EDL around the microfiber, the phase shifter can be achieved. Furthermore, the effects of ion concentration and molecular polarity of liquids on this phase shifter were studied. The fiber electric double-layer platform has the advantages of low voltage modulation and simple fabrication, which has the potential for use in wearable sensing devices, biopotential detection, and biomolecule detection.

The Effect of Bi and Zn Additives on Sn-Ag-Cu Lead-Free Solder Alloys for Ag Reduction

This study aimed to investigate the effects of the addition of Bi and Zn on the mechanical properties of Sn-Ag-Cu lead-free alloy frequently used as a soldering material in the semiconductor packaging process. To reduce the Ag content of the commercial alloy SAC305 (Sn-3Ag-0.5Cu) by 1 wt.%, Bi and Zn were admixed in different ratios and the changes in mechanical and electrical properties were analyzed. Compared to the SAC305 alloy, electrical conductivity and elongation at break decreased while tensile strength increased following the addition of the two elements. In particular, upon the addition of 1 wt.% Bi, the tensile strength increased to a maximum of 43.7 MPa, whereas the tensile strength was 31.9 MPa in the alloy with 1 wt.% Zn. Differential thermal analysis and scanning electron microscopy revealed that the changes in physical properties can be ascribed to a reduction in the activation energy required for formation intermetallic compound when Bi was added, and the refinement of the structure due to a decrease in undercooling degree when Zn was added. When Bi and Zn were added at the same time, each characteristic for the change in the microstructure was applied in a complex manner, but the effect on the change of the physical properties worked independently.

Impedance Characterization of OECT Behavior in Enzyme-Embedded Conductive Polymer Matrix

Latest generation glucose sensors use small-form wearables which provide continuous data. Thesedevices represent the commercial forefront aiming towards personalized and real-time point-of-carebiomedical applications. Currently, device lifetimes are limited due to unknown failure mechanisms andex-situ calibration strategies. Creating a method for in-situ sensor diagnostics will allow a bottom-upapproach for designing enzyme-supporting matrixes and calibration strategies inherent to biosensors. Tothis end, this work seeks to enhance the understanding of performance, stability, and failure mechanismsof biologically based electrochemical transistors using impedimetric measurements.Here, we reveal the fundamental interplay between glucose oxidase loading and the electronic propertiesof a commonly used PEDOT:PSS matrix as an encapsulating medium. Fundamental to these studies wasthe discovery of conductivity enhancing strategies compatible with preserving enzyme activity. Theenzyme-embedded conductive polymer matrix was used in an organic electrochemical transistor probedvia electrochemical impedance (EI) to determine the causes of performance loss over sensor lifetimes.Supporting spectroscopies aided in detailing film morphology and electrical property changes associatedwith sensor behavior.

Electrical, magnetic and microwave absorption properties of multiferroic NiFe2O4-BaTiO3 nanocomposites

Multiferroic nanocomposites of xNiFe2O4/(1-x)BaTiO3 (x = 0, 0.1, 0.2, 0.3, and 0.4) (denoted as NFO-BTO) with the particle size about of 70 nm were prepared by the high energy mechanical milling combined with the thermal annealing methods. The x-ray diffraction patterns show a presence of NiFe2O4 (NFO) and BaTiO3 (BTO) phases. The values of the characteristic parameters of nanocomposites such as the coercive field (E c), the residual polarization (P r), the remanent magnetization (M r), the saturation magnetization (M s), and the coercive force (H c) increase gradually with an increase in NFO concentration. For an applied electric field below 10 kV cm−1, the values P r and E c are found to be 0.004–0.038 μC cm−2 and 0.7–2.0 kV cm−1, corresponding x = 0.1–0.4, respectively. Changes in electrical and magnetic properties of composites depend heavily on the NFO content, which will be studied specifically. Additionally, the ability to absorb microwave at room temperature of a representative sample with x = 0.3 mixed in acrylic paint (denoted as NFO-BTO-AP) in a frequency range of f = 12–18 GHz has also been investigated. It shows a large negative reflection loss (RL) with RL = −39.8 dB occurring at around 16.8 GHz corresponding to the absorptivity of over 99.9% for an absorbing layer with thickness of 5.5 mm. This suggests that NFO-BTO nanocomposites could be considered as a potential material in the field of absorbing and shielding electromagnetic waves.

Influence of Annealing on Physical, Physiological and Electric Properties of Mono Nickel oxide Thick Films Prepared by using Screen-Printing Technique

To study changes in physical, physiological and electrical properties of AR grade Nickel monoxide (NiO), thick films of NiO were fabricated on a glass substrate and annealed at 250 0C - 400 0C. Using characterization techniques, such as XRD, SEM-EDS and static gas sensing system, the structure of the film was found to be polycrystalline with a cubic structure and chemical composition study confirmed its non- stoichiometric nature. Half bridge method is used for measurement of D.C. resistance of thick films in air atmosphere at 30 0C to 350 0C. The prepared thick films of NiO nanoparticles were analysed for electrical properties and it ascertained that they are semiconducting in nature. The TCR, activation energy as well as film resistivity were measured at selected annealing temperatures. The D.C electrical conductivity results obtained from electrical properties at room temperature is 0.086 × 104 (Ωm) 1. The crystallite size changes from 8.20 nm to 8.54 nm for strong predominant orientation (200) with increase in annealing temperature. Study of correlation between annealing temperature and electrical resistivity showed that there is decrease in resistance with increase in temperature.

Optical properties and radiation stability of polypropylene modified with MgO nanoparticles

Polymer composite materials are widely used in spacecraft and stations in thermal control coatings, as sealants, seals, thermal insulation, as well as in many other structures and products. The main characteristic of such materials is the stability of properties and performance characteristics to the action of space factors, among which various types of radiation are the main damaging ones. Therefore, it is relevant to study the influence of electron, proton, solar spectrum quanta on the change in optical, electrical, mechanical, and other properties of polymer composite materials. This paper presents the results of a investigation of the optical properties and radiation stability of nanocomposites based on polypropylene modified by the solid state method with MgO nanoparticles in the concentration range of 1–5 mass.%. Diffuse reflectance spectra were recorded in a vacuum of 2·10-6 Torr before and after electron irradiation (in situ, E = 30 keV, H = 2·1016 cm-2). The analysis of the nature of the absorption bands recorded in the diffuse reflection spectra, which are due to the formation of free radicals: – С3Н5 –, – С3Н6 –, – C4H6 –, – C4H7 –, – C4H8–, – C4H12 –, – C5H7 –, – C5H10 –, was performed. The optimal value of the concentration of nanoparticles was established, equal to 2 mass.%, at which the area of the integral absorption band at 360 nm after irradiation decreased by 3,35 times, its intensity at the maximum by 3,88 times compared with unmodified polypropylene.