Variation Of Electrical Properties Research Articles

Pressure-driven semiconducting-semimetallic transition in SnSe.

In this work, we report the pressure-dependent electrical transport and structural properties of SnSe. In our experiments an electronic transition from a semiconducting to semimetallic state was observed at 12.6 GPa, followed by an orthorhombic to monoclinic structural transition. Hall effect measurements indicate that both the carrier concentration and mobility vary abnormally accompanied by the semimetallic electronic transition. First-principles band structure calculations confirm the semiconducting-semimetallic transition, and reveal that the semimetallic character of SnSe can be attributed to the enhanced coupling of Sn-5s, Sn-5p, and Se-3p orbitals under compression that results in the broadening of energy bands and subsequently the closure of the band gap. The pressure modulated variations of electrical transport and structural properties may provide an approach to improving the thermoelectric properties of SnSe.

Variation of electric properties across the grain boundaries in BiFeO3 film

Stark differences in charge transport properties between the interior and the boundary regions of grains in an undoped BiFeO3 thin film have been found. The material is ferroelectric and each grain is a single domain. A spatial resolution that distinguishes between the grain interior and the boundary between the grains has been achieved by using piezoelectric force microscopy and conductive atomic force microscopy measurements. The local electric properties, as well as the local band gap show hysteresis only when probed in the grain interior, but do not show hysteresis when probed in the region around the boundary between two grains. The leakage current is more pronounced at the grain boundaries, and the region that carries significant current increases with the applied voltage.

Effect of aging of V2O5 sol on properties of nanoscale films

Nanoscale films having thicknesses in the range of 92nm–137nm were obtained by spin coating V2O5 sol at different stages of aging. The observed structural and morphological changes with time can be attributed to the reactions occurring in the sol. The film morphology changed from an indistinctive featureless film to a homogenous film having ribbon-like nanostructures with aging of sols. TGA and FTIR analysis confirmed loss in the amount of intercalated water content with aging giving rise to structural changes (decrease in interlayer spacing) which were observed using XRD. Variations in mechanical, electrical, and optical properties of the thin films were observed with aging of the sol. Strain in the films were found to decrease with aging. The electrical conductivity increased with aging and this can be correlated to the improved crystallinity of the films with aging. The optical bandgap (calculated from UV–Vis data) decreased and the transmittance increased with aging.

Photoluminescence Characterization of Interface Quality of Bonded Silicon Wafers

Wafer-to-wafer bonding is implemented in fabrication of backside illuminated (BSI) complimentary metal-oxide-semiconductor image sensor (CIS) devices in volume manufacturing. A wafer with illuminated imager and a wafer with readout and image processing electronics are fabricated separately and assembled using wafer-to-wafer bonding. Since the illuminated imager and a wafer with readout and image processing electronics are facing each other at the bonded interface, the quality of wafer-to-wafer bonding interface can affect the performance of finished devices. Room temperature photoluminescence (RTPL) technique was studied as a non-contact, in-line characterization technique for assessing bonding interface quality. Ordinary and bonded, 200 mm Si wafers, with different surface finishing conditions, were characterized by RTPL under two different excitation wavelengths (650 nm and 827 nm) to investigate the effects of surface finishing conditions. Significant variations in RTPL spectra and intensity, suggesting potential electrical property variations, were observed from bonded wafers. RTPL characterization results on ordinary and bonded wafers are introduced as a potential technique for in-line bonding interface quality monitoring.

Responses of electrical properties of tea leaves to low-temperature stress

Critical temperature is one of the most important parameters for the control of crop frost protection through airflow disturbance. It changes with complex weather conditions, thus it is difficult to be determined. A method of testing electrical property of tea leaves under cold stress was put forward to indicate critical temperature. The testing system was established to measure the capacitance, impedance, resistance and reactance of the samples under different air temperatures, air humidities and airflow velocities. The variation of the electrical property was also analyzed. The results show that at humidity below 70% and airflow velocity of 0 m/s the impedance and resistance increased slowly, while the reactance kept steady when air temperature decreased from 8.0°C to around −6.3°C, and then increased rapidly from around −6.3°C to −15.0°C. There were no significant differences of the above parameters and variation trend under different airflow velocities. There was an exponential relationship between the impedance and the temperature. The capacitance was rather small and almost no change occurred with air temperature under different conditions of air velocity and humidity, except a few abrupt peaks. The maximum peak capacitance was representative of its response at certain humidity and airflow velocity. The typical temperatures were close to a range, where the other three parameters began to increase rapidly. The typical temperature dropped to the lowest of −7.8°C at the airflow velocity of 0 m/s. Therefore, the characteristic response of the capacitance could indicate critical temperature of tea leaves. Keywords: low-temperature stress, electrical property, capacitance, Camellia Sinensis, critical temperature DOI: 10.3965/j.ijabe.20150805.1426 Citation: Lu Y Z, Hu Y G, Zhang X L, Li P P. Responses of electrical properties of tea leaves to low-temperature stress. Int J Agric & Biol Eng, 2015; 8(5): 170－175.

Variation in geometry and electrical conductance properties of asymmetric track-etched single nanopores: How uniform are they?

In this paper, the transport property uniformity of single asymmetric pores in polyethylene terephthalate membranes was investigated. Two types of films, Hostaphan RN and Hostaphan RNK, were used. The foils were irradiated with either single or multiple (∼108cm−2) Au and Xe ions. Samples were UV-treated and etched in surfactant-doped 5mol/L NaOH at 60°C for 6min and 30s in order to obtain nanopores with bullet-shaped tips. The geometry of the nanopores was determined from SEM images of multi-pore membrane cross sections. The reproducibility of the electrical characteristics of individual nanopores with bullet-like tips in two different types of polyethylene terephthalate foils was studied. The relationship between electro-conductive properties of the asymmetric nanopores and the polymer morphology is discussed.

Stretchable conducting gold films prepared with composite MWNT/PDMS substrates

Novel stretchable conducting films were prepared by depositing gold layers onto polymer nano-composites substrates formed by in-situ crosslinking of polydimethylsiloxane (PDMS) in the presence of multiwall carbon nanotubes (MWNT). The MWNT content interferes with the PDMS cure reaction giving variations in thermal degradation, solvent swelling, mechanical and electrical properties. Tensile cycling experiments were carried out on the gold-coated PDMS and nano-composite substrates SEM analysis and electrical measurements demonstrated that the crack widening and increased electrical resistance observed during strain cycling were reversible. The inclusion of 8 % MWNT into PDMS brought more micro-cracking in the gold layer yet reduced the electrical resistance of the gold-coated samples by 172X at 5 % strain, 38X at 10 % strain and 19X at 20 %. Hence, this improvement in conduction is attributed to assisted-conduction through the MWNT loaded substrate. This mechanism results in a more stable and reproducible electrical behaviour, making electrical conduction less critically dependent on defects in the gold layer.

Atomistic aspects of carrier concentration variation in post-annealed indium tin oxide films

Post-annealing environment-dependent optical and electrical properties of indium tin oxide films grown on glass were examined. X-ray diffraction measurements revealed that all of the films exhibited poly-crystallinity after annealing at 400 °C for 10 min O2, in-air and N2. The optical property measurements yielded >80% transmittances for all the films except for the as-grown and O2-annealed films, even though there were no significant optical band-gap energy differences. In the Hall measurements, all of the films exhibited n-type characteristics. However, the film annealed under the N2 environment showed the best electrical properties (highest carrier concentration and conductivity). The physical origin of electrical property variations due to annealing environment differences was explained by examining the core-level x-ray photoelectron spectra.

Improved electrical properties for Mn-doped lead-free piezoelectric potassium sodium niobate ceramics

The un-doped and doped lead-free piezoelectric potassium sodium niobate (K0.5Na0.5NbO3, KNN) ceramics with different amounts of Mn were prepared. The decreased dielectric losses and the improved electrical properties were observed in the Mn-doped KNN ceramics. However, the variation of electrical properties with the Mn contents was not continuously. The 0.5 mol.% Mn-doped KNN ceramic shows the highest dielectric loss and the worst electrical properties. The KNN ceramics doped with less than and more than 0.5 mol.% Mn all show improved electrical properties. The change of lattice position of Mn ions in KNN ceramics was the main reason. When the Mn content is less than 0.5 mol.%, the Mn ions occupied the cation vacancies in A-site. When the Mn content is higher than 0.5 mol.%, the Mn ions entered B-site of KNN perovskite structure and formed the defect complexes (MnNb″−VO⋅⋅) and (MnNb′−VO⋅⋅−MnNb′). They both led to a lower defect concentration. However, When the Mn content is up to 1.5 mol.%, the electrical properties of KNN ceramic became degraded because of the accumulation of Mn oxides at grain boundaries.

Preparation and electrical properties of Ni0.6Mn2.4−xTixO4 NTC ceramics

In this paper, spinel-type negative temperature coefficient (NTC) ceramics with general composition Ni0.6TixMn2.4−xO4 (x = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) were prepared by conventional solid-state reaction method. The effects of Ti content and sintering temperature on the phase composition, morphology and electrical properties were characterized by XRD, SEM and resistance–temperature measurements, respectively. The results showed that a single spinel structure of AB2O4 could be obtained at x ≤ 0.4, titanium oxide and manganese titanate were formed at x > 0.4. These samples could be sintered into relatively dense ceramics at a temperature of 1200 °C. For the samples sintered at 1200 °C, the grain size slightly increased when the Ti content increased from 0.1 to 0.3 and an abnormal grain growth was observed at x ≥ 0.4. The oversintering temperature decreased as the Ti content increased. The specific resistivity at 25 °C of the ceramics increased by adding Ti content and it increased sharply at x ≥ 0.4. The B values increased linearly with the increase of Ti content when the x value between 0.1 and 0.5, and then it decreased at x = 0.6. The variation of electrical properties is correlated with the occupation of Ti ions on the B-sites of the spinel structure and the decrease of Mn3+/Mn4+ on the B-sites.

UV laser induced changes to morphological, optical and electrical properties of conductive nanocrystalline diamond films

The possibility of laser induced variation of optical and electrical properties of conductive nanocrystalline diamond (CNCD) films has been demonstrated. The films were produced by microwave plasma chemical vapor deposition (MPCVD) from CH4:H2:N2 gas mixtures. The films were irradiated in air with 20ns pulses of an ArF excimer laser (λ=193nm). It was found that low laser pulse intensity (~0.05J/cm2), well below film surface graphitization (~0.3J/cm2) and nanoablation (~0.08J/cm2) thresholds, induces changes of the film properties. The effect requires multiple pulsed irradiation and results in a decrease of the film electrical conductivity, which is accompanied by optical bleaching of the diamond film absorption.

19. Augment, revival and repair

It is well known that decreased temperature results in the suppression of metabolic activity and, thus, in a reduction of the rate at which deterioration of an unnourished biological system would occur. The freezing process, however, is not necessarily benign; it generally induces extreme variations in chemical, thermal, and electrical properties that could be expected to alter cellular membranes, intracellular organelles, and the associated delicate intracellular system functions. Given the extreme complexity of even the simplest biological cells, it is therefore remarkable that a reversible state of suspended animation by freezing is possible at all. Biological responses to cold stress can include (among others) disassembly of cell cytoskeleton, apoptosis, osmotic stress, oxidative stress and attenuation of transcription and translation. As a result, surviving post thawed cells may not function immediately as they did before, or may have been completely compromised. As deeper understanding of the molecular mechanisms has been uncovered, issues affecting the transcriptome due to cold stress have become identifiable as areas requiring attention. While the goal of any preservation strategy should be geared towards outcomes with no change to the cell or biological system (e.g. tissue or organ) pre-preservation, the ability to repair cells post preservation could mitigate inevitable compromises. Additionally, arbitrary “viability” counts generally accepted by various regulatory bodies need to be examined from the standpoint of evidence. Historically, some situations, such as autologous peripheral blood hematopoietic stem cell transplantation, have required higher doses of cells with lower viability due to the nature of preserving that system. Outcomes from these transplants can still yield good results in vivo. Preservation protocols that combine optimized preservation, “adjuvants” and factors that can provide support in vivo might be key to solving the very complex situations in organ preservation and importantly, use.

Structure and electrochemical properties of polystyrene/CNT nanocomposites

The realization of the outstanding properties of CNTs (carbon nanotubes) is constrained by their inherent tendency to agglomerate. Emulsion polymerization was used for synthesizing poly(styrene)/CNT nanocomposites with functionalized CNTs. Chain transfer agents (CTAs) were incorporated to control polymer molar mass and end-use properties. Data from electrical impedance spectroscopy (EIS) at variable frequencies were analyzed to characterize and elucidate the electrical characteristics of poly(styrene) (PS)/CNT nanocomposites. The incorporation of CNT in the polymer matrix even at modest concentrations enhanced the electrical properties of the non-conductive poly(styrene) significantly as revealed by EIS spectra. The use of CTA enabled modulation of polymer molar mass and variation in the electrical properties for PS/CNT relative to composites with no CTA. The electrical behavior of PS/CNT dispersion has been shown to depend both on the CNT concentration and molecular weight of the substrate. The equivalent electrical circuit (EEC) analyses with the corresponding system parameters enabled determination of relative CNT arrangements for different types of PS/CNT composites. TEM images confirmed the CNT positions within the composites and helped support interpretation of EIS/EEC data.

Impedance spectroscopy of polymer electrolytes based on epoxidized natural rubber with 50 mol% epoxide content

Polymer electrolytes of epoxidized natural rubber with 50 mol% epoxide content (ENR-50) and lithium perchlorate (LiClO4) were studied with respect to variation of thermal and electric properties with salt content. Below salt content of 5% and above 12%, glass transition temperature stays constant. A steep increase is observed in between. Frequency dependence of impedance was studied over a wide range of salt concentration. Complex impedance plots exhibit one semicircle. Location of semicircles above 12% clearly points towards phase heterogeneity. Analysis of resistivity leads to the result that one phase's resistivity corresponds to salt content of 12%, whereas the second phase exceeds this resistivity by one order of magnitude. Imaginary part of impedance supports this behavior with respect to resistivity. Polarization relaxation time, however, does not change with salt content. It demonstrates that the phase with the excess resistivity does not contribute to polarization relaxation. Therefore, universal dielectric behavior can be observed also in the heterogeneous system. POLYM. ENG. SCI., 55:2250–2255, 2015. © 2015 Society of Plastics Engineers

Temperature dependence of electrical characteristics of n-InxGa1 − xN/p-Si hetero-junctions made totally by RF magnetron sputtering

The n-InxGa1−xN/p-Si hetero-junction diodes including their semiconductors and electrodes were grown directly on p-Si (100) wafer by magnetron sputtering. Targets for n-InxGa1−xN films with x=0, 0.15, and 0.4 were made by hot pressing with the mixture of metallic and nitride powders. SEM, AFM, and Hall measurement were carried out to analyze the surface morphology, topography, and electrical property of the n-InxGa1−xN films. Temperature dependent transport behavior of n-InxGa1−xN/p-Si hetero-junction diodes was determined by the I–V analyses. After measurements at room temperature, the turn-on voltage and ideality factor were determined to be 2.1V, 6.2 for n-GaN/p-Si, 1.8V, 5.2 for n-In0.15Ga0.85N/p-Si, and 1.4V, 4.3 for n-In0.4Ga0.6N/p-Si, respectively. In addition, with a 1mm2 contact of all devices, the current densities at 20V and the leakage current densities at −5V were calculated to be 0.183 and 5.96×10−5A·cm−2 for n-GaN/p-Si, 0.303 and 8.05×10−5A·cm−2 for n-In0.15Ga0.85N/p-Si, and 0.513 and 2.81×10−4A·cm−2 for n-In0.4Ga0.6N/p-Si. Our three devices strongly sustained under reverse bias and showed the breakdown voltage beyond 20V. The variations of electrical properties with the test temperature were also investigated up to 150°C. The barrier height, ideality factor, and series resistance of all hetero-junction diodes were also calculated by using equations based on the standard thermionic-emission (TE) mode and Cheung's method.

Phase width of kinetically stable ([PbSe]1+δ)1[formula omitted] ferecrystals and the effect of precursor composition on electrical properties

Synthesis and transport properties of ([PbSe]1+δ)1(TiSe2)1 ferecrystals made from several precursors of different compositions are reported. C-lattice parameters of crystallized compounds vary by under 0.01Å though relative cation compositions normalized to selenium content are shown to vary by over 30%. Even with a deliberate wide-range of starting precursor compositions crystallized under kinetic conditions, the variation in electrical properties of ferecrystals is less than in similar compounds grown under equilibrium conditions. The growth process of a ferecrystal appears to push impurities of excess starting material in the precursor to the surface, until impurity density becomes too high and defects are incorporated as inclusions, replacing small domains within the layered structure. Transport properties of the many compounds formed cluster into regions, with samples deposited during the same deposition cycle showing less variation.

Room Temperature Photoluminescence Characterization of Interface Quality of SiN/SiO2/Si Prepared under Various Deposition Techniques and Conditions

Various types of stacked dielectric films are used in complimentary metal-oxide-semiconductor (CMOS) devices in gates, capacitors and device isolation structures. They are also used as insulating materials between conductors, as inter-metal dielectrics (IMD) and inter-layer dielectrics (ILD). The preparation technique, structure and properties of dielectrics strongly influence the quality of the dielectrics/Si interface. Nominally, similar dielectrics/Si structures, even prepared by the same technique, often show different electrical properties depending on subtle differences in process conditions (hidden variables). Monitoring of physical dimensions and chemical compositions of dielectrics often miss unexpected variations in electrical properties. Non-contact electrical property characterization techniques lack lateral resolution and often results in impairment of the dielectrics/Si interface due to strong external electric fields from the measurement process. Alternative dielectrics/Si interface characterization techniques, which can provide insights into electrical properties without external electric field, would be very useful as a complimentary process and material quality monitoring technique. In this study, we have investigated the effect of SiN film deposition techniques on the interface quality of the resulting SiN/SiO2/Si using spectroscopic room temperature photoluminescence (RTPL) under multiwavelength excitation. The sample preparation procedures are as follows. First, ultra thin (~2.2 nm thick), gate oxide quality, thermal oxide films were grown on 300 mm Si(100) wafers. Nominally 5.0 nm thick SiN films were grown on ~2.0 nm thick SiO2/Si wafers using conventional low pressure chemical vapor deposition (LPCVD) and atomic layer deposition (ALD) under various nitrogen source flow conditions. The film thickness was measured (after SiO2 film deposition) before and after SiN deposition using ellipsometry. Figure 1 (a) and (b) show RTPL spectra measured at the center of seven different SiN/SiO2/Si wafers under 650 nm excitation and showing maximum RTPL intensity under 650 nm and 827 nm excitation. Significantly large RTPL intensity variations were measured among the seven SiN/SiO2/Si wafers. The SiN film deposition conditions have modified the underlying SiO2/Si interface characteristics. Non-contact RTPL measurements are very sensitive to the thin film deposition techniques and conditions. It is effective as a complimentary dielectrics/Si process and interface characterization and monitoring technique. Figure 1

Tuning the morphology of ZnO nanostructure by in doping and the associated variation in electrical and optical properties

In this work, Zn100−xInx (x=0, 1, 2.5, 5 and 7.5at%) compounds have been initially alloyed by melting method and used as precursors to prepare different nanostructures of indium (In) doped ZnO using chemical vapor deposition (CVD). The effect of In content on the structural, morphological, optical as well as electrical properties has been studied. XRD and Raman examinations demonstrate the substitution of Zn+2 ions by In+3 ions at lower indium concentrations, while In2O3 appears as separate phase at higher In ratios. The nanowires transform to nanoflakes then nanoflowers as the In concentration increases. With regard to the optical properties, the transparency increases with increasing In and decreases thereafter. The optical band gap values increase with In content reaching its maximum value (3.28eV) for the sample of x=5at%. The refractive index, extinction coefficient and Urbach tail are also affected by In doping. The electrical conductivity enhances at lower doping level due to formation of thermally activated donor levels, despite this, the phase separation and phonon scattering are factors responsible for conductivity decrease at higher In content.

Study of size dependent variation in electrical and structural properties of zinc nanowires

Nanowires have received much interest due to their unique properties and potential applications in nanoelectronics, plasmonics, sensors, superconductivity, nanoelectrodes, energy storage devices, generation of hydrogen energy etc. The understanding of electronic transport properties in nanowires is important for their applications in future nanoscale electronic devices. In the present work, the size and irradiation dependent variation in the electrical and structural properties of zinc nanowires is presented. Zinc nanowires with different diameters (80, 100, 200, 400 nm) were synthesized within the polycarbonate track-etched membranes using electrodeposition technique. I–V characteristics (IVC) recorded at room temperature showed higher electronic transport through nanowires with large diameter. The influence of diameter on the crystallite size and preferred orientation was carried out using X-ray diffraction (XRD). The synthesised nanowires were also irradiated with 40 MeV C4+ ion beam having fluence 1013 ions/cm2. The post irradiation IVC and XRD characterization revealed the variation in their electrical conductivity and preferred orientation.

Investigation of physical properties of screen printed nanosized ZnO films for optoelectronic applications

Nanosized ZnO particles derived from chemical co-precipitation route were used for casting ZnO films by screen printing method followed by sintering at two different temperatures. The variation in structural, optical and electrical properties of these films with temperature have been investigated by XRD, SEM, FTIR, Raman, UV-VIS, EPR and four probe analytical techniques. XRD patterns of these films exhibit polycrystalline nature with hexagonal wurtzite structure and SEM images reveal the smooth, dense and without any cracks/damage porous surface morphology. Infrared transmission spectra shows peaks pertaining to Zn-O stretching modes and their multiphonon modes. While Raman spectra exhibited strong peaks of E-2 (high) phonon and overtone of surface phonon mode at 429 cm(-1) and 1144 cm(-1) respectively with weak components of LO and TO branches. The direct band gap energy of these films showed narrowing of band gap from 3.21 eV to 3.12 eV on increasing sintering temperature from 500 degrees C to 600 degrees C. DC conductivity measurements confirmed semiconducting behaviour and showed lowering of activation energy. EPR spectra showed single narrow line resonance signal of g-value similar to 1.9469 due to oxygen vacancies which are produced during synthesis of ZnO nanoparticles by sol-gel process. These studies revealed that on increasing sintering temperature the crystallinity of the film improves with reduction in lattice deformations in these screen printed ZnO films.