Variation Of Electrical Properties Research Articles

Effects of Doping, Strain and Size on the Electrical Properties of MoS2 Nanoribbons

In this work, we have investigated size, doping and strain effect on the electrical properties of n-type and p-type MoS2 monolayer, one of the most interesting two-dimensional layered materials. We found that the bandgap of the MoS2 will reduce from 1.8 eV to 1.2 eV as the infinite lattice being shrunk into 10×10 nanoribbon. The electrical properties of a nanoscale MoS2 monolayer exhibited large variation (≈ 20%) as its doping level or dopant position changes, although the band-gap varies slightly. The study on the strain effect indicates that the bandgap of infinite MoS2 monolayer monotonically reduces as the increasing of the strain strength. The variation in electrical properties induced by size, doping and strain effect may post a serious challenge on the application in logic and memory devices.

Effects of Doping, Strain and Size on the Electrical Properties of MoS2 Nanoribbons

Two-dimensional (2D) transition metal dichalcogenides (TMDs), such as isolated monolayers or few-layers of MoS2 and WSe2, have recently gained intensive interest for their potential in future electronics [1]. The bulk of TMDs usually have a layer structure which is similar to graphene. Because the layers are bound together by weak van der Waals forces, an isolated monolayer of TMDs can be easily obtained by cleaving technique. Unlike graphene, these 2D materials have a significant band gap and exhibit attractive semiconductor properties. Therefore, the 2D TMDs have been widely considered for the ultimately thin channel materials in future Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) to suppress short channel effects. Especially, TMD monolayers usually have a direct band gap, very attractive for the mixed electronic and photonic application in future logic and memory devices [2].During the integration of these 2D materials into electronic devices, e.g., as the channel materials in MOSFETs, they will be defined by lithography into nanoribbons, doped into n- or p-type, and stressed by the strain induced from the metal contacts and dielectric interface. In this work, we have studied the effects of these factors on the band structure and electrical properties of MoS2monolayers by using a numerical simulation method based on density functional theory. We found that the doping, strain and size could induce significant variation in the electrical properties of these 2D materials. These will be very challenging issues for the 2D materials.In this work, we first studied the size effect on the properties of MoS2 monolayer nanoribbons. We found that the band gap of MoS2 nanoribbons changed from 1.8 eV of an infinite MoS2 sheet to 1.2 eV of a 10×10 (in molecule) MoS2 nanoribbons or 0.5 eV of a 5×10 MoS2 nanoribbons. We also found that the doping level and dopant position have a significant effect on the electrical properties of MoS2 nanoribbons. The doping level and dopant position can induce large variation (30%) in sheet resistance. This variation in electrical properties may post a serious challenge on the application in logic and memory devices. In addition, we found that the strain will also significantly affect the electrical and carrier transport properties of MoS2 monolayer. Under different strain, the MoS2 will change from direct band-gap to indirect band-gap semiconductor. As the strain further increases to certain value, the MoS2will become metallic.In summary, this work demonstrated that the size, doping and strain have a significant effect on the 2D materials and will induce large variation in electrical properties. Therefore, the future integration of such 2D materials for logic or memory circuit application, the size, doping and strain must be well engineered and controlled in order to minimize the device variation.

Fabrication of low phase transition temperature vanadium oxide films by direct current reactive magnetron sputtering and oxidation post-anneal method

Vanadium oxide thin films were deposited on ordinary glass substrates by direct current (DC) magnetron sputtering from a vanadium metal target and subsequent oxidation annealing. The deposition and annealing parameters were given in detail. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM). The phase transitions of films were observed by measuring their electrical and optical property variations at different temperature. The results indicated that the films fabricated had a semiconductor–metal phase transition temperature of about 30°C.

Nanoflower rod wire-like structures of dual metal (Al and Cr) doped ZnO thin films: Structural, optical and electronic properties

Transition metal (TM) doped ZnO thin-films are increasingly being investigated for the advancement of optoelectronic devices. Functional dual TMs doping into ZnO nanostructures might influence of the charge carrier recombination rate, optical, structural and interfacial electron-transport rate performance. In this study, we demonstrated the fabrication of nanostructured thin-films of pure-ZnO, aluminium doped-ZnO (Al:ZnO or AZO) and Al with chromium doped-ZnO (Al+Cr:ZnO or ACZO) by the pulsed laser deposition (PLD). Surface morphology of prepared thin-films resembled the distinctive shapes such as (pure-ZnO) nanowires, (AZO) nanorods and (ACZO) nanoflower-like structures, respectively. Variation of structural, optical, morphological and electrical properties were characterized by glancing incidence X-ray diffraction (GIXRD), micro-Raman scattering (μ-RS), electron microscopy and transport field emission (F–E) techniques. The electron transport F–E result shows that ACZO has high conductivity than the undoped films.

Effects of sub-bandgap illumination on electrical properties and detector performances of CdZnTe:In

The effects of sub-bandgap illumination on electrical properties of CdZnTe:In crystals and spectroscopic performances of the fabricated detectors were discussed. The excitation process of charge carriers through thermal and optical transitions at the deep trap could be described by the modified Shockley-Read-Hall model. The ionization probability of the deep donor shows an increase under illumination, which should be responsible for the variation of electrical properties within CdZnTe bulk materials with infrared (IR) irradiation. By applying Ohm's law, diffusion model and interfacial layer-thermionic-diffusion theory, we obtain the decrease of bulk resistivity and the increase of space charge density in the illuminated crystals. Moreover, the illumination induced ionization will further contribute to improving carrier transport property and charge collection efficiency. Consequently, the application of IR irradiation in the standard working environment is of great significance to improve the spectroscopic characteristics of CdZnTe radiation detectors.

Physical properties of spray pyrolyzed Ag-doped SnS thin films for opto-electronic applications

A spray pyrolysis technique was used to deposit the silver doped tin sulfide (SnS:Ag) thin films on glass substrates at the substrate temperature of 350°C. The variation in structural, optical and electrical properties of SnS with silver incorporation was investigated. The XRD spectra showed the improvement in crystallinity while increasing the doping concentration of Ag. The lower electrical resistivity of 8.63×10−1Ωcm and the optical band gap of 1.33eV were obtained at 8at% of Ag.

Research into the electrical property variation of undoped CdTe and ZnTe crystals grown under Te-rich conditions

Both undoped ZnTe and CdTe bulk single crystals are grown under Te-saturated conditions from the solution and melt, respectively. To give an insight into the variation of the electrical properties, the defects structures in both tellurides are discussed. According to the actual growth velocities and the entire cooling history, tellurium interstitials (Tei) and Zinc vacancies (VZn) are proposed as the dominant grown-in defects, account for the low resistivity of p-type ZnTe. However, relatively high pulling rates and slow cooling-down processes result in tellurium anti-sites (TeCd) as the principle grown-in defects, leading to the high resistivity of light n-type CdTe. Further low-temperature (8.6K) photoluminescence spectra of both tellurides are obtained. The donor–acceptor pair (DAP) and recombination of free electron to neutral acceptor (eA) dominate the luminescence, however, with their intensities are anti-correlated. eA is superior to DAP in undoped Te-rich ZnTe, suggests a high concentration of Tei or VZn. On the contrary, DAP is the principal emission for undoped Te-rich CdTe. In addition, V-line is clearly identified in undoped Te-rich ZnTe, which possibly associated with VZn or close Frenkel pair VZn–Zni.

Effect of dispersant agents on morphology and optical–electrical properties of nano indium tin oxide ink-jet ink

Abstract In this study, the effect of dispersant agents on rheology, surface tension, dynamic light scattering and morphology of two nano-ITO inks were investigated. The inks were formulated using two different dispersant agents and the rest of constituents remained unchanged. The inks were printed onto a glass substrate using an ink-jet printer. The printing task was set to one, three and five runs, in order to evaluate variations in optical and electrical properties, by changing the thickness of the printed film. Following initial drying of the printed pattern on to the substrate, the samples were subsequently heat-treated at different temperatures (350 °C, 450 °C, 550 °C) to assess the effect, if any, of heat-treatment temperature on morphology, optical and electrical properties of the treated ITO films. It was concluded that the type of dispersant, heat-treatment parameters and number of printing runs had a substantial effect on the electrical and optical properties of the ITO films.

Structural, Magnetic and Electrical Properties of Cu-Mg Ferrites

Cu1-xMgxFe2O4 ferrites with (x = 0.2, 0.4, 0.6, 0.8 and 1.0) has been synthesized by double sintering ceramic technique at 11500C for 2hr and investigated for their structure, microstructure, complex permeability behaviour, DC and AC resistivity, dielectric constant measurements. X-ray analysis indicated the formation of single-phase cubic spinel structure for all samples and the lattice parameter was found to decrease with increasing Mg content. Grain size was found to decrease from 34.36 to 4.16 mm with the increase of Mg contents. The real part of initial permeability (??) remained constant up to certain lower range of frequency after it decreased slightly to lower value of permeability at which imaginary part of permeability (?²) showed a maximum value. The decrease of ?? is observed with the increase of Mg content which is attributed to a decrease of grain size. DC electrical resistivity and dielectric constant decreased with increasing Mg content and AC resistivity decreased with increasing frequency, exhibiting normal ferrimagnetic behaviour. The observed variation of electrical and dielectric properties has been explained on the basis of the electronic hopping frequency between Fe2+ and Fe3+ ions in present samples. Keywords: Ferrites; XRD; Micrographs; Complex permeability; DC resistivity. © 2014 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. doi: http://dx.doi.org/10.3329/jsr.v6i2.17351 J. Sci. Res. 6 (2), 205-215 (2014)

Analysis of Breakdown Voltage and Cost Reduction of Transformer Oil by Using Nomex Paper and Filler

AC breakdown voltage characteristics of different insulation materials in transformer oil are investigated. The aim is to reduce the quantity of expensive transformer oil by adding Filler (insulation material) to reduce the cost of the transformer oil without compromising its electrical properties. Experiments are conducted for two insulation materials, aluminium oxide and silicon dioxide. Both of these materials are tested in horizontal and vertical electrode arrangements. After introducing the Filler and selecting its optimum quantity, Nomex paper (E 56) is added to enhance the breakdown strength of the model. Combination of Nomex paper (E 56) and Filler acts as a barrier and thus enhances the breakdown strength of the model. Dielectric constant, resistivity and conductivity are calculated to investigate the variations in electrical properties of the model. Based on experimentation, optimum condition for the addition of Filler and Nomex paper (E 56) in the transformer oil is proposed. Detailed result of using composite insulation is discussed in this paper.

Structural, optical, and electrical properties of NiO-In composite films deposited by radio frequency cosputtering

In-doped NiO films with indium concentrations ranging from 0 to 30.3 at. % were deposited on glass substrates to investigate corresponding structural, optical, and electrical property variations. The x-ray diffraction patterns show that all films display only NiO peaks. When In atoms were added to NiO films, the NiO peaks shifted to lower angles, indicating that the lattice parameters of the films increased due to the larger In ions substituting for the smaller Ni ions. An electrical resistivity (ρ) too high to be measured occurred when the indium concentration in the NiO film was less than 15.6 at. %. The ρ value dropped significantly to 0.06 Ω·cm as the indium concentration increased to 26.9 at. %. Upon further raising the In to 30.3 at. %, the ρ value decreased further to 0.01 Ω·cm. All the In-doped NiO films showed n-type conduction. The transmittance of undoped NiO film is as high as 96%. On raising the indium concentration to 15.6, 19.9, 26.9, and 30.3 at. %, the transmittances decreased further to 68%, 62%, 57%, and 47%, respectively. Introducing higher In concentrations improved the films’ thermal stability of electrical resistivity.

Thermoelectric properties of Cu2Ga4Te7 based compounds with Zn substitution for Cu and Ga

We present two series of Cu2Ga4Te7‐based compounds with Zn substituting for Cu (Cu‐poor) and Ga (Ga‐poor), and have observed enhanced thermoelectric performance. Generally, the Seebeck coefficient (α) and lattice thermal conductivity (κL) increase and electrical conductivity (σ) decreases with the Zn content increasing. The variation in electrical properties might be mainly due to the formation of antisite defects ( and ), the acceptors. The defects increase the local density of states (DOS) near the Fermi level and effective mass, leading to the increase in α, while on the other hand, they widen the bandgap (Eg) leading to the degradation of the electrical conductivity. The gradual enhancement in κL is attributed to the reduced phonon scattering resulting from the decrease in vacancy concentration. As a result, we attained the maximum ZT value of 0.46 for Cu‐CGT and 0.47 for Ga‐CGT at ∼770 K with a proper Zn content, which is about 20–22% higher than that of intrinsic Cu2Ga4Te7.

Effects of non-synchronized variations of electric and magnetic properties on transmitted waves at lossy interface

Generalized formulas of reflection and refraction are derived by simultaneously considering real valued boundary conditions and Poynting׳s theorem. It is proposed that the dynamic mechanics of reflection and refraction may be attributed to the minimization of the interface energy. In addition, it is predicted that non-synchronized variation among electric and magnetic parameters at the lossy interface may readjust distribution of energy flows between the reflected and transmitted waves, produce additional peak(s) in the curves for time averaged Poynting vector of the transmitted wave versus refracted angle, induce negative refraction of either TM or TE polarized wave without negative refraction index, and so on.

Effect of Sintering Time on the Structural, Magnetic and Electrical Transport Properties of Mg<sub>0.35</sub>Cu<sub>0.20</sub>Zn<sub>0.45</sub>Fe<sub>1.94</sub>O<sub>4</sub> Ferrites

Spinel-type Mg0.35Cu0.20Zn0.45Fe1.94O4 ferrites were synthesized by using the solid-state reaction technique. The XRD patterns of the sintered samples indicated the formation of single-phase cubic spinel structure. The apparent density of the sample is found to increase whereas porosity decreases with the increase in sintering time. The grain growth of the samples is enhanced with the increase in sintering time which is attributed to the liquid phase due to CuO during sintering. The initial permeability of the ferrite is found to increase with the increase in sintering time but the resonance frequency shifts towards the lower frequency. This increase in permeability is correlated to the increase of density and the grain size of the sample. The resistivity of the samples decreases with 103/T ensuring the semiconducting nature of the samples. Room temperature DC resistivity and activation energy of the samples decrease what is attributed to the increased Fe2+ ions content with the increase in sintering time. The dielectric constant (e￠) of the samples decreases with increasing frequency whereas e￠ increases as the temperature increases exhibiting normal dielectric behaviour of the magnetic semiconductor ferrite. The observed variation of electrical and dielectric properties is explained on the basis of Fe2+/Fe3+ ionic concentration as well as the electronic hopping frequency between Fe3+ and Fe2+ ions in the present ferrite sample.

Post-Silicon Characterization and On-Line Prediction of Transient Thermal Field in Integrated Circuits Using Thermal System Identification

Thermal system identification (TSI) is presented as a methodology to characterize and estimate the transient thermal field of a packaged IC for various workloads considering chip-to-chip variations in electrical and thermal properties. The time-frequency duality is used to identify the thermal system as a low-pass filter in frequency domain through on-line power/thermal measurements on a packaged IC. The identified characteristic system for an individual IC is used for on-line prediction of the transient thermal field of that specific IC for a power pattern. A test-chip, fabricated in 130-nm CMOS, demonstrates the effectiveness of TSI in post-silicon characterization and prediction of transient thermal field. The application TSI in thermal analysis of multicore processors is presented.

Role of Hydrogen in Variation of Electrical, Optical and Magnetic Properties of ZnSe-Fe Bilayer Thin Films Structure

This paper is reporting the role of hydrogen in preparation and characterization of dilute magnetic semiconductor of ZnSe-Fe bilayer thin film structure. These films are hydrogenated at different pressure to see the effect of hydrogen on electrical, optical, magnetic and structural properties of bilayer structure. Optical absorption in thin films is found to be decrease with hydrogen absorption. It may be due to interaction of hydrogen with bilayer structure and takes electron from the conduction band of thin film structure. The current-voltage characteristic of these films shows the variation in conductivity with hydrogenation due to decrease in electron density. Atomic Force Microscopy and scanning electron Microscope recorded to see the surface topography of bilayer thin films. It has been observed that deposited film have nano size structure that is favorable for hydrogen absorption having higher surface to volume ratio. The Electron diffraction X-ray analysis gives the information about composition of films. Raman spectra have used to see the presence of hydrogen. Super-conducting Quantum Interference Device gives the information of confirmation of diluted magnetic semiconductors and variation of magnetic momentum with hydrogenation.

Preparation and characterization of nanostructures of in-doped ZnO films deposited by chemically spray pyrolysis: Effect of substrate temperatures

We deposited undoped (ZnO) and indium-doped ZnO (IZO) films onto glass substrate via ultrasonic spray pyrolysis technique. The variation in structural, surface morphology, electrical, optical and photoluminescent properties as a function of substrate temperature is investigated. X-rays pattern confirms that as-synthesized IZO phase is grown along a (002) preferential plane. Nanosized grains (<50nm) are determined by X-ray analysis. Morphology of as-grown films shows broadened nanostructures which have grown along c-axis and nanostructures are found to be smooth (RMS∼60nm). Study by spectrophotometer reveals that the as-grown films are highly transparent in the visible and IR spectra (T∼88%), and that the bandgap is slightly narrowed (3.17eV). Electrical measurements confirm the enhancement of conductivity, ρ<1Ωcm, due to indium incorporation into the starting solution. An electron concentration of 1017cm−3 and a mobility of 3cm2/Vs are found for IZO films grown at 400°C. The photoluminescence analysis demonstrates strong yellow (2.1eV) and blue (2.8eV) light and weak green (2.3eV) emissions.

Stretch sensing properties of conductive knitted structures of PEDOT-coated viscose and polyester yarns

Wearable textile-based stretch sensors for health-care monitoring allow physiological and medical evaluation without interfering in the daily routine of the patient. In our previous work, we successfully coated viscose and polyester (PES) fibers with the conjugated polymer poly(3,4-ethylenedioxythiophene) (PEDOT), using a chemical vapor deposition (CVD) process. In the present paper we report the possibility of producing a large quantity of PEDOT-coated conductive fibers with acceptable mechanical strength and frictional properties, so that knitted stretch sensors can be produced. In utilizing these knitted structures we have demonstrated the possibility of producing a textile-based monitoring device which is more readily integrated into wearable clothing than the previous metal-containing structures. The performance of viscose and PES knitted structures as stretch sensors has been investigated using a cyclic tester of our own design. For imitation of respiratory and joint movement, the variation in electrical properties of the knitted structures was examined at 5 to 50% elongation, and the performance of knitted viscose and PES structures was then compared on the basis of the cyclic testing results. In order to determine the effect of washing on PEDOT coatings and the knitted structures, two washing cycles were performed. After washing, the persistence of PEDOT coating on knitted structures was investigated using FT–IR spectroscopy and thermogravimetric analysis. In the case of PES fiber, it was revealed that stretch sensing behavior persisted even after the washing cycles. These structures thus have the potential to be utilized in medical textiles for monitoring the physiological activities of patients, such as breathing rate and joint movement.

Study on Electrical Properties of Activated Carbon Black Filled Polypropylene Composites Using Impedance Analyzer

Carbon black was activated and then filled into polypropylene to prepare conductive composites, of which the electrical properties, including impedance Z, phase angelθ and dissipation factor tgδ, as a function of frequency and carbon black concentration were investigated using impedance analyzer. The percolation threshold of 5wt% carbon black concentration was obtained. It was found that the variation of AC electrical properties as a function of frequency is dramatic and dependent on the carbon black concentration. It was also found that dependence of the real part and the imaginary part of impedance on frequency decreases with the increased concentration of carbon black, while that of phase angle and dissipation factor increases. Based on the corresponding results, the conductive network model and the corresponding equivalent circuit were constructed.

Influence of La3+ Substitution on Electrical and Photocatalytic Behavior of Complex Bi2Sn2O7 Oxides

Pyrochlore-type Bi2–xLaxSn2O7 (0.0 ≤ x ≤ 0.20) system has been explored for its facile synthesis and electrical and photocatalytic functionalities. The highly distorted α-polymorph of Bi2Sn2O7 was synthesized, and successive La3+ substitutions were found to increase the lattice symmetry. Electric field dependent polarization measurements showed the ferroelectric hysteresis loop for pure Bi2Sn2O7 for the first time, and La3+ substitution was found to have a bearing on the ferroelectric properties with concomitant increase in leakage current. Temperature-dependent polarization studies were also performed on various nominal compositions. Diffuse reflectance spectroscopy established the tenability of the band gap as the function of La3+ content (2.5–3.0 eV). In order to explore the multifunctionality of this unique bismuth-containing system, the photocatalytic dye degradation of rhodamine B was investigated with Bi2–xLaxSn2O7 (0.0 ≤ x ≤ 0.20) system in both UV and visible regions. The variation in band gap introduced La3+ substitution significantly enhanced the photocatalytic behavior of bismuth stannate for rhodamine B degradation. The rate constant for the nominal composition Bi1.85La0.15Sn2O7 (17.6 × 10–2 min–1) is 6-fold the value for the pure Bi2Sn2O7 (2.75 × 10–2 min–1). The degradation profiles of rhodamine B in the UV and visible regions showed that dye degradation proceeds through different mechanisms which are discussed. The present study attempts to give an insight into the variation in electrical and photocatalytic properties and relate them to changes in structure. Bi2–xLaxSn2O7 (0.0 ≤ x ≤ 0.20) system is being proposed here as multifunctional candidates for lead-free electrical materials and efficient photocatalyst in the UV and visible regions.