Minimum Resistivity Research Articles

Effect of nanowire curviness on the percolation resistivity of transparent, conductive metal nanowire networks

We study the effect of nanowire curviness on the percolation resistivity of transparent, conductive metal nanowire networks by Monte Carlo simulations. We generate curvy nanowires as one-dimensional sticks using 3rd-order Bézier curves. The degree of curviness in the network is quantified by the concept of curviness angle and curl ratio. We systematically study the interaction between the effect of curviness and five other nanowire/device parameters on the network resistivity, namely nanowire density, nanowire length, device length, device width, and nanowire alignment. We find that the resistivity exhibits a power law dependence on the curl ratio, which is a signature of percolation transport. In each case, we extract the power-law scaling critical exponents and explain the results using geometrical and physical arguments. The value of the curl ratio critical exponent is not universal, but increases as the other nanowire/device parameters drive the network toward the percolation threshold. We find that, for randomly oriented networks, curviness is undesirable since it increases the resistivity. For well-aligned networks, on the other hand, some curviness is highly desirable, since the resistivity minimum occurs for partially curvy nanowires. We explain these results by considering the two competing effects of curviness on the percolation resistivity. The results presented in this work can be extended to any network, film, or nanocomposite consisting of one-dimensional nanoelements. Our results show that Monte Carlo simulations are an essential predictive tool for both studying the percolation transport and optimizing the electronic properties of transparent, conductive nanowire networks for a wide range of applications.

Influence of substrate temperature on the physical properties of SnS2 thin films prepared using nebulized spray pyrolysis technique

Influence of substrate temperature on the physical properties of Tin disulfide (SnS2) thin films is investigated. X-ray diffraction studies revealed that the SnS2 thin films are preferentially oriented as (001) plane. SEM analysis showed that SnS2 thin films had platelet-like grains. EDAX analysis clearly confirms the presence of expected elements of tin and sulfur in appropriate proportions. Multiple interference effects were predominant in all these thin films in wavelength region of 500–1100 nm. The direct optical band gap of tin disulfide thin films had decreased from 3.26 to 2.7 eV with the increase in substrate temperature. Photoluminescence studies expose that the intensity of NBE emission peaks differs according to the substrate temperature. A minimum resistivity value of 2.19 × 101 Ω cm was obtained for the film grown at Ts = 250 °C. Hall Effect measurement exhibited that all the SnS2 samples had n-type conductivity. Raman spectra exposed that SnS2 films had a broad peak at 314 cm− 1.

Influence of In-doping on microstructure, optical and electrical properties of sol–gel derived CdO thin films

Cadmium oxide thin films have been prepared on glass substrates by the sol–gel (SG) spin-coating technique. The structural, optical and electrical properties of the prepared films were studied as a function of the thicknesses. The results show that the optimum thickness for preparation of CdO films with high optical transparency and low resistivity is 211 nm. By using this optimized thicknesses and the same experimental conditions, transparent indium-doped cadmium oxide (In–CdO) thin films were deposited and annealed at 450 °C. Transparent and conducting In–CdO thin films for various concentrations of indium (1, 3 and 5 wt%), were prepared using the SG method. The electrical, optical and structural properties of these In–CdO films were investigated using different techniques, such as Hall measurements, optical transmission and X-ray diffraction (XRD). XRD patterns show that the films are polycrystalline. The structural analysis shows that all the samples have a cubic structure. Field emission scanning electron microscopy analysis reveals that the average grain size and surface morphology of CdO films are effectively changed by various In-doping concentrations. A minimum resistivity of 0.51 × 10−3 Ω cm and carrier concentration of 5.43 × 1020 cm−3 with high transmittance ~ 80% in the range 350–800 nm were achieved for 3 wt% indium doping. The band gap value starts at 2.32 eV for the undoped film and increases with doping concentration reaching the value of 3.07 eV for 5 wt% indium doping.

Resistivity behavior of hydrogen and liquid silane at high shock compression

To study the electrical properties of hydrogen rich compounds under extreme conditions, the electrical resistivity of density hydrogen and silane fluid was measured, respectively. The hydrogen sample was prepared by compressing pure hydrogen gas to 10 MPa in a coolant target system at the temperature of 77 K. The silane sample can be obtained with the same method. High-pressure and high-temperature experiments were performed using a two-stage light-gas gun. The electrical resistivity of the sample decreased with increasing pressure and temperature as expected. A minimum electrical resistivity value of 0.3 × 10-3 Ω cm at 138 GPa and 4100 K was obtained for silane. The minimum resistivity of hydrogen in the state of 102 GPa and 4300 K was 0.35 Ω cm. It showed that the measured electrical resistivity of the shock-compressed hydrogen was an order of magnitude higher than fluid silane at 50–90 GPa. However, beyond 100 GPa, the resistivity difference between silane and hydrogen was very minor. The carriers in the sample were hydrogen, and the concentration of hydrogen atoms in these two substances was close to each other. These results supported the theoretical prediction that silane was interpreted simply in terms of chemical decomposition into silicon nanoparticles and fluid hydrogen, and electrical conduction flows predominately dominated by the fluid hydrogen. In addition, the results also supported the theory of “chemical precompression”, the existence of SiH bond helped to reduce the pressure of hydrogen metallization. These findings could lead the way for further metallic phases of hydrogen-rich materials and experimental studies.

Identification of prospective significance levels for potential geothermal fields of India

Abstract This study aims to predict prospective significance levels of potential geothermal fields already identified by Geological Survey of India (GSI) and National Geophysical Research Institute (NGRI) by field investigations. Wide range of criteria's are considered in determining the relative significance level of each geothermal field in terms of cumulative score. These criteria's include useful resource base (URBfield), Areal extent (Afield), Minimum temperature as per geothermometry (Tmin), Maximum temperature as per geothermometry (Tmax), Utilization score (USfield), Cumulative discharge of thermal springs (Q), Minimum electrical resistivity (Rmin), Maximum electrical resistivity (Rmax) and Representative reservoir temperature as per Gas thermometry (Tgas). Fuzzy Analytical Hierarchy Process (Fuzzy AHP) is used to study the dominance of each geothermal field, evaluated over the aforementioned criteria to find cumulative score. URBfield depends on possible extraction temperature of reservoir estimated by COMSOL Multiphysics® modelling and simulation software. The geothermal fields are conceptualized as shallow homogenous reservoirs with injection and extraction wells. The attributes of remaining criteria are collected from published works of NGRI and GSI. The results of this study ratify that Puga geothermal field is the most significant site among the identified potential geothermal fields, to conduct further developmental works and for commercial extraction of geothermal energy.

Investigation on the Effects of SiO2 Content on the NTC Thermistor Properties of Ce1.2(1-x)Mn1-xSix System

Ce1.2(1-x)Mn1-xSix(x=0.1,0.2.0.3,0.4) NTC thermistor materials were prepared by the traditional solid-state reaction method. The effects of SiO2 content on the microstructure and electric properties of prepared materials are investigated through XRD, SEM, XPS and several instruments for electrical properties characterization. The results indicate that the average grain size increases with the increasing SiO2 content. The resistivity and materials constant B value exhibit opposite change laws. The minimum room resistivity of 7.18×105 Ω·cm and the maximum characteristic parameter B value of 5507K are obtained when x=0.2. And when x=0.1 the aging factor η is 0.34% and it decreases as the CeO2 content increases.

Influence of tin precursor concentration on physical properties of nebulized spray deposited tin disulfide thin films

ABSTRACTTin disulfide thin films were prepared with different molarities of tin species (MSn) at the optimized substrate temperature using the Nebulized Spray pyrolysis technique to obtain better crystallinity with mono phase thin films. The concentration of Tin IV chloride Penta hydrate precursor is varied from 0.05:0.4 to 0.25:0.4 (SnCl4.5H2O: thiourea) to achieve correct stoichiometry and to tune the concentration of Tin ions in the SnS2 thin films. These films were well adherent, uniform, and shiny. Lower concentrations of Tin yields highly textured SnS2 thin films with (001) crystallite orientation. On increasing the concentration, the multi-phases (SnS and Sn2S3) were found to be present along with SnS2 material. The platelet-like grains were observed from SEM analysis in these SnS2 films. Multiple interference effects were predominant in all these thin films in the wavelength region of 600–1100 nm. The direct optical band gap of tin disulfide thin films had decreased from 3.2 eV to 2.75 eV with an increase in MSn from 0.05 to 0.2 M, respectively, and further increased to 3.0 eV for 0.25 M concentration. Using Hall Effect measurement, the type of semiconductor is found to be of n-type. A minimum resistivity value of 2.19 × 103 Ω cm was obtained for the film grown at MSn = 0.2 M.

The effect of NaOH on room-temperature sintering of Ag nanoparticles for high-performance flexible electronic application

A composite silver nanoparticle (AgNP) ink was prepared by mixing the small AgNPs (10 nm in diameter), large AgNPs (50 nm in diameter), ethylene glycol, and deionized water at a mass ratio of 4:2:3:51. By spraying a sodium hydroxide solution, the AgNP pattern printed on the polyethylene terephthalate film surface can be sintered at room temperature with a minimum electric resistivity of 12.11 μΩ·cm, 0.7 times smaller than that sintered at 150 °C. Our study confirmed that OH− ions can partially replace citrates on AgNP surfaces at room temperature, resulting in the loss of the encapsulated density of citrates. Such loss can induce the particle agglomeration, cause the sintering necks to form, and finally create the three-dimensional conductive networks. This research is of great importance to the rapid manufacturing of low-cost, low-environmental-impact and high-performance flexible printed circuits.

Effect of different atmospheres on the electrical contact performance of electronic components under fretting wear

The effects of oxide etch on the surface morphology of metals for industrial application is a common cause of electrical contacts failure, and it has becomes a more severe problem with the miniaturization of modern electronic devices. This study investigated the effects of electrical contact resistance on the contactor under three different atmospheres (oxygen, air, and nitrogen) based on 99.9% copper/pogo pins contacts through fretting experiments. The results showed the minimum and stable electrical contact resistance value when shrouded in the nitrogen environment and with high friction coefficient. The rich oxygen environment promotes the formation of cuprous oxide, thereby the electrical contact resistance increases. Scanning electron microscope microscopy and electron probe microanalysis were used to analyze the morphology and distribution of elements of the wear area, respectively. The surface product between contacts was investigated by x-ray photoelectron spectroscopy analysis to explain the different electrical contact properties of the three tested samples during fretting.

Fabrication of antimony doped tin disulfide thin films by an inexpensive, modified spray pyrolysis technique using nebulizer

The SnS2 and antimony (Sb) doped SnS2 thin films were effectively synthesized on glass substrates for different antimony doping concentrations (2, 4, 6, 8 at. %) using nebulized spray pyrolysis technique. The XRD analysis showed that all the films are polycrystalline having hexagonal structure with (001) preferential orientation. It was seen from the SEM photographs that the doping causes remarkable changes in the surface morphology. EDAX analysis clearly confirms presence of expected elements tin, sulfur and antimony in the final product, in appropriate proportions. Optical study exhibits that the band gap value of SnS2 film decreases gradually with the increase in Sb doping concentration, reaching minimum band gap value of 2.55 eV at 6 at.% and starts increasing thereafter. Photoluminescence spectra depicted that the intensity of the emission peaks significantly varied with doping concentrations. The electrical study shows that the minimum resistivity value of 11 Ω cm with notable higher values of carrier concentration and mobility is achieved for 6 at.% of SnS2: Sb film. The Raman spectra exposed that SnS2 films had a broad peak at 314 cm−1.

Preparation and surface defect regulation of CdZnTe films based on GaN substrates

High quality polycrystalline CdZnTe (CZT) films were prepared on GaN substrates via close-spaced sublimation (CSS). Au electrodes were deposited on the surface of CZT films to form CZT/Au structure. XRD, SEM, EDAX and UV-Vis spectra were adopted to investigate the structure, composition and morphology of CZT films. XPS and I-V characterizations were used to investigate the surface defects and electrical properties of CZT films. The quantity of the surface defects is decreased with the extended growth times and remains stable when the deposition times exceed 20 min. The minimum resistivity of CZT thick films grown on GaN substrates is 1.12 × 109 Ω-cm, which is about two orders of magnitude higher than that on FTOs. The high resistivity can significantly reduce the leakage currents of CZT films and thus improve the signal-to-noise ratio of the radiation detector based on CZT films.

Solution-processed CuO thin films with various Cu2+ ion concentrations

Presented herein is a report on cupric oxide (CuO) thin films prepared on glass substrates by using a solution process with varying nominal concentrations of Cu2+ ions at 0.15 M, 0.20 M, and 0.25 M. X-ray diffraction patterns and scanning electron microscopy (SEM) micrographs were analyzed to evaluate the crystalline structure and surface morphology of the CuO thin films. The fabricated CuO thin films exhibited a single-phased monoclinic structure with (200) and (111) orientations. The grain size of the CuO thin films was observed to increase with higher concentration, by SEM observation. The electrical and optical properties of the CuO thin films were investigated using a four-probe measurement system and UV/VIS spectrometer, respectively. The thin films showed a minimum resistivity of 0.085 Ω cm corresponding to the 0.25 M concentration, and a bandgap energy ranging from 2.10 eV to 2.15 eV. In addition, the light-harvesting ability of CuO thin films was considered by the absorption figure of merit (a-FOM), in correlation with the global solar spectrum. A maximum a-FOM value of 12.79 Ω−1 cm−1 was attained for the sample with a Cu2+ ion concentration of 0.25 M.

Preparation and Characterizations of Monocrystalline Na Doped NiO Thin Films

In the present work, the effect of Na doping on optical, structural and electrical properties of Na doped NiO thin films were studied. The spray pneumatic method was used to deposit the Na doped NiO thin films in the range 0 to 5 wt.%, it are investigated at a substrate temperature of 420 °C with NiO solution 0.1 M. Firstly in the XRD specra, as found that a only (111) peak was observed for Na doped NiO thin film indicate that the Na doped NiO thin films a monocrystalline in nature with cubic structure. The maximum crystallite size of Na doped NiO thin films was 18.90 nm at 3 wt.%. Secondary, the optical transmissions spectra Na doped NiO thin films having a high transparency with comparing to undoped film in visible region. The band gap energy was decreased after doping by Na and reaching a minimum value is 3.53 eV at 2 wt.%. The minimum value of Urbach energy was 0.312 eV, it is obtained at 3 wt.%. In the end, the minimum electrical resistance of the Na doped NiO films was located at 5 wt.%. The optimum Na doping amount is achieved at 3 at %.

Effect of power density on the microstructure and properties of titanium diboride thin films by radio frequency magnetron sputtering method

Thermoelectric generators directly convert heat into electricity and offer a unique and very promising pathway for generating power. Titanium diboride, TiB2, is an ideal candidate for use as an electrode material in thermoelectric systems because of its refractory characteristic and excellent electrical conductivity. This study reports the effect of sputtering power density on microstructural, electrical and mechanical properties of TiB2 films fabricated by radio frequency magnetron sputtering. The TiB2 thin films were deposited at 500 °C with power densities of 5.1–12.7 W/cm2. As the power density increased, X-ray diffraction analysis showed a formation trend of highly crystallized hexagonal TiB2 with a (001) preferential orientation. X-ray photoelectron spectroscopy data revealed that only T–B chemical bonding states were present in the TiB2 phase. TiB2 films also exhibited a denser microstructure with a larger grain size. All three factors led to a lowering of the films' electrical resistivity. A minimum electrical resistivity of 6.5 × 10−4 Ωcm was obtained with a free-electron concentration of 1.2 × 1020 cm−3 and carrier mobility of 86.7 cm2 V−1 s−1. The hardness and elastic modulus were also found to increase with discharge power density from 19.5 to 26.6 GPa and from 165.2 to 196.8 GPa, respectively. This study demonstrated that the combination of high melting point and excellent electrical and mechanical properties makes TiB2 an ideal electrode material for thermoelectric applications.

Synthesis of Composites from Functionalized Carbon Nanotubes and Polyaniline

Modification of the surface of preliminarily functionalized multilayer carbon nanotubes (CNTs) with polyaniline is studied. The influence of the method and degree of functionalization of CNTs on oxidative polymerization process of aniline is studied. There is a correlation of the maximum value on the temperature curve of this reaction and the yield of its target product with the depth of preliminary oxidation of CNTs. The morphological characteristics and composition of a modifying layer are studied with transmission electron microscopy, FTIR spectroscopy, and Raman spectroscopy. The character of the dependence of electrically conductive properties of the composites and the magnitude of their specific surface on the degree of preliminary functionalization of CNTs with carboxyl groups is shown. The composites based on carboxylated CNTs with a degree of functionalization of 0.2 mmol/g possess minimum resistivity values (0.3 Ω cm). Materials with a maximum specific surface area (more than 170 m2/g) were obtained during use of CNTs, oxidized with concentrated nitric acid, as a substrate for precipitation of polyaniline. The experimental studies made it possible to substantiate a choice of the type of functionalized CNTs during modification with polyaniline for the use of synthesized composites as electrode materials and effective adsorbents.

Unusual Electrical Transport Driven by the Competition between Antiferromagnetism and Ferromagnetism in Antiperovskite Mn₃Zn1-xCoxN.

The magnetic, electrical transport and thermal expansion properties of Mn3Zn1−xCoxN (x = 0.2, 0.4, 0.5, 0.7, 0.9) have been systematically investigated. Co-doping in Mn3ZnN complicates the magnetic interactions, leading to a competition between antiferromagnetism and ferromagnetism. Abrupt resistivity jump phenomenon and negative thermal expansion behavior, both associated with the complex magnetic transition, are revealed in all studied cases. Furthermore, semiconductor-like transport behavior is found in sample x = 0.7, distinct from the metallic behavior in other samples. Below 50 K, resistivity minimum is observed in samples x = 0.4, 0.7, and 0.9, mainly caused by e-e scattering mechanism. We finally discussed the strong correlation among unusual electrical transport, negative thermal expansion and magnetic transition in Mn3Zn1−xCoxN, which allows us to conclude that the observed unusual electrical transport properties are attributed to the shift of the Fermi energy surface entailed by the abrupt lattice contraction.

Evaluation of the structural, optical and electrical properties of AZO thin films prepared by chemical bath deposition for optoelectronics

Aluminum doped zinc oxide (AZO) thin films for electrode applications were deposited on glass substrates using chemical bath deposition (CBD) method. The influence of deposition time on the structural, morphological, and opto-electrical properties of AZO films were investigated. Structural studies confirmed that all the deposited films were hexagonal wurtzite structure with polycrystalline nature and exhibited (002) preferential orientation. There is no other impurity phases were detected for different deposition time. Surface morphological images shows the spherically shaped grains are uniformly arranged on to the entire film surface. The EDS spectrum confirms the presence of Zn, O and Al elements in deposited AZO film. The observed optical transmittance is high (87%) in the visible region, and the calculated band gap value is 3.27 eV. In this study, the transmittance value is decreased with increasing deposition time. The room temperature PL spectrum exposed that AZO thin film deposited at (60 min) has good optical quality with less defect density. The minimum electrical resistivity and maximum carrier concentration values were observed as 8.53 × 10−3(Ω cm) and 3.53 × 1018 cm−3 for 60 min deposited film, respectively. The obtained figure of merit (ϕ) value 3.05 × 10−3(Ω/sq)- 1 is suggested for an optoelectronic device.

Interface chemical and electronic properties of LaAlO3/SrVO3 heterostructures

We have studied the chemical and electronic properties of LaAlO3/SrVO3 (SVO) ultrathin films by combining hard x-ray photoemission spectroscopy and transport measurements. We compare single SrVO3 (SVO) ultrathin films and SrVO3 buried below a polar LaAlO3 (LAO) thin layer, both epitaxially grown on SrTiO3. While ultrathin films (4 unit cells) of SVO do show insulating behavior over the entire temperature range, the LAO/SVO interface has a resistivity minimum at 250 K. When increasing the SVO layer thickness, the minimum is observed to shift to higher temperatures, but the resistivity always stays smaller than that of comparable SVO single films. Hard x-ray photoemission spectroscopy reveals a surface or interface related V5+ component in the V 2p spectra for SVO films and LAO/SVO heterostructures, respectively, attributed to a strongly oxidized component. This chemical reconstruction is weaker in LAO/SVO heterostructures compared to single SVO films. We show that this dead layer in SVO ultrathin films has to be considered when the film thickness reaches the few unit-cells limit and propose solutions on how to prevent this detrimental effect.

The Physical Properties Of Aluminium-7xxx Series Alloys Produced By Powder Metallurgy Method

Alumix-431 materials were prepared by cold and warm compaction method applying 350-400 MPa pressures at RT (room temperature) 50 and 80°C temperatures. The density measurements of materials were performed; the thermoelectric properties of materials were investigated at 5-300K under the He atmosphere, and the relationship between the measurements and sample properties was examined. The measurements of thermoelectric properties showed that maximum resistivity [Alumix -431-1] and thermal conductivity [Alumix -431-6] values were obtained 0.161Ωm and 24.31W/Km, respectively at 285-295K temperature ranges and minimum electrical resistivity and thermal conductivity values were obtained on Alumix-431-6 and Alumix-431-1 samples, respectively. It was observed that Seebeck coefficient values varied mostly from negative sign to positive sign indicated dominate from carriers. The maximum Figure of merit value was determined as 18.71×10 -2 ; on the Alumix-431-5 alloy at 96.904K

DC Magnetron Sputtered IZTO Thin Films for Organic Photovoltaic Application.

IZTO20 (In0.6Zn0.2Sn0.2O1.5) ceramic target was prepared from oxide mixture of In2O3, ZnO, and SnO2 powders. IZTO20 thin films were then deposited onto glass substrate at 400 °C by DC magnetron sputtering. The average optical transmittance determined by ultraviolet-visible spectroscopy was higher than 85% for all films. The minimum resistivity of the annealed IZTO20 thin film was approximately 6.1×10-4 Ω·cm, which tended to increase with decreasing indium content. Substrate heating and annealing were found to be important parameters affecting the electrical and optical properties. An organic photovoltaic (OPV) cell was fabricated using the IZTO20 film deposited under the optimized condition as an anode electrode and the efficiency of up to 80% compared to that of a similar OPV cell using ITO film was observed. Reduction of surface roughness and electrical resistivity through annealing treatment was found to contribute to the improved efficiency of the OPV cell.