Wide Range Of Electrical Properties Research Articles

A Versatile, Voltage-Pulse Based Read and Programming Circuit for Multi-Level RRAM Cells

In this work, we present an integrated read and programming circuit for Resistive Random Access Memory (RRAM) cells. Since there are a lot of different RRAM technologies in research and the process variations of this new memory technology often spread over a wide range of electrical properties, the proposed circuit focuses on versatility in order to be adaptable to different cell properties. The circuit is suitable for both read and programming operations based on voltage pulses of flexible length and height. The implemented read method is based on evaluating the voltage drop over a measurement resistor and can distinguish up to eight different states, which are coded in binary, thereby realizing a digitization of the analog memory value. The circuit was fabricated in the 130 nm CMOS process line of IHP. The simulations were done using a physics-based, multi-level RRAM model. The measurement results prove the functionality of the read circuit and the programming system and demonstrate that the read system can distinguish up to eight different states with an overall resistance ratio of 7.9.

Experimental determination of solidified lithium disilicate crystal bandgap energy using EELS and XPS

AbstractLithium disilicate (LS2) has been a crucial parent composition for glass‐ceramics since the 1950s because of its excellent chemical and physical durability. In addition, a wide range of electrical properties can be obtained by changing the composition and crystallinity. Bandgap energy is one of the critical electrical properties for designing new lithium silicate‐based materials. In this study, the bandgap energy of a synthesized LS2 crystal is evaluated using electron energy‐loss spectroscopy and X‐ray photoelectron spectroscopy. These two techniques unambiguously establish that the bandgap energy of LS2 is 7.7‐7.8 eV, which is in the vacuum ultraviolet region. This confirms the insulating nature of the LS2 crystal.

Structural Diversity and Electronic Properties of 3d Transition Metal Tetraphosphides, TMP4 (TM = V, Cr, Mn, and Fe).

Transition-metal (TM) phosphides attract increasing attention with applications for energy conversion and storage, due to their outstanding physical, chemical, and electronic properties. The 3d transition metal tetraphosphides (TMP4, TM = V, Cr, Mn, and Fe) possess multiple allotropies and rich electronic properties. Here, we perform the investigations of the structural, electronic, and elastic properties for 3d-TMP4 (TM = V, Cr, Mn, and Fe) using density functional theory (DFT) calculations. These compounds are featured with alternating buckled phosphorus sheets with ten-numbered phosphorus rings and varied transition-metal layers. Hybrid DFT calculations reveal that TMP4 compounds exhibit a wide range of electrical properties, ranging from metallic behavior for VP4 to semiconducting behavior for CrP4 with the narrow direct band gap of 0.63 eV to enlarged semiconducting MnP4 and FeP4 with band gap of 1.6-2.1 eV. The bonding analysis indicates that P-P and TM-P covalent interactions dominate in the phosphorus sheets and TMP6 octahedrons, which are responsible for the structural and electronic diversity.

Elaboration of a Conductive Textile by Coating for Clothes Equipped with Fourth-Generation Photovoltaic Cells

Conducting polymer coated in textiles possess a wide range of electrical properties. The surface resistivity is influenced by concentrations of the reactants, thickness of the coating, nature of the substrate surface, extent of penetration of the polymer into the textile structure and the strength of the binding of the coating to the textile surface. Low resistivity in fabric results from highly doped thicker coatings that penetrate well into the textile structure thus enabling good electrical contact between fibers. In this study, we had chosen copper as conductor polymer for coating. The electrical conductivity is influenced by the thickness of coating paste, the nature of the substrate surface. The thickness of the paste and the concentration of the copper were studied in this paper. Furthermore, the electrical surface resistance decreased from 68 MΩ to 8 MΩ with decreasing in coating thickness. However, the thickness of coated fabric is very important factor to determine conductivity and application of textile. In addition, we had noticed that the airflow is affected by the coating thickness which the penetration of the airflow differs from the lower thickness to the higher one. This study confirm that we can use coating woven fabric to develop a textile substrate responding to characteristics such as electrical resistance, drapability, air permeability and tensile strength, which are particularly important to be used as a support for flexible photovoltaic cells in clothes.

Elaboration of a Conductive Textile by Coating for Clothes Equipped with Fourth-Generation Photovoltaic Cells

Conducting polymer coated in textiles possess a wide range of electrical properties. The surface resistivity is influenced by concentrations of the reactants, thickness of the coating, nature of the substrate surface, extent of penetration of the polymer into the textile structure and the strength of the binding of the coating to the textile surface. Low resistivity in fabric results from highly doped thicker coatings that penetrate well into the textile structure thus enabling good electrical contact between fibers. In this study, we had chosen copper as conductor polymer for coating. The electrical conductivity is influenced by the thickness of coating paste, the nature of the substrate surface. The thickness of the paste and the concentration of the copper were studied in this paper. Furthermore, the electrical surface resistance decreased from 68 MΩ to 8 MΩ with decreasing in coating thickness. However, the thickness of coated fabric is very important factor to determine conductivity and application of textile. In addition, we had noticed that the airflow is affected by the coating thickness which the penetration of the airflow differs from the lower thickness to the higher one. This study confirm that we can use coating woven fabric to develop a textile substrate responding to characteristics such as electrical resistance, drapability, air permeability and tensile strength, which are particularly important to be used as a support for flexible photovoltaic cells in clothes.

Spectroscopic and luminescent properties of Co<sup>2+</sup> doped tin oxide thin films by spray pyrolysis

The wide variety of electronic and chemical properties of metal oxides makes them exciting materials for basic research and for technological applications alike. Oxides span a wide range of electrical properties from wide band-gap insulators to metallic and superconducting. Tin oxide belongs to a class of materials called Transparent Conducting Oxides (TCO) which constitutes an important component for optoelectronic applications. Co2+ doped tin oxide thin films were prepared by chemical spray pyrolysis synthesis and characterized by powder X-ray diffraction, SEM, TEM, FT-IR, optical, EPR and PL techniques to collect the information about the crystal structure, coordination/local site symmetry of doped Co2+ ions in the host lattice and the luminescent properties of the prepared sample. Powder XRD data revealed that the crystal structure belongs to tetragonal rutile phase and its lattice cell parameters are evaluated. The average crystallite size was estimated to be 26 nm. The morphology of prepared sample was analyzed by using SEM and TEM studies. Functional groups of the prepared sample were observed in the FT-IR spectrum. Optical absorption and EPR studies have shown that on doping, Co2+ ions enter in the host lattice as octahedral site symmetry. PL studies of Co2+ doped SnO2 thin films exhibit blue and yellow emission bands. CIE chromaticity coordinates were also calculated from emission spectrum of Co2+ doped SnO2 thin films.

Two-dimensional layered transition-metal dichalcogenides for versatile properties and applications

Abstract

The Effect of HCl Concentration on the Ionic Conductivity of Liquid PMMA Oligomer

To date gel and film type polymer electrolytes have been widely synthesized due to their wide range of electrical properties. However, these types of polymer electrolytes exhibit poor mechanical stability and poor electrode-electrolyte contact hence deprive the overall performance of a battery system. Therefore, in order to indulge the advantages of polymer as electrolyte, a new class of liquid-type polymer electrolyte was synthesized and investigated. To date this type of polymer electrolytre has not been extensively studied. This is due to the unavailability of liquid polymer for significance application. In this study, liquid poly (methyl methacrylate) (PMMA) electrolyte was synthesized using the simplest free radical polymerization technique using benzoyl peroxide as the initiator. It was found that this liquid PMMA oligomer has potential as electrolyte in proton battery when doped with small volume of various molarity of hydrochloric acid (HCl) in which the highest ionic conductivity achieved was 10-7 S/cm at room temperature. The properties of this liquid PMMA oligomer were further investigated using Fourier Transform Infrared Spectroscopy (FTIR).

Ultrasensitive photodetectors based on monolayer MoS2

Two-dimensional materials are an emerging class of new materials with a wide range of electrical properties and potential practical applications. Although graphene is the most well-studied two-dimensional material, single layers of other materials, such as insulating BN (ref.2) and semiconducting MoS2 (refs3, 4) or WSe2 (refs5, 6), are gaining increasing attention as promising gate insulators and channel materials for field-effect transistors. Because monolayer MoS2 is a direct-bandgap semiconductor due to quantum-mechanical confinement, it could be suitable for applications in optoelectronic devices where the direct bandgap would allow a high absorption coefficient and efficient electron-hole pair generation under photoexcitation. Here, we demonstrate ultrasensitive monolayer MoS2 phototransistors with improved device mobility and ON current. Our devices show a maximum external photoresponsivity of 880AW(-1) at a wavelength of 561nm and a photoresponse in the 400-680nm range. With recent developments in large-scale production techniques such as liquid-scale exfoliation and chemical vapour deposition-like growth, MoS2 shows important potential for applications in MoS2-based integrated optoelectronic circuits, light sensing, biomedical imaging, video recording and spectroscopy.

Metallized Film Power Capacitors End-of-Life Study Through Monitored Destruction Tests

A wide range of experiments was performed on metallized film capacitors. The monitoring of destruction tests was used to analyze the electrical properties of artificial critical defects. It is shown herein that these defects in the windings of the capacitors have a wide range of electrical properties and the behavior of the capacitor in the test is strongly related to these properties. A model is proposed to describe the degeneration of dielectric failure, the use of this model can help to predict the behavior of capacitors when they reach the end of life and to a more accurate design of the protection systems.

Semiconductor‐Insulator Transition in Undoped Rutile, TiO2, Ceramics

The electrical conductivity of undoped rutile ceramics is very dependent on sample processing conditions, especially the temperature and atmosphere during sintering and the subsequent cooling rate. Samples become increasingly semiconducting when quenched from temperatures above ~700°C without the need for a reducing atmosphere. Thus, samples quenched from 1400°C in air have conductivity ~1 × 10−2 Scm−1with activation energy ~0.01(1) eV over the temperature range 10–100 K, whereas similar samples that are slow cooled or annealed in air at 300°C–500°C are insulating with activation energy 1.67(2) eV and conductivity, e.g., 1 × 10−7 Scm−1 at 400°C. The very wide range of electrical properties is attributed to variations in oxygen content which are too small to be detected using thermogravimetry. Impedance analysis shows that, depending on cooling rate, partially oxidized samples may be prepared in which samples retain a semiconducting core, but have an oxidized outer layer.

Mechanical properties of ZnO thin films deposited on polyester substrates used in flexible device applications

ZnO is growing in importance as a functional film in flexible devices because of the wide range of electrical properties that can be achieved through appropriate doping and the relative abundance of Zn. We have deposited ZnO films with various thicknesses by sputtering on polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) flexible substrates and measured their mechanical properties using compression and scratch tests coupled with in-situ optical microscopy. The cracking of ZnO, during compression, is thickness dependent and at lower thicknesses the films sputtered on PEN exhibit the highest crack onset strains, around 2%. During scratch testing, two major scratch failure mechanisms are observed, analyzed and discussed. It is also found that scratch resistance of ZnO is thickness dependent for both PET and PEN. At high scratch loads a secondary failure mechanism due to impregnation of film debris into the polymer substrates is observed.

Correlation maps allow neuronal electrical properties to be predicted from single-cell gene expression profiles in rat neocortex.

The computational power of the neocortex arises from interactions of multiple neurons, which display a wide range of electrical properties. The gene expression profiles underlying this phenotypic diversity are unknown. To explore this relationship, we combined whole-cell electrical recordings with single-cell multiplex RT-PCR of rat (p13-16) neocortical neurons to obtain cDNA libraries of 26 ion channels (including voltage activated potassium channels, Kv1.1/2/4/6, Kvbeta1/2, Kv2.1/2, Kv3.1/2/3/4, Kv4.2/3; sodium/potassium permeable hyperpolarization activated channels, HCN1/2/3/4; the calcium activated potassium channel, SK2; voltage activated calcium channels, Caalpha1A/B/G/I, Cabeta1/3/4), three calcium binding proteins (calbindin, parvalbumin and calretinin) and GAPDH. We found a previously unreported clustering of ion channel genes around the three calcium-binding proteins. We further determined that cells similar in their expression patterns were also similar in their electrical properties. Subsequent regression modeling with statistical resampling yielded a set of coefficients that reliably predicted electrical properties from the expression profile of individual neurons. This is the first report of a consistent relationship between the co-expression of a large profile of ion channel and calcium binding protein genes and the electrical phenotype of individual neocortical neurons.

A numerical study of radiofrequency deposition in a spherical phantom using surface coils

The electromagnetic fields induced by a surface coil in a spherical phantom, having a wide range of electrical properties, is studied using numerical methods of calculation. The specific absorption rate (SAR), radiofrequency magnetic field (B 1), magnetic field energy within the phantom (E B), and the volume-averaged SAR (<SAR>) are calculated at 10, 63, and 200 MHz. They are analyzed with respect to dielectric constant, wavelength, and skin depth effects, which become increasingly important in high field magnetic resonance imaging (MRI) where safety and field homogeneity issues need further study. Particular attention is given to solutions representing neural tissue at each frequency. In general, the <SAR> data at high field strengths have local maxima, with a quasi-harmonic behavior, when the following two resonant conditions are satisfied: 1) skin depth becomes comparable to, or larger than, the sample diameter Ds; and 2) Ds is near an integral multiple of the wavelength. These are also the solutions with maximum E B values and the least homogeneous B 1. Samples undergoing resonance at 200 MHz are shown to have important off-axis B 1 maxima (affecting field homogeneity) and large <SAR> values. Some non-resonating 200-MHz phantoms, including simulations consistent with neural tissue, contain larger SAR maxima than the resonating samples, posing safety concerns in high field imaging of biologic tissue.

Atomic-Scale Structure and Properties of Thin Epitaxial SrRuO3 Films Grown on SrTiO3 (100) by Pulsed Laser Deposition

AbstractTransition metal oxides with perovskite structure exhibit a wide range of electrical properties. SrRuO3 (SRO), a perovskite oxide with high conductivity, finds applications as an electrode layer in ferroelectric devices and as a barrier layer in superconductor-normal metal-superconductor (SNS) Josephson junctions involving high Tc superconductors. Here we report on the structure and properties of thin SRO films on SrTiO3 (100) substrates grown by pulsed laser deposition. AFM investigations revealed that the SRO films exhibit island growth. The island size increases with thickness, and at a typical thickness of about 20 nm a connected network of islands is formed. The resistivity of the SRO films grown at different substrate temperatures (700 °C - 850 °C) exhibits metallic behavior with a ferromagnetic transition at 150 K. The films with typical thicknesses of 20 nm, grown at a substrate temperature of 775 °C exhibited the lowest resistivity of 200 μΩ-cm at 300 K, whereas the films grown at lower (700 °C) and higher (850 °C) temperatures showed a much higher resistivity at 300 K. By AFM and high resolution TEM investigations, this behavior is correlated with the atomicscale structure of the films. The film with the lowest room temperature resistivity showed an almost defect-free orthorhombic structure, whereas the film grown at 850 °C contained structural defects in high density, such as SrO-rich antiphase boundaries and twins located at the boundaries between the islands. The films grown at 700 °C showed a cubic perovskite structure, which is obviously the reason for their high resistivity.

The role of interfacial reactions in Pt/CdTe contact formation

The reactions at the interface between CdTe and the contact metal platinum have been studied using various approaches including theoretical and experimental ternary phase diagram determination, bulk and thin film diffusion couples and electrical characterization of elemental and compound contacts on p- and n-Cd0.95Zn0.05Te (CZT). At the interface of Pt/CdTe diffusion couples a non-planar reaction layer of the intermetallics PtCd and PtTe is formed. This is consistent with the studied ternary phase diagram. Additional compounds which are stable in direct contact to CdTe can also be identified using these data. The contact barrier heights of pure Pt and of alloys with Cd or Te on CZT substrates and their variation after various annealing procedures were determined both on etched (Te-rich) and on virtually stoichiometric CZT surfaces. All the Pt-based contacts on the etched CZT surface showed a similar behaviour, determined by the Te excess and the ensuing formation of PtTe in direct contact to CZT. In contrast to that, a wide range of electrical properties can be achieved on the stoichiometric surface by deposition of Pt with or without additional Cd or Te interlayers due to the variety of phases forming in direct contact to CZT after deposition and annealing.

The Role of Covalent and Metallic Radii in Covalent Metallic Superlattices and Two-Dimensional Isoelectronic Alloys

ABSTRACTCovalent metallic superlattices and isoelectronic alloys consist of ordered layers of, for example, Si/AlP, Ge/GaAs, and Si/Sb,etc. Depending on design, wide range of electrical properties can result. The covalent, metallic and ionic radii play a crucial role in the stoichiometry of epitaxial systems.

The influence of target oxidation and growth-related effects on the electrical properties of reactively sputtered films of tin-doped indium oxide

The electrical properties of tin-doped indium oxide films prepared by reactive r.f. magnetron sputtering were studied. The properties vary markedly with the added oxygen pressure and also with the film thickness owing to growth effects and target oxidation. The growth effects were analysed in terms of the grain size effects and of the target oxidation by a simple kinetic model. We show that films exhibiting a wide range of electrical properties can be prepared if the deposition conditions are carefully controlled. Films with conductivities as high as 2.5 × 103 ohms−1 cm−1 and with optical transmission greater than 85% averaged over the visible spectrum were deposited.