Electrical Current-voltage Characteristics Research Articles

Extracting the inherent ideality factor of a diode from electrical current–voltage characteristics

AbstractThe ideality factor of a diode gives the information on the current conduction or recombination processes occurring inside the device. The ideality factor obtained from the electrical current–voltage (I–V) characteristics by the conventional method is typically masked by the effect of the series resistance at high currents. In this study, from a careful analysis of the I–V characteristics, a new formula that can extract the inherent ideality factor without the effect of the series resistance is presented and experimentally tested with a blue light‐emitting diode. The new ideality factor thus obtained is compared with the one by the photovoltaic measurement.

Electrical Characterization of InGaZnO-Based Thin Film Transistor fabricated by Three-mask Process

Indium Gallium Zinc Oxide (InGaZnO) has gained increasing attention as a replacement for amorphous silicon in thin-film transistors (TFTs) owing to its excellent electrical and optoelectronic properties, chemical stability, and potential for low-temperature processing.
 However, efforts are being made to optimize the design to improve the performance and reduce costs.
 In this study, a top-contact top-gate (TCTG) structure of InGaZnO TFTs was fabricated using three lithography steps. The electrical current–voltage characteristics of the device were measured and used to extract the device parameters.
 The result shows transistor parameters with threshold voltage of –9 V, ON-OFF ratio of in the range of 103, maximum mobility of 1.15 cm2V-1 s-1, subthreshold slope of in the range of 103 mV/dec, and maximum interface trap density of 1.53x103 (cm-2eV-1) at maximum applied voltage of 5 V.

Multiwalled carbon nanotubes with ethyl viologen diperchlorate in polyethylene oxide to develop an electrochromic device

The electrochromic device was fabricated using multiwalled carbon nanotubes along with ethyl viologen diperchlorate in polyethylene oxide. Doping of multiwalled carbon nanotubes in the electrolytic gel of the device exploits its electrical transport potential. A fusion of (inorganic–organic) finished tools indicates the most efficient colour switching with a minute bias and high colour contrast when switched to neon-blue coloured states. The electrical current–voltage characteristics of the device properly validates its operating mechanism. The fabricated device is having capability to switch over from a transparent to the neon blue coloured state in presence of a potential. A contrast neon blue colour of the device was observed at 1.9 V.

Electron Transport through Nanoconfined Ferrocene Solution: Density Functional Theory─Nonequilibrium Green Function Approach

We investigate the transport of electrons in a ferrocene aqueous solution nanoconfined between two Pt electrodes using density functional theory and a nonequilibrium Green function method. The system consists of three characteristic phases: metal electrodes, the electrode–solution interface, and the nanoconfined solution phase. By performing the geometry optimization of such systems, it is found that the molecular configuration of water molecules at the Pt surface is adjusted due to the Pt–water interaction, and the charges at the Pt surface are redistributed. Next, by applying the external bias potential via the effective screening medium method during ab initio molecular dynamics simulations, it is revealed that water molecules are packed at the Pt–water interfacial region, and the electrostatic potential profile in the water phase is significantly changed due to aligned water layers. From the analysis of the electron transport characteristics, it is discovered that the ferrocene molecule generates a strong transmission function near the Fermi level and high electron density of states spatially connecting both electrodes through the water phase. These features explain the drastic enhancement in electrical current–voltage characteristics. Therefore, it is concluded that ferrocene enhances electron transport through nanoconfined solutions, indicating that it can be used as a signaling molecule in nanoscale systems for electrochemical sensor applications.

Electrical properties of ternary Cux(Ge3Se7)100-x thin films

Thin amorphous films of Cux(Ge3Se7)100-x (0 ≤ x ≤ 12 at. %) were prepared on glass substrates by the thermal evaporation method. The dc electrical resistivity (ρdc) and current-voltage (I–V) characteristics were measured within the temperature range from 190 to 420 K for the prepared films. For x ≤ 6 at. %, the electrical conductivity (σdc) shows three temperature regimes arise from three different conduction mechanisms, while for x = 9 and 12 at. %, only two distinct regimes were observed. The Fermi energy (Ef) and the charged carriers' mobility (μo) of the studied thin films were estimated. The variation of current density (J) as a function of electric field (E) indicating Ohmic behavior for low applied electric field (E < 2.4 × 105 V/cm). Above such electric field (at higher voltage V > 12 V), a space charge limited conduction (SCLC) occurs. By fitting the experimental data according to the SCLC, the density of localized states (DOS) close to Fermi level was estimated. The increasing of the DOS with an increase of the Cu content can be ascribed to increasing the defect states.

Power matrix of OPV mini-module under steady conditions of temperature and irradiance at large-area solar simulator

The knowledge of electrical current-voltage (I-V) characteristics of photovoltaic (PV) devices under various irradiance, temperature, and spectral conditions is essential for evaluating the output power and energy production of the devices under various climate conditions. The methods to measure the temperature and irradiance dependences of PV devices power are described in the standards IEC 60891 and IEC 61853-1. Newer PV technologies like organic (OPV) and dye-sensitized (DSSC) devices are rapidly evolving and considerable research effort has addressed alternative approaches to increase efficiency with promising values achieved in the last years. Measurements of the irradiance (G) and temperature (T) dependence of these emerging PV technologies are less established –when available– than those of Si-based devices. In this paper we present a first attempt of power-rating measurement for an OPV mini-module. The measurements were performed with a large-area steady-state solar simulator on a reduced (T,G) range compared to what the standard IEC 61853-1 requires. Nevertheless, they were sufficient to calculate the relative temperature coefficients alpha and beta, which have been satisfactorily compared to previous published values. Also, they provided a first data set for the irradiance dependence of OPV device performance. Finally, the power matrix built from these measurements represents at our knowledge the first data set available for energy rating of OPV technology, as the matrix was done for a single device and for both irradiance and temperature dependencies together.

Ion current rectification: from nanoscale to microscale

Ion current rectification (ICR) is an electrodynamic phenomenon in electrolyte solution which is defined as the asymmetric potential-dependent ion flux through a confined environment, giving rise to asymmetric electrical current-voltage characteristics induced by the influence of an asymmetric electrical double layer structure. Since the discovery of the ICR phenomenon, the observation and application of ICR at nanoscale and microscale have been widely investigated experimentally and theoretically. Here, the recent progress of ICR from nanoscale to microscale is systematically reviewed. Nano/micropore structures of different materials, shapes and pore sizes are first discussed. Then, the factors influencing ICRs by thermodynamically or kinetically regulating the electrical double layer structure are introduced. Moreover, theoretical models are presented to explain the mechanism of ICRs. Based on the understanding of this phenomenon, the applications, especially in biosensors, are discussed. Finally, future developments of this area are briefly presented. This review covers the representative related literature published since 2010 and is intended to give a systematic introduction to this area.

Estimation of particle size distribution of nanoparticles from electrical characteristics

An indirect method of estimation of size distribution of nanoparticles in a nanocomposite is proposed in this paper. The present approach exploits DC electrical current–voltage characteristics (CVC) of ZnO nanocomposite specimen in bio-polymer background. The nature of DC CVC is found to be oscillatory with respect to applied voltage. The nature of CVC is a consequence of Coulomb blockade (CB) phenomena of electrical conduction through a tiny nanoparticle. Considering the ZnO nanocomposites to be spherical, Coulomb-blockade model of quantum dot is applied here. The size distribution of particle is estimated from that model and compared with the results obtained from AFM and XRD analyses. The results from CVC are found to be consistent with these conventional microscopic results.

Thermal assisted reset modelling in nickel oxide based unipolar resistive switching memory

This paper utilizes an analytical and a filament dissolution model to calculate the local temperature increase in conducting filaments (CFs) of pulsed laser ablated unipolar NiO resistive switching memory devices. Electrical current voltage characteristics indicate unipolar switching. The formation of NiO phases is confirmed from the X-ray diffraction study. Transmission electron microscopy confirms the polycrystalline nature of NiO films having a thickness of ∼20 nm. Electrothermal simulations based on the filament dissolution model are performed using COMSOL Multiphysics® to model the CF rupture during the reset transition in the samples owing to the Joule heating effect. Obtained temperature profiles from the simulations are compared with the analytical model. Both the models corroborate with each other, allowing us to closely approximate the maximum temperature across the CF (Tcrit). This is the point corresponding to which the voltage applied across the cell (Vreset) drives the device into the reset state. The effect of annealing temperature on the maximum temperature, reset voltage, and CF diameter of the device is also discussed. The CF diameter and area of the filament are precisely estimated from the simulation.

Electrical and nonlinear current-voltage characteristics of La-doped BiFeO3 ceramics

Multiferroic Bi1-xLaxFeO3(x=0, 0.05, 0.1, 0.2, and 0.3) ceramics with particle sizes of ~67–19nm were prepared by a simple co-precipitation method. The effects of La dopant on the microstructure, giant dielectric response, and electrical properties were investigated. The grain size of Bi1-xLaxFeO3 ceramics significantly decreased with increasing La doping ions. The Bi0.95La0.05FeO3 ceramic exhibited the highest leakage current density value. Interestingly, it strongly decreased as the concentration of La increased. The nonlinear coefficient of La doped BFO slightly decreased with increasing La. This shows a space-charge-limited conduction mechanism, which is involved in low electric field regions for all samples investigated. La substitution significantly enhanced the breakdown field. It was found that the potential barrier height at the grain boundary was slightly reduced from 0.3 to 0.16eV by substitution of La ions. Using impedance spectroscopy analysis, except for the Bi0.7La0.3FeO3 ceramic, the grain boundary resistance at room temperature was affected by dc bias, whereas the grain resistance of all samples was independent of dc bias. This result was well consistent with the variation in low-frequency dielectric constant and loss tangent value due to the effect of dc bias. These results were closely related to the existence of the interfacial polarization at the grain boundary.

Electrical conductivity and magnetic field dependent current-voltage characteristics of nanocrystalline nickel ferrite

We have studied the grain size dependent electrical conductivity, dielectric relaxation and magnetic field dependent current voltage (I−V) characteristics of nickel ferrite (NiFe2O4). The material has been synthesized by sol-gel self-combustion technique, followed by ball milling at room temperature in air environment to control the grain size. The material has been characterized using X-ray diffraction (refined with MAUD software analysis) and Transmission electron microscopy. Impedance spectroscopy and I−V characteristics in the presence of variable magnetic fields have confirmed the increase of resistivity for the fine powdered samples (grain size 5.17±0.6nm), resulted from ball milling of the chemical routed sample. Activation energy of the material for electrical charge hopping process has increased with the decrease of grain size by mechanical milling of chemical routed sample. The I−V curves showed many highly non-linear and irreversible electrical features, e.g., I−V loop and bi-stable electronic states (low resistance state-LRS and high resistance state-HRS) on cycling the electrical bias voltage direction during I-V curve measurement. The electrical dc resistance for the chemically routed (without milled) sample in HRS (∼3.4876×104Ω) at 20V in presence of magnetic field 10kOe has enhanced to ∼3.4152×105Ω for the 10h milled sample. The samples exhibited an unusual negative differential resistance (NDR) effect that gradually decreased on decreasing the grain size of the material. The magneto-resistance of the samples at room temperature has been found substantially large (∼25–65%). The control of electrical charge transport properties under magnetic field, as observed in the present ferrimagnetic material, indicate the magneto-electric coupling in the materials and the results could be useful in spintronics applications.

Voltage-Rectified Current and Fluid Flow in Conical Nanopores.

Ion current rectification (ICR) refers to the asymmetric potential-dependent rate of the passage of solution ions through a nanopore, giving rise to electrical current-voltage characteristics that mimic those of a solid-state electrical diode. Since the discovery of ICR in quartz nanopipettes two decades ago, synthetic nanopores and nanochannels of various geometries, fabricated in membranes and on wafers, have been extensively investigated to understand fundamental aspects of ion transport in highly confined geometries. It is now generally accepted that ICR requires an asymmetric electrical double layer within the nanopore, producing an accumulation or depletion of charge-carrying ions at opposite voltage polarities. Our research groups have recently explored how the voltage-dependent ion distributions and ICR within nanopores can induce novel nanoscale flow phenomena that have applications in understanding ionics in porous materials used in energy storage devices, chemical sensing, and low-cost electrical pumping of fluids. In this Account, we review our most recent investigations on this topic, based on experiments using conical nanopores (10-300 nm tip opening) fabricated in thin glass, mica, and polymer membranes. Measurable fluid flow in nanopores can be induced either using external pressure forces, electrically via electroosmotic forces, or by a combination of these two forces. We demonstrate that pressure-driven flow can greatly alter the electrical properties of nanopores and, vice versa, that the nonlinear electrical properties of conical nanopores can impart novel and useful flow phenomena. Electroosmotic flow (EOF), which depends on the magnitude of the ion fluxes within the double layer of the nanopore, is strongly coupled to the accumulation/depletion of ions. Thus, the same underlying cause of ICR also leads to EOF rectification, i.e., unequal flows occurring for the same voltage but opposite polarities. EOF rectification can be used to electrically pump fluids with very precise control across membranes containing conical pores via the application of a symmetric sinusoidal voltage. The combination of pressure and asymmetric EOF can also provide a means to generate new nanopore electrical behaviors, including negative differential resistance (NDR), in which the current through a conical pore decreases with increasing driving force (applied voltage), similar to solid-state tunnel diodes. NDR results from a positive feedback mechanism between the ion distributions and EOF, yielding a true bistability in both fluid flow and electrical current at a critical applied voltage. Nanopore-based NDR is extremely sensitive to the surface charge near the nanopore opening, suggesting possible applications in chemical sensing.

Fabrication of thermally evaporated Al thin film on cylindrical PET monofilament for wearable computing devices

During the initial development of wearable computing devices, the conductive fibers of Al thin film on cylindrical PET monofilament were fabricated by thermal evaporation. Their electrical current-voltage characteristics curves were excellent for incorporation into wearable devices such as fiber-based cylindrical capacitors or thin film transistors. Their surfaces were modified by UV exposure and dip coating of acryl or PVP to investigate the surface effect. The conductive fiber with PVP coating showed the best conductivities because the rough surface of the PET substrate transformed into a smooth surface. The conductivities of PET fiber with and without PVP were 6.81 × 103 Ω−1cm−1 and 5.62 × 103 Ω−1cm−1, respectively. In order to understand the deposition process of Al thin film on cylindrical PET, Al thin film on PET fiber was studied using SEM (Scanning Electron Microscope), conductivities and thickness measurements. Hillocks on the surface of conductive PET fibers were observed and investigated by AFM on the surface. Hillocks were formed and grown during Al thermal evaporation because of severe compressive strain and plastic deformation induced by large differences in thermal expansion between PET substrate and Al thin film. From the analysis of hillock size distribution, it turns out that hillocks grew not transversely but longitudinally.

Temperature dependence of electrical resistivity of composite films based on multi-walled carbon nanotubes

The temperature dependence of the electrical resistivity (ρ) and current-voltage characteristics of composite films based on multi-walled carbon nanotubes and a 95/5 wt % polymer have been investigated in the temperature range of 300–450 K. An unstable behavior of the composite film structure upon cyclic heating has been observed. It has been found that the resistivity ρ has maxima at T ≈ 340 and ≈420 K, which are responsible for intrinsic defects. The current-voltage characteristics have been studied in the stationary and pulsed modes at different temperatures. They prove to be purely linear and correlate with temperature variations in ρ.

Transport engineering design of AND and NOR gates with a 1,4-2-phenyl-dithiolate molecule

We have explored logical AND and NOR gate responses of a 1,4-2-phenyl-dithiolate molecule threaded by a magnetic flux ϕ in two-terminal junctions by using the Green's function method in the framework of a nearest-neighbor tight-binding approximation. Here, we put emphasis on the logical gate voltages, and obtain the electrical transmission and current-voltage characteristics with metal-molecule-metal (m-M-m) tunnel junctions. The hopping integral among two neighboring atoms in the molecule was quantitatively estimated by means of density functional theory (DFT) calculations. Our results show that the AND and NOR responses are explored through our molecular junction for a typical value of the magnetic flux. The numerical results may shed light on the next applications of molecular systems and make them a good, promising candidate for field-effect transistors.

Growth and Characterization of High-Quality Dielectric Sputtered Zinc Oxide Films from the First Principle

In this article, we investigate the effect of thermal treatment on a piezoelectric material, zinc oxide, which has found numerous applications in sensors and actuators. Even though the exact mechanisms rendering electrical properties are less known, we suspect that the thermal treatments are responsible for improvement of electrical characteristics of the deposited thin films. We establish that the thermal agitation is responsible for improvement of orders of magnitude in electrical characteristics of sputtered ZnO thin films. The surface quality of the thin films deposited is process dependent. ZnO films were deposited using a dielectric sputtering method, on oxidized silicon 100 n-type wafers. Further, these films were thermally annealed in oxygen ambient at 600 °C in a tube furnace with 2 mL/min pressure. It is observed that, after thermal annealing, the quality of the films is improved by orders of magnitude. The luminance, crystalline quality, and surface morphology of these thin films was measured with atomic force microscopy, scanning electron microscopy with BSD detector (BSD-SEM), and Fourier transform infrared spectroscopy (FTIR). The results infer that the film’s surface is very smooth and dense. The surface roughness is improved by 1.3149 nm from 7.882 nm prior to thermal annealing to post-annealing surface roughness with 6.5671 nm. Post-thermal annealing process reveals average grain size was 50 nanometers; the surface roughness is reduced to 6.5671 nm. A significant improvement in electrical current-voltage characteristics was recorded with I-V curve. It is suspected to be due to substantial enhancement in electrical conductivity as a result of thermal treatment and improved spectral response recorded a FTIR peak shift of 1 wave number in total. The FTIR peak shift is suspected to be due to evaporation and reduction in oxygen vacancies due to thermal annealing process. The post-annealed ZnO films will be used for actuation in the future.

Characterization of Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Thin Films Deposited by PLD

Aluminium Oxide (Al2O3) thin films have been widely used in many kinds of applications due to their excellent properties such as good mechanical strength, high abrasive and insulating characteristics. In this work, Al2O3 thin films are deposited on silicon (100) substrates using pulsed laser deposition (PLD). The deposition is done using different chamber environments. The crystal structure of the thin films is investigated using Grazing Incidence Diffraction (GID). The surface morphology and thicknesses of the thin films are studied by Field Emission Scanning Electron Microscopy (FESEM). The electrical current-voltage (I-V) characteristics of the thin films are measured using Signaton H150 Probe Station with Keithly 302 source measurement. It was found that the different process parameters greatly influenced the characteristics of the thin films obtained. FESEM images show high quality, smooth and dense films obtained using the PLD method. Generally, all films show rectifying behaviour.

Influence of thermal treatment on the formation of ohmic contacts based on Ti/Al/Ni/Au metallization to n-type AlGaN/GaN heterostructures

Interfacial reactions between Ti/Al/Ni/Au metallization and GaN(cap)/AlGaN/GaN heterostructures at various annealing temperatures ranging from 715 to 865 °C were studied. Electrical current-voltage (I–V) characteristics, van der Pauw Hall mobility measurements and surface topography measurement with atomic force microscopy (AFM) were performed. The ohmic metallizations were annealed at various temperatures in a rapid thermal annealing system and the annealing time of 60 seconds was kept for all samples. To study the influence of the parameters of annealing process on the properties of the 2 dimensional electron gas (2DEG) the van der Pauw Hall mobility measurement was used. Interfacial reactions between the contact metals and heterostructures were analyzed through depth profiles of secondary ion mass spectroscopy. It was observed that transition from nonlinear to linear I-V behavior occurred after the annealing at 805 °C. For the studied samples, the most promising results were obtained for the annealing temperature of 805 °C. This temperatue ensured not only low contact resistance but also made possible to preserve the 2DEG.

Effect of ionizing irradiation on the mechanism of current passage in TlInSe2 single crystals

The temperature dependence of the electrical conductivity and current-voltage characteristics of γ-irradiated TlInSe2 single crystals with an electrical resistivity of ∼108 Ω cm have been investigated. It has been established that the anomalies of the conductivity observed in weak electric fields and at low dozes of irradiation are related to the decomposition of neutral complexes containing an interstitial cation atom. In strong electric fields, a thermal-field ionization of traps occurs. The main mechanism of radiation defect formation is the formation of complexes [VIn−Ini+], [VSe−Sei−], and others with the structural defects characteristic of unirradiated crystals. The activation energy, trap concentrations, and the potential well shape near the traps have been determined.

Nanobonding for Multi-Junction Solar Cells at Room Temperature

Direct nanobonding of p-Si/n-GaAs wafers based on surface activation that uses an Argon (Ar)-fast atom beam at room temperature has been investigated. The bonding strength of the interface was 14.4 MPa at room temperature, and remained nearly constant after annealing up to 600 °C. An amorphous layer with a thickness of 11.5 nm was found across the interface without annealing. After annealing, the electrical current-voltage (I-V) characteristics were improved and the amorphous layer was diminished across the interface. The thermal stability of the interfacial properties of Si/GaAs indicates its potential use on the fabrication of multi-junction solar cells with Si substrate to lower the cost while improving the solar cells' efficiency. The thickness dependence of p-Si/n-Si interfacial I-V characteristics using COMSOL simulation indicates the decrease of breakdown voltage and current with the increase of the junction thickness.