Terms Of Current-voltage Characteristics Research Articles

Fabrication of graphene, graphite and multi wall carbon nano tube based thin films and their potential application as strain sensor

Carbon based nanomaterials are extensively used in the manufacturing of flexible electronic devices due to their numerous favorable properties. Such devices have shown remarkable sensitivity with excellent stability when implemented in various flexible environments. But the formulation of conductive inks using carbon based nanomaterials presented some challenges in the optimization of various ink parameters like rheology, surface tension, particle size etc. In this paper, we present graphite, graphene and multi-wall carbon nano tube (MWCNT) based flexible resistive strain sensors on polymer substrate using a simple and solvent free fabrication process. A controllable conductive thin film is obtained and designed into two different patterns viz. ‘Straight Line’ (line) and ‘Serpentine’ (serp) to enhance the sensing performance of the film. The electrical performance has been evaluated in terms of current-voltage characteristics. The result indicates the resistive behavior of all the devices under investigation. The bending measurements have been conducted; the resistive strain sensor exhibits significant resistance variation during bending applications. There has been a significant change in the electrical resistance of each sample for different strain level i.e. ∼ 20% for MWCNT(line) and MWCNT (serp), ∼30% for Graphite(line) and Graphene (line) and ∼50% to 60% for Graphite (serp) and Graphene (serp). High sensitivity of the ‘Serpentine’ patterns in comparison to ‘Straight Line’ patterns indicates the importance of various patterns in the manufacturing of flexible sensors. Surface morphology and structural information of the fabricated devices have also been analyzed and investigated.

A new approach for nano-structuring of glassy selenium (g-Se) using silver nanoparticles (AgNPs) as precursor

Various routes have been proposed for the synthesis of chalcogen based nanostructured materials but the search of conventional and cost-effective method for the nanostructuring of chalcogenides is an ongoing research activity. This unique work reports the synthesis and the characterization of a novel kind of glassy nanocomposite material belonging to the nano-structuring of g-Se with the help of silver nanoparticles. The local structure is analyzed with the help of X-ray diffraction, Scanning electron microscopy, Raman spectroscopy, and Differential Scanning Calorimetry. It was found that the addition of AgNPs in glassy Se creates fine nano-wires of trigonal Selenium (t-Se) in the glass matrix of g-Se. The electrical, mechanical, and thermal characterizations of the present glassy nanocomposite material have been done in terms of current-voltage characteristics, d.c. conductivity, micro-hardness, and kinetic parameters of glass/crystal phase transformation. A comparative analysis of present glassy composites with a conventional Ag containing glassy alloy (g-Se98Ag2) has also been done to understand the role of incorporation of silver nanoparticles over the normal silver powder. The detailed analysis shows that different physical properties [e.g., thermal stability, modulus of elasticity, micro-hardness, the threshold voltage (i.e., turn-on voltage for resistive switching), and d.c. conductivity] are enhanced more effectively when the nano-structuring of g-Se by using AgNPs is executed as compared to the routine way of alloying.

Slow electron energy balance for hybrid models of direct-current glow discharges

In this paper, we present the formulation of slow electron energy balance for hybrid models of direct current (DC) glow discharge. Electrons originating from non-local ionization (secondary) contribute significantly to the energy balance of slow electrons. An approach towards calculating effective energy brought by a secondary electron to the group of slow electrons by means of Coulomb collisions is suggested. The value of effective energy shows a considerable dependence on external parameters of a discharge, such as gas pressure, type, and geometric parameters. The slow electron energy balance was implemented into a simple hybrid model that uses analytical formulation for the description of non-local ionization by fast electrons. Simulations of short (without positive column) DC glow discharge in argon are carried out for a range of gas pressures. Comparison with experimental data showed generally good agreement in terms of current-voltage characteristics, electron density, and electron temperature. Simulations also capture the trend of increasing electron density with decreasing pressure observed in the experiment. Analysis shows that for considered conditions, the product of maximum electron density ne and electron temperature Te in negative glow is independent of gas pressure and depends on the gas type, cathode material, and discharge current. Decreasing gas pressure reduces the heating rate of slow electrons during Coulomb collisions with secondary electrons, which leads to lower values of Te and, in turn, higher maximum ne.

High responsivity SiGe heterojunction phototransistor on silicon photonics platform

We report on a novel near infrared SiGe phototransistor fabricated by a standard silicon photonics foundry. The device is first investigated by simulations. The fabricated devices are characterized in terms of current-voltage characteristics at different optical power. Typical phototransistors exhibit 1.55µm record responsivity at low optical power exceeding 232A/W and 42A/W at 5V and 1V bias, respectively. A differential detection scheme is also proposed for the dark current cancellation to significantly increase the device sensitivity.

Dual-frequency glow discharges in atmospheric helium

In this paper, the dual-frequency (DF) glow discharges in atmospheric helium were experimented by electrical and optical measurements in terms of current voltage characteristics and optical emission intensity. It is shown that the waveforms of applied voltages or discharge currents are the results of low frequency (LF) waveforms added to high frequency (HF) waveforms. The HF mainly influences discharge currents, and the LF mainly influences applied voltages. The gas temperatures of DF discharges are mainly affected by HF power rather than LF power.

Inverted organic solar cells comprising a solution-processed cesium fluoride interlayer

We investigate the influence of solution-processed cesium fluoride (CsF) interlayers on the performance of inverted polymer solar cells comprising a blend of poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl C61-butyric acid methyl ester. The thickness of the CsF layer is optimized in terms of current-voltage characteristics by a variation of the solid content in solution. Capacitance-voltage characteristics reveal a shift of the built-in voltage at the cathode interface by about 0.3 V as compared to devices without a CsF layer, giving rise to an increase in open-circuit voltage by the same value. The vertical distribution of Cs+ and F+ ions is studied by secondary ion mass spectroscopy, indicating a strong diffusion of the alkaline fluoride into the organic layer stack.

Design and characterization of a YBa2Cu3O7-δ dc-superconducting quantum interference device for magnetic microscopy

A dc-SQUID (Superconducting Quantum Interference Device) based magnetometer for magnetic microscopy applications has been designed and tested. A square loop has been chosen as pick-up coil and a direct coupling configuration with the SQUID has been realized. On this scale dimension, the strips connecting SQUID and pick-up coil induce a non-negligible effect on the device performances. In particular, a reduction of the effective area is predicted. A SQUID device has been fabricated on symmetric 30° [001]-tilt YBa2Cu3O7-x bicrystal and its behavior has been tested. Characterization results in terms of current-voltage characteristics and magnetic field response are reported. They well agree with expected behaviors. Moreover, magnetometer response to a localized magnetic field has also been investigated.

High efficacy plasma display panel with vertically raised bus electrodes

The authors propose a high efficacy alternating current plasma display panel utilizing vertically raised multilayer bus electrodes. The cell structure was designed to provide an opposite discharge mode and low discharge current in a relatively long gap. The test panels having discharge gaps of 330, 350, and 370μm were fabricated and basic properties of the panel were investigated in terms of current-voltage characteristics, luminance, and luminous efficiency. The cells with proposed structure show higher luminance and lower current simultaneously. The improvement in luminous efficiency is found to be a factor of 2 compared with the conventional coplanar structure having an electrode gap of 60μm. Emission spectra and spatio-temporal distribution of infrared light in discharge were measured. It is shown that high luminous efficiency of proposed cell originates from high excitation efficiency, low surface loss of charged particles, and enlarged discharge volume.

Low dark current and blue enhanced a-Si:H∕a-SiC:H heterojunction n-i-δi-p photodiode for imaging applications

This paper presents an a-Si:H∕a-SiC:H heterojunction n-i-δi-p photodiode with low dark current and enhanced short wavelength responsivity suitable for low-level light detection applications. Junction properties and carrier transport are investigated in terms of current-voltage characteristics, photocurrent transient measurements, and spectral photoresponse. It is demonstrated that introduction of a thin (∼40Å) undoped a-SiC:H buffer (δi) at the p-i interface significantly reduces the reverse dark current and recombination losses at this interface. A dark current density of ∼10pA∕cm2 at reverse bias of 1V is achieved for the n-i-δi-p structure, in which the p-type a-SiC:H window layer and the undoped δi buffer layer have a band gap of 2eV.

Temperature-dependent interface reactions and electrical contact properties of titanium on 6H-SiC

In this study the system Ti-Si-C was investigated in terms of two aspects, metallurgical and electrical, in order to understand the formation and the properties of Ti electrical contacts on n-type 6H-SiC. For the metallurgical investigation bulk diffusion couples were prepared from monocrystalline 6H-SiC and Ti and annealed between 700 and 1200 degrees C for different lengths of time. The reaction zones were investigated using a SEM (secondary electron and backscattered electron images as well as energy-dispersive X-ray analysis). For the investigation of the electrical properties Ti contacts were sputter-deposited onto 6H-SiC wafer stripes and annealed at similar temperatures. The contact properties were measured in terms of current-voltage characteristics. We discovered that, over the whole temperature range investigated, the reaction layer growth follows a parabolic growth law which is thermally activated. Above 1200 degrees C the diffusion path from SiC to Ti is SiC/Ti3SiC2/Ti5Si3/two-phase Ti5Si3+TiC1-y/Ti5Si3/Ti. The contacts show ohmic behaviour. Between 1000 and 800 degrees C the diffusion path is: SiC/Ti3SiC2/Ti5Si3/two-phase Ti5Si3+TiC1-y/Ti3Si/Ti. The contacts are also ohmic. Below 700 degrees C the diffusion path is SiC/TiC1-y/two-phase Ti5Si3+TiC1-y/Ti3Si/Ti. The contacts are of Schottky type. It is concluded that the phase in contact with the SiC determines the electrical properties of the junction and the possibility of manufacturing a complete Schottky diode using n-type 6H-SiC and Ti only is demonstrated.

Properties of AlN films deposited on N-implanted Al

The mechanical and electrical properties of aluminum nitride (AlN) films deposited on N-implanted aluminum have been investigated. Prior to the deposition of AlN films, the Al substrates were implanted with 100 keV N + 2 ions at different doses (1 × 10 17−1 × 10 18 ions/cm 2). AlN films were prepared by rf ion plating on these N-implanted Al substrates. The adhesion of the films was evaluated by a scratch test, the microhardness measurement was made with load-penetration depth characteristics, and wear tests were performed without lubrication. The electrical resistivity was measured in terms of current-voltage characteristics. Furthermore, the change of crystalline structure was determined by X-ray diffraction, and the chemical composition and the depth profile were examined by Auger electron spectroscopy combined with Ar sputtering. It was found that adhesion, microhardness, wear and electrical resistivity were improved significantly when AlN films were deposited on N-implanted Al substrates, as compared to unimplanted Al substrates.

DC Corona Discharge Characteristics and Ion-Flow Distribution for Several Types of Rods under Low Pressure

The dc corona discharge characteristics and ion flow distributions for differently shaped discharge rods in a model electrostatic precipitator unit at low relative air density & = 0.21-1 (0.21-1 atm at room temperature) are described. The purpose of this experiment was to clarify the electrical characteristics of hot-site electrostatic precipitators based on the similarity law of electrical gas discharges. Three types of discharge rods were used: 1-5-mm round rods, 4-mm square rods, and rods with attached pins. Results are reported for both polarities in terms of current-voltage characteristics, corona onset and flashover voltages, and ion-flow distributions.