I–V characteristics of a vertical single Ni nanowire by voltage-applied atomic force microscopy

We report the measurement of the electrical resistivity of a vertical single Ni nanowire. A vertical array of Ni nanowires was fabricated on a Si substrate by electrodeposition using a nanoporous alumina template. The Ni nanowires possessed a face-centered-cubic polycrystalline structure. A voltage-applied atomic force microscope was used to make a nanometer-scale point contact on top of the vertical grown single Ni nanowire. The measured resistance was 1.1 MΩ for a nanowire with length of 3 μm and diameter of 20 nm.     

6H-SiC Schottky barrier source／drain NMOSFET with field-induced source／drain extension

A novel SiC Schottky barrier source/drain NMOSFET (SiC SBSD-NMOSFET) with field-induced source/drain (FISD) extension is proposed and demonstrated by numerical simulation for the first time. In the new device the FISD extension is induced by a metal field-plate lying on top of the passivation oxide, and the width of Schottky barrier is controlled by the metal field-plate. The new structure not only eliminates the effect of the sidewalls but also significantly improves the on-state current. Moreover, the performance of the present device exhibits very weak dependence on the widths of sidewalls.     

Variation with temperature of the I–V characteristics of polyacetylene nanofibres

The current–voltage (I–V) characteristics of individual nanofibres of doped polyacetylene show a dramatic change from very strong nonlinearities for lightly-doped samples at low temperatures, to nearly ohmic behaviour for higher temperatures and doping levels. At low temperatures (below 10–30 K), the I–V characteristics are independent of temperature and follow the expression for Zener-type tunnelling, as predicted for field-induced tunnelling of the conjugated bond system. At higher temperatures, the I–V characteristics deviate from Zener-type behaviour and the current increases with temperature as thermally-assisted conduction mechanisms become important. The I–V characteristics for the most conductive sample are consistent with our calculations of fluctuation-induced tunnelling.     

I–V characteristics of vanadium-flavonoid complexes based Schottky diodes

In this study, we have investigated the current–voltage characteristics of the Schottky diodes of two vanadium complexes, VO₂(3-fl) (1) (3-fl=3-hydroxyflavone) and VO(acac)₂ (2), (acac=acetylacetonate), and their composites with TiO₂. Thin films of vanadium complexes and their composites were deposited by the centrifugation method. Current–voltage characteristics of the samples were processed by the modified Shockley equation, Cheung functions and space-charge limited currents (SCLC) approaches. Different junction parameters, such as series resistances, reverse saturation currents, ideality factors and barrier height of the samples, were determined.     

Ordered Si/Si–O nanowire array and its optical properties

Glancing angle deposition (GLAD) has been employed to fabricate the Si/Si–O nanowires (NWs). The perpendicular NW on silicon substrate shows the amorphous nature. The visible light emission from the NWs was observed from the Si/Si–O nanoparticles. High light absorption inside the Si/Si–O NW structure was recorded.     

Possible two non-linear regions in the I–V characteristics of ZnO varistors

We report here structural and I–V characteristics of ZnO varistor with Fe₂O₃ nanoparticles additions (≤200 nm). It was found that the addition of Fe does not influence the wurtzite structure of ZnO ceramics, while the average grain size was affected. Interestingly, the nonlinear region was clearly observed in the I–V characteristics of the samples with Fe = 2.5%, 5% and 10%. Whereas, two nonlinear regions were only observed with further increase of Fe addition above 10% (30% and 50%). Although the values of non-linear coefficient are decreased by the additions of Fe, the breakdown field could be increased up to 7900 V/cm. Furthermore, the electrical conductivity was improved by increasing Fe up to 10%, followed by a decrease with further increase of Fe up to 50%. These results were discussed in terms of Fe₂O₃ nanosize grains which were formed and localized at the grain boundaries of ZnO ceramics.     

I–V characteristics of ZnO/Cu2O thin film n–i–p heterojunction

ZnO/Cu₂O thin film n–i–p heterojunctions were fabricated by magnetron sputtering. The microstructure, optical, and electrical properties of n-type (n‐) ZnO, insulating (i‐) ZnO, and p-type (p‐) Cu₂O films deposited on glass substrates were characterized by X-Ray diffraction (XRD), spectrophotometer, and the van der Pauw method, respectively. XRD results show that the mean grain size of i-ZnO film is much larger than that of n-ZnO film. The optical band gap energies of n-ZnO, i-ZnO, and p-Cu₂O film are 3.27, 3.47, and 2.00 eV, respectively. The carrier concentration of n-ZnO film is two orders of magnitude larger than that of p-Cu₂O film. The current–voltage (I–V) characteristics of ZnO/Cu₂O thin film n–i–p heterojunctions with different i-ZnO film thicknesses were investigated. Results show that ZnO/Cu₂O n–i–p heterojunctions have well-defined rectifying behavior. All ideality factors of these n–i–p heterojunctions are larger than 2.0. The forward bias threshold voltage and ideality factor increase when i-ZnO layer thickness increases from 100 to 200 nm. An energy band diagram was proposed to analyze the I–V characteristics of these n–i–p heterojunctions.     

Neutron irradiation effects on I–V characteristics of Au/n-GaAs Schottky diodes

Diodes are one of the most important and widely used components of electronic circuits. These devices can be damaged especially when they are used in radiation fields whose effects depend on radiation type and energy. To investigate these effects, the Au/n-GaAs type Schottky diodes have been irradiated by neutrons emitted from a ²⁵²Cf source which provides neutrons at an average energy of 2.14 MeV. The diode parameters barrier height (Φ_b0), ideality factor (n) and series resistance (R_s) have been obtained from forward current–voltage (I–V) characteristics before and after irradiation and the results are discussed.     

Experimental study of V–I characteristics of wire–plate electrostatic precipitators under clean air conditions

In this paper a laboratory-scale model for prediction of the voltage–current characteristics of wire–plate electrostatic precipitators under clean air conditions is presented and experimentally validated. The model investigates the effect of electrode configurations, wire diameter, spacing between wire electrodes, number of discharge wires and distance between collecting plates that on voltage–current characteristic of wire–plate electrostatic precipitators. Also, this paper presents a simulation model, based on the Finite Difference Method (FDM), to simulate electric conditions of wire–plate electrostatic precipitators under clean air conditions. The experimental results of some models are compared with those obtained from the simulation models.     

Voltage–current and voltage–flux characteristics of asymmetric high TC DC SQUIDs

We report measurements of transfer functions and flux shifts of 20 on-chip high T_C DC SQUIDs half of which were made purposely geometrically asymmetric. All of these SQUIDs were fabricated using standard high T_C thin-film technology and they were single layer ones, having 140 nm thickness of YBa₂Cu₃O_7?x film deposited by laser ablation onto MgO bicrystal substrates with 24° misorientation angle. For every SQUID the parameters of its intrinsic asymmetry, i.e., the density of critical current and resistivity of every junction, were measured directly and independently. We showed that the main reason for the on-chip spreading of SQUIDs’ voltage–current and voltage–flux characteristics was the intrinsic asymmetry. We found that for SQUIDs with a relative large inductance (L > 120 pH) both the voltage modulation and the transfer function were not very sensitive to the junctions asymmetry, whereas SQUIDs with smaller inductance (L ? 65–75 pH) were more sensitive. The results obtained in the paper are important for the implementation in the sensitive instruments based on high T_C SQUID arrays and gratings.     

On the effect of boundary conditions on I–V characteristics of HTSC tunnel junctions

The pairing potential distribution over the thickness of superconducting CuO₂ layers in cuprate HTSCs is determined within the Ginzburg–Landau (GL) theory using the microscopic justification of this theory by Gor’kov. It is found that the pairing potential in them is significantly suppressed due to the effect of non-superconducting interlayers, which results in a decrease in the critical temperature of these superconductors. The temperature dependences of the effective energy gap and current–voltage (I–V) characteristic of tunnel junctions of the “break junction” type made of these superconductors are calculated.     

The effect of gradually constricted channel on the I–V characteristics of graphene sheets

Ideal graphene is a gapless semiconductor consisting of a single layer of carbon atoms regularly arranged in a honeycomb lattice having infinite spatial extent in the (x,y)-plane, in which electrons behave as Dirac massless fermions. Even neglecting interactions with the anchoring substrate, a graphene sheet in real world has finite extent, leading to distinctive features in the conductivity of a given sample. In this letter we study the effect of a gradual channel constriction in graphene nanoribbons on their I–V characteristics, using non-equilibrium Green's function formalism. The constriction width and the border cutting angle are the main parameters to be varied. We found that transmission through the channel is considerably affected by these parameters, presenting sharp peaks at specific energies, which can be attributed to a resonance due to the tuning of energy eigenvalues.     

Double threshold behaviour of I－V characteristics of CoSi2/Si Schottky contacts

The forward current－voltage (I－V) characteristics of polycrystalline CoSi₂/n-Si(100) Schottky contacts have been measured in a wide temperature range. At low temperatures (≤200K), a plateau-like section is observed in the I－V characteristics around 10^-4A·cm^-2. The current in the small bias region significantly exceeds that expected by the model based on thermionic emission (TE) and a Gaussian distribution of Schottky barrier height (SBH). Such a double threshold behaviour can be explained by the barrier height inhomogeneity, i.e. at low temperatures the current through some patches with low SBH dominates at small bias region. With increasing bias voltage, the Ohmic effect becomes important and the current through the whole junction area exceeds the patch current, thus resulting in a plateau-like section in the I－V curves at moderate bias. For the polycrystalline CoSi₂/Si contacts studied in this paper, the apparent ideality factor of the patch current is much larger than that calculated from the TE model taking the pinch-off effect into account. This suggests that the current flowing through these patches is of the tunnelling type, rather than the thermionic emission type. The experimental I－V characteristics can be fitted reasonably well in the whole temperature region using the model based on tunnelling and pinch-off.     

Computation and measurement of corona current density and V–I characteristics in wires-to-plates electrostatic precipitator

This paper deals with experimental and numerical investigation of wire-duct type electrostatic precipitator under clean air conditions. A laboratory-scale model is used to provide measurements of corona current–voltage characteristics and current density. Different configurations of electrodes are tested in order to improve the performance of the electrostatic precipitator. Moreover, the corona governing equations are successfully solved using Comsol Multiphysics. The present work simulates the whole geometry including all discharge wires in order to take into account their mutual effect. The results of the numerical model are compared with the experimental measurements of current density and current–voltage characteristics and the general agreement is quite good.     

I–V characteristics and magnetic field profile studies in high Tc BSCCO based Helmholtz coil

A double pancake wound high T_c Helmholtz coil has been fabricated using commercial grade BSCCO tape. The current voltage (I–V) characteristics of this HTS coil has been carried out using standard four probe technique. From the I–V characteristics, the critical current based on self field dependent of HTS coil and quality index “n” value have been calculated. Magnetic field profiles have been studied along the axis of this coil for various amplitudes of applied current ranging from 10 A to 50 A at 77 K. The measured field profiles have a very good agreement with that of theoretical values predicted in the literature.     

The effects of high-energy ion irradiations on the I–V characteristics of silicon NPN transistors

The silicon NPN rf power transistors were irradiated with different linear energy transfer (LET) ions such as 50?MeV Li³⁺, 80?MeV C⁶⁺ and 150?MeV Ag¹²⁺ ions in the dose range of 1–100?Mrad. The SRIM simulation was used to understand the energy loss and range of these ions in the transistor structure. The different electrical parameters such as Gummel characteristics, excess base current (ΔI_B), DC current gain (h_FE), displacement damage factor (K) and output characteristics were systematically studied before and after irradiation. The ion irradiation results were compared with ⁶⁰Co-gamma irradiation result in the same dose range. A considerable increase in base current (I_B) and a decrease in h_FE and I_CSat were observed after irradiation. The degradation in the electrical parameters was comparably very high for Ag¹²⁺ ion-irradiated transistor when compared to other ion-irradiated transistors, whereas the degradation in the electrical parameters for Li³⁺ and C⁶⁺ ion-irradiated transistors was comparable with gamma-irradiated transistor. The isochronal annealing study was conducted on the 100?Mrad irradiated transistors up to 500°C to analyze the recovery in different electrical parameters. The h_FE and other electrical parameters of irradiated transistors were almost recovered after 500°C for 50?MeV Li³⁺, 80?MeV C⁶⁺ ion and ⁶⁰Co-gamma-irradiated transistors, whereas for 150?MeV Ag¹²⁺ ion-irradiated transistor, the recovery in electrical characteristics is not complete.     

On the recovery of moving source characteristics using time–frequency approach

Four time–frequency analysis techniques, namely the short-time Fourier transform, the wavelet transform, the polynomial phase estimation and the Chirplet transform, are used in the present study to recover the moving speed, the sound frequency and the strength of a point source moving with a subsonic speed relevant to those of the road vehicles. Their performances in the presence of background random noises are tested in detail. The instant of the highest rate of change of the Doppler frequency is used as the time reference in the parameter recovery process. Results suggest that the performances of short-time Fourier transform and the wavelet transform, especially the former, are not satisfactory when compared to those of the other two methods even when the signal-to-noise ratio is reasonably high. The Chirplet transform gives a performance which is the least affected by the signal-to-noise ratio, while the accuracy of the polynomial phase estimation is the best among the four methods tested.