Anodic Bias Research Articles

Fabrication of Ti/TiO<sub>2</sub>/MO<sub>x</sub> Electrodes Using Photoelectrodeposition Technique

Photoelectrochemical deposition of metallic oxide (PbO2, RuOx, NiOOH, and CoOOH) onto a Ti substrate was studied and the electrochemical behavior of the prepared Ti/TiO2/MOx electrodes was examined. The photoelectrochemical deposition of MOx occurred in the solutions containing Mn+ ions on the Ti substrate under anodic bias. Electron holes produced on the TiO2 film surface under illumination may contribute the MOx formation. The prepared Ti/TiO2/MOx electrodes showed a tunneling current under anodic bias.

Emission Properties of Nanostructured Carbon Field-Emission Cathodes

AbstractPlanar field-emission cathode structures consisting of nanostructured carbon flakes have been investigated as an electron source for flat panel display application.Layers of nanoflakes were grown on silicon and molybdenum substrates using a high- temperature pyrolitic plasma-assisted CVD method. The result is a vertically oriented nanocluster layer of 1-2 micrometer height chemically bonded with the substrates. Additional orientation of the flakes, occurring during the first activation of the cathodes, was observed.Field emission properties of the emitters were studied in a vacuum chamber and in sealed flat-panel prototype devices with non-patterned low-voltage phosphor screens. Emitters with an area up to 1 square inch were tested under DC currents up to 100 microamps in diode mode. Anode bias up to 1.5 kV was applied. Current fluctuations of 1-2% were achieved using loading resistor.

Adhesion of copper on polyimide deposited by arc-enhanced deposition

Polyimide films of Kapton EN were coated with copper by arc-enhanced deposition. This deposition method offers the possibility to influence the degree of ionization by setting the anodic arc current without varying other deposition parameters. Estimation of the electron density depending on the anodic arc current is given by flat probe measurements. Adhesion measurements by pull test and peel test were carried out to examine the influence of vapor ionization on adhesion. The adhesion measurements do not show a uniform dependence on the anodic arc current and bias voltage, and the adhesion strength never reached values obtained by thermally evaporated copper coatings. Apparently, either ion impact or vacuum ultraviolet radiation of the anodic arc damages the polymer by a significant amount.

In situ Raman and Vis-NIR spectroelectrochemistry at single-walled carbon nanotubes

The population of valence-band electronic states of single-walled carbon nanotubes (SWCNT) was tuned electrochemically in aqueous electrolyte solution. Depending on the applied potential, reversible changes of intensity and frequency of the Raman-active tangential mode and radial breathing mode were observed. The maximum intensity occurs at ca. −0.2 V vs. Ag/AgCl independent of the electrode material used as a support (Pt, Au, Hg). SWCNT are sensitive to photoanodic breakdown upon prolonged exposure to anodic bias and laser light. Reversible bleaching of the first band-gap transition in semiconducting tubes (at 0.7 eV) occurs after anodic polarization.

Photoelectrocatalytic Degradation of Sulfosalicylic Acid and Its Electrochemical Impedance Spectroscopy Investigation

A three-electrode system composed of TiO2/Ni as the working electrode, porous nickel as the counter electrode, and saturated calomel electrode (SCE) as the reference electrode was used for the photoelectrocatalytic degradation of organic compounds. The photoelectrocatalytic degradation of sulfosalicylic acid (SSal) under anodic bias potential was investigated. It is shown that SSal can be degraded effectively as the external potential is increased up to 700 mV (vs SCE). The characteristics by electrochemical impedance spectroscopy (EIS) of the photoelectrocatalytic degradation of sulfosalicylic acid (SSal) was also investigated. It is shown from the EIS that the photoelectrocatalytic degradation appears to be a simple reaction on the electrode surface, suggesting that only one step of charge transfer is involved in the electrode process. The value of the resistance of charge transfer for the photoelectrocatalytic reaction of SSal manifests itself not only in the reaction rate, but also in the separation efficiency of the photogenerated electron -hole pairs. The separation efficiency of the electron-hole pairs under N2 atmosphere is higher than that under O2 atmosphere.

Electrochemistry and Photoetching of n‐GaN

The (photo)electrochemical behavior of n‐GaN[0001] in various aqueous solutions was studied using rotating‐disk voltammetry, cyclic voltammetry, and electrical impedance measurements. It was found that the bandedges of the semiconductor shift over 60 mV/pH unit, indicating acid‐base equilibria at the interface. In and KOH solutions, the photocurrent under anodic bias is associated with the oxidation of the semiconductor according to a three‐equivalent reaction, leading to dissolution and roughening of the surface. In 1.2 M HCl solutions, n‐GaN is stabilized for anodic decomposition due to the competing oxidation of ions. In the presence of oxalic acid and citric acid, anodic photocurrent multiplication was observed. Under cathodic polarization in the dark, , , , in acid medium and in alkaline medium are electrochemically reduced at a diffusion‐limited rate. In 1 M KOH a high reactivity for reduction is observed, explaining why n‐GaN can be photoetched under open‐circuit conditions in this solution. © 2000 The Electrochemical Society. All rights reserved.

Pulsed Electroreduction of CO 2 on Cu‐Ag Alloy Electrodes

Highly selective reduction of to , compounds such as , , and has been achieved on CuAg alloy electrodes by pulsed electroreduction. The faradaic efficiencies of compounds produced on CuAg alloy electrodes were varied with the atomic ratio of Cu to Ag. The total value of faradaic efficiencies for these compounds was 54.2% for the pulsed electroreduction on a CuAg alloy electrode (Cu/Ag = 28/72) with an anodic bias of and a cathodic bias of vs. Ag/AgCl. It was found that the formation of an oxide layer on Cu and the desorption of intermediates on Ag under anodic bias were key factors for the selective reduction of to compounds on CuAg alloy electrodes. © 2000 The Electrochemical Society. All rights reserved.

Lateral Silicon Field-Emission Devices using Electron Beam Lithography

We fabricated field-emission vacuum microelectronic devices such as diode and triode devices, using high-resolution electron-beam lithography in combination with the reactive ion etching (RIE) technique. The turn-on voltage of the diode is 13 V, which is the lowest value reported for single-crystalline lateral silicon field-emission devices. An emission current of 1.4 µA was obtained at an anode bias of 40 V. Field emission was confirmed by the linearity of the Fowler-Nordheim plots. The anode current of the triode was effectively modulated as a function of gate voltage. The device stability results show that the proposed devices are stable and reproducible.

28.1: Novel 20‐inch Color Field Emission Display Prototype

AbstractThe fabrication processes and the display characteristics of color field emission display (FED) with screen diagonal of 20‐ inch were described. FEDs were developed with thin film, screen‐print and surface activation techniques. They could display Chinese characters, English letters and simple cartoon images in 50 Hz. The pixel size of FED prototype was 0.15×0.5 mm2 for color FED or 0.5×0.5 mm2 for monochrome FED. The pixel number was 358×358×3 for color FED or 358×358 for monochrome FED. The thickness of FED panel was about 2.2 mm. Under about 300V anode bias, the maximum emission current of one pixel of monochrome FED was about 26 mA and the screen brightness of monochrome FED with conventional CRT phosphors was 300 cd/m2.

Selective Formation of Nanoholes with (100)-Face Walls by Photoetching of n-TiO2 (Rutile) Electrodes, Accompanied by Increases in Water-Oxidation Photocurrent

Nanometer-sized rectangular holes or grooves in the 〈001〉 direction were formed when single-crystal rutile-type n-TiO2 (001), (110), and (100) electrodes were illuminated in 0.05 M H2SO4 under anodic bias, accompanied by increases in water-oxidation photocurrents. Interestingly, only the (100) face was selectively exposed at the walls of the photoproduced holes and grooves, irrespective of crystal faces of electrode surfaces, though the (110) face for rutile TiO2 is known to be the thermodynamically most stable, that is, to have the lowest surface Gibbs energy. On the other hand, no (100) face was exposed at the walls of rectangular holes produced by chemical etching with hot H2SO4 and hydrogen reduction at elevated temperatures, indicating that the selective exposition of the (100) face is characteristic of photoetching in H2SO4. A possible explanation is given by assuming that the selective exposition of the (100) face is due to a kinetics-controlled mechanism. It is tentatively suggested that the photoetching, which makes the surface structure changeable, may be much slower than the water photooxidation at the (100) surface, though not so much slower at other surfaces such as (110) and (001).

Electrochemical luminescence of ZnGa 2O 4 semiconductor electrodes activated with Cr and Co

Electrochemical luminescence of ZnGa 2O 4:Cr and ZnGa 2O 4:Co semiconductor electrodes was studied. Under cathodic polarization in Na 2S 2O 8 electrolyte, these electrodes generated emission of ZnGa 2O 4 with a broad band from 350 to 650 nm together with red emission attributed to Cr 3+ and Co 2+. These emissions are explained by recombination between electrons and holes. Under anodic bias in Na 2SO 4 electrolyte, only the red emission was observed, accompanied with a sharp rise of anodic current at ca. +12.5 V. The emissions were explained by collision excitation of Cr 3+ and Co 2+ emission centers owing to avalanche breakdown.

Dependence of Macropore Formation in n‐Si on Potential, Temperature, and Doping

Subjecting illuminated n‐type silicon wafers to anodic bias in an HF containing electrolyte results in the formation of macropores under certain conditions. In this paper the formation of randomly nucleated macropores is studied as a function of the applied potential, the temperature, and the doping levels of the samples. A large number of micrographs was evaluated by computerized image processing and the data obtained are compared to predictions of pore formation models. It was found that the formation of randomly nucleated macropores involves a prolonged nucleation phase. Starting from a polished surface, first macropores occur after a certain amount of Si has been homogeneously dissolved. In this nucleation phase the thickness of the homogeneously dissolved Si depends strongly on the doping level and the temperature, but only weakly on the applied bias. In a second phase of stable pore growth, the density of pores is investigated as a function of temperature and anodic potential. For low‐doped material a strong influence of the space‐charge region on the average macropore density is observed in accordance with existing models; an increased anodic bias, e.g., decreases the density of pores. For highly doped silicon the situation reverses; increasing anodic bias increases the pore density, in contrast to predictions. The pore growth in this region is not very sensitive to the space‐charge region but seems to be dominated by the chemical‐transfer rate. © 2000 The Electrochemical Society. All rights reserved.

Potential, Temperature and Doping Dependence for Macropore Formation on n-Si with Backside-Illumination

Applying an anodic bias on a silicon HF contact and illuminating the backside of a n-type silicon wafer allows to create macropores. The formation of “random macropores” is studied in this paper by determination of the influences of the potential, the temperature and the doping level. A statistical approach is used to evaluate the micrographs. The formation of the macroporous layer consists of two phases. Beginning with a plane surface and homogeneous dissolution of silicon, first pores occur after some time. In this nucleation phase the thickness of the homogeneously dissolved Si depends strongly on the doping level and the temperature but only weakly on the applied bias. In a second phase of stable pore growth the density of pores is investigated as a function of temperature and anodic potential. For low doped material we find a strong stabilisation influence of the deep space charge region (SCR) in the nucleation as well as in the stable pore growth phase. Thus an increased anodic bias decreases the density of pores. For highly doped silicon no stabilisation influence of the SCR is found. The pore growth is dominated by the electrochemical dissolution rate, i.e. increasing the potential increases the density of the macropores.

Under-Gate Triode Type Field Emission Displays with Carbon Nanotube Emitters

ABSTRACTA new structure of triode type field emission displays based on single-walled carbon nanotube emitters is demonstrated. In this structure, gate electrodes are situated under cathode electrodes with an in-between insulating layer, so called under-gate type triode. Electron emission from the carbon nanotube emitters is modulated by changing gate voltages. A threshold voltage is approximately 70 V at the anode bias of 275 V.

Production and evolution of composition, morphology, and luminescence of microcrystalline arsenic oxides produced during the anodic processing of (100) GaAs

GaAs when exposed to a 7 V anodic bias in aqueous HCl, forms pitted structures from which visible photoluminescence has been observed. Previous work in our laboratory identified the source of the luminescence to be arsenic oxide microcrystals, formed during the electrochemical oxidation, which evolve in composition and morphology during the course of the anodic processing. The density and size of pits is dependent on the solution conditions as well as the applied potential program (stepped vs swept to 7 V. At early times (t<30 min) the pits are composed of a mixture of small (∼1 μm) and larger (10’s of μm) faceted microcrystals identified by x-ray photoelectron spectroscopy and energy-dispersive x-ray analysis to be a combination of As(III) and As(V) oxides. At longer times As(III) oxides predominate, and the smaller microcrystals are no longer observed, suggesting that the smaller microcrystals are As(V) oxide, and that they evolve chemically into As(III) oxide over the course of the oxidation. A suitable reaction pathway which explains the observed predominance of As(III) species is suggested. The luminescence properties of these electrochemically produced structures were investigated by near-field excitation. The luminescent properties evolve in parallel with the morphology and composition although the form of the spectrum is invariant in time and consistent with that obtained from bulk As2O3 and As2O5. The similarity of emission obtained from the two types of microcrystals suggests an impurity-related origin.

Development of a 7‐in. WIDE Screen Full‐Color FED

AbstractWe already presented a 5″QVGA full color FED, which has a good focusing characteristic and a new anode drive system called ‘Anode‐Bias Drive’ and a wiring matrix called ‘Full‐Duty Architecture’. Recently, we confirmed the effect of the anode bias drive by applying to a 5″QVGA panel and a new wiring matrix was designed to decrease crosstalks by modifying the full‐duty architecture. Furthermore, we successfully developed a 7″WIDE screen (480 × RGB × 240 pixels) full color FED utilizing these technologies. As a result of this development, the anode voltage was driven at 800V and the luminance of the panel reached around 300cd/m2.

Effect of the Initial Treatment on the Structure of Thin Anodic Films on Aluminum

The influence of different initial treatments of the metallic surface on the solid‐state and dielectric properties of thin anodic films grown on aluminum specimens, anodized in inorganic salt‐containing solutions, was investigated in situ by photocurrent and impedance spectroscopy. The presence or the absence of photoresponse under anodic bias of the electrodes was related to the different structure of the surface passive layers on specimens submitted to various surface treatments. The anodic photocurrent behavior was compared with the frequency response of the metal/passive film/electrolyte junction recorded within the blocking potential region. The values derived for the components of the equivalent electrical circuit of the interface were related to the more or less insulating properties of the layers, which affect both the photocurrent behavior and the kinetics of growth of the anodic films. Different absorption edges for the anodic photocurrent were attributed to surface layers with variable hydration degree, having different optical bandgap values. The presence of two absorption edges was related to duplex surface films, with an external more hydrated layer. In this case a more complex electrical equivalent circuit was necessary in order to fit the frequency dispersion of the junction. © 1999 The Electrochemical Society. All rights reserved.

Field emission properties of the polycrystalline diamond-coated silicon emitters

This work examines the electron emission characteristics of a polycrystalline diamond-coated silicon field emitter fabricated by hot filament chemical vapor deposition. The electron emission behavior of a polycrystalline diamond-coated Si field emission array (D/Si-FEA) was compared with that of an uncoated Si field emission array (Si-FEA) and flat-diamond film coated on Si substrate (flat-D/Si). From Raman spectrum and x-ray diffraction pattern analyses, it was revealed that the overcoated diamond film involved structural defects, graphite inclusion, grain boundaries, and a negative electron affinity surface. The direct current current–voltage (I–V) characteristics exhibited linear ohmic emission behavior at low anode voltages and Fowler–Nordheim emission behavior at high anode voltages. The threshold voltages for the D/Si-FEA, Si-FEA, and flat-D/Si were about 250, 666, and 800 V, respectively. The maximum emission current for the D/Si-FEA, 0.23 mA, was obtained for a 500 V anode bias. The low onset voltage of the D/Si-FEA was attributed to the cone-shaped emitter and the excellent properties of the overcoated diamond film.

Experimental study of the nonlinear dynamics of a harmonically forced double layer

A plasma double layer is created by an anode grid in the target chamber of the double plasma device. When the separation grid of the double plasma device is floating, very coherent plasma oscillations, triggered by the unstable double layer, are observed. The oscillations have a frequency close to 1 kHz and very high amplitude. The amplitude and frequency of these oscillations depend on the anode bias and on the discharge voltage of the plasma source. The anode characteristics exhibit hysteresis. When plasma oscillations are coupled to the external oscillator, by modulating the floating potential of the separation grid, synchronization and periodic pulling are observed. When external oscillations are tuned to the second, third or fourth harmonics, period doubling bifurcations are observed, when the external amplitude is increased. At synchronization with the third and fourth harmonics, oscillations become chaotic after the first period doubling bifurcation. The correlation dimension of the underlying attractor is found to be fractal between 2.3 and 2.8, with a positive largest Lyapunov exponent.

Parametric Model of a Class C Tube Amplifier for Industrial Ilk Applications

This paper presents a parametric model of a triode which introduces seven parameters. It allows calculation of the a.c, and d.c. electrical variables of a class C amplifier from the d.c. anode and grid bias voltages, the load impedance and the a.c. exciting signal This model can be used for designing the input and the output circuits and for optimizing the performence of the amplifier by choosing the best bias conditions.