Gold Cathode Research Articles

Resonances in low-energy electron transmission through organized organic films: Evidence for molecular quantum wells

Energy-resolved transmission spectroscopy of low-energy photoelectrons through self-assembled monolayer films on a gold cathode are used to identify electron resonances in the film. For films composed of benzene, naphthalene, and anthracene aromatic moieties, the transmission spectra reveal well-defined vibronic structure, which is quite similar to that found for the corresponding aromatic molecules in the gas phase. In contrast, the electronic state positions are not molecular and indicate a ``quantum-well'' structure formed by the monolayer film.

Efficiency of copper and gold cathode in initiation of secondary emission in nitrogen-filled tube

The efficiency of secondary electron emission induced by ions and atoms remaining from previous discharge during the initiation of electrical breakdown in a nitrogen-filled tube with bulk copper and gold plated electrodes has been investigated. This investigation was done by measuring the electrical breakdown time delay as a function of afterglow period τ, glow current i g and electrode gap d. The results show that the gold plated cathode is more efficient in secondary electron emission caused by nitrogen atom impact on its surface than that of bulk copper. This phenomenon can be explained by different adsorption ability of nitrogen atoms on the copper and gold surface.

Plasma polymerized hexamethyldisiloxane: discharge and film studies

Films were grown in hexamethyldisiloxane (HMDS)-argon mixtures in a diode sputtering system with a gold cathode. Quantitative optical emission spectroscopy (OES)-actinometry revealed that the electron density or mean electron energy (or both) increased with increasing Ar concentrations in the gas feed. Increasing concentrations of Ar produced greater sputtering of the cathode and hence greater plasma Au concentrations. Fragmentation of the HMDS molecule resulted in species such as CH, H, and Si which were detected by OES. Film deposition rate, as determined by optical interferometry, was found to be increased by the inclusion of Ar in the gas feed. Transmission electron microscopy revealed particles, probably of Au, embedded in the polymer films. Actinometric measurements of Au in the discharge and electron probe microscopy of the deposited material showed that film Au concentrations increase with increasing concentrations of Au in the plasma. A relatively low fragmentation of HMDS molecules in the dc plasma was revealed by the very small Si-H IR absorption band which is usually prominent in spectra of plasma polymerized HMDS films.

Feasibility study of photocathode electron projection lithography

Photocathode electron projection is an electron lithography technique that may be used to pattern semiconductors at the deep submicron level. Using a robust gold cathode, mask features in the range of 0.11–0.54 μm have been transferred to electron resist coated wafers with adequate depth of focus (≂5 μm) and large field of view (≂2 cm2). Low accelerating voltages ∼3 keV minimize proximity effects, and with a mask to wafer spacing of a few millimeters, the necessary magnetic field is ≂0.46 T.

Template electrodeposition of nanowire arrays on gold foils fabricated by pulsed-laser deposition

A novel procedure to generate stable and rigid metal nanowire arrays with diameters between 100 and 600 nm and densities of ∼108 cm−2 is presented. It combines 1.(a) pulsed-laser deposition of an adherent and homogeneous gold cathode foil on a polycarbonate track-etch template2.(b) reinforcement and levelling by electroplating, and3.(c) the potentiostatic growth of the nanowire array through the etch tracks under convection control in an electrochemical jet cell.

Electrochemical sensor for monitoring atmospheric corrosion of zinc alloy coated steel

AbstractThe construction and operation of an electrochemical sensor capable of monitoring the corrosion performance of zinc alloy coated steel under controlled atmospheric conditions are described. Sensors were fabricated from zinc and zinc alloy coated steel sheet with and without chromate conversion treatments. Corrosion behaviour was monitored by measuring the potential and polarisation resistance of the coating and the galvanic current flowing between the coating and a gold cathode. It has been shown that this sensor is sufficiently sensitive to detect different corrosion rates for different types of zinc alloy coating in a similar environment, changes in the corrosion rate associated with changes in environmental conditions, and increases in corrosion activity associated with defects in the coatings. The sensor has potential for development as a simple and inexpensive method of assessing relative long term performance of a wide range of zinc alloy and other metallic coating systems, in a range of env...

Charge and mass resolved time of flight observations of 140 fs laser produced ions

Ions from this plasma are self-extracting with energies of 0.1 to 100 keV, the extraction potential being one of the desired observables. The charge/mass (z/μ, μ is mass in AMU) separation is provided by a static magnetic field (B⋅L=1280 G cm, FWHM=14 mm) located 5 cm from the linear (1−d) detector. Displacement along the detector axis is thus proportional to z/μ(1/v). The detector is a gold cathode MCP with a fast (sub-ns) phosphor. The phosphor output is coupled into a streak camera (typical sweep 8.5 or 24 μs total) through a coherent fiber bundle. Streak images are grabbed with a 14-bit CCD. The signature of any specific ion is a straight line of slope proportional to z/μ. Since there are usually more than one charge state of a given ion, integer multiple slopes appear. Thus z and m can be found. Absolute calibration is taken from the slope of the proton streak, which is always present with our plasmas. While providing the same information as a Thomson parabola, the straight line images are easier to extract information from and offer resolution with less energy dependence. By providing mass and time of flight information, the product of z⋅Te can be determined unambiguously during the hydrodynamic acceleration of the plasma.

Poisoning and Activation of the Gold Cathode during Electroreduction of CO 2

Carbon dioxide reduction at polycrystalline gold cathode in 0.1 M solution has been re‐examined. Like two other group Ib metal cathodes, Ag and Cu, the Au electrode is shown to undergo progressive deactivation during the electrolysis runs. A periodic, electrochemical activation treatment of the gold electrode is described.

Self-affine fractal electrodeposited gold surfaces: Characterization by scanning tunneling microscopy.

The morphological evolution of columnar gold electrodeposits grown at 100 nm ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$ by electroreducing a gold oxide layer on a gold cathode has been studied at a nanometer level by scanning tunneling microscopy. The interface thickness (\ensuremath{\xi}) depends on the scan length (L) as \ensuremath{\xi}\ensuremath{\propto}${\mathit{L}}^{\mathrm{\ensuremath{\alpha}}}$ with \ensuremath{\alpha}=0.49\ifmmode\pm\else\textpm\fi{}0.07 for Lg${\mathit{d}}_{\mathit{s}}$, where ${\mathit{d}}_{\mathit{s}}$ is the average top columnar size, and \ensuremath{\alpha}=0.90\ifmmode\pm\else\textpm\fi{}0.07 for L${\mathit{d}}_{\mathit{s}}$. These results prove that the growing surface can be described as a self-affine fractal for length scales greater than the columnar size. Conversely, the columnar surface approaches the behavior of an Euclidean surface.

Mechanism of the solid state battery: magnesium/ poly(thionaphtheneindole/gold)

The mechanism of a battery, that was assembled by including poly(thionaphtheneindole) (pTNI) pressed pellets between a gold cathode and a magnesium or zinc anode, was investigated. The importance of the water content of the pTNI in assuring proton migration in the polymer was established. Electrochemical reactions for magnesium oxidation at the anode and H+ reduction at the cathode are proposed.

Excess Heat Evolution during Electrolysis of H2O with Nickel, Gold, Silver, and Tin Cathodes

Excess heat evolution was measured on nickel, gold, silver, and tin in aqueous K[sub 2]CO[sub 3], Na[sub 2]CO[sub 3], Na[sub 2]SO[sub 4], and Li[sub 2]SO[sub 4] solutions under galvanostatic electrolysis conditions. Steady evolution of excess heat in various electrode-electrolyte systems, but not in Ni/Na[sub 2]CO[sub 3], Ni/Na[sub 2]SO[sub 4], and Ni/Li[sub 2]SO[sub 4], was observed for at least several days of observation. The largest excess heat observed was 907 mW on tin in K[sub 2]SO[sub 4]. 9 refs., 2 figs., 4 tabs.

Fractal surfaces of gold and platinum electrodeposits: dimensionality determination by scanning tunneling microscopy

The structure of gold and platinum deposits grown on gold and platinum wire cathodes, respectively, by electroreduction of the corresponding oxide layers has been analyzed in terms of surface fractals by measuring the perimeters L and area A of intergranular voids. Perimeter and area were determined from scanning tunneling microscopy (STM) topographic images of the deposit surfaces.

Electrochemical method for direct measurement of oxygen concentration and diffusivity in the intervertebral disc: electrochemical characterization and tissue-sensor interactions

A method was developed for the in vivo measurement of oxygen concentration and diffusivity in the intervertebral disc using a bare gold cathode. The effects of surface adsorption were quantified using electrochemical methods and it was demonstrated that valid data can be obtained despite interactions between the electrode and the macromolecules of the intervertebral disc. The technique is used to show the dependence of the oxygen transport properties on tissue water content.

Development of a miniature clark-type oxygen electrode using semiconductor techniques and its improvement for practical applications

A disposable minature Clark-type oxygen electrode has been fabricated using semiconductor techniques. The oxygen electrode consists of: (a) anisotropically etched U- or V-grooves on a (100) silicon substrate as the electrolyte container; (b) a calcium alginate gell containing a 0.1 M KCl electrolyte; and (c) a directly formed gas-permeable membrane. A two-electrode configuration is used with a gold cathode and a gold anode. A novel fabrication process has been developed to allow miniaturization and mass production. Several important factors which influence the oxygen electrode characteristics have been examined. A 90% response time of 10 s is attained. A linear relationship is observed for a wide range of oxygen concentrations at 27°C. 34% of the oxygen electrodes work normally after sterlization in an autoclave. The oxygen electrode can be operated continuously for more than 40 h.

Pattern marking on synthetic diamond film by Penning discharge sputtering

Method and apparatus to perform micro-etching and micro-inlay of patterns and numerals on synthetic diamond films by Penning discharge sputtering has been developed and evaluated. In this apparatus, selection of etching and inlay modes are made by a change of anode position. In etching mode, etching beam originates in a Penning discharge space and is guided through a duct in order to reach the diamond film surface covered with a pattern mask and then forms an etching pattern on the surface. After the etching is made, a new position of anode is selected for inlay process and the metal atoms that sputtered from the cathode surface through the duct deposit on the previously etched portion on the diamond film. A 5.3 μm thick diamond film formed by microwave plasma CVD. A flat dish-shaped etching of 2.5 mmφ and a same size inlay with gold were made with a mask having 2.5 mmφ hole and gold cathodes. In this case, etching rate of diamond film is 0.07–0.12 μm min −1 and deposition rate of gold 0.06 μm min −1. By the same technique, etching and gold inlay shaped after the numeral “5” with 120 μm in width and 180 μm in length was produced.

Microminiature enzyme sensors for glucose and lactate based on chamber oxygen electrodes

Biosensors for glucose and lactate were produced by the immobilization of agarose membranes containing glucose oxidase and lactate oxidase respectively inside 2 μm high chamber-type oxygen sensors. The well-defined microvolume elements of these chambers provided a reproducible method of generating a thin enzyme layer over the electrode area. The chambers also acted to anchor the enzyme membrane in place without the need for any surface modification. The extent of the enzyme reaction was monitored by the decrease in oxygen reduction current at the gold cathode, and the normalized current decrease related to the concentration of the substrate (glucose or lactate). Enzyme entrapment inside low-temperature gelling agarose resulted in sensors with response times of approximately 10 s, but with calibration curves that were under enzyme kinetic control. Loss of response sensitivity with time was observed and was attributed primarily to enzyme diffusion out of the membrane. By casting a cellulose acetate membrane on top of the agarose-enzyme gel it was possible to improve both the stability of the sensors and their linear response range. This approach produced a lactate sensor with an upper limit of detection enhanced ten-fold to a limit of about 10 mM lactate, compared to a limit of about 1 mM in the absence of the cellulose acetate.

A galvanic gas sensor using poly (ethylene oxide) complex of silver trifluoromethane sulphonate electrolyte

A galvanic sensor for monitoring nitrogen dioxide was developed by using a poly(ethylene oxide) complex of silver trifluoromethanesulphonate electrolyte. The sensor, which is expressed as Au/P(EO)4.5 AgCF3SO3/Ag, is a small disk (i.d. 13 mm). The polymeric electrolyte film was made by casting the mixture of acetonitrile solutions of both P(EO) (MW 6×105) and AgCF3SO3. The working electrode was made by sputtering of gold in argon. The thicknesses of the desposited gold, polymeric electrolyte film and silver are 25 nm, 30 μm and 1 mm, respectively. When the sample gas containing nitrogen dioxide impinges at 20 ml min−1 on the gold cathode, the current flowing in the external circuit was linearly related to the concentration of nitrogen dioxide from 20 ppb to about 10 ppm. The current efficiency of the cell was 0.051%. The cell's response time was about 2 min for 0.5 ppm of nitrogen dioxide.

Sputter deposition of gold in rare-gas (Ar,Ne)–O2 discharges

In the present study, we investigate the films that result when a gold cathode is sputtered in rare-gas (Ne, Ar)–O2 discharges. Si(111) substrates were used. The results show that a large increase in resistivity, a decrease in reflectivity to one-half the value for metallic gold, and the possible formation of a second phase with no long-range crystallographic order detectable by x-ray diffraction are coincident with the formation of Au–O bonds in the films. Au–O bond formation occurs at a lower gas O2 content when Ne rather than Ar is used as the rare-gas component of the discharge.

The influence of hemorrhagic hypotension on spinal cord tissue oxygen tension.

In order to investigate the spinal cord surface PO2 (sPO2) reaction to hypovolemic hypotension, nine female pigs (25 kg bw) were premedicated, anesthetized, intubated and artificially ventilated with N2O:O2 = 3:1. Following laminectomy from L3 to L5, sPO2 was measured on the dorsal side of the exposed spinal cord using six gold cathodes (luminal diameter 15 microns) while MAP (mean +/- SD) was lowered in steps of about 10 Torr by bleeding into a reservoir from 69.3 +/- 10.1 Torr to extreme low values of 13.3 +/- 3.1 Torr. Only a slight decrease of lumbar sPO2 (mean +/- SD) from 33.5 +/- 7.2 Torr to 27.6 +/- 4.8 Torr was evaluated from the data in response to MAP reduction to 50.2 +/- 3.5 Torr. Below that value, a marked proportional decrease of sPO2 and MAP was observed (0.65 Torr/Torr) corresponding to pressure passive flow behavior of the Hagen Poisseuille Law ("loss of autoregulation"). Four to five minutes after start of reinfusion both sPO2 and MAP showed an overshoot with maximum values of 54.0 +/- 11.1 Torr resp. 102.6 +/- 18 Torr. Initial values were approximated about 15 min. later. Histograms plotted from the individual sPO2 values of all pigs and of all the different experimental stages showed signs of severe hypoxia only if MAP was reduced below about 30 Torr. In general, this situation was reversible within reinfusion, only one of the nine pigs did not tolerate hemorrhagic hypoxia induced by MAP reduction to less than 30 Torr for at least 5-10 min. Nevertheless, the experiments showed a considerable circulatory stability in the investigated pigs.

Electrochemistry of Molten Calcium Nitrate Tetrahydrate

The electrochemical properties of calcium nitrate tetrahydrate were studied by voltammetry, coulometry, and chemical analysis. The electrolyte anode reaction was oxidation of water to oxygen on either gold or platinum. The major reaction at a gold cathode was reduction of nitrate to nitrite and a solid calcium hydroxide electrode film. Small amounts of oxygen and more than the theoretically predicted quantity of nitrite were detected, suggesting a secondary chemical reaction. The reduction reaction at platinum gave 50–75% of the theoretical yield of nitrite. The voltammetric behavior of OH−, , and in this system were studied.