Porous Gold Films Research Articles

Preparation of regularly structured porous metal membranes with two different hole diameters at the two sides

Using a two step replication process, porous gold or nickel films could be obtained from anodic porous aluminum oxide films having two different hole diameters in its interior. The specifically tailored nanostructure of the starting material could be replicated to form through-hole nickel or gold membranes with an ordered linear structure having diameters of either 120 nm or 40 nm on one side and 57 or 23 nm respectively on the other side of the film.

Redox conduction in poly-[Ru(2,2'-bipyridine) 2(3-{pyrrol-1-ylmethyl}pyridine) 2](ClO 4) 2 and enhancement of electron transport rates

The in situ electron transport properties of the title polymer and its copolymers with 3-methyl-thiophene have been investigated by rotating disc voltammetry (RDV) and dual electrode (sandwich) voltammetry (DEV). In the RDV experiment the rate of mediated oxidation of Cr(2,2'-bipyridine) 3 2+ at an electrode coated with the polymer provides a measure of the electron transport rate as a function of potential. Similar data are obtained from the DEV experiment, in which the electron source at the polymer solution interface is a porous gold film at 0 V vs SSCE. Both techniques show that the Ru complex homopolymer conducts solely by electron hopping between the Ru sites. There is no evidence of conduction by the pyrrole linkages. Copolymerization with 3-methylthiophene increases the diffusion coefficient for electron hopping. As the thiophene : Ru complex mole ratio is increased above 1:1, increasing conduction due to the thiophene/pyrrole linkages is observed at potentials significantly less positive than the Ru formal potential. The conductivity of films containing 3-methylthiophene becomes increasingly susceptible to oxidative degradation as the thiophene content is increased. This is attributed to destruction of the conjugated pathway that the thiophene/pyrrole linkages provide for electron transfer between Ru sites.

Measuring the quasi-fermi levels and flat band potential of an illuminated Au/nGaAs 0.6P 0.4 anode

The positions of the quasi-Fermi levels, nE f ∗ and pE f ∗, in the illuminated semiconductor electrode, relative to the redox potentials of the electrolyte, play a key role in the operation of semiconductor liquid-junction solar cells. A simple method for determining the hole quasiFermi level, pE f ∗ s, at the anode surface of such a 〈 Au/ n GaAsP 0∥ K 2 SO 4 at pH = 4.6∥ Pt〉 cell is presented. Here Au is a 15 nm porous gold film evaporated onto the GaAsP 0 = GaAs 0.6P 0.4 surface. The method consists in monitoring the anode potential, V n, and the gold film potential, V Au, relative to a SCE reference electrode, as the external load and applied potential are varied, and assuming that V n = nE f ∗ and V Au = pE f ∗ s . The near-equality of V Au and pE f ∗ s , under 2 am 1 illumination, follows from the much larger rate of photohole tunnelling between GaAsP 0 and Au, compared to the sum of the rates of all other hole-consuming processes at the surface. Initial hole oxidation of the GaAsP 0 surface is postulated to generate a high resistivity surface film which physically isolates the GaAsP 0 from the bulk of the electrolyte, so that the flat band potential for the Au/GaAsP 0 anode is no longer determined by the GaAsP ∗/electrolyte interaction.

The Glazing of Vacuum‐Evaporated Gold‐Chromium Films with a Lead‐Containing Glass at 775°C

The glazing of vacuum‐evaporated gold‐chromium duplex films on alumina substrates at 775°C using a lead‐containing glass has been investigated. This process forms a part in the construction of a multilayer hybrid circuit. A detailed examination of a unique glazing defect using electron beam analytical facilities has led to the identification of a fine needlelike deposit associated with the defect as single crystals of the compound .Examination of the other characteristic features of the defect, a central black spot and a porous gold film, has involved a study of the thermal stability of gold‐chromium duplex films under nonglazing and glazing conditions. From the nonglazing experiments it is concluded that the chromium content of the needlelike deposit results from grain boundary diffusion of chromium through the gold film to be followed by oxidation at the gold/air interface during the heating cycle of the glazing schedule. The resistivity changes observed to occur in films at 400°C appear qualitatively consistent with this view. The cohesion and adhesion of gold chromium films of various thickness ratios were found to be maintained or improved after heating at 775° C for 2 hr. Glazing the as‐deposited film gives rise to attack of the gold film by the lead constituent of the glass causing the black spot and a porous gold film.