The evolution of hydrogen and oxygen was studied on diamond electrodes containing approximately 1021 boron atom/cm3. Voltammetry showed a wide potential window [−1.25 to +2.3 V vs. standard hydrogen electrode (SHE)] without significant water decomposition. This window was much narrower for poor quality diamond films with appreciable sp2 content. A redox couple observed at +1.7 V indicates oxidation of the diamond surface prior to oxygen evolution. The extent of surface oxidation increased with sp2 content. Anodic polarization made the diamond surface hydrophilic; x‐ray photoelectron spectroscopy showed an increase in oxygen coverage and the presence of carbon‐oxygen bonds. The estimated capacitance of the interface ranged from 0.05 μF/cm2 for high quality diamond to 5 μF/cm2 for low quality diamond. Preliminary measurements of the exchange current densities for oxygen and hydrogen evolution indicated slow kinetics compared to metals or highly oriented pyrolytic graphite.

Electrodeposition of copper in the presence of additives mixture that is typically used in ''bottom-up'' fill of sub-micrometer vias and trenches on semiconductor wafers is analyzed. The time-dependent additives interactions, accounting for their transport and adsorption kinetics, are incorporated in a via-fill model. Transient polarization measurements provide the adsorption time constants for polyethylene glycol ͑PEG͒ and bis͑3-sulfopropyl͒ disulfide ͑SPS͒. Experiments indicate that the fast PEG adsorption on the electrode is diffusion controlled, while the slow SPS adsorption is controlled by the adsorption kinetics. The results are applied to a transport-kinetics model that provides the additives distribution inside a via. It is noted that the PEG diffusion to the via bottom is extremely slow due to the PEG adsorption on the sidewalls. The role of SPS in the bottom-up fill is characterized by simulating the transport within the via through analogous transport to a flat rotating disk electrode. It is observed that SPS is essential for maintaining fast deposition at the via bottom by preventing PEG adsorption. The critical necessity for a three-additive system comprised of chloride ions, PEG, and SPS is explained, and process parameters essential for bottom-up fill are identified.

In developing advanced fuel cells and other electrochemical reactors, it is desirable to combine the advantages of solid polymer electrolytes with the enhanced catalytic activity associated with temperatures above 100~ This will require polymer electrolytes which retain high ionic conductivity at temperatures above the boiling point of water. One possibility is to equilibrate standard perfluorosulfonic acid polymer electrolytes such as Nafion TM, with a high boiling point Bronsted base such as phosphoric acid. The Nafion/H3P04 electrolyte has been evaluated with respect to water content, ionic conductivity and transport of oxygen, and methanol vapor. The results show that at elevated temperatures reasonably high conductivity (>0.05 ~Q-1 cm-1) can be obtained. Methanol permeability is shown to be proportional to the methanol vapor activity and thus decreases with increasing temperature for a given methanol partial pressure. Comparisons and distinctions between this electrolyte and pure phosphoric acid are also considered.

Electrodeposition of copper in the presence of a multicomponent additives mixture, consisting of an inhibitor ͓e.g., poly͑ethylene glycol͔͒ and an accelerator ͓e.g., bis͑3-sulfopropyl͒ disulfide͔ that is typically used in the "bottom-up" fill of submicrometer vias and trenches on semiconductor wafers, is analyzed. The additives transport, adsorption, and interactions are incorporated in a time-dependent multicomponent model that provides the additives distribution inside the via. The additives distribution is translated into location-and time-dependent copper deposition rates to simulate the via-fill process. All model parameters are based on experimentally measured transient copper deposition kinetics in the presence of additives. The effect of the local area reduction during the via fill on the additives distribution is incorporated into the simulations. The model indicates that the short time scale additives transport and adsorption processes provide a differential additives coverage between the via top and its bottom sufficient to initiate bottom-up growth. The long time-scale accelerator-inhibitor interactions in combination with the local area reduction effects provide further enhancement to the additives-induced differential plating rates. The latter generates the bottom-up deposition necessary for the "void-free" gap fill of high aspect ratio structures.

The electro-osmotic drag coefficient of water in two polymer electrolytes was experimentally determined as a function of water activity and current density for temperatures up to 200°C. The results show that the electro-osmotic drag coefficient varies from 0.2 to 0.6 in Nafion®/H3P04 membrane electrolyte, but is essentially zero in phosphoric acid-doped FBI (polybenzimidazole) membrane electrolyte over the range of water activity considered. The near-zero electro-osmotic drag coefficient found in FBI indicates that this electrolyte should lessen the problems associated with water redistribution in proton exchange membrane fuel cells.