Distinguishing physical mechanisms using GISAXS experiments and linear theory: the importance of high wavenumbers.

In this work we analyze GISAXS measurements of the structure factor of Si surfaces evolving during 1 keV Ar+ ion bombardment. Using newly-developed methods sensitive to the full range of experimentally-available wavenumbers q, we extract the linear amplification rate R(q) governing surface stability over a range of wavenumbers 4-5 times larger than has previously been obtained. Comparing with theoretical models also retaining full wavenumber-dependence, we find an excellent fit of the experimental data over the full range of irradiation angles and wavenumbers.

Simultaneous detection of electronic structure changes from two elements of a bifunctional catalyst using wavelength-dispersive X-ray emission spectroscopy and in situ electrochemistry.

Multielectron catalytic reactions, such as water oxidation, nitrogen reduction, or hydrogen production in enzymes and inorganic catalysts often involve multimetallic clusters. In these systems, the reaction takes place between metals or metals and ligands to facilitate charge transfer, bond formation/breaking, substrate binding, and release of products. In this study, we present a method to detect X-ray emission signals from multiple elements simultaneously, which allows for the study of charge transfer and the sequential chemistry occurring between elements.

Oxygen-atom transfer chemistry and thermolytic properties of a di-tert-butylphosphate-ligated Mn4O4 cubane.

[Mn4O4{O2P(OtBu)2}6] (1), an Mn4O4 cubane complex combining the structural inspiration of the photosystem II oxygen-evolving complex with thermolytic precursor ligands, was synthesized and fully characterized. Core oxygen atoms within complex 1 are transferred upon reaction with an oxygen-atom acceptor (PEt3), to give the butterfly complex [Mn4O2{O2P(OtBu)2}6(OPEt3)2]. The cubane structure is restored by reaction of the latter complex with the O-atom donor PhIO.

Efficient and sustained photoelectrochemical water oxidation by cobalt oxide/silicon photoanodes with nanotextured interfaces.

Plasma-enhanced atomic layer deposition of cobalt oxide onto nanotextured p(+)n-Si devices enables efficient photoelectrochemical water oxidation and effective protection of Si from corrosion at high pH (pH 13.6). A photocurrent density of 17 mA/cm(2) at 1.

Photofunctional construct that interfaces molecular cobalt-based catalysts for H2 production to a visible-light-absorbing semiconductor.

Molecular cobalt-containing hydrogen production catalysts are grafted to a visible-light-absorbing semiconductor. The attachment procedure exploits the UV-induced immobilization chemistry of vinylpyridine to p-type (100) gallium phosphide (GaP). Single step surface-initiated photopolymerization yields a covalently attached polymer with pendent pyridyl groups that provide attachment points for assembling cobaloxime catalysts.

Evidence for Family-Meakin dynamical scaling in island growth and coalescence during vapor phase deposition.

Using real-time grazing-incidence small-angle x-ray scattering, we find that the processes of island formation and coalescence during the room-temperature vapor phase deposition of aluminum lead to dynamical scaling of the evolving surface morphology. The scaling is quantitatively consistent with the self-similarity predicted by the Family-Meakin model, which was developed to describe liquid droplet deposition, growth, and coalescence. The Family-Meakin model assumes only that atomic diffusion over the substrate between islands or droplets is negligible and that diffusion between impinging islands or droplets is sufficient to give complete coalescence.

Mass redistribution causes the structural richness of ion-irradiated surfaces.

We show that the "sputter patterning" topographical instability is determined by the effects of ion impact-induced prompt atomic redistribution and that erosion--the consensus predominant cause--is essentially irrelevant. We use grazing incidence small angle x-ray scattering to measure in situ the damping of noise or its amplification into patterns via the linear dispersion relation. A model based on the effects of impact-induced redistribution of those atoms that are not sputtered away explains both the observed ultrasmoothening at low angles from normal incidence and the instability at higher angles.