No abstract

A method to calculate the location of all Bragg diffraction peaks from nanostructured thin films for arbitrary angles of incidence from just above the critical angle to transmission perpendicular to the film is reported. At grazing angles, the positions are calculated using the distorted wave Born approximation (DWBA), whereas for larger angles where the diffracted beams are transmitted though the substrate, the Born approximation (BA) is used. This method has been incorporated into simulation code (called NANOCELL) and may be used to overlay simulated spot patterns directly onto two-dimensional (2D) grazing angle of incidence small-angle X-ray scattering (GISAXS) patterns and 2D SAXS patterns. The GISAXS simulations are limited to the case where the angle of incidence is greater than the critical angle (alpha(i) > alpha(c)) and the diffraction occurs above the critical angle (alpha(f) > alpha(c)). For cases of surfactant self-assembled films, the limitations are not restrictive because, typically, the critical angle is around 0.2 degrees but the largest d spacings occur around 0.8 degrees 2theta. For these materials, one finds that the DWBA predicts that the spot positions from the transmitted main beam deviate only slightly from the BA and only for diffraction peaks close the critical angle. Additional diffraction peaks from the reflected main beam are observed in GISAXS geometry but are much less intense. Using these simulations, 2D spot patterns may be used to identify space group, identify the orientation, and quantitatively fit the lattice constants for SAXS data from any angle of incidence. Characteristic patterns for 2D GISAXS and 2D low-angle transmission SAXS patterns are generated for the most common thin film structures, and as a result, GISAXS and SAXS patterns that were previously difficult to interpret are now relatively straightforward. The simulation code (NANOCELL) is written in Mathematica and is available from the author upon request.

Preparation of well-ordered continuous mesoporous carbon films without the use of an intermediate inorganic template was achieved by spin coating of a thermosetting phenolic resin, resorcinol/phloroglucinol/formaldehyde, and a thermally-decomposable organic template, Pluronic F127 (PEO 106 -PPO 70 -PEO 106 ). The carbon films were deposited onto silicon, platinum/ silicon, copper, glass, and quartz substrates. Afterwards, decomposition of the organic template and solidification of the carbon precursors are simultaneously performed through a carbonization process. The resulting films referred to as CKU-F69, are (010)-oriented, and possess a facecentered orthorhombic Fmmm symmetry. Film periodicity is maintained even after a 68% uniaxial contraction perpendicular to the substrate brought on by carbonization at 800 uC. This method could facilitate the mass-production and creation of new carbon and carbon-polymer porous films that find broad potential applications in catalysis, separation, hydrogen storage, bioengineering, nanodevices, and nanotemplates.

Nanoporous silica films with the double-gyroid structure offer tremendous technological potential for sensors and separations because of their high surface area and potentially facile transport properties. Further, metals and semiconductors with similar structure open up new opportunities for high-surfacearea electrodes, photoelectrochemical devices, photovoltaics, and thermoelectrics. Here, we report a new robust synthesis of highly ordered nanoporous silica films with the double-gyroid structure by evaporationinduced self-assembly (EISA) at room temperature and laboratory humidity using a commercially available EO 17 -PO 12 -C 14 surfactant. The continuous nanoporous films are synthesized on conducting electrodes. Electrochemical impedance spectroscopy is then used to quantitatively measure the accessible surface area of the underlying electrode via transport through the pore system. It is found that the double-gyroidstructure silica films expose a much higher fraction of the electrode than other commonly synthesized nanostructures such as 2D centered rectangular or 3D rhombohedral nanostructures. The double-gyroid nanoporous-film-coated electrodes are then used to fabricate inverse double-gyroid platinum nanostructures by electrodeposition, followed by etching to remove the silica. The structure of both the nanoporous silica films and the nanoporous platinum films (after etching) have been elucidated using high-resolution field-emission scanning electron microscopy (FESEM), comparing measured and simulated 2D grazing angle-of-incidence small-angle X-ray scattering (GISAXS) patterns, and comparing observed and simulated transmission electron microscopy (TEM) images. Both films are highly (211) oriented and described by a cubic Ia3 hd space group that has undergone uniaxial contraction perpendicular to the substrate. Upon this contraction, Ia3 hd symmetry is broken, but the films retain the double-gyroid topology. The nanoporous silica and the platinum nanowires have a characteristic wall or wire thicknesses of approximately 3 nm. This nanofabrication process opens up a facile general route for fabrication of ordered structures on the sub-5 nm length scale.

The Porcupine Seabight Basin is a north‐south trending, extensional sedimentary basin situated on the continental shelf west of Ireland. It is filled with sedimentary rocks which range in age from Devonian to present‐day. A large amount of geological and geophysical data is now available for this basin, mainly as a result of oil industry exploration. In this paper, information from 23 well logs and from regional seismic reflection surveys is used to determine the lithospheric stretching history of the basin. Subsidence analyses indicate that there was one main phase of stretching which began in late Liassic times (∼ 180 Ma), ending in earliest Cretaceous (∼ 145 Ma). Stretching factors at the northern end of the basin are relatively small (β = 1.1–1.7) but increase rapidly southwards along the axis of the Main Porcupine Basin. In the southern part of the region (the Seabight Basin), β is greater than 6. The simplest way to accommodate this rapid variation in stretching is by clockwise rotation of the Porcupine Ridge through approximately 20°, away from the Irish Shelf. Subsidence‐derived stretching values are in reasonable agreement with those determined previously from crustal thicknesses based on gravity models and deep seismic data (normal incidence and wide‐angle). The existence, location, and inferred age of the Porcupine Median Volcanic Ridge are also consistent with the subsidence‐derived stretching factors. After intermittent Paleocene igneous activity, an anomalous increase in the rate of subsidence occurred in the Eocene, between 55 and 42 Ma. There is little evidence that this rapid increase is caused by lithospheric stretching, and we conclude that it must be associated in some unknown way with melt generated by development of the Iceland hotspot.