David D. Allred received Alumni Professorship Award

A series of multislice simulations to quantify the effect of various degrees of order, composition, and thickness on the electron diffracted intensities were performed using the L1(0) FePt system as the case study. The dynamical diffraction studies were done in both a convergent electron beam diffraction and selected area electron diffraction condition. The L1(0) symmetry demonstrated some peculiar challenges in the simulation, in particular between the {111} plane normal and the < 111 > direction, which are not equivalent because of tetragonality. A hybrid weighting function atom of Fe-Pt was constructed to account for S < 1 or nonequiatomic compositions. This statistical approach reduced the complexity of constructing a crystal with the probability that a particular atom was at a particular lattice site for a given order parameter and composition. Considerations of accelerating voltage, convergent angle, and thermal effects are discussed. The simulations revealed significant differences in intensity ratios between films of various compositions but equivalent unit cell numbers and degree of order.

Eight FePt thin film specimens of various thicknesses, compositions, and order parameters have been analyzed to determine the robustness and fidelity of multislice simulations in determining the chemical order parameter via electron diffraction (ED). The shape of the simulated curves depends significantly on the orientation and thickness of the specimen. The ED results are compared to kinematical scattering order parameters, from the same films, acquired from synchrotron X-ray diffraction (XRD). For the specimens analyzed with convergent beam electron diffraction conditions, the order parameter closely matched the order parameter as determined by the XRD methodology. However, the specimens analyzed by selected area electron diffraction conditions did not show good agreement. This has been attributed to substrate effects that hindered the ability to accurately quantify the intensity values of the superlattice and fundamental reflections.

Carbon-nanotube-templated microfabrication (CNT-M) of porous materials is demonstrated. Partial chemical infiltration of 3D carbon-nanotube structures with silicon results in a mechanically robust material, structured from the 10 nm scale to the 100 μm scale. The nanoscale dimensions are determined by the diameter and spacing of the resulting silicon/carbon nanotubes, while the microscale dimensions are controlled by the lithographic patterning of the CNT growth catalyst. We demonstrate the utility of this hierarchical structuring approach by using CNT-M to fabricate thin-layer-chromatography (TLC) separations media with precise microscale channels for fluid-flow control and nanoscale porosity for high analyte capacity. Chemical separations done on the CNT-M-structured media outperform commercial high-performance TLC media.

Here, the authors report the fabrication of transparent polymer templates for nanostructured amorphous siliconphotovoltaics using low-cost nanoimprint lithography of polydimethylsiloxane. The template contains a square two-dimensional array of high-aspect-ratio nanoholes (300 nm diameter by 1 μm deep holes) on a 500×500 nm2 pitch. A 100 nm thick layer of a-Si:H was deposited on the template surface resulting in a periodically nanostructured film. The optical characterization of the nanopatterned film showed lower light transmission at 600–850 nm wavelengths and lower light reflection at 400–650 nm wavelengths, resulting in 20% higher optical absorbance at AM 1.5 spectral irradiance versus a nonpatterned film.

The plastic substrates, reflective layers, dyes, and adhesives of four archival-grade, recordable DVDs and one standard-grade recordable DVD were analyzed to determine their chemical compositions and/or physical dimensions. Chemical analyses by attenuated total internal reflection Fourier transform infrared spectroscopy, time-of-flight secondary ion mass spectrometry, x-ray photoelectron spectroscopy, energy-dispersive x-ray/scanning transmission electron microscopy, and Rutherford backscattering spectrometry show that all these DVDs use very similar polycarbonate plastic substrates and acrylate-based adhesives, but different reflective layers and dye write layers. In addition, physical measurements by atomic force microscopy show differences in the DVD groove depth, width, and other dimensions. These chemical and physical analyses may help explain variations in DVD lifetimes and facilitate development of the next-generation archival-grade DVDs. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3529981]