We used electron-energy-loss spectrometry to measure the intensities of the white lines found at the onsets of the L2 and L3 absorption edges for most of the 3d and 4d transition metals. The intensities of the white lines, normalized to the trailing background, decreased nearly linearly with increasing atomic number, rejecting the filling of the d states. One-electron Hartree-Slater calculations of the white-line intensities were in good agreement with observed spectra. Empirical correlations between normalized white-line intensity and d-state occupancy provide a method for measuring changes in d-state occupancy due to alloying.
We report a linear correlation between the total intensities of the L2,3 white lines in electron energy loss spectra and the number of unoccupied 3d states in 3d transition metals. We show that this correlation can be used to obtain quantitative information about electronic changes during alloying and during solid-state phase transformations.
The preparation of thin metallic membranes containing uniform, patterned voids with diameters as small as 40 nanometers and packing densities greater than 3 x 1 O9 voids per square centimeter is described. These membranes, made of platinum, gold, tungsten, and molybdenum, have been fabricated by thin-film deposition with nanochannel glass wafers as substrates. The membranes are well suited for use as masks in substrate patterning applications such as ion implantation, reactive ion etching, and materials deposition. Results are presented on their use in the parallel patterning of silicon by direct materials deposition with features in the 100-nanometer size regime.T h e scientific and technological interest in materials engineered on a nanometer scale is widespread, impacting research and development in many disciplines. These materials have found use in electronic and optical devices ( I ), filtration (2), and biomedical applications (3, 4). In addition, these materials provide an opportunity to study quantum effectylot observed in bulk materials.In this report we describe the fabrication and patterning applications of nanochannel glass replica membranes. These membranes, prepared thus far from refractory and noble metals, are thin films that contain uniform. nanometer-scale voids, the sizes, positions, geometric patterns, and packing densities of which may be controlled to a high degree. In addition, the thicknesses of the membranes. and thus the asvect ratios of the voids, may also be controlled. These properties make nanochannel glass revlica mem--branes somewhat different than polymeric track-etch membranes and porous alumina membranes, which have been used in replication studies (5), as hosts for the fabrication of other materials (3, 6), and as electrochemically switchable filters (7). Currently, we have prepared tungsten, molybdenum, platinum, and gold membranes with void diameters as small as 40 nm at packing densities greater than 3 x lo9 voids per square centimeter. The aspect ratios of the voids present in these membranes have ranged from 0.06 to approximately 2, reflecting our primary interest in low-aspectratio masks for patterning applications.The processes used in the preparation of these membranes, however, are not limited to the materials nor the asDect ratios listed above. In principle, membranes with larger aspect ratios may be prepared, and other materials that can be deposited by physical vapor deposition may be used, provided the resulting membranes possess the necessary robust character and chemical stability to withstand the processing conditions en-
We demonstrate the ability to fabricate large-scale patterned two-dimensional arrays of identical nanometer size metallic wires with high aspect ratios and packing densities of greater than 3 X 10' elements/cm2. The arrays are made by electrodeposition into nanochannel glass templates. Scanning electron microscopy and tunneling electron microscopy have been used to characterize the nanostructures. Magnetic characterizations of the ferromagnetic wire arrays using a superconducting quantum interference device magnetometer and a magnetic force microscope reveal one-dimensional characteristics with preferred magnetization direction perpendicular to the array film plane and enhanced coercivities compared to the bulk values. Preliminary results on fabrication of nanometer size metallic tubes are also presented. InfroductionNanostructured materials exhibit a host of interesting new phenomena directly related to their reduced dimensionality. They provide a means of studying quantum size effects, excitons, and electron-electron interactions.1'2 Magnetic nanostructures such as nanometer scale particles and wires tend to be single-domain with large coercive fields and high remanent magnetizations.3'4 The abil-
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