Molecular Random-Access Memory Cell Demonstrated
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Extending their Monte Carlo simulation to three dimensions, the researchers said it elucidates the process and the mechanism of the nanoporosity evolution in selective dissolution. HAILONG HUANG
Molecular Random-Access Memory Cell Demonstrated As a result of the common computer user’s demands, both the software and hardware industries are struggling to push technological resources to the farthest limits possible. However, the traditional limits appear to be not that far away, so research focuses on faster and smaller microprocessors, faster and larger memory, and larger data-storage capabilities, for example. Researchers at Yale and Rice Universities have developed and demonstrated devices that exhibit electronically programmable and erasable memory bits compatible with conventional threshold levels, but at a molecular monolayer level. They reported their work in the May 28 issue of Applied Physics Letters. Electronic memories that operate at the charge limit (single electron effects) have been previously demonstrated by other research teams, but without addressing yet the dimensional limit of a single molecule, which this team now believes is achievable. They have observed a charge storage in a self-assembled nanoscale molecular device that is operated as a random-access memory with practical thresholds and output under natural ambient operation, and with a bit retention time of 15 min. They said that their device can potentially be scaled to the single-molecule level. The molecular systems investigated were Au-(1)-Au (1: 2’-amino-4-ethynylphenyl-4’ethynylphenyl-5’-nitro-1-benzenethiolate); Au-(2)-Au (2: 4-ethynylphenyl-4’-ethynylphenyl-2’-nitro-1-benzenethiolate); Au-(3)Au (3: 2’-amino-4-ethynylphenyl-4’ethynylphenyl-1-benzenethiolate); and Au(4)-Au (4: 4-ethynylphenyl-4’-ethynylphenyl-1-benzenethiolate). The first two combinations were observed to change conductivity state upon application of a voltage pulse, indicating the responsible molecular moiety. Although the size of the nanoscale structures built was determined by the limitations of the lithographic technique used for defining the contacts, there are no indications in the observed characteristics that limitations exist in scaling down to one the number of molecules in the active region of the device, assuming that an appropriate fabrication scheme can be identified. CLAUDIU MUNTELE
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Use of Area Array Detector for X-Ray Fluorescence Holography Allows Simultaneous Recording of the Full Hologram without Sacrificing Angular Accuracy Holography has traditionally, as in the case of lasers, been limited by the radiation wavelength, the source size, and the detector resolving power. X-ray fluorescence holography (XFH) has recently been studied as a method for creating holograms of bulk structures with atomic-scale resolution. The primary hurdle to developing XFH into a practical investigative tool has been the difficulty associated with measuring the fluorescent radiation with an acceptable signal-to-noise ratio. While typically a solid-state detector with
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