NEWS FROM THE WORLD OF MATERIALS

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Image in Focus

Nano Spaghetti & Meatballs
Colorized and overlaid scanning electron microscope images of "Spaghetti & Meatballs" made out of Au and Si. The 'spaghetti' is a collection of electrodeposited Au nanowires, 100 nm in diameter, that have been released from the substrate and bundled together. The 'meatballs' are Si nanoparticles, ~1.5 um in diameter, with Au nanocrystals on the surface that were grown on carbon-coated substrates using ultra-high vacuum molecular beam epitaxy.

(One of three first place winners of the the Science as Art competition at the 2009 MRS Spring Meeting. Submitted by Blythe G. Clark, Sandia National Lab., and Dan Gianola, Forschungszentrum Karlsruhe GmbH)

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Materials in Focus

Electric field acts as a switch in a multiferroic
Multiferroics are potential cornerstones in future magnetic data storage and spintronic devices, provided a simple and fast way can be found to turn their electric and magnetic properties on and off. A research group working with a prototypical multiferroic has successfully demonstrated just such a switch -- electric fields. Using electric fields, they were able to create, erase and invert p–n junctions in a calcium-doped bismuth ferrite multiferroic film.

Gold nanorods boost capacity of next-generation optical disks 
Traditional DVDs and Blu-ray optical disks store data in two dimensions and there's been a recent push to increase their capacity by creating multi-layered disks that store data across three dimensions. Researchers are now stepping into hyperspace, by encoding information in two new dimensions — the wavelength and polarization of the laser light used to write the data. The key was to find a material for the disk that could store this extra information. The ideal material contains gold, rod-shaped nanoparticles of different sizes and orientations. The team has demonstrated that by using two polarizations and three colors, one can pack 1.6 terabytes of data in one DVD-sized disk. A Blu-ray disk, by comparison, can store around 50 gigabytes. Adding an extra dimension by using another polarization could ramp that up further to 7.2 terabytes.

Carbon atomic wires obtained from graphene 
Researchers show that using a high-energy electron beam, they can transform graphite into graphene, and further into separate strings of carbon atoms in a transmission electron microscope. By focusing a high-energy, high-current beam on a spot on a carbon flake, they removed carbon atoms and thinned the flake until they were able to expose a single atomic carbon layer. Further irradiation at high energy and intensity produced two neighboring holes in the graphene layer, separated by a graphene nanoribbon, which they can continued to thin with more irradiation. At the last stage of narrowing the nanoribbon, when the two edges came together, the ribbon could be seen to break up into two parallel single-atom strands. The observed chains are longer than what has been previously observed, up to 2.1 nm, or 16 carbon atoms in a row.

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