[交流] 【原创】Nature对耶鲁大学Jan Schroers教授非晶工作的报道

Nature 457, 762 (12 February 2009) | doi:10.1038/7231762a; Published online 11 February 2009 Making the paper: Jan Schroers Metallic glasses remove a barrier to moulding tiny components. Nanotechnology promises to transform industries as diverse as biomedicine, computing and optics, but crafting tiny components has proved challenging. One difficulty has been finding a low-cost, durable means of moulding features smaller than 100 nanometres into the materials currently used in the manufacture of devices such as next-generation DVDs and computer chips. Silicon-based moulds used to make the latter are brittle and short-lived, and although metals would offer stronger moulds, their grains are too large to be useful at the nanoscale. For the past ten years, physicist Jan Schroers and his team at Yale University have been exploring a class of amorphous — or noncrystalline — metals called bulk metallic glasses (BMGs), which have no grain-size limit. They have now found that BMGs could serve as both the mould and the material from which nanostructures are formed, or 'imprinted' — a breakthrough that promises to revolutionize materials science. "Metallic glasses always looked like the perfect materials on paper, but no one could form them into usable structures," says Schroers. Having had no luck treating the BMGs like metals, Schroers and his colleagues pursued a different path. "Amorphous metals such as BMGs are really nothing more than extremely slow-flowing liquids. This makes them unique among metals, and permits us to process them like plastics," says Schroers. He and his team found that heating BMGs to a certain temperature caused them to soften drastically to a point at which they took on complex shapes unachievable with any other metal. However, the method still didn't allow them to create nanoscale structures. Schroers knew they needed to determine what was happening physically that was preventing these structures from forming. The team predicted that, at dimensions smaller than 100 nanometres, high surface tension creates strong capillary forces between BMG molecules. These, the team surmised, were preventing BMGs from being moulded at nanoscale dimensions. The breakthrough came when postdoc Golden Kumar found that the capillary forces were drastically reduced when specific BMGs were combined with the aluminium materials usually used in imprinting. This led to the discovery that combinations of certain BMGs could, in effect, allow BMGs to be used both to mould and imprint devices — provided the BMG used for the mould was stronger than that used for imprinting. Whereas previously the minimum dimensions BMGs could be moulded with were about 100 nanometres, they are now just 13 nanometres, thanks to the technique outlined on page 868. And Schroers thinks he can make them even smaller. "Our amorphous metals should have a minimum size limitation of a single atom," he says. Schroers says that the most immediate application will be in the semiconductor industry, where it has long been hoped that nanoimprinting would replace the lithographic techniques currently used to make computer chips. These are too expensive to be commercially viable at the nanoscale because the silicon moulds are not durable enough to be cost-effective. The strength of BMGs should make nanoimprinting feasible. Schroers expects that other applications will soon follow in biomedical devices and data-storage products. "Plastics revolutionized society when they were first invented 50 years ago," he says. "I expect that will happen again as these metallic glasses combine the best of metals and plastics to eventually replace both." http://www.nature.com/nature/journal/v457/n7231/full/7231762a.html [ Last edited by hslining on 2009-9-10 at 14:40 ]

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