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Thursday, 21 July 2011

Making Stuff with Molecular Precision

Technology Review
July 21, 2011

For more than a decade, scientists have been touting the promise of nanomaterials as a source of new and better products, from stronger structural materials to speedy but power-efficient computers to drugs that target and kill diseased cells. But making commercial products from nanomaterials is tricky.

In these materials, tiny structural changes lead to very different properties, and precision manufacturing is critical. For example, making a structural material from slightly larger or smaller nanoparticles can dramatically affect its strength or toughness. In a nanotube integrated circuit, a single misaligned tube can cause a short, and a nanotube slightly too big or small in diameter can change the operating voltage. "You have to tune your dimensions very carefully to get the desired behavior," says Placid Ferreira, associate director of the Center for Nanoscale Chemical-Electrical-Mechanical Manufacturing Systems at the University of Illinois at Urbana-Champaign. "In order to exploit nanoscale phenomena in products, you need to have manufacturing tools that give you precision, in quantity, and cheaply."

The semiconductor industry has been tremendously successful at making chips by laying down thin films on the surface of silicon wafers. But chip makers are continually scaling down transistors to pack more computing power in each chip; chips in the generation that will hit the market in the coming months have transistors that measure just 22 nanometers. At such small sizes, defects at the molecular and even atomic scale become more problematic, so semiconductor equipment makers such as ASM and Applied Materials keep providing ever more precise and expensive tools. In one manufacturing technique, parts of the transistor structure are laid down one atomic layer at a time. When manufacturing layered structures this thin, contamination by just a few atoms can significantly degrade a chip's speed and energy efficiency
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