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Honolulu, Hawaii, United States, 2006/10/27 - Affordable surfaces with well-controlled nanostructures over a large area open new applications not only in electronics but also in the physical world through their unique properties originating from their nanoscale geometry.
As scientific interests and engineering applications delve down to the nanometer scale, there is a strong need to fabricate nanostructures with good regularity and controllability of their pattern, size, and shape. Furthermore, the nanostructures are useful in many applications only if they cover a relatively large sample area and the manufacturing cost is reasonable. Researchers at UCLA have now achieved a breakthrough by developing a simple but efficient fabrication method to produce well-regulated silicon nanostructures over a large sample area with excellent control of their pattern, size, and shape. Affordable surfaces with well-controlled nanostructures over a large area open new applications not only in electronics but also in the physical world through their unique properties originating from their nanoscale geometry.
While several nanoscale patterning techniques are known and available, most of them involve a serial method such as e-beam lithography inapt for covering areas larger than squre millimeters. X-ray lithography is parallel and can pattern a large area, but it is too expensive for most applications. Soft lithography-based fabrication, such as nanoimprinting, replicates patterns in a parallel fashion, but it still needs a master mold first manufactured by e-beam or X-ray lithography. Most non-lithographic methods, such as the use of nanotemplates (e.g., copolymers) or the direct growth of nanostructures (e.g., carbon nanotubes), lack the regularity some applications demand over a large area.
Professor Chang-Jin "CJ" Kim and Chang-Hwan Choi from the Micro- and Nanomanufacturing Laboratory at UCLA's Mechanical and Aerospace Engineering Department, came up with a simple but efficient nanofabrication method to create a dense (nanoscale pitch) array of silicon nanostructures (post and grate) of varying height and shape over a large sample area.
Choi explained their findings to Nanowerk: "We coupled interference lithography with deep reactive ion etching (DRIE), which is a new nanofabrication approach. Interference lithography is currently considered the most efficient way to make submicron-scale periodic patterns over a large area (up to a meter range, reportedly) with excellent control of pattern regularity. Although DRIE has rarely been used to construct nanostructures because the rippling of sidewalls (so-called ‘scalloping effect’) is too prominent on the nanoscale, we demonstrated that a common DRIE process could produce well-defined tall nanostructures by controlling etching parameters and even tailor the sidewall profiles of the nanostructures as desired."
Read the full article on the Nanowerk website.
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By Michael Berger, Copyright 2006 Nanowerk LLC