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Nanofabrication method paves way for new optical devices
October 08, 2007EVANSTON, Ill. --- An innovative and inexpensive way of making nanomaterials on a large scale has resulted in novel forms of advanced materials that pave the way for exceptional and unexpected optical properties. The new fabrication technique, known as soft lithography, offers many significant advantages over existing techniques, including the ability to scale-up the manufacturing process to produce devices in large quantities.
The research, led by Northwestern University chemist Teri Odom, appears as the cover story in the September 2007 issue of the journal Nature Nanotechnology.
The optical nanomaterials in this research are called 'plasmonic metamaterials' because their unique physical properties originate from shape and structure rather than material composition only. Two examples of metamaterials in the natural world are peacock feathers and butterfly wings. Their brightly colored patterns are due to structural variations at the hundreds of nanometers level, which cause them to absorb or reflect light.
Through the development of a new nanomanufacturing technique, Odom and her colleagues have succeeded in making gold films with virtually infinite arrays of circular perforations as small as 100 nanometers in diameter -- 500 to 1,000 times smaller than the diameter of a human hair. On a magnified scale, these perforated gold films look like Swiss cheese except the perforations are well-ordered and can spread over macroscale distances. The researchers' ability to make these optical metamaterials inexpensively and on large wafers or sheets is what sets this work apart from other techniques.
"One of the biggest problems with nanomaterials has always been their 'scalability,'" said Odom, associate professor of chemistry in the Weinberg College of Arts and Sciences. "It's been very difficult or prohibitively expensive to pattern them over areas larger than about one square millimeter. This research is exciting not only because it demonstrates a new type of patterning technique that is cheap, but also one that can produce very high quality optical materials with interesting properties."
For example, if the perforations or holes are patterned into microscale "patches," they show dramatically different transmission behavior of light compared to an infinite array of holes. The patches appear to focus light while the infinite arrays do not.
Moreover, their optical transmission can be altered simply by changing the geometry of perforations rather than having to "cook" a new composition of materials. This feature makes them very attractive in terms of tuning their behavior to a given need with ease. These materials also can be superior as optical sensors, and they open the possibility of ultra-small sources of light. Furthermore, given their precise organization, they can serve as templates for making their own clones or for making other ordered structures at the nanoscale, such as arrays of nanoparticles.
"This work is exactly the kind of high-risk, high-potential transformative research NSF's Division of Materials Research is interested in supporting," said Harsh Deepak Chopra, program manager at the National Science Foundation (NSF), which funded the research. "The early results are extremely promising and suggest a whole new generation of optical devices."
Northwestern University
Through the development of a new nanomanufacturing technique, Odom and her colleagues have succeeded in making gold films with virtually infinite arrays of circular perforations as small as 100 nanometers in diameter -- 500 to 1,000 times smaller than the diameter of a human hair. On a magnified scale, these perforated gold films look like Swiss cheese except the perforations are well-ordered and can spread over macroscale distances. The researchers' ability to make these optical metamaterials inexpensively and on large wafers or sheets is what sets this work apart from other techniques.
"One of the biggest problems with nanomaterials has always been their 'scalability,'" said Odom, associate professor of chemistry in the Weinberg College of Arts and Sciences. "It's been very difficult or prohibitively expensive to pattern them over areas larger than about one square millimeter. This research is exciting not only because it demonstrates a new type of patterning technique that is cheap, but also one that can produce very high quality optical materials with interesting properties."
For example, if the perforations or holes are patterned into microscale "patches," they show dramatically different transmission behavior of light compared to an infinite array of holes. The patches appear to focus light while the infinite arrays do not.
Moreover, their optical transmission can be altered simply by changing the geometry of perforations rather than having to "cook" a new composition of materials. This feature makes them very attractive in terms of tuning their behavior to a given need with ease. These materials also can be superior as optical sensors, and they open the possibility of ultra-small sources of light. Furthermore, given their precise organization, they can serve as templates for making their own clones or for making other ordered structures at the nanoscale, such as arrays of nanoparticles.
"This work is exactly the kind of high-risk, high-potential transformative research NSF's Division of Materials Research is interested in supporting," said Harsh Deepak Chopra, program manager at the National Science Foundation (NSF), which funded the research. "The early results are extremely promising and suggest a whole new generation of optical devices."
Northwestern University
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North Carolina State University engineers have created a new material that would allow a fingernail-size computer chip to store the equivalent of 20 high-definition DVDs or 250 million pages of text, far exceeding the storage capacities of today's computer memory systems.
New insights into health and environmental effects of carbon nanoparticles
A new study raises the possibility that flies and other insects that encounter nanomaterial "hot spots," or spills, near manufacturing facilities in the future could pick up and transport nanoparticles on their bodies, transferring the particles to other flies or habitats in the environment.
Nanotech particles affect brain development in mice
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Remote-control closed system invented for inserting radio-active atoms inside fullerenes
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Research explores interactions between nanomaterials, biological systems
The recent explosion in the development of nanomaterials with enhanced performance characteristics for use in commercial and medical applications has increased the likelihood of people coming into direct contact with these materials.
Scientists advance safety of nanotechnology
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Novel approach estimates nanoparticles in environment
Without knowing how much of an industrial chemical is being produced, it is almost impossible for scientists to determine if it poses any threat to the environment or human health.
New Tool for Next-Generation Cancer Treatments using Nanodiamonds
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Nano-sandwich Triggers Novel Electron Behavior
A material just six atoms thick in which electrons appear to be guided by conflicting laws of physics depending on their direction of travel has been discovered by a team of physicists at the University of California, Davis. Working with computational models, the team has found that the electrons in a thin layer of vanadium dioxide sandwiched between insulating sheets of titanium dioxide exhibit one set of properties when moving in forward-backward directions, and another set when moving left to right.
Revealing new applications for carbon nanomaterials in hydrogen storage
An international research team, involving Professor Rajeev Ahuja at Uppsala University and researchers in the USA, set out to understand the mechanism behind the catalytic effects of carbon nanomaterials.
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