The use of a fabrication technique borrowed from the semiconductor industry brings metamaterial applications a step closer to reality
Artificial materials engineered to have properties not found in nature, such as a negative refractive index
are engineered to interact with light and sound waves in ways that natural materials cannot. They thus have the potential to be used in exciting new applications, such as invisibility cloaks, high-resolution lenses, efficient and compact antennas, and highly sensitive sensors.
While the theory of this interaction is relatively well understood, it has been challenging to fabricate metamaterials that are large enough to be practical. Now, Yi Zhou and colleagues at the A*STAR Data Storage Institute in Singapore have demonstrated a promising new fabrication technique that can produce large areas of an important class of metamaterial, known as fishnet metamaterials1.
Most optical metamaterials consist of tiny repeated metallic structures. When light of a particular frequency falls on them, it establishes oscillating fields inside each structure. These fields can resonate with each other and thereby produce desirable collective behavior. Fishnet metamaterials usually have several vertically stacked repeat units spread out over much larger lateral dimensions. Because they are structured both vertically and laterally, they are called three-dimensional materials.
Fishnet metamaterials are usually made in one of two ways. They can be fabricated by carefully patterning individual films and then stacking these films on top of each other. However, this multilayer process is difficult, as it requires careful alignment of the films.
The second approach is to pattern a sacrificial substrate and then deposit repeated layers onto it. This ‘pattern-first’ process suffers from its own difficulties, the most important of which is that the total thickness of the final fishnet material is typically limited to tens of nanometers or less. This restricts the kind of resonances that can be achieved and, in turn, the functionality of the final film.
Zhou and colleagues were able to increase the total thickness of pattern-first fishnet films to around 300 nanometers, allowing five bilayers of film to be deposited and resulting in a strong characteristic resonance and pronounced metamaterial behavior. To achieve this, they adopted a technique called trilayer lift-off, which is commonly used in industry but seldom applied in research laboratories. It involves patterning a sacrificial layer of a photoresist resting on a layer of silicon dioxide under which lies a second photoresist layer.
By alternating the patterning and etching steps, the A*STAR team could achieve a film thickness greatly exceeding the size of the lateral patterns etched into the film. “This technique will help researchers design large-area three-dimensional nanodevices more easily,” says Zhou, “and help bring the science of metamaterials to reality.”
The A*STAR-affiliated researchers contributing to this research are from the Data Storage Institute
Zhou, Y., Chen, X. Y., Fu, Y H., Vienne, G., Kuznetsov, A. I., & Luk’yanchuk, B. Fabrication of large-area 3D optical fishnet metamaterial by laser interference lithography. Applied Physics Letters 103, 123116 (2013).
3-D-printed structures 'remember' their shapes
29.08.2016 | Massachusetts Institute of Technology
Crystal unclear: Why might this uncanny crystal change laser design?
29.08.2016 | National Institute of Standards and Technology (NIST)
Scientists at the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute, HHI have developed a method by which the realistic image of a person can be transmitted into a virtual world. The 3D Human Body Reconstruction Technology captures real persons with multiple cameras at the same time and creates naturally moving dynamic 3D models. At this year’s trade fairs IFA in Berlin (Hall 11.1, Booth 3) and IBC in Amsterdam (Hall 8, Booth B80) Fraunhofer HHI will show this new technology.
Fraunhofer HHI researchers have developed a camera system that films people with a perfect three-dimensional impression. The core of this system is a stereo...
Scientists and engineers striving to create the next machine-age marvel--whether it be a more aerodynamic rocket, a faster race car, or a higher-efficiency jet...
Waveguides are widely used for filtering, confining, guiding, coupling or splitting beams of visible light. However, creating waveguides that could do the same for X-rays has posed tremendous challenges in fabrication, so they are still only in an early stage of development.
In the latest issue of Acta Crystallographica Section A: Foundations and Advances , Sarah Hoffmann-Urlaub and Tim Salditt report the fabrication and testing of...
Electrochemists at TU Graz have managed to use monocrystalline semiconductor silicon as an active storage electrode in lithium batteries. This enables an integrated power supply to be made for microchips with a rechargeable battery.
Small electrical gadgets, such as mobile phones, tablets or notebooks, are indispensable accompaniments of everyday life. Integrated circuits in the interiors...
Recent findings indicating the possible discovery of a previously unknown subatomic particle may be evidence of a fifth fundamental force of nature, according...
25.08.2016 | Event News
24.08.2016 | Event News
12.08.2016 | Event News
31.08.2016 | Life Sciences
31.08.2016 | Power and Electrical Engineering
31.08.2016 | Life Sciences