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).
Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern
20.07.2018 | Princeton University
Relax, just break it
20.07.2018 | DOE/Argonne National Laboratory
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences