Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Advance brings 'hyperbolic metamaterials' closer to reality

15.05.2014

Researchers have taken a step toward practical applications for "hyperbolic metamaterials," ultra-thin crystalline films that could bring optical advances including powerful microscopes, quantum computers and high-performance solar cells.

New developments are reminiscent of advances that ushered in silicon chip technology, said Alexandra Boltasseva, a Purdue University associate professor of electrical and computer engineering.


"Hyperbolic metamaterials" could bring optical advances including powerful microscopes, quantum computers and high-performance solar cells. The graphic at left depicts a metamaterial's "hyperbolic dispersion" of light. At center is a high-resolution transmission electron microscope image showing the interface of titanium nitride and aluminum scandium nitride in a "superlattice" that is promising for potential applications. At right are two images created using a method called fast Fourier transform to see individual layers in the material. (Purdue University image)

Optical metamaterials harness clouds of electrons called surface plasmons to manipulate and control light. However, some of the plasmonic components under development rely on the use of metals such as gold and silver, which are incompatible with the complementary metal–oxide–semiconductor (CMOS) manufacturing process used to construct integrated circuits and do not transmit light efficiently.

Now researchers have shown how to create "superlattice" crystals from layers of the metal titanium nitride and aluminum scandium nitride, a dielectric, or insulator. Superlattices are crystals that can be grown continuously by adding new layers, a requirement for practical application.

"This work is a very important step in terms of fundamental contributions in materials science and optics as well as paving the way to some interesting applications," Boltasseva said. "We believe this demonstration brings a paradigm shift to the field of metamaterials similar to developments that led to dramatic advances in silicon technology."

Research findings are detailed in a paper appearing this week in the online Early Edition of Proceedings of the National Academy of Sciences.

Researchers created the superlattices using a method called epitaxy, "growing" the layers inside a vacuum chamber with a technique known as magnetron sputtering. It is difficult to use the technique to create structures that have sharply defined, ultra-thin and ultra-smooth layers of two different materials.

"This is one of the first reports of a metal-dielectric epitaxial superlattice,"said Purdue doctoral student Bivas Saha, co-lead author of the PNAS paper with Gururaj V. Naik, a former Purdue doctoral student and now a postdoctoral scholar at Stanford University.

The list of possible applications for metamaterials includes a "planar hyperlens" that could make optical microscopes 10 times more powerful and able to see objects as small as DNA, advanced sensors, more efficient solar collectors, and quantum computing.

"Plasmonic and metamaterial devices require good material building blocks, both plasmonic and dielectric, in order to be useful in any real-world application," Boltasseva said. "Here, we develop both plasmonic and dielectric materials that can be grown epitaxially into ultra-thin and ultra-smooth layers with sharp interfaces."

Metamaterials have engineered surfaces that contain features, patterns or elements, such as tiny antennas or alternating layers of nitrides that enable unprecedented control of light. Under development for about 15 years, the metamaterials owe their unusual potential to precision design on the scale of nanometers.

The PNAS paper was authored by Naik; Saha; doctoral students Jing Liu and Sammy M. Saber; Eric Stach, a researcher at Brookhaven National Laboratory; Joseph Irudayaraj, a professor in Purdue's Department of Agricultural and Biological Engineering; Timothy D. Sands, executive vice president for academic affairs and provost and Basil S. Turner Professor of Engineering in the Schools of Materials Engineering and Electrical and Computer Engineering; Vladimir M. Shalaev, scientific director of nanophotonics at Purdue's Birck Nanotechnology Center and a distinguished professor of electrical and computer engineering; and Boltasseva.

"This work results from a unique collaboration between nanophotonics and materials science," Boltasseva said.

The hyperbolic metamaterial behaves as a metal when light is passing through it in one direction and like a dielectric in the perpendicular direction. This "extreme anisotropy" leads to "hyperbolic dispersion" of light and the ability to extract many more photons from devices than otherwise possible, resulting in high performance.

The layers of titanium nitride and aluminum scandium nitride used in this study are each about 5 to 20 nanometers thick. However, researchers have demonstrated that such superlattices can also be developed where the layers could be as thin as 2 nanometers, a tiny dimension only about eight atoms thick.

"People have tried for more than 50 years to combine metals and semiconductors with atomic-scale precision to build superlattices," Saha said. "However, this is one of the first demonstrations of achieving that step. The fascinating optical properties we see here are a manifestation of extraordinary structural control that we have achieved."

The feat is possible by choosing a metal and dielectric with compatible crystal structures, enabling the layers to grow together as a superlattice. The researchers alloyed aluminum nitride with scandium nitride, meaning the aluminum nitride is impregnated with scandium atoms to alter the material's crystal lattice to match titanium nitride's.

"The possibility of growing both metal and dielectric material components as a whole epitaxial system is indispensable for realizing high-performance metamaterials," Saha said. "One of the stumbling blocks is the fact that common dielectrics such as silica, alumina and other oxides cannot be used in combination with metallic components such as metal nitrides because the deposition processes are not compatible with each other."

Both of the materials should possess the same or compatible crystal structures.

"In general, a lattice mismatch of less than 5 percent is necessary for growing epitaxial quality films," he said.

A U.S. patent application has been filed through the Purdue Office of Technology Commercialization.

The material has been shown to work in a broad spectrum from near-infrared to visible light, potentially promising a wide array of applications.

"That's a novel part of this work - that we can create a superlattice metamaterial showing hyperbolic dispersion in the visible spectrum range," Boltasseva said.

The near-infrared is essential for telecommunications and optical communications, and visible light is important for sensors, microscopes and efficient solid-state light sources.

"Most interesting is the realm of quantum information technology," she said.

Computers based on quantum physics would have quantum bits, or "qubits," that exist in both the on and off states simultaneously, dramatically increasing the computer's power and memory. Quantum computers would take advantage of a phenomenon described by quantum theory called "entanglement." Instead of only the states of one and zero used in conventional computer processing, there are many possible "entangled quantum states" in between one and zero, increasing the capacity to process information.

The research has been funded in part by the U.S. Army Research Office and the National Science Foundation. 

Writer: Emil Venere, 765-494-4709, venere@purdue.edu  

Sources: Alexandra Boltasseva, 765-494-0301, aeb@purdue.edu 

Bivas Saha, bsaha@purdue.edu 

Emil Venere | Eurek Alert!
Further information:
http://www.purdue.edu/newsroom/releases/2014/Q2/advance-brings-hyperbolic-metamaterials-closer-to-reality.html

Further reports about: Computer Engineering Nanotechnology Optical PNAS Sciences lattice optics spectrum structures titanium vacuum

More articles from Materials Sciences:

nachricht New Multiferroic Materials from Building Blocks
29.09.2016 | National Institute for Materials Science

nachricht Silicon Fluorescent Material Developed Enabling Observations under a Bright “Biological Optical Window”
29.09.2016 | National Institute for Materials Science

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New welding process joins dissimilar sheets better

Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of light metals.
Scientists at the University of Stuttgart have now developed two new process variants that will considerably expand the areas of application for friction stir welding.
Technologie-Lizenz-Büro (TLB) GmbH supports the University of Stuttgart in patenting and marketing its innovations.

Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of...

Im Focus: First quantum photonic circuit with electrically driven light source

Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.

Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

HLF: From an experiment to an establishment

29.09.2016 | Event News

European Health Forum Gastein 2016 kicks off today

28.09.2016 | Event News

Laser use for neurosurgery and biofabrication - LaserForum 2016 focuses on medical technology

27.09.2016 | Event News

 
Latest News

New Multiferroic Materials from Building Blocks

29.09.2016 | Materials Sciences

Silicon Fluorescent Material Developed Enabling Observations under a Bright “Biological Optical Window”

29.09.2016 | Materials Sciences

X-shape Bio-inspired Structures

29.09.2016 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>