In an advance that could boost the efficiency of LED lighting by 50 percent and even pave the way for invisibility cloaking devices, a team of University of Michigan researchers has developed a new technique that peppers metallic nanoparticles into semiconductors.
It’s the first technique that can inexpensively grow metal nanoparticles both on and below the surface of semiconductors. The process adds virtually no cost during manufacturing and its improved efficiency could allow manufacturers to use fewer semiconductors in finished products, making them less expensive.
The metal nanoparticles can increase the efficiency of LEDs in several ways. They can act as tiny antennas that alter and redirect the electricity running through the semiconductor, turning more of it into light. They can also help reflect light out of the device, preventing it from being trapped inside and wasted.
The main growth chamber of the molecular epitaxy beam apparatus used to make the nanoparticle-infused gallium nitride semiconductors. The semiconductors could boost LED efficiency by up to 50 percent, and even lead to invisibility cloaking devices.
Image credit: Joseph Xu, Michigan Engineering
The process can be used with the gallium nitride that’s used in LED lighting and can also boost efficiency in other semiconductor products, including solar cells. It’s detailed in a study published in the Journal of Applied Physics.
“This is a seamless addition to the manufacturing process, and that’s what makes it so exciting,” said Rachel Goldman, U-M professor of materials science and engineering, and physics. “The ability to make 3-D structures with these nanoparticles throughout is going to open a lot of possibilities.”
The key innovation
The idea of adding nanoparticles to increase LED efficiency is not new. But previous efforts to incorporate them have been impractical for large-scale manufacturing. They focused on pricey metals like silver, gold and platinum. In addition, the size and spacing of the particles must be very precise; this required additional and expensive manufacturing steps. Furthermore, there was no cost-effective way to incorporate particles below the surface.
Former materials science PhD student Sunyeol Jun prepares the molecular beam epitaxy apparatus that’s used to make the nanoparticle-infused gallium nitride semiconductors. The semiconductors could boost LED efficiency by up to 50 percent, and even lead to invisibility cloaking devices.
Image credit: Joseph Xu, Michigan Engineering
Goldman’s team discovered a simpler way that integrates easily with the molecular beam epitaxy process used to make semiconductors. Molecular beam epitaxy sprays multiple layers of metallic elements onto a wafer. This creates exactly the right conductive properties for a given purpose.
The U-M researchers applied an ion beam between these layers—a step that pushes metal out of the semiconductor wafer and onto the surface. The metal forms nanoscale particles that serve the same purpose as the pricey gold and platinum flecks in earlier research. Their size and placement can be precisely controlled by varying the angle and intensity of the ion beam. And applying the ion beam over and over between each layer creates a semiconductor with the nanoparticles interspersed throughout.
“If you carefully tailor the size and spacing of nanoparticles and how deeply they’re embedded, you can find a sweet spot that enhances light emissions,” said Myungkoo Kang, a former graduate student in Goldman’s lab and first author on the study. “This process gives us a much simpler and less expensive way to do that.”
A microscopy photo showing an array of precisely placed metallic nanoparticles on the surface of a gallium arsenide semiconductor.
Image courtesy: Rachel S. Goldman, Michigan Engineering
Researchers have known for years that metallic particles can collect on the surface of semiconductors during manufacturing. But they were always considered a nuisance, something that happened when the mix of elements was incorrect or the timing was off.
“From the very early days of semiconductor manufacturing, the goal was always to spray a smooth layer of elements onto the surface. If the elements formed particles instead, it was considered a mistake,” Goldman said. “But we realized that those ‘mistakes’ are very similar to the particles that manufacturers have been trying so hard to incorporate into LEDs. So we figured out a way to make lemonade out of lemons.”
Toward invisibility cloaks
Because the technique allows precise control over the nanoparticle distribution, the researchers say it may one day be useful for cloaks that render objects partially invisible by inducing a phenomenon known as “reverse refraction.”
Reverse refraction bends light waves backwards in a way that doesn’t occur in nature, potentially directing them around an object or away from the eye. The researchers believe that by carefully sizing and spacing an array of nanoparticles, they may be able to induce and control reverse refraction in specific wavelengths of light.
“For invisibility cloaking, we need to both transmit and manipulate light in very precise ways, and that’s very difficult today,” Goldman said. “We believe that this process could give us the level of control we need to make it work.”
The team is now working to adapt the ion beam process to the specific materials used in LEDs—they estimate that the higher-efficiency lighting devices could be ready for market within the next five years, with invisibility cloaking and other applications coming further in the future.
The Latest on: Invisibility cloaking devices
- Trump Continues to Claim F-35 Jets Are Literally Invisible: ‘They’re Stealth, You Can’t See Them’ on November 15, 2018 at 2:08 pm
Someone might want to check and see if Donald Trump knows that the stealth capabilities of an F-35 fighter jet aren’t the same thing as a cloaking device. The president ... they are not literally “inv... […]
- Comic strip shines light on Israeli invisibility research on November 12, 2018 at 11:20 pm
In 2012, he received an ERC grant to support his project, “Transformation Optics: Cloaking, Perfect Imaging and ... Could a person be made invisible? “An invisibility device has never been made — it’s ... […]
- My iPhone has become my all-situations security blanket on November 7, 2018 at 3:13 pm
My iPhone works as a security blanket, it's my invisibility cloak. It works in all situations ... Screen Time feature was so people could better understand and manage their device usage "By understand... […]
- New cloaking technique lets light pass right on through on August 27, 2018 at 1:02 am
The concept of an invisibility cloak sounds like pure science fiction, but hiding something from view is theoretically possible, and in some very-controlled cases it's experimentally possible too. Now ... […]
- Spectral cloaking could make objects invisible under realistic conditions on August 11, 2018 at 11:39 am
wearable invisibility cloak, the demonstrated spectral cloaking device could be useful for a range of security goals. For example, current telecommunication systems use broadband waves as data signals ... […]
- Harry Potter’s invisibility cloak could soon be a reality on June 29, 2018 at 7:03 am
Scientists are a step closer to a “Harry Potter”-style invisibility cloak. They have developed a device that makes solid objects completely vanish. The gadget, called a spectral cloak, even worked in ... […]
- Full ‘invisibility cloak’ is possible in the real world: scientists on June 28, 2018 at 12:16 pm
However, one could theoretically program a cloaking device to ignore the full visible spectrum, effectively rendering an object invisible to the naked eye. The study demonstrated that a one-dimensiona... […]
- Spectral cloaking could make objects invisible under realistic conditions on June 28, 2018 at 8:35 am
a significant step in the development of practical invisibility cloaking technologies. Most current cloaking devices can fully conceal the object of interest only when the object is illuminated with j... […]
- Scientists Made a Working Invisibility Cloak (But There's a Catch) on May 10, 2018 at 8:30 am
Whether the invisibility cloak in Harry Potter, the cloaking device in Star Trek, or the various government agencies investing in invisibility R&D, humans have long fantasized about technology capable ... […]
via Google News and Bing News