 |
|
Cheaper LEDs from breakthrough in zinc oxide (ZnO) nanowire research, Nano Letters study says
January 04, 2007Engineers at UC San Diego have synthesized a long-sought semiconducting material that may pave the way for an inexpensive new kind of light emitting diode (LED) that could compete with today's widely used gallium nitride LEDs, according to a new paper in the journal Nano Letters.
To build an LED, you need both positively and negatively charged semiconducting materials; and the engineers synthesized zinc oxide (ZnO) nanoscale cylinders that transport positive charges or "holes" - so-called "p-type ZnO nanowires." They are endowed with a supply of positive charge carrying holes that, for years, have been the missing ingredients that prevented engineers from building LEDs from ZnO nanowires. In contrast, making "n-type" ZnO nanowires that carrier negative charges (electrons) has not been a problem. In an LED, when an electron meets a hole, it falls into a lower energy level and releases energy in the form of a photon of light.
Deli Wang, an electrical and computer engineering professor from UCSD's Jacobs School of Engineering, and colleagues at UCSD and Peking University, report synthesis of high quality p-type zinc oxide nanowires in a paper published online by the journal Nano Letters.
"Zinc oxide nanostructures are incredibly well studied because they are so easy to make. Now that we have p-type zinc oxide nanowires, the opportunities for LEDs and beyond are endless," said Wang.
Wang has filed a provisional patent for p-type ZnO nanowires and his lab at UCSD is currently working on a variety of nanoscale applications.
"Zinc oxide is a very good light emitter. Electrically driven zinc oxide single nanowire lasers could serve as high efficiency nanoscale light sources for optical data storage, imaging, and biological and chemical sensing," said Wang.
To make the p-type ZnO nanowires, the engineers doped ZnO crystals with phosphorus using a simple chemical vapor deposition technique that is less expensive than the metal organic chemical vapor deposition (MOCVD) technique often used to synthesize the building blocks of gallium nitride LEDs. Adding phosphorus atoms to the ZnO crystal structure leads to p-type semiconducting materials through the formation of a defect complex that increases the number of holes relative to the number of free electrons.
"Zinc oxide is wide band gap semiconductor and generating p-type doping impurities that provide free holes is very difficult - particularly in nanowires. Bin Xiang in my group worked day and night for more than a year to accomplish this goal," said Wang.
The starting materials and manufacturing costs for ZnO LEDs are far less expensive than those for gallium nitride LEDs. In the future, Wang expects to cut costs even further by making p-type and n-type ZnO nanowires from solution.
For years, researchers have been making electron-abundant n-type ZnO nanowire crystals from zinc and oxygen. Missing oxygen atoms within the regular ZnO crystal structure create relative overabundances of zinc atoms and give the semiconductors their n-type, conductive properties. The lack of accompanying p-type ZnO nanowires, however, has prevented development of a wide range of ZnO nanodevices.
While high quality p-type ZnO nanowires have not previously been reported, groups have demonstrated p-type conduction in ZnO thin films and made ZnO thin film LEDs. Using ZnO nanowires rather than thin films to make LEDs would be less expensive and could lead to more efficient LEDs, Wang explained.
Having both n- and p-type ZnO nanowires - complementary nanowires - could also be useful in a variety of applications including transistors, spintronics, UV detectors, nanogenerators, and microscopy. In spintronics applications, researchers could use p-type ZnO nanowires to make dilute magnetic semiconductors by doping ZnO with magnetic atoms, such as manganese and cobalt, Wang explained.
Transistors that rely on the semiconducting properties of ZnO are also now on the horizon. "P-type doping in nanowires would make complementary ZnO nanowire transistors possible," said Wang.
University of California - San Diego
"Zinc oxide nanostructures are incredibly well studied because they are so easy to make. Now that we have p-type zinc oxide nanowires, the opportunities for LEDs and beyond are endless," said Wang.
Wang has filed a provisional patent for p-type ZnO nanowires and his lab at UCSD is currently working on a variety of nanoscale applications.
"Zinc oxide is a very good light emitter. Electrically driven zinc oxide single nanowire lasers could serve as high efficiency nanoscale light sources for optical data storage, imaging, and biological and chemical sensing," said Wang.
To make the p-type ZnO nanowires, the engineers doped ZnO crystals with phosphorus using a simple chemical vapor deposition technique that is less expensive than the metal organic chemical vapor deposition (MOCVD) technique often used to synthesize the building blocks of gallium nitride LEDs. Adding phosphorus atoms to the ZnO crystal structure leads to p-type semiconducting materials through the formation of a defect complex that increases the number of holes relative to the number of free electrons.
"Zinc oxide is wide band gap semiconductor and generating p-type doping impurities that provide free holes is very difficult - particularly in nanowires. Bin Xiang in my group worked day and night for more than a year to accomplish this goal," said Wang.
The starting materials and manufacturing costs for ZnO LEDs are far less expensive than those for gallium nitride LEDs. In the future, Wang expects to cut costs even further by making p-type and n-type ZnO nanowires from solution.
For years, researchers have been making electron-abundant n-type ZnO nanowire crystals from zinc and oxygen. Missing oxygen atoms within the regular ZnO crystal structure create relative overabundances of zinc atoms and give the semiconductors their n-type, conductive properties. The lack of accompanying p-type ZnO nanowires, however, has prevented development of a wide range of ZnO nanodevices.
While high quality p-type ZnO nanowires have not previously been reported, groups have demonstrated p-type conduction in ZnO thin films and made ZnO thin film LEDs. Using ZnO nanowires rather than thin films to make LEDs would be less expensive and could lead to more efficient LEDs, Wang explained.
Having both n- and p-type ZnO nanowires - complementary nanowires - could also be useful in a variety of applications including transistors, spintronics, UV detectors, nanogenerators, and microscopy. In spintronics applications, researchers could use p-type ZnO nanowires to make dilute magnetic semiconductors by doping ZnO with magnetic atoms, such as manganese and cobalt, Wang explained.
Transistors that rely on the semiconducting properties of ZnO are also now on the horizon. "P-type doping in nanowires would make complementary ZnO nanowire transistors possible," said Wang.
University of California - San Diego
Nanowires Current Events and Nanowires News RSSUnderstanding mechanical properties of silicon nanowires paves way for nanodevices
Silicon nanowires are attracting significant attention from the electronics industry due to the drive for ever-smaller electronic devices, from cell phones to computers.
LANL Roadrunner simulates nanoscale material failure
Very tiny wires, called nanowires, made from such metals as silver and gold, may play a crucial role as electrical or mechanical switches in the development of future-generation ultrasmall nanodevices.
Science at the Petascale: Roadrunner Results Unveiled
The world's fastest supercomputer, Roadrunner, at Los Alamos National Laboratory has completed its initial "shakedown" phase doing accelerated petascale computer modeling and simulations of a variety of unclassified, fundamental science projects.
Transforming Nanowires Into Nano-Tools Using Cation Exchange Reactions
A team of engineers from the University of Pennsylvania has transformed simple nanowires into reconfigurable materials and circuits, demonstrating a novel, self-assembling method for chemically creating nanoscale structures that are not possible to grow or obtain otherwise.
Berkeley researchers create first hyperlens for sound waves
Ultrasound and underwater sonar devices could "see" a big improvement thanks to development of the world's first acoustic hyperlens. Created by researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), the acoustic hyperlens provides an eightfold boost in the magnification power of sound-based imaging technologies.
Nanowire biocompatibility in the brain: So far so good
The biological safety of nanotechnology, in other words, how the body reacts to nanoparticles, is a hot topic. Researchers at Lund University in Sweden have managed for the first time to carry out successful experiments involving the injection of so-called 'nanowires.'
Harvard scientists bend nanowires into 2-D and 3-D structures
Taking nanomaterials to a new level of structural complexity, scientists have determined how to introduce kinks into arrow-straight nanowires, transforming them into zigzagging two- and three-dimensional structures with correspondingly advanced functions.
Putting a Strain on Nanowires Could Yield Colossal Results
In finally answering an elusive scientific question, researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have shown that the selective placement of strain can alter the electronic phase and its spatial arrangement in correlated electron materials.
Friction force differences could offer a new means for sorting and assembling nanotubes
Nanotubes and nanowires are promising building blocks for future integrated nanoelectronic and photonic circuits, nanosensors, interconnects and electro-mechanical nanodevices. But some fundamental issues remain to be resolved - among them, how to position and manipulate the tiny tubes.
Making more efficient fuel cells
Bacteria that generate significant amounts of electricity could be used in microbial fuel cells to provide power in remote environments or to convert waste to electricity.
More Nanowires Current Events and Nanowires News Articles
 |
Oakley Men's Nanowire 2.0 Iridium Polarized Sunglasses,Polished Black Frame/VR28 Black Lens,one size by Oakley The Oakley Nanowire 2.0 Sunglasses feature featherweight titanium alloy wire frames and Unobtanium rubber earpieces that comfortably hug the contours your head. These polarized sunglasses offer a fit for medium to large face sizes. While you're out on the road, the Nanowire's lenses give you the quality distortion-free and glare-destroying polarized optics you'd expect from a genuine Oakley product. The Nanowire frame features memory metal technology, which means the super bendy metal adjusts automatically to comfortably fit your faceit returns to how it's original form when you take these shades off. To keep your sunglasses in pristine condition, Oakley applied a permanent hydrophobic coating so the lens surface repels water, oil, and dust, thus giving you clear vision. |
 |
Inorganic Nanowires: Applications, Properties, and Characterization by M. Meyyappan (Author), Mahendra K. Sunkara (Author) Advances in nanofabrication, characterization tools, and the drive to commercialize nanotechnology products have contributed to the significant increase in research on inorganic nanowires (INWs). Yet few if any books provide the necessary comprehensive and coherent account of this important evolution. Presenting essential information on both popular and emerging varieties, Inorganic Nanowires: Applications, Properties, and Characterization addresses the growth, characterization, and properties of nanowires. Authors Meyyappan—a NASA scientist and renowned leader in nanoscience and technology—and Sunkara—a major contributor to nanowire literature—offer an in-depth overview of various types of nanowires, including semiconducting, metallic, and oxide varieties.... |
 |
Oakley Men's Nanowire 3.0 Iridium Polarized Sunglasses,Polished Black Frame/Black Lens,one size by Oakley OAKLEY NANOWIRE 3.0 POLARIZED 12-919 SUNGLASSES FRAME: POLISHED BLACK LENS: BLACK IRIDIUM POLARIZED MODEL # 12-919 |
 |
Oakley Oakley Nanowire 2.0 Men's Polarized Active Race Wear Sunglasses - Color: Pewter/Black Iridium, Size: One Size Fits All by Oakley Our athletes spend a lot of time defying gravity, so we figured they should have a lifestyle sunglass that does the same. It's made of an ultra-lightweight titanium alloy that lets us create sculptural contours without sacrificing flexibility, so even if you're just competing in the rat race, you can take advantage of memory metal that offers an adaptable fit. But the real marvel of engineering is the way we packed so much innovation into so light a frame. The unbeatable clarity of HIGH DEFINITION OPTICS (HDO) has been matched with the finest technologies ever to tame light rays. OAKLEY NANOWIRE blocks glare with 99% polarization efficiency, thanks to the best polarized lenses on the planet. Our permanent HYDROPHOBIC lens coating repels water, skin oils and dust. IRIDIUM lens... |
 |
Oakley Men's Nanowire 3.0 Iridium Polarized Sunglasses,Brown Chrome Frame/VR28 Black Lens,one size by Oakley The Oakley Nanowire 3.0 Sunglasses offer the largest lens size in the Nanowire family. These sunglasses features a ultra-lightweight titanium memory metal frame and polarized lenses to give you a wrap-around sunglass that's comfy enough to wear all day. Oakley's patented High Definition Optics give you precision-milled lenses to give you distortion-free vision so you maintain your visual acuity whether you're driving in rush hour traffic or staring down a bottleneck fairway on the links. Oakley placed adjustable silicon nosepieces to give you a snug yet comfortable fit. The Nanowire 3.0's lenses block out 100% of UVA rays and harmful UVB rays. Product FeaturesFrame: Titanium alloyHinge Type: Titanium alloyLens: Plutonite polycarbonateInterchangeable Lens: NoPolarized: YesFace... |
 |
Nanowires and Nanobelts: Materials, Properties and Devices: Volume 1: Metal and Semiconductor Nanowires by Zhong Lin Wang (Editor) This two volume reference, Nanowires and Nanobelts: Materials, Properties and Devices, provides a comprehensive introduction to the field and reviews the current state of the research. Volume 1, Metal and Semiconductor Nanowires covers a wide range of materials systems, from noble metals (such as Au, Ag, Cu), single element semiconductors (such as Si and Ge), compound semiconductors (such as InP, CdS and GaAs as well as heterostructures), nitrides (such as GaN and Si3N4) to carbides (such as SiC). The objective of this volume is to cover the synthesis, properties and device applications of nanowires based on metal and semiconductor materials. The volume starts with a review on novel electronic and optical nanodevices, nanosensors and logic circuits that have been built using... |
 |
Oakley Men's Nanowire 4.0 Iridium Polarized Sunglasses,Matte Black Frame/Black Lens,one size by Oakley Oakley crafted the Nanowire 4.0 Polarized Sunglasses with a high quality titanium alloy and its high Definition Optics for a light weight and glare-reducing performance, whether you're on the slopes or the water. The Nanowire's titanium memory metal provides a flexible and adaptable fit, and the Unobtanium pads increase their grip when you sweat. The hydrophobic coating repels water, dust, dirt and skin oils, and an Iridium lense coating balances light transmission and filters 100% of UV rays. Product FeaturesFrame: Titanium alloy Hinge Type: SteelLens: Glass, PolycarbonateInterchangeable Lens: No Polarized: Yes Face Size: MediumCase Type: Hard Nose Pads: Yes Arm Pads: Yes Recommended Use: Casual, activeManufacturer Warranty:... |
 |
Nanotubes and Nanowires (Selected Topics in Electronics and Systems) by Peter John Burke (Author), Peter John Burke (Editor) The field of nanotubes and nanowires is evolving at a rapid pace, with many potential applications in electronics, optics, and sensors, to name a few. In this book, various prominent researchers summarize our current understanding of these new materials systems, as well as some of these potential applications. A snapshot of the state-of-the-art in the field of nanowires and nanotubes, the contributions give an instructive mix of experimental, theoretical, and visionary material to give the reader an indication of where the field is now, and where it is going. |
 |
Oakley Nanowire 1.0 Men's Polarized Active Lifestyle Racewear Sunglasses - Color: Brown Chrome/Tungsten Iridium, Size: One Size Fits All by Oakley |
 |
Oakley Oakley Nanowire 4.0 Men's Polarized Active Sports Wear Sunglasses $259.00 by Oakley If you get a sinking feeling that the world is disappearing before your eyes, it's probably just hiding in a haze of glare. When light reflects off flat surfaces, the resulting glare can be 10 times brighter. That's not a good thing if you're driving a car, avoiding a water hazard on the back nine or playing any sport to win. Oakley polarized lenses block glare with efficiency greater than 99%, and we make them with a process that eliminates the haze and optical distortion found in ordinary polarized lenses. You won't find satellites or lunar rovers on our product list but when we engineer a sunglasses frame for unparalleled durability and minimized weight, we earn our place in the space race. That's because we start with the same metal used in orbital vehicles, titanium, and we... |
| © 2009 BrightSurf.com |