 |
|
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 RSSLANL 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.
Caltech and IBM scientists use self-assembled DNA scaffolding to build tiny circuit boards
Scientists at the California Institute of Technology (Caltech) and IBM's Almaden Research Center have developed a new technique to orient and position self-assembled DNA shapes and patterns-or "DNA origami"-on surfaces that are compatible with today's semiconductor manufacturing equipment.
More Nanowires Current Events and Nanowires News Articles
 |
Enhanced Field Emission from Metallic Surfaces and Nanowires by Arti Dangwal-Pandey (Author) The role of material properties, surface preparation and cleaning techniques on Nb and Cu was studied for EFE , which is disastrous for high field vacuum devices. Dry ice cleaning is found to suppress EFE from the metallic surfaces very efficiently. High purity single crystal and large grain Nb samples showed the onset of FE at high fields (120 ? 200 MV/m).For the first time, the grain boundary assisted field emission was observed for Nb. A correlationbetween size of emitters and onset fields is obtained, which sets a threshold for the tolerable defect size to achieve the envisaged accelerating gradients in cavities reliably.Additionaly, the systematic study performed on electrochemically deposited Cu, Ni and Au nanowires of different aspect ratios and spatial distribution for cold... |
 |
Oakley Men's Nanowire 4.0 Iridium Polarized Sunglasses,Matte Black Frame/Black Lens,one size by Oakley Frame : Matte Black , Lenses : Black , Iridium Polarized , |
 |
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 Polarized Nanowire 3.0 Olive Chrome / Tungsten Iridium by Oakley Plutonite material for supreme visual clarity O-Matter frame material offers superb construction quality 100 percent UVA/UVB filtration Optical clarity exceeds all ANSI Z87.1 standards |
 |
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 Nanowire 1.0 Black Chrome/VR28 Black Iridium Polarized by Oakley Frame:Black Chrome Lenses:VR28 Black Iridium Polarized |
|
SNAP yields high density circuits. (Electronics and Magnetics).(superlattice nanowire pattern transfer): An article from: Nanoparticle News by Business Communications Company, Inc. (Publisher) This digital document is an article from Nanoparticle News, published by Business Communications Company, Inc. on May 1, 2003. The length of the article is 819 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser. Citation Details Title: SNAP yields high density circuits. (Electronics and Magnetics).(superlattice nanowire pattern transfer) Publication: Nanoparticle News (Magazine/Journal) Date: May 1, 2003 Publisher: Business Communications Company, Inc. Volume: 6 Issue: 4 Page: 3(3) Distributed by Thomson... | |
 |
Oakley Men's Nanowire 2.0 Iridium Polarized Sunglasses,Polished Black Frame/VR28 Black Lens,one size by Oakley Plutonite material for supreme visual clarity O-Matter frame material offers superb construction quality 100 percent UVA/UVB filtration Optical clarity exceeds all ANSI Z87.1 standards |
 |
Nanowires and Nanobelts: Materials, Properties and Devices: Volume 2: Nanowires and Nanobelts of Functional Materials by Zhong Lin Wang (Editor) Nanowires, nanobelts, nanoribbons, nanorods ..., are a new class of quasi-one-dimensional materials that have been attracting a great research interest in the last few years. These non-carbon based materials have been demonstrated to exhibit superior electrical, optical, mechanical and thermal properties, and can be used as fundamental building blocks for nano-scale science and technology, ranging from chemical and biological sensors, field effect transistors to logic circuits. Nanocircuits built using semiconductor nanowires demonstrated were declared a "breakthrough in science" by Science magazine in 2001. Nature magazine recently published a report claiming that "Nanowires, nanorods, nanowhiskers, it does not matter what you call them, they are the hottest property in nanotechnology"... |
 |
Oakley Nanowire 1.0 Men's Polarized Active Lifestyle Racewear Sunglasses - Color: Brown Chrome/Tungsten Iridium, Size: One Size Fits All by Oakley |
| © 2009 BrightSurf.com |