Monday 27 January 2014
Wednesday 15 January 2014
Summer Fellowship
Enroll to Summer fellowship at IIT Madaras for 3rd year students in B.tech.
Topper may applied have good ranks in university exams.
To apply click below.
Click here
Topper may applied have good ranks in university exams.
To apply click below.
Click here
Sunday 12 January 2014
Spintronics might be the future of electronics, but what is it?
tation in electronics: that electrons have charge and every time a charge is moved to do something, some of the effort gets turned into heat.
Quite separately from charge, electrons have a property called spin, and it is this property that might one day be exploited in spintronics to move information without losing so much energy.
So, what is spin?
“An electron has charge which is electrical and spin which is magnetic. In spintronics, we would use spin in addition to charge,” Dr Paul Steffens, a neutron scientist studying magnetism at the ILL neutron lab in Grenoble. “Magnetism can come from loop of current: a loop of wire, or an electron circling an atom, or an electron’s magnetic moment. It is not completely absurd to think of spin as a little current loop. It is a picture that can help. Think of it as a tiny magnet which you can manipulate with a magnetic field.”
Spin is already used commercially, in ‘GMR’ read heads within hard disc drives.
“There are many things that can happen with spin. On a large scale, iron staying magnetic is the most useful example. Data storage on a hard disc with information in magnetic regions is on the limit of where quantum effects play a role, where we have to think in terms of quantum mechanics,” said Steffens.
For the purposes of spintronics, the spin of a particular electron can either be ‘spin up’ or ‘spin down’, and the handy thing about spin is that it can move around without capacitively coupling into the surroundings wasting energy.
“If you could just move the spin part of the electron, you would generate less heat, but if you only have one electron, you can’t move spin and not charge,” ILL theoretical physicist Dr Tim Ziman told Electronics Weekly. “If there are many electrons, we can move spin ups in one direction and spin downs in the other direction. Then, to a first approximation, spin is actually moving but there is no net movement of charge because there is no net movement of electrons.”
A first approximation?
“They do exchange charge and spin, but that is not the important thing,” said Ziman.
Charge current and spin current have different characteristics, he went on to explain: Charge current keeps on moving while spin current is at the mercy of ‘spin diffusion’ – the random flipping of spin states – which means net spin flow soon peters out.
Luckily, spin diffusion need not be a barrier to spintronics as, in good conditions, spin can travel over micrometres before it diffuses, which is plenty if spintronics is to follow the ever-smaller model of electronics. This does mean that data has to arrive and leave in electronic form, with suitable converters around the spintronics.
“One of the problems, which is partially solved, is to convert charge current into spin current and then detect spin as electrical polarisation,” said Ziman, whose is seeking ways to make strong spin currents: “I am looking at co-operative scattering, for example spin waves.”
‘Skew scattering’ one way of separating spin up and spin down electrons, said Ziman: “You need to do it efficiently. I don’t think anyone has made a useful circuit yet.”
Methods of both storing and moving information have been proposed and, with the less-than-perfect conversion available, “people have made devices in last five to ten years, and have integrated them into normal electronic circuits”, said Ziman.
Quantum computing
Spintronics is closely related to two other research fields, and developments in any of them can benefit all three.
One is quantum computing. “Devices are feasible. You want quantum interference; it is part of the same technology, at a similar stage, with a similar community working on it,” said Ziman.
The other is manipulating magnetic domain walls with electrical currents. “This is similar to spintronics, it is really part of it, for memory rather than logical operations. There is a lot of similar physics.”
Slightly less related is a push to move NMR – the body scanning technique – into the nano world. “It could revolutionise biology,” said Ziman.
Why do magnetics and spin scientist work at a neutron laboratory?
The answer is that neutrons have spin, but carry no charge.
Just as x-rays can reveal the structure of molecules and crystals – as they did with DNA – neutrons can reveal a material’s spin structure without being confused by its internal charge structure.
In the ILL case, the beam comes from a nuclear reactor and is the most powerful in the world, according to Ziman. It is around 1cm in diameter, and its diffraction is analysed after it has passed through a sample of the material under scrutiny.
“Neutrons are best for looking at the magnetic properties of bulk material. You can’t put a nanowire into a neutron beam and expect a result,” said Ziman. “Neutrons are also good for viewing domain walls, and exotic things like magnetic skyrmions which are the smallest domains and form lattices that could store data.”
Thursday 9 January 2014
MRAM
Extremely Fast Magnetic Random Access Memory (MRAM) Computer Data Storage Within Reach
Magnetic random access memory (MRAM) is the most important new module on the market of computer storage devices. Like the well known USB sticks, they store information into static memory, but MRAM offers short access times and unlimited writing properties. Commercial MRAMs have been on the market since 2005. They are, however, still slower than the competitors they have among the volatile storage media.
 |
| Electron-microscopic recording of an MRAM storage cell. (Credit: PTB) |
An invention made by the Physikalisch-Technische Bundesanstalt (PTB)
changes this situation: A special chip connection, in association with
dynamic triggering of the component, reduces the response from -- so far
-- 2 ns to below 500 ps. This corresponds to a data rate of up to 2
GBit (instead of the approx. 400 MBit so far). Power consumption and the
thermal load will be reduced, as well as the bit error rate. The
European patent is just being granted this spring; the US patent was
already granted in 2010. An industrial partner for further development
and manufacturing such MRAMs under licence is still being searched for.
Fast computer storage chips like DRAM and SRAM (Dynamic and Static Random Access Memory) which are commonly used today, have one decisive disadvantage: in the case of an interruption of the power supply, the information stored on them is irrevocably lost. The MRAM promises to put an end to this. In the MRAM, the digital information is not stored in the form of an electric charge, but via the magnetic alignment of storage cells (magnetic spins). MRAMs are very universal storage chips because they allow -- in addition to the non-volatile information storage -- also faster access, a high integration density and an unlimited number of writing and reading cycles.
However, the current MRAM models are not yet fast enough to outperform the best competitors. The time for programming a magnetic bit amounts to approx. 2 ns. Whoever wants to speed this up, reaches certain limits which have something to do with the fundamental physical properties of magnetic storage cells: during the programming process, not only the desired storage cell is magnetically excited, but also a large number of other cells. These excitations -- the so-called magnetic ringing -- are only slightly attenuated, their decay can take up to approx. 2 ns, and during this time, no other cell of the MRAM chip can be programmed. As a result, the maximum clock rate of MRAM is, so far, limited to approx. 400 MHz.
Until now, all experiments made to increase the velocity have led to intolerable write errors. Now, PTB scientists have optimized the MRAM design and integrated the so-called ballistic bit triggering which has also been developed at PTB. Here, the magnetic pulses which serve for the programming are selected in such a skilful way that the other cells in the MRAM are hardly magnetically excited at all. The pulse ensures that the magnetization of a cell which is to be switched performs half a precision rotation (180°), while a cell whose storage state is to remain unchanged performs a complete precision rotation (360°). In both cases, the magnetization is in the state of equilibrium after the magnetic pulse has decayed, and magnetic excitations do not occur any more.
This optimal bit triggering also works with ultra-short switching pulses with a duration below 500 ps. The maximum clock rates of the MRAM are, therefore, above 2 GHz. In addition, several bits can be programmed at the same time which would allow the effective write rate per bit to be increased again by more than one order. This invention allows clock rates to be achieved with MRAM which can compete with those of the fastest volatile storage components.
Fast computer storage chips like DRAM and SRAM (Dynamic and Static Random Access Memory) which are commonly used today, have one decisive disadvantage: in the case of an interruption of the power supply, the information stored on them is irrevocably lost. The MRAM promises to put an end to this. In the MRAM, the digital information is not stored in the form of an electric charge, but via the magnetic alignment of storage cells (magnetic spins). MRAMs are very universal storage chips because they allow -- in addition to the non-volatile information storage -- also faster access, a high integration density and an unlimited number of writing and reading cycles.
However, the current MRAM models are not yet fast enough to outperform the best competitors. The time for programming a magnetic bit amounts to approx. 2 ns. Whoever wants to speed this up, reaches certain limits which have something to do with the fundamental physical properties of magnetic storage cells: during the programming process, not only the desired storage cell is magnetically excited, but also a large number of other cells. These excitations -- the so-called magnetic ringing -- are only slightly attenuated, their decay can take up to approx. 2 ns, and during this time, no other cell of the MRAM chip can be programmed. As a result, the maximum clock rate of MRAM is, so far, limited to approx. 400 MHz.
Until now, all experiments made to increase the velocity have led to intolerable write errors. Now, PTB scientists have optimized the MRAM design and integrated the so-called ballistic bit triggering which has also been developed at PTB. Here, the magnetic pulses which serve for the programming are selected in such a skilful way that the other cells in the MRAM are hardly magnetically excited at all. The pulse ensures that the magnetization of a cell which is to be switched performs half a precision rotation (180°), while a cell whose storage state is to remain unchanged performs a complete precision rotation (360°). In both cases, the magnetization is in the state of equilibrium after the magnetic pulse has decayed, and magnetic excitations do not occur any more.
This optimal bit triggering also works with ultra-short switching pulses with a duration below 500 ps. The maximum clock rates of the MRAM are, therefore, above 2 GHz. In addition, several bits can be programmed at the same time which would allow the effective write rate per bit to be increased again by more than one order. This invention allows clock rates to be achieved with MRAM which can compete with those of the fastest volatile storage components.
Electronics Research..
Engineers Make World's Fastest Organic Transistor, Herald New Generation of See-Through Electronics
 |
Transparent
transistors on glass Transparent transistors on this postage-stamp size
glass have speed characteristics rivaling some forms of silicon
transistors. The device used a new process to make this world
record-setting organic transistor, paving the way for a new generation
of cheap, transparent electronic devices. (Credit: Jinsong Huang and
Yongbo Yuan)
|
Two university research teams have worked together to produce the
world's fastest thin-film organic transistors, proving that this
experimental technology has the potential to achieve the performance
needed for high-resolution television screens and similar electronic
devices.
For years engineers the world over have been trying to use inexpensive, carbon-rich molecules and plastics to create organic semiconductors capable of performing electronic operations at something approaching the speed of costlier technologies based on silicon. The term "organic" was originally confined to compounds produced by living organisms but now extended to include synthetic substances based on carbons and includes plastics.
In the Jan. 8 edition of Nature Communications, engineers from the University of Nebraska-Lincoln (UNL) and Stanford University show how they created thin-film organic transistors that could operate more than five times faster than previous examples of this experimental technology.
Research teams led by Zhenan Bao, professor of chemical engineering at Stanford, and Jinsong Huang, assistant professor of mechanical and materials engineering at UNL used their new process to make organic thin-film transistors with electronic characteristics comparable to those found in expensive, curved-screen television displays based on a form of silicon technology.
They achieved their speed boost by altering the basic process for making thin-film organic transistors.
Typically, researchers drop a special solution, containing carbon-rich molecules and a complementary plastic, onto a spinning platter -- in this case, one made of glass. The spinning action deposits a thin coating of the materials over the platter.
In their Nature Communications paper, the collaborators describe two important changes to this basic process.
First they spun the platter faster. Second they only coated a tiny portion of the spinning surface, equivalent to the size of a postage stamp.
These innovations had the effect of depositing a denser concentration of the organic molecules into a more regular alignment. The result was a great improvement in carrier mobility, which measures how quickly electrical charges travel through the transistor.
The researchers called this improved method "off-center spin coating." The process remains experimental, and the engineers cannot yet precisely control the alignment of organic materials in their transistors or achieve uniform carrier mobility.
Even at this stage, off-center spin coating produced transistors with a range of speeds much faster than those of previous organic semiconductors and comparable to the performance of the polysilicon materials used in today's high-end electronics.
Further improvements to this experimental process could lead to the development of inexpensive, high-performance electronics built on transparent substrates such as glass and, eventually, clear and flexible plastics.
Already, the researchers have shown that they can create high-performance organic electronics that are 90 percent transparent to the naked eye.
Other key members of the research teams included Yongbo Yuan, a postdoctoral associate at UNL's Nebraska Center for Materials and Nanoscience, Gaurav Giri, a graduate student in chemical engineering at Stanford and Alex Ayzner, a postdoctoral researcher at the Stanford Synchrotron Radiation Lightsource.
The work was funded by the U.S. Defense Advanced Research Projects Agency (DARPA), the Air Force Office of Scientific Research and the National Science Foundation.
For years engineers the world over have been trying to use inexpensive, carbon-rich molecules and plastics to create organic semiconductors capable of performing electronic operations at something approaching the speed of costlier technologies based on silicon. The term "organic" was originally confined to compounds produced by living organisms but now extended to include synthetic substances based on carbons and includes plastics.
In the Jan. 8 edition of Nature Communications, engineers from the University of Nebraska-Lincoln (UNL) and Stanford University show how they created thin-film organic transistors that could operate more than five times faster than previous examples of this experimental technology.
Research teams led by Zhenan Bao, professor of chemical engineering at Stanford, and Jinsong Huang, assistant professor of mechanical and materials engineering at UNL used their new process to make organic thin-film transistors with electronic characteristics comparable to those found in expensive, curved-screen television displays based on a form of silicon technology.
They achieved their speed boost by altering the basic process for making thin-film organic transistors.
Typically, researchers drop a special solution, containing carbon-rich molecules and a complementary plastic, onto a spinning platter -- in this case, one made of glass. The spinning action deposits a thin coating of the materials over the platter.
In their Nature Communications paper, the collaborators describe two important changes to this basic process.
First they spun the platter faster. Second they only coated a tiny portion of the spinning surface, equivalent to the size of a postage stamp.
These innovations had the effect of depositing a denser concentration of the organic molecules into a more regular alignment. The result was a great improvement in carrier mobility, which measures how quickly electrical charges travel through the transistor.
The researchers called this improved method "off-center spin coating." The process remains experimental, and the engineers cannot yet precisely control the alignment of organic materials in their transistors or achieve uniform carrier mobility.
Even at this stage, off-center spin coating produced transistors with a range of speeds much faster than those of previous organic semiconductors and comparable to the performance of the polysilicon materials used in today's high-end electronics.
Further improvements to this experimental process could lead to the development of inexpensive, high-performance electronics built on transparent substrates such as glass and, eventually, clear and flexible plastics.
Already, the researchers have shown that they can create high-performance organic electronics that are 90 percent transparent to the naked eye.
Other key members of the research teams included Yongbo Yuan, a postdoctoral associate at UNL's Nebraska Center for Materials and Nanoscience, Gaurav Giri, a graduate student in chemical engineering at Stanford and Alex Ayzner, a postdoctoral researcher at the Stanford Synchrotron Radiation Lightsource.
The work was funded by the U.S. Defense Advanced Research Projects Agency (DARPA), the Air Force Office of Scientific Research and the National Science Foundation.
Tuesday 7 January 2014
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