Memory Device Inventions
To summarize, there are two important speeds - the speed of the message telling all the electrons to
begin their drifting motion in one direction and the speed at which the electrons themselves move.
These two speeds are actually radically different. The speed of the message is the speed of light
while the speed of the electrons is literally slow as molasses.
An example of how slow the electrons are can be found in gel electrophoresis. Gel electrophoresis
is a method for analysing large biological molecules such as DNA fragments. It's often used in areas
like forensic science to analyse DNA samples taken from rapes or violent crimes. You've probably
seen it on CSI or some place like that. At any rate, the method applies an electric field to a gel
where a sample of DNA (or some other sample) has been placed. Due to the presence of the
electric field, the DNA (or other sample) molecules begin to drift through the gel. If you've ever done
this you'll notice that it takes a very long time. I actually performed this experiment back in high
school when I took a forensic science class. At any rate, the reason why it takes so long is because
you're separating the molecules by causing them to drift through the medium; in other words, you're
relying on the fact that the particles will drift slowly through the material. You're also relying on the
fact that particles of different masses will be separated at different rates, though this latter fact is not
important for us here.
The velocity and the electrical resistance outside a conduction is often assumed by the propagation
speed of an electromagnetic wave. In simplified systems, the speed of electricity is given as the
electromagnetic wave which conveys information (data), not the movement of electrons.
Electromagnetic wave propagation is fast and depends on the dielectric constant of the material.
In a vacuum the wave travels at the speed of light and almost that fast in air. Propagation speed is
affected by insulation, such that in an unshielded copper conductor range 95 to 97% that of the
speed of light, while in a typical coaxial cable it is about 66% of the speed of light.
Hybrid Spintronic Chips Open Door to New Functionality
Researchers have created the first electronic circuit to merge traditional inorganic semiconductors
with organic “spintronics” — devices that utilize the spin of electrons to read, write and manipulate
data. Ezekiel Johnston-Halperin, assistant professor of physics at Ohio State University, and his
team combined an inorganic semiconductor with a unique plastic material that is under
development in colleague Arthur J. Epstein’s lab.
Last year, Epstein, Distinguished University Professor of physics and chemistry and director of the
Institute for Magnetic and Electronic Polymers at Ohio State, demonstrated the first successful data
storage and retrieval on a plastic spintronic device. Now Johnston-Halperin, Epstein and their
colleagues have incorporated the plastic device into a traditional circuit based on gallium arsenide.
Two of their now-former doctoral students, Lei Fang and Deniz Bozdag, had to devise a new
fabrication technique to make the device.
In a paper published online in the journal Physical Review Letters, they describe how they
transmitted a spin-polarized electrical current from the plastic material, through the gallium
arsenide, and into a light-emitting diode (LED) as proof that the organic and inorganic parts were
working together.
“Hybrid structures promise functionality that no other materials, neither organic nor inorganic, can
currently achieve alone,” Johnston-Halperin said. “We’ve opened the door to linking this exciting
new material to traditional electronic devices with transistor and logic functionality. In the longer
term, this work promises new, chemically based functionality for spintronic devices.”
Normal electronics encode computer data based on a binary code of ones and zeros, depending
on whether an electron is present or not within the material. But researchers have long known that
electrons can be polarized to orient in particular directions, like a bar magnet. They refer to this
orientation as spin — either “spin up” or “spin down” — and this approach, dubbed spintronics, has
been applied to memory-based technologies for modern computing. For example, the terabyte
drives now commercially available would not be possible without spintronic technology.
If scientists could expand spintronic technology beyond memory applications into logic and
computing applications, major advances in information processing could follow, Johnston-Halperin
explained. Spintronic logic would theoretically require much less power, and produce much less
heat, than current electronics, while enabling computers to turn on instantly without “booting up.”
Hybrid and organic devices further promise computers that are lighter and more flexible, much as
organic LEDs are now replacing inorganic LEDs in the production of flexible displays.
A spintronic semiconductor must be magnetic, so that the spin of electrons can be flipped for data
storage and manipulation. Few typical semiconductors — that is, inorganic semiconductors — are
magnetic. Of those that are, all require extreme cold, with operating temperatures below -150
degrees Fahrenheit or -100 degrees Celsius. That’s colder than the coldest outdoor temperature
ever recorded in Antarctica.
“In order to build a practical spintronic device, you need a material that is both semiconducting
and magnetic at room temperature. To my knowledge, Art's organic materials are the only ones
that do that,” Johnston-Halperin said. The organic magnetic semiconductors were developed by
Epstein and his long-standing collaborator Joel S. Miller of the University of Utah.
The biggest barrier that the researchers faced was device fabrication. Traditional inorganic devices
are made at high temperatures with harsh solvents and acids that organics can’t tolerate. Fang and
Bozdag solved this problem by building the inorganic part in a traditional cleanroom, and then
adding an organic layer in Epstein’s customized organics lab — a complex process that required a
redesign of the circuitry in both parts.
“You could ask, why didn’t we go with all organics, then?” Johnston-Halperin said. “Well, the reality is
that industry already knows how to make devices out of inorganic materials. That expertise and
equipment is already in place. If we can just get organic and inorganic materials to work together,
then we can take advantage of that existing infrastructure to move spintronics forward right away.”
He added that much work will need to be done before manufacturers can mass-produce hybrid
spintronics. But, as a demonstration of fundamental science, this first hybrid circuit lays the
foundation for technologies to come.
For the demonstration, the researchers used the organic magnet, which they made from a polymer
called vanadium tetracyanoethylene, to polarize the spins in an electrical current. This electrical
current then passed through the gallium arsenide layer and into an LED.
To confirm that the electrons were still polarized when they reached the LED, the researchers
measured the spectrum and polarization of light shining from the LED. The light was indeed
polarized, indicating the initial polarization of the incoming electrons.
The fact that they were able to measure the electrons’ polarization with the LED also suggests that
other researchers can use this same technique to test spin in other organic systems.
Coauthors on the paper included former doctoral student Chia-Yi Chen and former postdoctoral
researcher Patrick Truitt. This research was funded by the National Science Foundation’s Materials
Research Science and Engineering Centers program, Ohio State’s Institute for Materials Research,
and the Department of Energy.
Next
To summarize, there are two important speeds - the speed of the message telling all the electrons to
begin their drifting motion in one direction and the speed at which the electrons themselves move.
These two speeds are actually radically different. The speed of the message is the speed of light
while the speed of the electrons is literally slow as molasses.
An example of how slow the electrons are can be found in gel electrophoresis. Gel electrophoresis
is a method for analysing large biological molecules such as DNA fragments. It's often used in areas
like forensic science to analyse DNA samples taken from rapes or violent crimes. You've probably
seen it on CSI or some place like that. At any rate, the method applies an electric field to a gel
where a sample of DNA (or some other sample) has been placed. Due to the presence of the
electric field, the DNA (or other sample) molecules begin to drift through the gel. If you've ever done
this you'll notice that it takes a very long time. I actually performed this experiment back in high
school when I took a forensic science class. At any rate, the reason why it takes so long is because
you're separating the molecules by causing them to drift through the medium; in other words, you're
relying on the fact that the particles will drift slowly through the material. You're also relying on the
fact that particles of different masses will be separated at different rates, though this latter fact is not
important for us here.
The velocity and the electrical resistance outside a conduction is often assumed by the propagation
speed of an electromagnetic wave. In simplified systems, the speed of electricity is given as the
electromagnetic wave which conveys information (data), not the movement of electrons.
Electromagnetic wave propagation is fast and depends on the dielectric constant of the material.
In a vacuum the wave travels at the speed of light and almost that fast in air. Propagation speed is
affected by insulation, such that in an unshielded copper conductor range 95 to 97% that of the
speed of light, while in a typical coaxial cable it is about 66% of the speed of light.
Hybrid Spintronic Chips Open Door to New Functionality
Researchers have created the first electronic circuit to merge traditional inorganic semiconductors
with organic “spintronics” — devices that utilize the spin of electrons to read, write and manipulate
data. Ezekiel Johnston-Halperin, assistant professor of physics at Ohio State University, and his
team combined an inorganic semiconductor with a unique plastic material that is under
development in colleague Arthur J. Epstein’s lab.
Last year, Epstein, Distinguished University Professor of physics and chemistry and director of the
Institute for Magnetic and Electronic Polymers at Ohio State, demonstrated the first successful data
storage and retrieval on a plastic spintronic device. Now Johnston-Halperin, Epstein and their
colleagues have incorporated the plastic device into a traditional circuit based on gallium arsenide.
Two of their now-former doctoral students, Lei Fang and Deniz Bozdag, had to devise a new
fabrication technique to make the device.
In a paper published online in the journal Physical Review Letters, they describe how they
transmitted a spin-polarized electrical current from the plastic material, through the gallium
arsenide, and into a light-emitting diode (LED) as proof that the organic and inorganic parts were
working together.
“Hybrid structures promise functionality that no other materials, neither organic nor inorganic, can
currently achieve alone,” Johnston-Halperin said. “We’ve opened the door to linking this exciting
new material to traditional electronic devices with transistor and logic functionality. In the longer
term, this work promises new, chemically based functionality for spintronic devices.”
Normal electronics encode computer data based on a binary code of ones and zeros, depending
on whether an electron is present or not within the material. But researchers have long known that
electrons can be polarized to orient in particular directions, like a bar magnet. They refer to this
orientation as spin — either “spin up” or “spin down” — and this approach, dubbed spintronics, has
been applied to memory-based technologies for modern computing. For example, the terabyte
drives now commercially available would not be possible without spintronic technology.
If scientists could expand spintronic technology beyond memory applications into logic and
computing applications, major advances in information processing could follow, Johnston-Halperin
explained. Spintronic logic would theoretically require much less power, and produce much less
heat, than current electronics, while enabling computers to turn on instantly without “booting up.”
Hybrid and organic devices further promise computers that are lighter and more flexible, much as
organic LEDs are now replacing inorganic LEDs in the production of flexible displays.
A spintronic semiconductor must be magnetic, so that the spin of electrons can be flipped for data
storage and manipulation. Few typical semiconductors — that is, inorganic semiconductors — are
magnetic. Of those that are, all require extreme cold, with operating temperatures below -150
degrees Fahrenheit or -100 degrees Celsius. That’s colder than the coldest outdoor temperature
ever recorded in Antarctica.
“In order to build a practical spintronic device, you need a material that is both semiconducting
and magnetic at room temperature. To my knowledge, Art's organic materials are the only ones
that do that,” Johnston-Halperin said. The organic magnetic semiconductors were developed by
Epstein and his long-standing collaborator Joel S. Miller of the University of Utah.
The biggest barrier that the researchers faced was device fabrication. Traditional inorganic devices
are made at high temperatures with harsh solvents and acids that organics can’t tolerate. Fang and
Bozdag solved this problem by building the inorganic part in a traditional cleanroom, and then
adding an organic layer in Epstein’s customized organics lab — a complex process that required a
redesign of the circuitry in both parts.
“You could ask, why didn’t we go with all organics, then?” Johnston-Halperin said. “Well, the reality is
that industry already knows how to make devices out of inorganic materials. That expertise and
equipment is already in place. If we can just get organic and inorganic materials to work together,
then we can take advantage of that existing infrastructure to move spintronics forward right away.”
He added that much work will need to be done before manufacturers can mass-produce hybrid
spintronics. But, as a demonstration of fundamental science, this first hybrid circuit lays the
foundation for technologies to come.
For the demonstration, the researchers used the organic magnet, which they made from a polymer
called vanadium tetracyanoethylene, to polarize the spins in an electrical current. This electrical
current then passed through the gallium arsenide layer and into an LED.
To confirm that the electrons were still polarized when they reached the LED, the researchers
measured the spectrum and polarization of light shining from the LED. The light was indeed
polarized, indicating the initial polarization of the incoming electrons.
The fact that they were able to measure the electrons’ polarization with the LED also suggests that
other researchers can use this same technique to test spin in other organic systems.
Coauthors on the paper included former doctoral student Chia-Yi Chen and former postdoctoral
researcher Patrick Truitt. This research was funded by the National Science Foundation’s Materials
Research Science and Engineering Centers program, Ohio State’s Institute for Materials Research,
and the Department of Energy.
Next
Inventbot, inventing new creatures
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