Ultra-Thin Memory Storage For Nanocomputer

Engineers worldwide have been developing alternative ways to provide greater memory storage capacity on even smaller computer chips. Previous research into two-dimensional atomic sheets for memory storage has failed to uncover their potential — until now. A team of electrical engineers at The University of Texas at Austin, in collaboration with Peking University scientists, has developed the thinnest memory storage device with dense memory capacity, paving the way for faster, smaller and smarter computer chips for everything from consumer electronics to big data to brain-inspired computing.

For a long time, the consensus was that it wasn’t possible to make memory devices from materials that were only one atomic layer thick,” said Deji Akinwande, associate professor in the Cockrell School of Engineering’s Department of Electrical and Computer Engineering. “With our new ‘atomristors,’ we have shown it is indeed possible.”

Made from 2-D nanomaterials, the “atomristors” — a term Akinwande coined — improve upon memristors, an emerging memory storage technology with lower memory scalability. He and his team published their findings in the January issue of Nano Letters.

Atomristors will allow for the advancement of Moore’s Law at the system level by enabling the 3-D integration of nanoscale memory with nanoscale transistors on the same chip for advanced computing systems,” Akinwande said.

Memory storage and transistors have, to date, always been separate components on a microchip, but atomristors combine both functions on a single, more efficient computer system. By using metallic atomic sheets (graphene) as electrodes and semiconducting atomic sheets (molybdenum sulfide) as the active layer, the entire memory cell is a sandwich about 1.5 nanometers thick, which makes it possible to densely pack atomristors layer by layer in a plane. This is a substantial advantage over conventional flash memory, which occupies far larger space. In addition, the thinness allows for faster and more efficient electric current flow.

Given their size, capacity and integration flexibility, atomristors can be packed together to make advanced 3-D chips that are crucial to the successful development of brain-inspired computing. One of the greatest challenges in this burgeoning field of engineering is how to make a memory architecture with 3-D connections akin to those found in the human brain.

The sheer density of memory storage that can be made possible by layering these synthetic atomic sheets onto each other, coupled with integrated transistor design, means we can potentially make computers that learn and remember the same way our brains do,” Akinwande said.

Source: https://news.utexas.edu

Memristors Retain Data 10 Years Without Power

The internet of things ( IoT) is coming, that much we know. But still it won’t; not until we have components and chips that can handle the explosion of data that comes with IoT. In 2020, there will already be 50 billion industrial internet sensors in place all around us. A single autonomous device – a smart watch, a cleaning robot, or a driverless car – can produce gigabytes of data each day, whereas an airbus may have over 10 000 sensors in one wing alone.

Two hurdles need to be overcome. First, current transistors in computer chips must be miniaturized to the size of only few nanometres; the problem is they won’t work anymore then. Second, analysing and storing unprecedented amounts of data will require equally huge amounts of energy. Sayani Majumdar, Academy Fellow at Aalto University (Finland), along with her colleagues, is designing technology to tackle both issues.

Majumdar has with her colleagues designed and fabricated the basic building blocks of future components in what are called “neuromorphiccomputers inspired by the human brain. It’s a field of research on which the largest ICT companies in the world and also the EU are investing heavily. Still, no one has yet come up with a nano-scale hardware architecture that could be scaled to industrial manufacture and use.

The probe-station device (the full instrument, left, and a closer view of the device connection, right) which measures the electrical responses of the basic components for computers mimicking the human brain. The tunnel junctions are on a thin film on the substrate plate.

The technology and design of neuromorphic computing is advancing more rapidly than its rival revolution, quantum computing. There is already wide speculation both in academia and company R&D about ways to inscribe heavy computing capabilities in the hardware of smart phones, tablets and laptops. The key is to achieve the extreme energy-efficiency of a biological brain and mimic the way neural networks process information through electric impulses,” explains Majumdar.

In their recent article in Advanced Functional Materials, Majumdar and her team show how they have fabricated a new breed of “ferroelectric tunnel junctions”, that is, few-nanometre-thick ferroelectric thin films sandwiched between two electrodes. They have abilities beyond existing technologies and bode well for energy-efficient and stable neuromorphic computing.

The junctions work in low voltages of less than five volts and with a variety of electrode materials – including silicon used in chips in most of our electronics. They also can retain data for more than 10 years without power and be manufactured in normal conditions.

Tunnel junctions have up to this point mostly been made of metal oxides and require 700 degree Celsius temperatures and high vacuums to manufacture. Ferroelectric materials also contain lead which makes them – and all our computers – a serious environmental hazard.

Our junctions are made out of organic hydro-carbon materials and they would reduce the amount of toxic heavy metal waste in electronics. We can also make thousands of junctions a day in room temperature without them suffering from the water or oxygen in the air”, explains Majumdar.

What makes ferroelectric thin film components great for neuromorphic computers is their ability to switch between not only binary states – 0 and 1 – but a large number of intermediate states as well. This allows them to ‘memoriseinformation not unlike the brain: to store it for a long time with minute amounts of energy and to retain the information they have once received – even after being switched off and on again.

We are no longer talking of transistors, but ‘memristors’. They are ideal for computation similar to that in biological brains.  Take for example the Mars 2020 Rover about to go chart the composition of another planet. For the Rover to work and process data on its own using only a single solar panel as an energy source, the unsupervised algorithms in it will need to use an artificial brain in the hardware.

What we are striving for now, is to integrate millions of our tunnel junction memristors into a network on a one square centimetre area. We can expect to pack so many in such a small space because we have now achieved a record-high difference in the current between on and off-states in the junctions and that provides functional stability. The memristors could then perform complex tasks like image and pattern recognition and make decisions autonomously,” says Majumdar.

Source: http://www.aalto.fi/

30 Billion Switches Onto The New IBM Nano-based Chip

IBM is clearly not buying into the idea that Moore’s Law is dead after it unveiled a tiny new transistor that could revolutionise the design, and size, of future devices. Along with Samsung and Globalfoundries, the tech firm has created a ‘breakthrough’ semiconducting unit made using stacks of nanosheets. The companies say they intend to use the transistors on new five nanometer (nm) chips that feature 30 billion switches on an area the size of a fingernail. When fully developed, the new chip will help with artificial intelligence, the Internet of Things, and cloud computing.

For business and society to meet the demands of cognitive and cloud computing in the coming years, advancement in semiconductor technology is essential,” said Arvind Krishna, senior vice president, Hybrid Cloud, and director, IBM Research.

IBM has been developing nanometer sheets for the past 10 years and combined stacks of these tiny sheets using a process called Extreme Ultraviolet (EUV) lithography to build the structure of the transistor.

Using EUV lithography, the width of the nanosheets can be adjusted continuously, all within a single manufacturing process or chip design,” IBM and the other firms said. This allows the transistors to be adjusted for the specific circuits they are to be used in.

Source: http://www.wired.co.uk/

All Carbon Spin Transistor Is Quicker And Smaller

A researcher with the Erik Jonsson School of Engineering and Computer Science at UT Dallas has designed a novel computing system made solely from carbon that might one day replace the silicon transistors that power today’s electronic devices.

The concept brings together an assortment of existing nanoscale technologies and combines them in a new way,” said Dr. Joseph S. Friedman, assistant professor of electrical and computer engineering at UT Dallas who conducted much of the research while he was a doctoral student at Northwestern University.

The resulting all-carbon spin logic proposal, published by lead author Friedman and several collaborators in the June 5 edition of the online journal Nature Communications, is a computing system that Friedman believes could be made smaller than silicon transistors, with increased performance.

Today’s electronic devices are powered by transistors, which are tiny silicon structures that rely on negatively charged electrons moving through the silicon, forming an electric current. Transistors behave like switches, turning current on and off.

In addition to carrying a charge, electrons have another property called spin, which relates to their magnetic properties. In recent years, engineers have been investigating ways to exploit the spin characteristics of electrons to create a new class of transistors and devices called “spintronics.”

Friedman’s all-carbon, spintronic switch functions as a logic gate that relies on a basic tenet of electromagnetics: As an electric current moves through a wire, it creates a magnetic field that wraps around the wire. In addition, a magnetic field near a two-dimensional ribbon of carbon — called a graphene nanoribbon — affects the current flowing through the ribbon. In traditional, silicon-based computers, transistors cannot exploit this phenomenon. Instead, they are connected to one another by wires. The output from one transistor is connected by a wire to the input for the next transistor, and so on in a cascading fashion.

Source: http://www.utdallas.edu/

Nanocomputer: Carbon Nanotube Transistors Outperform Silicon

For decades, scientists have tried to harness the unique properties of carbon nanotubes to create high-performance electronics that are faster or consume less power — resulting in longer battery life, faster wireless communication and faster processing speeds for devices like smartphones and laptops. But a number of challenges have impeded the development of high-performance transistors made of carbon nanotubes, tiny cylinders made of carbon just one atom thick. Consequently, their performance has lagged far behind semiconductors such as silicon and gallium arsenide used in computer chips and personal electronics.

Now, for the first time, University of Wisconsin–Madison materials engineers have created carbon nanotube transistors that outperform state-of-the-art silicon transistors. Led by Michael Arnold and Padma Gopalan, UW–Madison professors of materials science and engineering, the team’s carbon nanotube transistors achieved current that’s 1.9 times higher than silicon transistors. The researchers reported their advance in a paper published in the journal Science Advances.

carbon nanotube integrated circuits

This achievement has been a dream of nanotechnology for the last 20 years,” says Arnold. “Making carbon nanotube transistors that are better than silicon transistors is a big milestone. This breakthrough in carbon nanotube transistor performance is a critical advance toward exploiting carbon nanotubes in logic, high-speed communications, and other semiconductor electronics technologies.”

This advance could pave the way for carbon nanotube transistors to replace silicon transistors and continue delivering the performance gains the computer industry relies on and that consumers demand. The new transistors are particularly promising for wireless communications technologies that require a lot of current flowing across a relatively small area.

Source: http://news.wisc.edu/

Nanocomputer: How To Grow Atomically Thin Transistors

In an advance that helps pave the way for next-generation electronics and computing technologies—and possibly paper-thin gadgets —scientists with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) developed a way to chemically assemble transistors and circuits that are only a few atoms thick. What’s more, their method yields functional structures at a scale large enough to begin thinking about real-world applications and commercial scalability“This is a big step toward a scalable and repeatable way to build atomically thin electronics or pack more computing power in a smaller area,” says Xiang Zhang*, a senior scientist in Berkeley Lab’s Materials Sciences Division who led the study.

Their work is part of a new wave of research aimed at keeping pace with Moore’s Law, which holds that the number of transistors in an integrated circuit doubles approximately every two years. In order to keep this pace, scientists predict that integrated electronics will soon require transistors that measure less than ten nanometers in length (nanocomputer). Transistors are electronic switches, so they need to be able to turn on and off, which is a characteristic of semiconductors. However, at the nanometer scale, silicon transistors likely won’t be a good option. That’s because silicon is a bulk material, and as electronics made from silicon become smaller and smaller, their performance as switches dramatically decreases, which is a major roadblock for future electronics.

Researchers have looked to two-dimensional crystals that are only one molecule thick as alternative materials to keep up with Moore’s Law. These crystals aren’t subject to the constraints of silicon. In this vein, the Berkeley Lab scientists developed a way to seed a single-layered semiconductor, in this case the TMDC molybdenum disulfide (MoS2), into channels lithographically etched within a sheet of conducting graphene. The two atomic sheets meet to form nanometer-scale junctions that enable graphene to efficiently inject current into the MoS2. These junctions make atomically thin transistors.

assembly of 2D crystals
This schematic shows the chemical assembly of two-dimensional crystals. Graphene is first etched into channels and the TMDC molybdenum disulfide (MoS2) begins to nucleate around the edges and within the channel. On the edges, MoS2 slightly overlaps on top of the graphene. Finally, further growth results in MoS2 completely filling the channels.

This approach allows for the chemical assembly of electronic circuits, using two-dimensional materials, which show improved performance compared to using traditional metals to inject current into TMDCs,” says Mervin Zhao, a lead author and Ph.D. student in Zhang’s group at Berkeley Lab and UC Berkeley.

Optical and electron microscopy images, and spectroscopic mapping, confirmed various aspects related to the successful formation and functionality of the two-dimensional transistors. In addition, the scientists demonstrated the applicability of the structure by assembling it into the logic circuitry of an inverter. This further underscores the technology’s ability to lay the foundation for a chemically assembled atomic computer or nanocomputer, the scientists say. “Both of these two-dimensional crystals have been synthesized in the wafer scale in a way that is compatible with current semiconductor manufacturing. By integrating our technique with other growth systems, it’s possible that future computing can be done completely with atomically thin crystals,” says Zhao.

*Zhang also holds the Ernest S. Kuh Endowed Chair at the University of California (UC) Berkeley and is a member of the Kavli Energy NanoSciences Institute at Berkeley. Other scientists who contributed to the research include Mervin Zhao, Yu Ye, Yang Xia, Hanyu Zhu, Siqi Wang, and Yuan Wang from UC Berkeley as well as Yimo Han and David Muller from Cornell University.

Source: http://newscenter.lbl.gov/

Electronic Circuits Mimic The Human Brain

Researchers of the MESA+ Institute for Nanotechnology and the CTIT Institute for ICT Research at the University of Twente in The Netherlands have demonstrated working electronic circuits that have been produced in a radically new way, using methods that resemble Darwinian evolution. The size of these circuits is comparable to the size of their conventional counterparts, but they are much closer to natural networks like the human brain. The findings promise a new generation of powerful, energy-efficient electronics, and have been published in the journal Nature Nanotechnology. The approach of the researchers at the University of Twente is based on methods that resemble those found in Nature. They have used networks of gold nanoparticles for the execution of essential computational tasks. Contrary to conventional electronics, they have moved away from designed circuits. By using ‘designless‘ systems, costly design mistakes are avoided. The computational power of their networks is enabled by applying artificial evolution. This evolution takes less than an hour, rather than millions of years. By applying electrical signals, one and the same network can be configured into 16 different logical gates. The evolutionary approach works around – or can even take advantage of – possible material defects that can be fatal in conventional electronics.

One of the greatest successes of the 20th century has been the development of digital computers. During the last decades these computers have become more and more powerful by integrating ever smaller components on silicon chips. However, it is becoming increasingly hard and extremely expensive to continue this miniaturisation. Current transistors consist of only a handful of atoms. It is a major challenge to produce chips in which the millions of transistors have the same characteristics, and thus to make the chips operate properly. Another drawback is that their energy consumption is reaching unacceptable levels. It is obvious that one has to look for alternative directions, and it is interesting to see what we can learn from nature. Natural evolution has led to powerful ‘computers’ like the human brain, which can solve complex problems in an energy-efficient way. Nature exploits complex networks that can execute many tasks in parallel.

Source: http://www.utwente.nl/

Nanotube-based Transistor For Nanocomputers

Individual transistors made from carbon nanotubes are faster and more energy efficient than those made from other materials. Going from a single transistor to an integrated circuit full of transistors, however, is a giant leap.

carbon nanotube integrated circuits

A single microprocessor has a billion transistors in it,” said Northwestern Engineering’s Mark Hersam. “All billion of them work. And not only do they work, but they work reliably for years or even decades.

When trying to make the leap from an individual, nanotube-based transistor to wafer-scale integrated circuits, many research teams, including Hersam’s, have met challenges. For one, the process is incredibly expensive, often requiring billion-dollar cleanrooms to keep the delicate nano-sized components safe from the potentially damaging effects of air, water, and dust. Researchers have also struggled to create a carbon nanotube-based integrated circuit in which the transistors are spatially uniform across the material, which is needed for the overall system to work.

Now Hersam and his team have found a key to solving all these issues. The secret lies in newly developed encapsulation layers that protect carbon nanotubes from environmental degradation.

Supported by the Office of Naval Research and the National Science Foundation, the research appears online in Nature Nanotechology on September 7. Tobin J. Marks,  professor of materials science and engineering in the McCormick School of Engineering, coauthored the paper. Michael Geier, a graduate student in Hersam’s lab, was first author. “One of the realities of a nanomaterial, such as a carbon nanotube, is that essentially all of its atoms are on the surface,” said Hersam, the Walter P. Murphy Professor of Materials Science and Engineering. “So anything that touches the surface of these materials can influence their properties. If we made a series of transistors and left them out in the air, water and oxygen would stick to the surface of the nanotubes, degrading them over time. We thought that adding a protective encapsulation layer could arrest this degradation process to achieve substantially longer lifetimes.

Hersam compares his solution to one currently used for organic light-emitting diodes (LEDs), which experienced similar problems after they were first realized. Many people assumed that organic LEDs would have no future because they degraded in air. After researchers developed an encapsulation layer for the material, organic LEDs are now used in many commercial applications, including displays for smartphones, car radios, televisions, and digital cameras. Made from polymers and inorganic oxides, Hersam’s encapsulation layer is based on the same idea but tailored for carbon nanotubes.

To demonstrate proof of concept, Hersam developed nanotube-based static random-access memory (SRAM) circuits. SRAM is a key component of all microprocessors, often making up as much as 85 percent of the transistors in the central-processing unit in a common computer. To create the encapsulated carbon nanotubes, the team first deposited the carbon nanotubes from a solution previously developed in Hersam’s lab. Then they coated the tubes with their encapsulation layers.

Using the encapsulated carbon nanotubes, Hersam’s team successfully designed and fabricated arrays of working SRAM circuits. Not only did the encapsulation layers protect the sensitive device from the environment, but they improved spatial uniformity among individual transistors across the wafer. While Hersam’s integrated circuits demonstrated a long lifetime, transistors that were deposited from the same solution but not coated degraded within hours.

After we’ve made the devices, we can leave them out in air with no further precautions,” Hersam said. “We don’t need to put them in a vacuum chamber or controlled environment. Other researchers have made similar devices but immediately had to put them in a vacuum chamber or inert environment to keep them stable. That’s obviously not going to work in a real-world situation.”

Source: http://www.mccormick.northwestern.edu/

Ultrathin Electronics At Nano Scale

Semiconductors, metals and insulators must be integrated to make the transistors that are the electronic building blocks of your smartphone, computer and other microchip-enabled devices. Today’s transistors are miniscule—a mere 10 nanometers wide—and formed from three-dimensional (3D) crystals.

But a disruptive new technology looms that uses two-dimensional (2D) crystals, just 1 nanometer thick, to enable ultrathin electronics. Scientists worldwide are investigating 2D crystals made from common layered materials to constrain electron transport within just two dimensions. Researchers had previously found ways to lithographically pattern single layers of carbon atoms called graphene into ribbon-like “wires” complete with insulation provided by a similar layer of boron nitride. But until now they have lacked synthesis and processing methods to lithographically pattern junctions between two different semiconductors within a single nanometer-thick layer to form transistors, the building blocks of ultrathin electronic devices. Now for the first time, researchers at the Department of Energy’s Oak Ridge National Laboratory (ONRL) have combined a novel synthesis process with commercial electron-beam lithography techniques to produce arrays of semiconductor junctions in arbitrary patterns within a single, nanometer-thick semiconductor crystal.

scalable arrays of semiconductor junctions

We can literally make any kind of pattern that we want,” said Masoud Mahjouri-Samani, who co-led the study with David Geohegan. Geohegan, head of ORNL’s Nanomaterials Synthesis and Functional Assembly Group at the Center for Nanophase Materials Sciences, is the principal investigator of a Department of Energy basic science project focusing on the growth mechanisms and controlled synthesis of nanomaterials.
Millions of 2D building blocks with numerous patterns may be made concurrently, Mahjouri-Samani added. In the future, it might be possible to produce different patterns on the top and bottom of a sheet.

Source: http://www.ornl.gov/

Graphene Boosts By 30 Percent Chips Speeds

A typical computer chip includes millions of transistors connected with an extensive network of copper wires. Although chip wires are unimaginably short and thin compared with household wires, both have one thing in common: in each case the copper is wrapped within a protective sheath. For years a material called tantalum nitride has formed a protective layer around chip wires.

Now Stanford-led experiments demonstrate that a different sheathing material, graphene, can help electrons scoot through tiny copper wires in chips more quickly.

Graphene is a single layer of carbon atoms arranged in a strong yet thin lattice. Stanford electrical engineer H.-S. Philip Wong says this modest fix, using graphene to wrap wires, could allow transistors to exchange data faster than is currently possible.  And the advantages of using graphene could become greater in the future as transistors continue to shrink.

graphene Stanford

“Researchers have made tremendous advances on all of the other components in chips, but recently there hasn’t been much progress on improving the performance of the wires,” he said.

Wong, the Willard R. and Inez Kerr Bell Professor in the School of Engineering, led a team of six researchers, including two from the University of Wisconsin-Madison, who will present their findings at the Symposia of VLSI Technology and Circuits in Kyoto, Japan, a leading venue for the electronics industry. Ling Li, a graduate student in electrical engineering at Stanford and first author of the research paper, will explain why changing the exterior wrapper on connecting wires can have such a big impact on chip performance.

Source: http://engineering.stanford.edu/