Science category

Single Atom Transistor

Single Atom Transistor With Ultra-low Power Consumption

Karlsruhe Institute of Technology (KIT) researchers in Germany have developed a single-atom transistor that can reduce the power consumption of electronic systems significantly. The device is being developed by Professor Thomas Schimmel and his team at the Institute of Applied Physics (APH). The single-atom transistor switches electrical current by controlled repositioning of a single atom in a gel electrolyte. The device works at room temperature and consumes a very small amount of energy. It also has the potential of opening up an entirely new perspective for information technology.

Single Atom Transistor
Single Atom Transistor developed by the KIT researchers

Prof Schimmel, who conducts research at the APH, the Institute of Nanotechnology (INT), and the Material Research Center for Energy Systems (MZE) of KIT said,

This quantum electronics element enables switching energies smaller than those of conventional silicon technologies by a factor of 10,000,

Earlier this year, Professor Schimmel, who is recognized as the pioneer of single-atom electronics, was appointed Co-Director of the Center for Single-Atom Electronics and Photonics established jointly by KIT and ETH Zurich.

The experts produced two-minute metallic contacts with a gap as wide as a single metal atom. The gap was tested with a source-drain current ranging from 1 to 8 µA. With the help of an electrically controlled pulse, they positioned a single silver atom into this gap and closed the circuit. Just when the silver atom is removed from the gap, the circuit is interrupted and the flow of current is stopped. Thus it acts just like a switch and can be used for high-speed electronic switching circuits.

The world’s smallest transistor switches current through the controlled reversible movement of a single atom. It’s also a contrary to conventional quantum electronics components. The single-atom transistor has a broad range of working temperature from near absolute zero to the room temperature. This can be a breakthrough for future electronics.

The single-atom transistor is made of metal only without any semiconductors. This results in extremely low electric voltages and, hence, an extremely low energy consumption. Previous devices of this category developed at KIT have used a liquid electrolyte, but this latest version uses a solid electrolyte.

The gel electrolyte was produced by gelling an aqueous silver electrolyte with pyrogenic silicon dioxide combines the advantages of a solid with the electrochemical properties of a liquid. In this way, both safety and handling of the single-atom transistor are improved.

Femtosecond near-field coupling of NIR pulses to THz stripline modes

Femtosecond Electronics With Plasmonic Hot Electron Nano-emitters

A team led by the Technical University of Munich (TUM) physicists Alexander Holleitner and Reinhard Kienberger has found success for the first time in generating ultrashort electric pulses on a chip. They made this possible by using asymmetric metal antennas only a few nanometers in dimension, then running the signals a few millimeters above the surface and receiving them in a controlled way.

Traditional electronics allow frequencies up to around 100 GHz. Optoelectronics can produce electric pulses at 10 THz range by applying electromagnetic phenomenon. The range in between them is referred as the terahertz gap, since components for signal generation, conversion, and detection have been remarkably difficult to achieve.

The TUM physicists succeeded in generating electric pulses in the frequency range up to 10 THz using tiny, so-called plasmonic antennas and run them over a chip. Researchers call the antennas plasmonic because of their shape, they amplify the light intensity at the metal surfaces. The shape of these plasmonic antennas is very important. They are asymmetrical in shape. One side of the nanometer-sized metal structures is more pointed than the other. When a lens-focused laser pulse excites the antennas, they emit more electrons on their pointed side than on the opposite flat ones. An electric current flows between the contacts — but only as long as the antennas are excited with the laser light.

Femtosecond near-field coupling of NIR pulses to THz stripline modes
Femtosecond near-field coupling of NIR pulses to THz stripline modes

In photoemission, the light pulse causes electrons to be emitted from the metal into the vacuum,

explains Christoph Karnetzky, lead author of the Nature paper.

All the lighting effects are stronger on the sharp side, including the photoemission that we use to generate a small amount of current. The light pulses were present in only a few femtoseconds.

Correspondingly short were the electrical pulses in the antennas.  In this way, a femtosecond laser pulse with a frequency of 200 THz could generate an ultra-short THz signal with a frequency of up to 10 THz in the circuits on the chip, according to Karnetzky.

The researchers chose sapphire as the chip material, because it cannot be excited optically and, thus, causes no interference. With an eye on future applications, they used 1.5-micron wavelength lasers deployed in traditional internet fiber-optic cables. Holleitner and his colleagues also made yet another amazing observation that both the electrical and the THz pulses were non-linearly dependent on the excitation power of the laser used. This means that the photoemission in the antennas is triggered by the absorption of multiple photons per light pulse.

Alexander Holleitner said,

Such fast, nonlinear on-chip pulses did not exist hitherto

Utilizing this effect he hopes to discover even faster tunnel emission effects in the antennas and to use them for chip applications.

Unlimited Source of Energy- As good as it Sounds

In recent decades, humans realized that fossil fuels are a finite source of energy that not only pollutes the environment but is also difficult to extract (it can even be dangerous). Because of this, there has been a huge increase in the development of new ways to extract energy from other sources such as solar, wind, geothermal etc. Following this trend, researchers at King Abdullah University of Science and Technology have developed a diode that generates electricity using infrared energy.

Not all sources of energy have been exploited by humans, and infrared energy is one of them. This was mainly because of the small wavelength of these waves which made it hard to harvest energy. Unlike, solar power or wind, infrared energy can be harvested 24 hours a day because it does not depend on day and night or weather conditions, and unlike solar power it is not limited only to the visible spectrum.

The diode works by using a rectifier (semiconductor diode) to transform alternating signals received by special antennas into electric current. The diode will harvest infrared radiation and waste heat from industrial processes and does this by transitioning quadrillionth- of- a- second wave signals into useful electricity.

The project leader Atif Shamim said :

There is no commercial diode in the world that can operate at such high frequency

that’s why they decided to use quantum tunneling to solve the problem. They used a bowtie- shaped Nano-antenna holding the insulator film between two metallic arms to generate the fields needed for tunneling. One of the researchers mentioned that one of the biggest challenges was working in a nanoscale that require precise alignment for it to work.

These new methods might be still less efficient than fossil fuels, but with the development of the technology used they could improve and be just as efficient, or even more. Additionally, the energy provided by the device is clean and comes from a renewable source. Infrared radiation is emitted all around us at all times and its estimated to be millions of Gigawatts per second. The device has already been tested and it successfully harvested energy solely from radiation and not from thermal effects, and as the project leader said “This is just the beginning- a proof concept”.

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Researchers Developed a Very Powerful Mini Synchrotron That Can Fit On A Tabletop

A synchrotron is a particular type of cyclic particle accelerator which is used to accelerate quantum level charged particles at a very high velocity, traveling around a fixed closed-loop path.

It is one of the first accelerator concepts to enable the construction of large-scale facilities because they are very efficient in beam focusing, bending, and splitting the beam into different components. The most powerful modern particle accelerators such as Large Hadron Collider (LHC) in Switzerland uses bigger versions of the synchrotron design.

Scientists design mini synchrotron that is only 4m long

A synchrotron is mainly used for the production of X-ray in many medical, engineering or industrial fields. Researchers at Eindhoven University of Technology and Delft University of Technology will build and develop a new scaled down version of a synchrotron which will even fit on a tabletop. The intensity of the X-ray radiation of this device will be just as powerful as the larger ones. Smart*Light” is the name of this new synchrotron which they officially took under research on 23rd January.

With Smart*Light, the consortium wants to build a ‘scaled down synchrotron‘. A compact and tunable X-ray source which is less than 4 meters long, which can be used in any lab. The potential of application for such a device is huge in medical diagnostics, high-tech industries, aircraft, car, and ship manufacturing.

Using Smart*Light there is the opportunity to analyze the chemical composition of old or new artworks layer by layer. This does not only have importance for conservation but, also for research into authenticity too.

The operation of this revolutionary X-ray source is based on the physical concept where X-rays are produced from collisions between LASER light and accelerated electrons. The theory is known as Inverse Compton Scattering, and has already been recognized for decades, but only recently has the necessary technology been modern enough to be developed.

Understanding Flash Memory And How It Works

Flash memory is one of the most widely used types of non-volatile memory. NAND Flash is designed for modern file storage which replaced old disk drives. This article provides a brief understanding of how NAND Flash technology works.

The basic storage component used in Flash memory is a modified transistor. In a standard transistor, the flow of current through a channel between two contacts is turned on by a voltage applied to the gate. The channels are separated by an insulating layer of Oxide. In a Flash storage cell, there is an extra electrically isolated gate called “floating gate”. It is added to the control gate and the channel of the modified transistor.

Different Flash Storages
Different Flash Memory Devices

High voltage is applied to the control gate of The Flash cell to program it. This pushes electrons to pass through the oxide layer to the floating gate (a process known as tunneling). The presence of these trapped electrons on the floating gate changes the required voltage to turn on the transistor. Thus, a transistor with no charge on the floating gate can easily turn on at a certain voltage, representing a 1, while a programmed cell will not turn on, representing a 0.

This kind of memory is non-volatile because the floating gate is surrounded by dielectric layers, it traps the electric charge even when the power is removed. Erasing a cell reverses this process by introducing a large negative voltage to the control gate to force the electrons to tunnel out of the floating gate.

NANAD Flash storage internal
NAND Flash Memory storage internal

A number of cells, typically 32 to 128, are connected in a string. Strings are organized in blocks. To program cells in a block, the data is put on the bit lines and a high voltage is applied. Because programming can only change a cell from a 1 to a 0, any cells where the new data is a 1, will be left in their current state. Therefore, all the cells must be erased before writing. This process ensures that any cells that will not be programmed already contain a 1.

As explained above, each cell can store a single binary value, 0 or 1. It is also possible to inject varying amounts of charge onto the floating gate so that the cell can express multiple values. A multi-level cell (MLC) can store four different levels to represent two bits. However, the performance is reduced because of the complexity of accurate voltage controls. For the same reason, MLC Flash memory is more inclined to errors.

Although flash memory has a limited number of write-erase cycles, the high voltages cause a small amount of damage to the cells which makes them harder to read-write over time. The main drawback of using a flash memory is that it has a lifetime of about 100,000 cycles or fewer for MLC Flash.

Researches Solve Problems of Organic Thin Film Transistors By Developing Nanostructured Gate Dielectric

Amorphous silicon-based Thin-film transistors (TFTs) are the foundation of many modern-day technologies, such as smartphones and flat-panel TVs. Still, it comes with a few drawbacks like performance limitations due to limited carrier mobility. Provoking the researchers in search of something better.

As a result, Organic thin-film transistors (OTFTs) were developed. OTFTs have solved the problem with carrier mobility to an extent. Although it introduced new problems such as the critical performance parameter of large threshold voltage instabilities. Threshold voltages—also known as gate voltages—are the minimum voltage differential needed between a gate and the source to create a conducting path between the source and drain terminals.

Nanostructured Gate dielectric opens new possibilities in OTFTs

Latest works of the researchers at Georgia Institute of Technology seems to overcome the voltage instability problem with OTFTs. They have developed a nanostructured gate dielectric that can regulate voltage threshold fluctuations in OTFTs.

gate dielectric is an important component of every thin-film transistor. It acts as the electrically insulating layer between the gate terminal and the semiconductor. It should have a high dielectric constant, be very thin, and have a high dielectric strength for the transistor to function at low voltage.

On applying a voltage across the gate electrode, the resulting electric field across this insulating layer changes the density of carriers in the semiconductor layer. It regulates the current that is flowing between the source and the drain electrodes. Many different materials are used to make this insulating layer. Such as dielectric polymers, inorganic oxides or combinations of different organic and inorganic materials.

The Georgia Tech researchers used Atomic Layer Deposition (ALD) technique to build a thin metal oxide layer on top of a perfluorinated dielectric polymer. They chose ALD for its ability to produce layers that are free from any defects. Bernard Kippelen, a professor at Georgia Tech, and leader of the research said:

The low defect density reduces the diffusion of moisture into the underlying organic semiconductor layer, preventing its degradation.

The performance of the new organic thin-film transistors seems to surpass that of hydrogenated amorphous silicon technology. According to Kippelen, it revolutionizes OTFTs in terms of charge mobility and stability. He stated:

It is premature and difficult at this stage to provide a direct comparison with what is currently on the market; nevertheless, we believe that the level of stability that is achieved is an important step for printed electronics.

Before the future applications, Kippelen and his team will further investigate the mechanical properties of these printed transistors since they show great potential with flexible form factor products. Further information can be found on the Research paper published in the journal Science Advances.

Researcher Create More Lifelike Soft Robots That Can Mimic Biological Muscle

A group of researchers from the University of Colorado in Boulder (US) is working on the next generation of robots. Instead of the metallic droids concept, these robots are made from soft materials that are more similar to biological systems. Such soft robots hold a huge potential for future applications. They can adjust to dynamic environments and also suitable for close human interaction. Christoph Keplinger from the University of Colorado said,

We draw our inspiration from the astonishing capabilities of biological muscle,

The soft devices, including the muscle actuator, can perform a variety of tasks
The soft robots, including the muscle actuator, can perform a variety of tasks

The newly developed class of soft, electrically activated devices are capable of simulating the expansion and contraction of actual muscles. These devices can be constructed from a wide range of low-cost materials. They are able to self-sense their movements and self-heal from electrical damage.

They developed hydraulically amplified self-healing electrostatic (HASEL) actuators which eliminate the bulky, rigid pistons, valves, pumps and motors of conventional robots. The soft structures of HASEL react to applied voltage with a wide range of movement. According to the study published in the journal Science Robotics on January 5, these flexible robots can perform a variety of tasks. They can handle delicate objects like raspberry or raw egg, as well as lift heavy objects. Keplinger said,

HASEL actuators synergize the strengths of soft fluidic and soft electrostatic actuators, and thus combine versatility and performance like no other artificial muscle before,

He also added,

Just like a biological muscle, HASEL actuators can reproduce the adaptability of an octopus arm, the speed of a hummingbird and the strength of an elephant.

HASEL actuators can simulate the strength, speed, flexibility, and efficiency of biological muscle which may enable artificial muscles for human-like robots. HASEL can make next generation of prosthetic limbs more cost-effective and reliable. This is an important step forwards for soft robotics.

The team is already working on new HASEL actuators that would work with five times lower voltage levels than those described in the studies. The voltage published in the papers is similar to the low-current shock one might get from static electricity, and it’s not hazardous to humans.

The work of this researchers promises a huge improvement in the world of robotics and prosthetic limbs. Their dream is to create robotics that is lifelike. More information can be found in an article appeared in Science recently.

Physicists Of University of Rochester Have Created Polariton – A Particle With Negative Mass

A group of researchers led by Nick Vamivakas from the University of Rochester has successfully produced particles which have negative mass in an atomically thin semiconductor material. According to the researchers, they have created a device that can generate LASER light using a significantly small amount of energy. All made possible with the help of this so-called negative mass particles. Quantum physicist Nick Vamivakas from Rochester’s Institute of Optics says,

It also turns out the device we’ve created presents a way to generate laser light with an incrementally small amount of power. Interesting and exciting from a physics perspective,

Polariton – A new particle that has negative mass

Mass is often observed as a resistance or response to a force. It’s harder to push and to stop a bowling ball than a marble because of the inertia associated with the mass of the object. All objects that are made of matter must have the property of ‘mass’. Even elementary particles without rest mass have something called relativistic mass. They react to an externally applied force in the way you expect them to. Particles with ‘negative mass’ however exhibit the opposite reaction to an applied force. They tend to move toward the applied force direction than to move away from it.

“That’s kind of a mind-bending thing to think about because if you try to push or pull it, it will go in the opposite direction from what your intuition would tell you,” says Vamivakas.

The device they created to make negative mass consists of two mirrors. It is used to make an optical microcavity to capture light at different colors of the spectrum depending on the mirror spacing. An atomically thin Molybdenum diselenide semiconductor is then implanted into the microcavity. This interacts with the captured light. The small particles called excitons from the semiconductor combine with photons of the trapped light to form polaritons. This process of an exciton giving up its identity to a photon to produce a polariton results in an object with negative mass associated with it. Simply means when you try to push or pull it, it goes off in the opposite direction to the way you would assume.

The most probable practical applications according to the researchers would be:

  •  The physics of negative mass: It will enrich the understanding of the reaction behavior of polaritons on electric fields and external forces.
  •  As a laser fabrication substrate: Due to polaritons, lasers would function more efficiently than the conventional ones. They will require much lower power input.

Further information is available in the journal Nature Physics, with the title Anomalous dispersion of microcavity trion-polaritons.

eVscope – Reaching for the stars as never before

Humanity has always been trying to reach for the stars, this lead to huge scientific developments that got the man into the moon, rovers into mars and a lot more. NASA often unveils photographs of space objects with bright colors and high definition, but these photos are taken using millions of dollars in telescopes and image software. Most amateur telescopes give blurry, opaque images (if you get to see anything at all). As a result, astronomy amateurs are often disappointed because of their high expectations regarding what they would see in the telescope. The company Unistellar optics combined two different technics to create a telescope that could fulfill hobbyist expectations.

As only a very small amount of light from stellar objects reaches earth, it’s important to collect as much light as possible which can be done with a lens (or mirror with a large diameter), or by exposing a photographic film for a long period of time. Nowadays, astronomers don´t use photographic film anymore because electronic cameras can take hundreds of pictures and overlap them to make one bright picture. However, the equipment to do all this can be expensive (professional camera, good telescope, mirrors with huge diameters), and they can also be complicated because of the need for a very dark sky, certain weather etc.

The eVscope (enhanced vision) made by Unistellar optics has a built in high quality image sensor, and instead of lenses an eye piece with an OLED display is used. Additionally, it has a computer controlled mount and drive, all in modest dimensions. It costs about 1300 dollars and works by taking short exposures and staking them in real time to simulate a larger instrument.

This device has already been tried by many amateur astronomers, and university students with very positive results. Also, the eVscope has an autonomous field detection which makes it easy for learners to pinpoint specific places, and with the smartphone connection capabilities people can save and share their pictures, and unlike other telescopes it is portable and autonomous. Currently, Unistellar optics has a Kickstarter campaign for this product with more than 2000 backers. eVscope is 100 times more powerful than a classical telescope and could change the way people see the sky and learn about astronomy.

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A new type of transistor (a) harnesses a property called negative capacitance.

Researchers Demonstrate New More Efficient FET By Implementing Negative Capacitance

A group of Researchers from Purdue University in Lafayette, Indiana demonstrated the effect called negative capacitance by making a new type of more energy efficient transistor. This new kind of Field Effect Transistor (FET) proves a theory introduced in 2008 by Supriyo Datta, the Thomas Duncan Distinguished Professor of Electrical and Computer Engineering, and Sayeef Salahuddin, who is a professor of Electrical Engineering and Computer Sciences at the University of California, Berkeley.

A new type of transistor (a) harnesses a property called negative capacitance.
A new type of field effect transistor harnesses a property called negative capacitance.

The researchers from Purdue University made a much thinner layer using the semiconductor Molybdenum disulfide. It creates a channel adjacent to an important part of transistors called the gate. By using a “ferroelectric material” called hafnium zirconium oxide, they created a negative capacitor which is a key component in the newly designed gate.

Capacitance is the property of any dielectric or conductor to store electrical charge. It is ordinarily a positive quantity. With the help of ferroelectric materials, the new FET gate structure allows a negative capacitance. Due to this the energy needed to switch the FET is considerably reduced. This new design just substitutes hafnium oxide with hafnium zirconium oxide. Hafnium oxide is a conventional material to use in modern FETs as a dielectric material to isolate the gate. This work is led by Peide Ye, Richard J. and Mary Jo Schwartz of Purdue University.  Ye said,

The overarching goal is to make more efficient transistors that consume less power, especially for power-constrained applications such as mobile phones, distributed sensors, and emerging components for the internet of things

Transistors act like a tiny electronic switch. They can turn on and off very fast, allowing computers to process information in binary code. A proper switching off state is very important to ensure that no electricity “leaks” through. This switching normally needs a minimum of 60 millivolts for every tenfold increase in current. This requirement called the thermionic limit. However, transistors using negative capacitance can break this fundamental limit, because they can switch at far lower voltages resulting in smaller power consumption.

New findings from the research group have advanced the conventional transistor technology to a much efficient and faster level. Only time will justify if the new ‘negative capacitance‘ FETs can revolutionize the modern electronics.