Lună: aprilie 2016

Echipa construiește primul laser cu cascadă cuantică pe siliciu(Team builds first quantum cascade laser on silicon)

au construit primul laser cu cascadă cuantică pe siliciu. Progresul poate avea aplicații care se întind de la spectroscopia de legături chimice și de detectarea gazelor, până la astronomia și comunicațiile spațiului liber.construirea acestor dispozitive fotonice cu siliciu pentru lungimi de undă mai lungi în mijlocul infraroșiei, pentru o gamă de aplicații de detectare și detectare, cum ar fi spectroscopia de legături chimice, senzația de gaz, astronomia, senzorizarea oceanografică, imagistica termică, spațiul liber de comunicații.

Posted: Apr 20, 2016

Team builds first quantum cascade laser on silicon

(Nanowerk News) A team of researchers from across the country, led by Alexander Spott, University of California, Santa Barbara, USA, have built the first quantum cascade laser on silicon. The advance may have applications that span from chemical bond spectroscopy and gas sensing, to astronomy and free-space communications.
Quantum Cascade Lasers Integrated above Silicon Waveguide
3-D artistic depiction of multiple Quantum Cascade Lasers integrated above silicon waveguides. (Image: Alexander Spott)
Integrating lasers directly on silicon chips is challenging, but it is much more efficient and compact than coupling external laser light to the chips. The indirect bandgap of silicon makes it difficult to build a laser out of silicon, but diode lasers can be built with III-V materials such as InP or GaAs. By directly bonding an III-V layer on top of the silicon wafer and then using the III-V layers to generate gain for the laser, this same group has integrated a multiple quantum well laser on silicon that operates at 2 µm. Limitations in diode lasers prevent going to longer wavelengths where there are many more applications, so the group turned their attention to using quantum cascade lasers instead.
Building a quantum cascade laser on silicon was a challenging task made more difficult by the fact that silicon dioxide becomes heavily absorptive at longer wavelengths in the mid-infrared.
„This meant that not only did we have to build a different type of laser on silicon, we had to build a different silicon waveguide too,” Spott explained. „We built a type of waveguide called a SONOI waveguide [silicon-on-nitride-on-insulator], which uses a layer of silicon nitride [SiN] underneath the silicon waveguide, rather than just SiO2.”
The breakthrough could lead to several applications, Spott explained. Traditionally, silicon photonic devices operate at near-infrared wavelengths, with applications in data transmission and telecommunications. However, there is emerging research interest in building these silicon photonic devices for longer mid-infrared wavelengths, for a range of sensing and detection applications, such as chemical bond spectroscopy, gas sensing, astronomy, oceanographic sensing, thermal imaging, explosive detection, and free-space communications.
The next step for the team is to improve the heat dissipation to improve the performance of these QCLs and to allow them to make continuous-wave QCLs on silicon. „We generally hope to improve the design to get higher powers and efficiency,” Spott said. „This brings us closer to building fully integrated mid-infrared devices on a silicon chip, such as spectrometers or gas sensors. Silicon is inexpensive, the fabrication can be scaled up to significantly reduce the cost of individual chips, and many small devices can be built on the same silicon chip for example multiple different types of sensors operating at different mid-infrared wavelengths.”
About the Presentation
The presentation „Quantum Cascade Laser on Silicon at 4.8 µm,” by Alexander Spott, Jon Peters, Michael Davenport, Eric Stanton, Charles Merritt, William Bewley, Igor Vurgaftman, Jerry Meyer, Jeremy Kirch, Luke Mawst, Dan Botez, John Bowers, will take place from 14:00 – 16:00, Thursday, 09 June 2016, San Jose Convention Center, San Jose, California, USA.
Source: The Optical Society

Inovațiile LGS au acordat un contract de forță aeriană de 11,2 milioane USD pentru a dezvolta senzor chimic la distanță(LGS Innovations Awarded $11.2M Air Force Contract to Develop Remote Chemical Sensor )

Sistem bazat pe laser pentru a ajuta la detectarea armelor chimice, a explozivilor, a narcoticelor și multe altele

LGS

Inovațiile LGS au acordat contractul privind Forțele Aeriene pentru a dezvolta senzor chimic la distanță(LGS Innovations Awarded Air Force Contract to Develop remote Chemical sensor )

Sistem de laser pentru detectia armelor chimice, explozibile , narcotice ,etc

Mark 24

Sistem bazat pe laser pentru a ajuta la detectarea armelor chimice, a explozivilor, a narcoticelor și multe altele(Laser-based system to aid in detection of chemical weapons, explosives, narcotics, and more)

sistem de dectie al armelor chimice , explozive, narcotice ,etc . Proiect de dezvoltare-cercetare al fortelor aeriene

Mark 22

Generarea de materiale magnetice personalizate(Generation of tailored magnetic materials)

fizicienii sunt interesați de o generație de materiale artificiale, ale căror proprietăți pot fi controlate. Cercetătorii de la Universitatea din Geneva (UNIGE), Elveția, în colaborare cu echipele franceze și engleze, au reușit să manipuleze proprietățile a doi oxizi care alcătuiesc materialul artificial, mai exact au reușit să modifice proprietățile magnetice care pot fi fie feromagnetice sau antiferomagnetic; adică, cu sau fără moment magnetic net.

Posted: Apr 15, 2016

Generation of tailored magnetic materials

(Nanowerk News) Every day, new technologies require more precision in the intrinsic properties of the materials used. To meet increasingly specific requirements, physicists are interested in a generation of artificial materials, the properties of which can be controlled. Researchers at the University of Geneva (UNIGE), Switzerland, in collaboration with French and English teams, have succeed in manipulating the properties of two oxides which make up the artificial material, more exactly they managed to modify the magnetic properties which can be either ferromagnetic or antiferromagnetic; that is, with or without net magnetic moment.
The scientists have demonstrated, in their study published in Nature Communications („Interlayer coupling through a dimensionality-induced magnetic state”), that they are able now to control the magnetism in this type of materials and that they could, in the near future, offer tailored materials for the devices of tomorrow.
text
Artist view of the manipulation of the magnetic properties achieved in the oxide materials LaNiO3and LaMnO3 when few atomic layers of each material are grown one on top of the other successively. In this case, LaNiO3, which initially was conducting and non-magnetic, is found to become insulating and magnetic when in contact with LaMnO3. (Image: Marta Gibert Gutierrez – UNIGE)
When two materials are in contact, they interact in different ways and, sometimes, exchange electrons. But what happens when one stacks up ultrathin layers, of the order of one nanometer? «We have combined two materials, LaNiO3, a metallic paramagnet (without magnetic order), and LaMnO3, an insulating antiferromagnet, by alternating a layer of the first, then of the second, etc. We then observed what the influence of interactions at the interfaces was and we noticed a profound change in the intrinsic properties of the two materials», said a statement from Jean-Marc Triscone, professor at the Department of quantum matter physics in the Faculty of Science of UNIGE.
LaNiO3 and LaMnO3 have the same cubic crystalline structure, and thus the researchers can stack the elemental unit cells of these compounds, that is the small „cubes” made of just a few atoms, by using state-of-the-art technology. They then manage to create an artificial structure with a perfect alignment of the unit cells. To do this, the physicists deposit one unit cell after the other on a substrate; that is a small heated crystal tile. The layers are very thin and their thickness of about a nanometer is controlled precisely at the unit cell.
Goldsmith precision
«In order to realise a perfect structure on the crystal tile, we had to find the exact temperature and pressure conditions required to grow the materials one on top of the other. Then we investigated the properties of the interfaces depending on the number of layers stacked», explain Marta Gibert, researcher in physics at UNIGE and first author of the study. «Measurements of the physical properties then revealed that the properties of LaNiO3 are very different when in contact with LaMnO3. From being a metal without magnetic order, it becomes not only magnetic but also insulating. Moreover, the overall properties of the artificial material depend on the individual thickness of the layer of each material and they can also change as a function of the chosen thickness», added the physicist.
Thanks to this discovery, the researchers are therefore able to control the magnetic state of these materials – a track to build artificial tailored materials according to specific needs in the future. Such control of the magnetic interactions could especially be used to develop future magnetic memories, allowing the high dissipation energy of current processors to be reduced.
This research is not limited to magnetic materials, but it is also of interest for materials that are simultaneously magnetic and ferroelectric, another way to new memories or even to superconducting materials working at higher temperatures – a dream which may be not so distant.
Source: Université de Genève

TNVC / Unitate Tactical CLUTCH Curea de combatere a centurii de luptă / tactică / bătătură cu material textil cu întindere în două direcții, suporturi de acoperire BlackPoint Tactical Kydes și purtători / pungi Mag (Magazine) și placă de bază Gen-2 PMAG Mag(TNVC/Unity Tactical CLUTCH Belt Covert Combat/Tactical/Battle Belt with 2-Way-Stretch Fabric, BlackPoint Tactical Kydes Concealment Holsters and Mag (Magazine) Carriers/Pouches, and Gen-2 PMAG Mag Base Plate )

Cureaua TNVC / Unity Tactical CLUTCH este concepută special pentru transportul ascuns / ascuns pentru operatorii implicați în misiuni de operațiuni ascunse, dar se poate dubla ca o centură de combatere rapidă / reacție de urgență / tactică / luptă pentru operațiuni shooter activ / contraterorism

TNVC

Senzorul pe bază de grafen detectează poluarea dăunătoare a aerului în casă(Graphene-based sensor detects harmful air pollution in the home)

au dezvoltat un senzor pe bază de grafen și un comutator care poate detecta poluarea dăunătoare a aerului în casă cu o consumare de energie foarte scăzută

Graphene

Senzor electric pe bază de hârtie dezvoltat pentru a monitoriza rata de respirație(Paper-based electrical sensor developed to monitor respiration rate)

A fost creat un senzor simplu dar eficient pentru monitorizarea ratei de respirație a persoanelor

Paper

Oamenii de știință dezvoltă un material bazat pe oxid de hafniu pentru un nou tip de memorie nevolatilă(Scientists grow a material based on hafnium oxide for a new type of non-volatile memory)

Oamenii de stiinta de la MIPT au reusit sa dezvolte pelicule feroelectrice ultra-subtiri (2,5 nanometri) pe baza de oxid de hafniu care ar putea fi folosite pentru a dezvolta elemente de memorie nevolatile numite jonctiuni tunel feroelectrice.

Posted: Apr 14, 2016

Scientists grow a material based on hafnium oxide for a new type of non-volatile memory

(Nanowerk News) Scientists from MIPT have succeeded in growing ultra-thin (2.5-nanometre) ferroelectric films based on hafnium oxide that could potentially be used to develop non-volatile memory elements called ferroelectric tunnel junctions. The results of the study have been published in the journal ACS Applied Materials & Interfaces („Ultrathin Hf0.5Zr0.5O2 Ferroelectric Films on Si”).
Function of a silicon-based ferroelectric tunnel junction
Function of a silicon-based ferroelectric tunnel junction. Information is written by applying an external electric field, which changes the direction of the ferroelectric’s polarization vector, and this in turn changes the shape of the potential barrier. Information is read by measuring the tunnel current, which depends on the shape of the barrier. (Image courtesy of the authors of the study)
Humans are constantly expanding the volume of stored and processed information, which according to statistics is doubling every 1.5 years. To store this information, we need increasing amounts of computer memory, especially non-volatile memory, which stores information even in the event of a power outage. Scientists all over the world are trying to develop faster and more compact storage devices. The ideal would be a “universal” memory device with the speed of RAM, the capacity of a hard drive, and the non-volatility of a flash drive.
There are many known principles that can be used to build memory, but each one has its drawbacks. This is why modern computers and mobile devices have multiple types of memory.
Non-volatile memory based on ferroelectric tunnel junctions is a promising development that has not yet been fully implemented. A ferroelectric is a material that is able to “remember” the direction of an externally applied electric field by the residual polarization charge.
Thin-film ferroelectrics have for a long time been used to make non-volatile memory devices, however it is extremely difficult to miniaturize them and, in addition to this, they are made of materials that are “incompatible” with the production processes used in modern microelectronics.
About ten years ago, after ferroelectric properties were demonstrated in ultra-thin single-crystal films of perovskites, an alternative concept for memory devices was proposed – based on the use of the tunnel effect.
Ferroelectrics are generally insulators and do not conduct electricity. However, if the ferroelectric layer is very thin, electrons can “slip” through with a certain probability, thanks to the quantum tunnelling effect. The probability of tunnelling depends on the size and shape of the potential barrier (the energy characteristics of the structure), and the electrons that “pass through” create a tunnel current.
The movement of the electrons in this case is similar to an obstacle course race, and the size of the obstacle is determined by the direction of the polarization vector, which alters the shape of the potential barrier (see image below). Information is written by applying a voltage to the electrodes next to the ultra-thin ferroelectric, and it is read by measuring the tunnelling current.
In theory, this type of memory may have an extremely high density, fast reading and writing speeds, and a low level of power consumption. It could become a non-volatile alternative to DRAM (dynamic random-access memory). Modern DRAM has a short retention time (approximately 0.1 seconds), after which the data is either lost or overwritten. Using this type of memory requires a large amount of power. Memory based on ferroelectric tunnel junctions will be able to save power, which is especially important for portable devices that run on batteries. However, until now, all prototypes of devices based on conventional ferroelectrics have not been compatible with silicon technology, which is used in the production of most modern chips.
The team of researchers from MIPT’s Laboratory of Functional Materials and Devices for Nanoelectronic, with the participation of their colleagues from the University of Nebraska (USA) and the University of Lausanne (Switzerland), have for the first time experimentally demonstrated that polycrystalline fused films of hafnium and zirconium oxides with a thickness of just 2.5 nm (see image below) retain their ferroelectric properties.
Hafnium oxide is already used in the production of modern silicon logic chips, and a few years ago ferroelectric properties were discovered in one of its modifications. In their study, the scientists from MIPT succeeded in growing an ultra-thin, tunnel-transparent film of this material on a silicon substrate, while maintaining the ferroelectric properties.
a polycrystalline fused film of hafnium and zirconium oxides grown on a highly doped Si substrate
Cross section of the structure developed: a polycrystalline fused film of hafnium and zirconium oxides grown on a highly doped Si substrate (upper electrode – titanium nitride) (Image courtesy of the authors of the study)
It is important to note that the method of atomic layer deposition (ALD) was used to grow the film. This technique is widely used today in the production of modern microprocessors and one of its particular benefits is that it enables functional layers to be grown in three-dimensional structures.
“Since the structures of this material are compatible with silicon technology, we can expect that new non-volatile memory devices with ferroelectric polycrystalline layers of hafnium oxide will be able to be built directly onto silicon in the near future,” says the corresponding author of the study and head of the Laboratory of Functional Materials and Devices for Nanoelectronics, Andrei Zenkevich.
Furthermore, if ferroelectric tunnel junctions based on hafnium oxide are developed, it can be hoped that they will be able to demonstrate memristor properties. This is a prerequisite for creating electronic synapses, which could be used in neuromorphic systems that are currently being developed. These systems have a fundamentally different computing architecture that simulates the functioning principles of the human brain.
Source: Moscow Institute of Physics and Technology

Senzorul pe bază de grafen detectează poluarea dăunătoare a aerului în casă(Graphene-based sensor detects harmful air pollution in the home)

au dezvoltat un senzor și un comutator bazat pe grafen, care pot detecta poluarea dăunătoare a aerului la domiciliu cu un consum foarte redus de energie.
Senzorul detectează moleculele individuale de CO 2 și moleculele de gaze volatile ale compușilor organici volatili (VOC) găsite în materialele de construcție și interioare, mobilier și chiar bunuri de uz casnic, care afectează în mod negativ locuința noastră în case moderne cu izolație bună.
Aceste gaze chimice dăunătoare au concentrații scăzute ale nivelurilor de ppb (părți per miliard) și sunt extrem de dificil de detectat cu tehnologia actuală a senzorilor de mediu, care poate detecta numai concentrațiile de ppm.

Posted: Apr 14, 2016

Graphene-based sensor detects harmful air pollution in the home

(Nanowerk News) Scientists from the University of Southampton, in partnership with the Japan Advanced Institute of Science and Technology (JAIST), have developed a graphene-based sensor and switch that can detect harmful air pollution in the home with very low power consumption.
The sensor detects individual CO2 molecules and volatile organic compound (VOC) gas molecules found in building and interior materials, furniture and even household goods, which adversely affect our living in modern houses with good insulation.
These harmful chemical gases have low concentrations of ppb (parts per billion) levels and are extremely difficult to detect with current environmental sensor technology, which can only detect concentrations of parts per million (ppm).
In recent years, there has been an increase in health problems due to air pollution in personal living spaces, known as sick building syndrome (SBS), along with other conditions such as sick car and sick school syndromes.
The research group, led by Professor Hiroshi Mizuta, who holds a joint appointment at the University of Southampton and JAIST, and Dr Jian Sun and Assistant Professor Manoharan Muruganathan of JAIST, developed the sensor to detect individual CO2 molecules adsorbed (the bond of molecules from a gas to a surface) onto the suspended graphene (single atomic sheet of carbon atoms arranged in a honeycomb-like hexagonal crystal lattice structure) one by one by applying an electric field across the structure.
By monitoring the electrical resistance of the graphene beam, the adsorption and desorption (whereby a substance is released from or through a surface) processes of individual CO2molecules onto the graphene were detected as ‘quantised’ changes in resistance (step-wise increase or decrease in resistance). In the study, published today in Science Advances, the journal of the American Association for the Advancement of Science (AAAS), a small volume of CO2 gas (equivalent to a concentration of approximately 30 ppb) was released and the detection time was only a few minutes.
Professor Mizuta said: “In contrast to the commercially available environmental monitoring tools, this extreme sensing technology enables us to realise significant miniaturisation, resulting in weight and cost reduction in addition to the remarkable improvement in the detection limit from the ppm levels to the ppb levels.”
Research group members, Dr Harold Chong from Southampton and Dr Marek Schmidt and Dr Jian Sun of JAIST, have also recently developed graphene-based switches (published in the March issue of Nanoscale, the journal of the Royal Society of Chemistry) using a uniquely thin film developed at the University of Southampton.
The switches, which require remarkably low voltages (below three volts), can be used to power electronic components on demand, greatly improving the battery lifetime of personal electronic devices.
Professor Mizuta and the research group are now aiming to bring the two technologies together to create ultra-low-power environmental sensor systems that can detect single molecules.
Source: University of Southampton