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Evaluation of the results of the latest research in the field of microelectronics in terms of their innovation potential

2012-12-17
Andrew (Gabriel) Livshits

In the high-tech industry is still key to the success of high-tech product innovation is the use of high performance microelectronic components
At the same time remain unchanged basic technical requirements for specified components, the main ones are the maximum possible microminiaturization, the maximum possible reliability, resilience, ease the process of manufacturing and low cost
First look at the research, opening the way for the creation of fundamentally new sources of supply, as the most important components of microelectronic systems
The developers of the new technology as a rule in the current conditions dictating widespread savings and maximum use of so-called green technologies, mainly characterized by obtaining energy from sunlight
Silicon as the base material for solar cells is becoming more scarce and it determines the value of the following studies and experiments
Physicists at the University of Pennsylvania have created a thin silicon optical fibers that can capture light and produce electricity from it. The work of scientists published in the journal Advanced Materials, and its summary is provided in a university news release.
Initially team of writers to work on the problem of the connection of optical fibers with flat silicon chips. However, the survey found that, based on silicon can create fibers with integrated electronics.
On cross-section shows that the fiber is actually made up of three classic semiconductor zones. When exposed to light, such fibers generate electricity, although the effectiveness of this process is not specified in the message.
With their thin (with a diameter of about 10 microns), the fibers may not damaged, it is easy to bend. The authors hope that these fibers can be woven into a yarn to create electricity tissues. At this point the length of the fibers produced is about a meter, but, according to the researchers, may be increased to 10 meters.
The vast majority of existing solar panels are crystalline or amorphous silicon. The latter allows for a device with a certain level of flexibility.
The conversion efficiency of light to electricity of the best solar cells is currently about 40 percent. Also, are now actively being developed panels, where carbon nanotubes and graphene partially or completely replace silicon and metal electrodes.
Constantly increasing requirements for systems and photoelectric devices, force us to seek new and effective solutions in the field of PV technology
Engineers at Stanford University have created the world's first solar cell that consists entirely of various carbon compounds. The work of scientists published in the journal ACS Nano, and its summary can be found on the website of the university.
For the absorption of light in the device meet carbon nanotubes and fullerenes - spherical carbon compounds C60. Unlike silicon, they can effectively absorb not only visible light, but infrared radiation.
Earlier, another group of researchers have used carbon nanotubes to create solar cells instead of silicon. However, at this time were made of carbon and electrodes formed in the outlet unit electricity.
This usually in film solar panels are used metals and indium tin oxide. The new device engineers replaced them with graphene - monatomic carbon compound. With their thin it is transparent to light, but a good conductor of electricity.
The effectiveness of the prototype of a new solar cell is still small - less than one percent. In this case, the best at the moment solar cells convert light into electricity with an efficiency of up to 24 percent.
However, according to the authors, the effectiveness of the carbon panels can be increased considerably. At the same time, the cost of rare metals needed to make traditional solar cells, in the foreseeable future will continue to grow.
For several years, experts, to compensate and overcome the shortage of silicon are trying to reduce the thickness of the amorphous silicon photovoltaic devices
Engineers have shown that the thickness of the amorphous silicon solar cells can be reduced by placing it in the folds of the dielectric. The paper was published in the journal Nano Letters, her summary is available on the website of the University of North Carolina.
Scientists have found that a layer of amorphous silicon efficiently absorb sunlight and convert it into electricity, when to give it the shape of the folds. Silicon layer thickness of about 70 nanometers, in the shape of folds and absorbs the same fraction of the radiation, as well as a flat layer thickness of 400 nm.
A layer of amorphous silicon authors placed in the "sandwich" between two dielectric layers. To do so, on the surface of a dielectric with classic photolithography received microscopic folds, and then they sprayed a layer of amorphous silicon. Top of another layer of dielectric.
Scientists have shown that the effectiveness of the developed scheme depends primarily on the ratio of the thickness of layers of silicon and dielectric, and not on their chemical nature. The same design can be applied to increase the sensitivity of photo-detectors, sensors, solid-state LEDs.
Previously, engineers from the Massachusetts Institute of Technology have shown that the layer of silicon solar cells can be reduced by applying it in the form of microscopic inverted pyramids. To create such a structure, the authors also used the method of photolithography, but solar cell, which was devoted to the work, which is comprised of amorphous and crystalline silicon.
The researchers also asked the composite materials for possible replacement of silicon in solar panels
This issue is hundreds of small research groups and start-up companies
Another independent group of researchers has recently developed consisting of a carbon nanotube solar cells that can absorb infrared radiation. It carries about 40 percent of the energy of the sun, but not used in the solar cells on silicon. Researchers have proposed the use of carbon solar panels as an additional outer layer to the silicon.
Of particular interest in the scientific and technology areas are contributing to the development of ways of using organic in concept and design of solar cells
Physicists from Japan and Austria have created ultrathin - about 1.5 micrometers thick - organic solar cells. Article scientists appeared in Nature Communications.
The new battery is a few layers of organic layers - for example, polythiophene - joined together. On both sides of the battery is covered by a Mylar film that protects organic damage. Applied over the film-coated electrodes, as well as elastic bands that provide flexibility and protects the battery from the electrodes breaks.
According to the researchers in the laboratory film is converted into electricity to 4 percent of the energy of the incident light. Despite the fact that it is lower than some of the silicon cells, the ratio of weight-to-performance, these batteries are noticeably superior to their semiconductor competitors. The researchers say that their invention will be used to create, such as drones.
Development of Austrian and Japanese relevant because now actively being developed to build aircraft operating on the energy of sunlight. The most famous example - a solar-powered aircraft Solar Impulse. In the summer of 2010 he set a record stay in the air, having worked without a break in the sky over Switzerland 26 hours 10 minutes and 19 seconds
The special effect is the use of nanotechnology to address the issue of effective modification solar
American physicists at Stanford University have developed a technology for creating silicon nano-spheres, the use of which can significantly increase the efficiency of solar cells. The article appeared in the scientific journal Nature Communications, and its summary results in the publication itself.
The first stage of the balls were made of pure quartz. After that, the balls covered with silicon and hydrofluoric acid etched crystal structures obtained from the inside. As a result of the disposal of the scientists were silicon sphere diameter of a few nanometers. Based on these areas were created solar panels.
According to the researchers, the sphere can significantly increase the amount of light absorbed by the batteries, thanks to the effect of "whispering gallery". The point is that in some areas a whisper at one point perfectly audible to another with a remote. This is due to the resonance phenomenon in the propagation of sound (standing resonant modes).
With these modes, scientists were able to "lock" inside the spheres more light than if the structure of the battery was solid. The effectiveness of the battery of 50-nm layer of spheres was comparable with the efficiency of the battery microns thick. For certain wavelengths of light absorption was achieved at the level of 75 percent.
According to scientists, the new technology may be required to create efficient solar cells. In particular, it reduces the amount of material used in the creation of such batteries, and as a result, a lot. Physicists hope that will reduce the consumption of materials used in the manufacture of batteries expensive connection.
In late December 2011, in Physical Review Letters published a work in which scientists suggested partitioning scheme excitons (quasiparticles in a material consisting of an electron and a hole) using carbon nanotubes. This division plays a key role in the development of the electric current in the photovoltaic batteries.
Now a few words about the integrative technical solutions that can, in principle, be the basis for microelectronic systems in the short term, especially in the rapidly developing technology for biomedical applications

Swiss engineers have learned how to create composite materials with variable elasticity, which can be useful for the creation of flexible electronics. The work of scientists published in the journal Nature Communications, a summary of its results LiveScience.
Creating flexible electronics requires the protection of those parts of the device, which can not be stretched, such as integrated microchips. At the same time, direct connection brittle and elastic components leads to the fact that such devices tensile tear in the joints.
Swiss engineers have proposed to solve this problem by creating a material with elasticity, smoothly varying from point to point. They used a composite material - polyurethane with filler.
Varying the amount of filler, the authors were able to do different parts of the material is more or less elastic. In this case, the mechanical properties in different parts of the material differ by five orders of magnitude.
As a prototype, engineers produced elastic bandage with integrated LED, which could be stretched to more than three times. LED is surrounded by a zone of low elasticity of the device, which, if you extend help to prevent injury.
The authors believe that such materials might be useful not only for the creation of flexible electronics, but also for the prosthetic tendon, which also have a variable elasticity.
Recently, Japanese engineers have submitted fabric with integrated LEDs, which, as well as new material is flexible, but could not stretch.
For maximum adaptability of new technologies with existing, now-familiar technologies, interesting development of innovative components of microelectronic systems with up to now unprecedented flexibility
Korean engineers have created a flexible battery and based on them the first fully assembled Flex device. The paper was published in the journal Nano Letters, its summary can be read at EurikAlert.
The device is a lithium-ion battery with inorganic electrodes deposited on a flexible substrate. In its manufacture electrodes first form on mica, and then transferred to plastic – poli-dimetilsulfoksan. In this case, the method of transfer has low material, of which the electrodes themselves.
Korean scientists created battery is able to bend with a radius of about 3 mm, without changing the voltage generated electricity. During the test, the device he bent over 20,000 times, but it almost did not change the voltmeter connected to the battery.
As an experiment, the researchers connected to the battery flexible LED display, and gathered, so the first fully bendable electronic device in the world.
Lithium-ion batteries have long regarded by engineers as a good candidate for flexible power devices. The difficulties that arise in their manufacture, primarily associated with the electrodes, which should keep the folds in good contact with the electrolyte.
To do this, scientists are trying to use or flexible organic conductors or inorganic thin-film conductors. Disadvantages associated with the first low stability, the second - with the difficulty of transferring to a flexible substrate.
Physicists have also developed a new method to produce graphene nanoribbons with smooth edges and specified performance characteristics, making them suitable for the creation of electronic devices of the new generation. The work of researchers published in the journal Nature. Short of it writes portal Physics World.
Graphene - monatomic layer of carbon, which has unusual electronic and mechanical properties. It was created in 2004.
Scientists believe graphene a promising material for the development of nanoscale electronic devices, which may in the future "to press the" traditional semiconductor devices. Although graphene semiconductors superior in ease, strength and mobility of the charge carriers, it does not possess in the state of the so-called gap.
The band gap, or the gap - the difference between the maximum energy of the valence electrons of an atom (that is involved in the formation of chemical bonds) and the minimum energy of the conduction electrons - the electrons, which can under the influence of an external electric field to separate from its atom and participate in the collective motion, creating a current.
The band gap determines the conductive properties of the material - field applied to the material, so he started to conduct, should be imparted to the electron energy is not less than the width of the band gap in order to enable them to leave. Thanks to the band gap semiconductors are widely used in electronics.
To make the semiconducting properties of graphene it is manufactured in the form of thin films: due to quantum size effects on the electron motion is restricted to one direction, according to their energy is well-defined levels and the band gap.
Previously, for the manufacture of graphene ribbons were mainly used technology "top-down" exfoliation of graphene arrays or deployment and cutting carbon. Jagged edges such tapes strongly impair their conductive properties and hinder research and monitoring of their performance.
The new technology is the so-called method of "bottom-up", or chemical methods. On a substrate made of gold or silver is deposited carbon layer cyclic monomers, which are then concatenated into polymers.
The polymer is heated, resulting in the formation carbon tape one atom thick, straight or zigzag, depending on the composition of the starting materials. The width of these bands is 10 to 50 nm, and the width of the band gap is sufficient for the tasks of electronics.
Moreover, the edges of these bands are flat, with minimal incorporation of external atoms, and this greatly improves the conductivity and makes it possible to study the magnetic properties of small objects, depending on the shape of the edge.
For this technology in the future, scientists plan to produce graphene ribbons with interspersed nitrogen and boron, which will create additional energy levels and varying electronic properties of tapes, and receive hetero-junctions - connected tapes of different thickness (ie, with different band gaps).

All these structures can be used in solar power and high frequency devices.

... to be continued

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