Showing posts with label Nanofabrication. Show all posts
Showing posts with label Nanofabrication. Show all posts

Tuesday, July 21, 2020

Chemical thermometers – a breakthrough that cater the need in microelectronics industry

With the massive miniaturisation of electronic components, density of the electronic components has been enhanced significantly along with the flowing of heat which results in overheating of the components. But conventional methods are unable to estimate the temperature in the electronic components due to limitation imposed by size of it.

Researchers have recently devised a solution of the above issue by fabricating a molecular film and using it in an electronic component of a nanometric scale. The film is made by spin crossover molecules, a temperature sensitive molecule, which is extremely stable even after several uses. Due to the bi-stability property of these molecules, these molecules exist into two electronic states with difference physical property and interchange the states by absorbing and loosing energy.

Once deposited in the form of a film on an electronic component, the optical properties of SCO molecules change depending on the temperature, enabling this chemical thermometer to establish a nanometric-scale thermal map of the surface of microelectronic circuits. The devise will soon be sued at industrial scale with improved design.


Sunday, May 10, 2020

Storage solution using silicon in battery with the aid of nanotechnology


Silicon along with carbon nanotubes has been used to develop a nanostructure to make an effective design for battery anodes. CNT is used to strengthen the material and modify the way the silicon interacts with lithium, which has been extensively used in electrical cars and other devices.


Scientists at the U.S. Department of Energy's Pacific Northwest National Laboratory have used a novel way to use silicon. Silicon, used in computer chips is attractive as it can hold 10 times the electrical charge per gram compared to graphite. The trouble is, silicon expands greatly when it encounters lithium, and it is too weak to withstand the pressure of electrode manufacturing.


To tackle these issues, a unique nanostructure that prevents silicon's expansion when it is mixed with carbon. Scientist work, which was recently published in the journal Nature Communications, could inform new electrode material designs for other types of batteries and eventually help increase the energy capacity of the lithium-ion batteries in electric cars, electronic devices, and other equipment.


How they do it!!


A conductive and stable form of carbon, graphite is well suited to packing lithium ions into a battery's anode as it charges. Silicon can take on more lithium than graphite, but it tends to expand about 300 percent in volume, causing the anode to break apart. The researchers created a porous form of silicon by aggregating small silicon particles into microspheres about 8 micrometers in diameter.


The electrode with porous silicon structure exhibits a change in thickness of less than 20 percent while accommodating twice the charge of a typical graphite anode. However, unlike previous versions of porous silicon, the microspheres also exhibited extraordinary mechanical strength, thanks to carbon nanotubes that make the spheres resemble balls of yarn.


The researchers created the structure sequentially, starting by coating the carbon nanotubes with silicon oxide. Next, the nanotubes were put into an emulsion of oil and water. Then they were heated to boiling. The coated carbon nanotubes condense into spheres when the water evaporates. Then aluminum and higher heat is used to convert the silicon oxide into silicon, followed by immersion in water and acid to remove by-products. What emerges from the process is a powder composed of the tiny silicon particles on the surface of carbon nanotubes.

Sunday, March 29, 2020

Device fabricated to produce high power high frequency waves


Recently Researchers have succeeded to develop a nanodevice that can run 10 times faster than present transistors. The device enables the generation of high-power terahertz waves which are difficult to produce otherwise. Terahertz (THz) waves fall between microwave and infrared radiation in the electromagnetic spectrum, oscillating at frequencies of between 100 billion and 30 trillion cycles per second. Generation of these waves have immense impact on security and medical imaging, sensing, cancer therapy and high-speed wireless communications due to the ability to carry vast quantities of data. These waves can penetrate paper, clothing, wood and walls. It can detect air pollution.


However, THz waves are not widely used because they are costly and cumbersome to generate. But researchers led by Prof. Elison Matioli, built a nanodevice that can generate extremely high-power THz waves.


The compact, cheaper fully electric nanodevice generates high-intensity waves by producing a voltage from 10 V (or lower) to 100 V in the range of a picosecond. The device consists of two metal plates placed very close together, down to 20 nanometres apart. When potential difference between these two plates is applied, electrons surge towards one of the plates (plasma). Once the voltage reaches a certain threshold, the electrons are emitted almost instantly to the second plate. This rapid movement enabled by such fast switches creates a high-intensity pulse that produces high-frequency waves. When hooked up to antennas, the system can produce and radiate high-power THz waves.


The new nanodevice can create both high-energy and high-frequency pulses, unlike present high frequency semiconductor devices, which can only sustain with a few volts before breaking out. The new device has been proposed to surmount these constraint by  nanoplasma and state-of-the-art nanoscale fabrication techniques

Sunday, June 1, 2014

Modulated Nanostructure: Nanowire bridging transistors: The new Buzz word for next-generation electronics

Silicon has been established as one of the widely used material in the integrated circuit since approximately 60 years. It is used to fabricate transistors using conventional method, where etching of the layers was done to formulate some structures. However, circuit based on silicon reach its operational speed limit and does not work above certain temperature. In addition to that, ever increasing demand of miniaturization has led to the development of advanced manufacturing technique where nanostructure material plays significant roles along with the addition of other semiconducting material such as gallium nitride. It does not only show promise for a new generation of fast, robust electronic and photonic devices, but also opens up the scope of innovation for the researchers. Such is the case of three dimensional nanowire transistors, developed by scientists of University of California.


 
 One of the technical problem silicon substrate is facing over the years is the lattice parameter mismatch with other materials. Match is necessary due to the growth technique associated with integrated circuit, which in turn faces major limitation as far as the growth material is concerned. To overcome these challenges, nanowire made of semiconductor materials was made on top of silicon surfaces. Due to the lower surface area of nanowire which acquires the place of silicon, problem of lattice mismatch does not arise. The new technology could be used, for example, to build sensors that can operate under high temperatures, for example inside aircraft engines. In the near future, machine will be dependent on a variety of sensors and control systems that operate in extreme environments, such as motor vehicles, boats, airplanes, terrestrial oil and ore extraction, rockets, spacecraft, and bodily implants.


 
The researchers have been able to make these nanowires operate as transistors, and combine them into more complex circuits as well as devices that are responsive to light. They have developed techniques to control the number of nanowires, their physical characteristics and consistency. The technology also leverages the well-established technology for manufacturing silicon integrated circuits.

Friday, May 23, 2014

Self assembled nanostructure through field assisted phase transition


In the year of 2012, scientist developed the idea of using nanoparticles as building block of functional material which can be engineered to make a computer chip that can assemble itself.

The research carried out by researchers of NASA and University of Delware reported an article about the self assembled with specific structures, built by nanomaterials.

They have observed transition of paramagnetic colloids from random structures to organised crystalline structures when an external magnetic field with desired frequency and field strength was applied into it. This kind of phase separation/transition provides the opportunity to build crystals using magnetic field. It is also useful in understanding the phenomena/mechanisms through which the materials are turned into crystalline.

This new phenomenon could prove worthy for manufacturing new nanoscale self assembled components due to a definite relationship between applied electric field and the conversion of disorder to order structure.

For further reading regarding field assisted phase transition:
http://www.pnas.org/content/109/40/16023.full.pdf+html?sid=d4c55815-5d87-4419-b4da-dd7cc0eaeb9c

Thursday, January 13, 2011

Mass production of non-reflective polymer surfaces (nanofabrication) yields more efficiency in solar energy

A key hurdle in realizing high-efficiency, cost-effective solar energy technology is the low efficiency of current power cells. In order to achieve maximum efficiency when converting solar power into electricity, ideally there is a need for solar panel that can absorb nearly every single photon of light across the entire spectrum of sunlight and irrespective of the sun's position in the sky.

One way to achieve suppression of sunlight's reflection over a broad spectral range is by using nanotextured surfaces that form a graded transition of the refractive index from air to the substrate. Researchers in Finland have now demonstrated a scalable, high-throughput fabrication method for such non-reflecting nanostructured surfaces.

The main advances of this work are in the field of nanofabrication. It was published in a recent paper in Advanced Materials ("Non-Reflecting Silicon and Polymer Surfaces by Plasma Etching and Replication").

The process involves a maskless deep reactive ion etching process that produces nanospikes on a silicon wafer. The process is known as black silicon process. The geometry of the nanospikes i.e. height, width and also the density can be controlled by changing the etching parameters. The main strength of the maskless method is its high throughput.

Different applications require different types of surfaces, and in this study the Finnish team shows that the densest arrays of nanospikes with slightly positively tapered sidewalls had the lowest optical reflectance, while pyramid-shaped nanospikes were ideal for use as templates for polymer replication. Polymer replication techniques are typically high-throughput and low-cost methods which make them very attractive.

In this research it has been shown that both hot-embossing and UV-embossing of polymer is possible with the PDMS stamp. The use of polymers instead of silicon would be useful in high-volume applications due to lower costs. Nanospike-structured polymeric and silicon surfaces are non-reflective and additionally they can be made ultrahydrophobic and self-cleaning, by coating them with a low-surface energy coating. These kinds of inexpensive, non-reflective and self-cleaning surfaces have many applications, for instance in sensors and solar cells.

Another important issue is the mechanical durability of the nanostructured surfaces. At the moment the nanostructured surfaces damage quite easily but the team is studying ways to make the surfaces more robust.

To do this, first, an elastomeric stamp is produced by casting a PDMS layer on top of the nanospike-structured silicon surface (the original nanospikes were fabricated on full silicon wafers using the black silicon process). The PDMS is thermally cured and peeled off. Then, the PDMS stamp can be used to replicate the original nanospike pattern into other polymers, such as PMMA.

Wednesday, March 24, 2010

About Soft Interference Lithography (SIL)

Researchers at Northwestern University had developed a nano manufacturing technique (2007) which can be used to produce nanostructures measuring tens of square centimeters. This new technique, dubbed ‘soft interference lithography’ (SIL), can lead to nanomaterials with optical properties mimicking some metamaterials in the natural world such as peacock feathers and butterfly wings. As said the researchers, their SIL technique combines the ability of interference lithography to produce wafer-scale nanopatterns with the versatility of soft lithography and used it to create plasmonic metamaterials.

Here is how scientists described SIL. “The optical nanomaterials in this research are called ‘plasmonic metamaterials’ because their unique physical properties originate from shape and structure rather than material composition only. Two examples of metamaterials in the natural world are peacock feathers and butterfly wings. Their brightly colored patterns are due to structural variations at the hundreds of nanometers level, which cause them to absorb or reflect light. Through the development of a new nanomanufacturing technique, researchers succeeded in making gold films with virtually infinite arrays of perforations as small as 100 nanometers — 500-1000 times smaller than a human hair. On a magnified scale, these perforated gold films look like Swiss cheese except the perforations are well-ordered and can spread over macroscale distances. The researchers’ ability to make these optical metamaterials inexpensively and on large wafers or sheets is what sets this work apart from other techniques.”

In the research section of her site, Mrs. Odom describes plasmonic materials and their optical properties. “Plasmonics is an exciting and emerging area that uses metal nanostructures to manipulate light on the nanoscale. Depending on their size, shape, and materials properties, noble metal nanoparticles can scatter and absorb light to produce colors ranging from the ultra-violet to the near-infrared. In addition, significantly more light can be transmitted through metal films perforated with subwavelength hole arrays than is permitted by geometric optics, a phenomena known as enhanced optical transmission.”

And she gives some additional details. “We focus primarily on the optical properties of two different but complementary systems that can control light on the nanometer scale: (i) metallic films of nanohole arrays and (ii) pyramidal nanoparticles. The former have properties dominated by SPPs, and the latter have properties dominated by LSPs. Such nanostructures are easily made by our innovative fabrication scheme, PEEL, for preparing large-area, free-standing films of nanoscale holes and particles. PEEL is a simple procedure which combines Phase-shifting photolithography, Etching, Electron-beam deposition, and Lift-off of the metal film.”

Tuesday, March 16, 2010

RAPID: A NEW NANOFABRICATION PROCESS

For exploring the full potentiality of nanotechnology and its sea like vast application in elctronics and hardware industry, the ability to create tiny patterns is important. They are extremely important for fabrication of computer chips and many other application. Yet, creating ever smaller features, through a widely-used process called photolithography, has required the use of ultraviolet light, which is difficult and expensive to work with. John Fourkas, Professor of Chemistry and Biochemistry in the University of Maryland College of Chemical and Life Sciences, and his research group have developed a new, table-top technique called RAPID (Resolution Augmentation through Photo-Induced Deactivation) lithography that makes it possible to create small features without the use of ultraviolet light. Photolithography uses light to deposit or remove material and create patterns on a surface. There is usually a direct relationship between the wavelength of light used and the feature size created. Therefore, nanofabrication has depended on short wavelength ultraviolet light to generate ever smaller features.

The RAPID lithography technique have been developed to create patterns twenty times smaller than the wavelength of light employed; by this process it streamlines the nanofabrication process. That’s how RAPID can be used in many applications in areas such as electronics, optics, and biomedical devices.

In this process, two laser lights of same color have been used for controlling the operation. First, short burst of light used to harden the material and secondly, a constant light source used to prevent it. The technique has been highly appreciated for its easiness to implement, as there is no need to control the timing between two different pulsed lasers.

Tuesday, October 13, 2009

INTEGRATION OF NANOWIRES WITH CMOS SEMICONDUCTOR CHIPS

For fabrication of CMOS semiconductor chips optolithographic process has widely been used since the dawn of fabrication. It has proved its worth over the years and successfully outsmarts the other technologies which have been used in the silicon based industry.

Present CMOS chip fabrication process can go further down may be to 10 nm. To fabricate CMOS chips of such a size range with such high precision and accuracy call for expensive equipments. The best way to go further down is to deviate from optolithographic process to self aligning nano elements called nanowires or nanotubes. Semiconductor industry is not ready to abruptly dump the lithography based equipment for nanowire based process due to cost and strategic reasons.

That’s why researchers are working out a smooth transition from the present CMOS to nano-element based by initially combining both methods and use much of the present technologies for some time at least in moving over to a totally different process.
Silicon, being abundant and most affordable metal will stay during the transition. So the challenge for the nano-technology researchers is to commercialize their Nano technology idea by effectively using present CMOS process, Silicon and its friends.
Few breakthrough in this direction from researchers around the world were noticed:

France based nano technology researcher Leti got step closer to integrating Silcon nanowires into traditional CMOS semiconductor chip making process.

Leti researchers have created silicon nanowire at temperature of 400˚C by using a copper-based catalyst using a method different from normal. The highlight of the research is that they could generate nano devices at low temperature of 400˚C which is far less than what others are achieved. Most of Silicon based nanowires were made in the temperature of 600˚C to 1000˚C inside a furnace. Another highlight is that researchers have created nanowires on oxidized metals.

Achieving at temperature convenient for making CMOS semiconductor chips and on oxide material brings Leti close to integrating nanowires on CMOS semiconductor chip. In this way future System-on-Chip (SoC) can house sensors and other nanotechnology based components mainly the Optoelectronic devices.

University of California, Berkeley has put on its website a report of its research work of growing Au-catalyzed vapor-liquid-solid nanowire via metal-organic chemical vapor deposition. It state "The nanoneedles grow on GaAs, silicon and sapphire substrates and exhibit bright room-temperature photoluminescence. The growths are conducted at 380 to 420 °C, making the process ideal for silicon-CMOS integration".
In another development researchers at Stanford University have developed method of stacking and crystalline semiconductor layers that sets the potential for three-dimensional microchips.

Due to their high surface-to-volume ratio, nanowires are highly suitable for the electrical detection of chemical or biological substances, converting solar to electrical energy and in developing high energy storing batteries. The immediate applications of nanowire integrated CMOS chips are in health, environment and solar energy conversion. Consequently energy generation will become far easier.

Wednesday, November 26, 2008

NIL: AN ULTRA LOW COST, LARGE AREA WAY FOR NANOELECTRONICS FABRICATION




Nanoimprinting lithography (NIL) is a simple pattern transfer process that is emerging as an alternative nanopatterning technology to traditional photolithography. NIL allows the fabrication of two-dimensional or three-dimensional structures with submicrometer resolution and the patterning and modification of functional materials. A key benefit of nanoimprint lithography is its sheer simplicity. There is no need for complex optics or high-energy radiation sources with a nanoimprint tool. There is no need for finely tailored photoresists designed for both resolution and sensitivity at a given wavelength. The simplified requirements of the technology allow low-cost, high-throughput production processes of various nanostructures with operational ease. NIL already has been applied in various fields such as biological nanodevices, nanophotonic devices, organic electronics, and the patterning of magnetic materials.

Recently researchers have taken this process one step further by demonstrating that direct nanoimprinting of metal nanoparticles enables low temperature metal deposition as well as high-resolution patterning. This approach has substantial potential to take advantage of nanoimprinting for the application in ultralow cost, large area printed electronics.

In nanoimprinting, a mold with nanostructures is pressed to deform and shape a thin material film deposited on a substrate. That is why nanoprinting for metal is harder to achieve. Therefore, to achieve successful nanoimprinting, the material needs to have proper flow properties (viscosity and surface tension) adjustable for complete mold pattern replication within reasonable processing temperatures and pressures. Ideal materials usually are thermoplastics, thermoset polymers, or other deformable materials with the desired flow properties.

Metal nanoimprinting is typically an indirect process where a polymer (e.g., PMMA) pattern is first created by nanoimprinting, which is then used as mask for dry etching of a predeposited metal film or as part of the metal lift-off process. It is conventional metal nanoimprinting involves multiple steps and expensive processes, thereby increasing the cost of manufacturing and offsetting the advantages of the nanoimprinting process. Very few direct metal nanoimprinting processes have been demonstrated so far due to the high melting temperature of metals.

The advantage of this process is that it eliminates the need of intermediate polymer nanoimprinting steps for dry etching or vacuum deposition. Also metal nanoparticle solution is also there as a precursor to use the solution processable form of the metal component for the nanoimprinting process, thereby eliminating the need to exceed the bulk metal melting temperature. The nanoimprinted nanoparticles can be transformed into conductive and continuous metal films by low-temperature nanoparticle melting.