Nav: Home

Obtaining of silicon nanowires becomes eco-friendly

October 18, 2016

Scientists from the Faculty of Physics, the Lomonosov Moscow State University have worked out a new and more eco-friendly method of silicon nanowires obtaining, which allows to replace hydrofluoric acid (HF) by ammonium fluoride (NH4F).

Silicon nanowires are streamlined, almost parallel to each other nanostructures, looking like wires. Nanowires diameter varies from 50 to 200 nm, and the distance between structures - from 100 to 500 nm. Nanowires length, depending on etching time, could be from 100 nm and up to 10s of microns. Interest for silicon nanowires is caused by perspectives of their application in micro- and optoelectronics, photonics, PV, sensorics. They could be used even in biomedicine as silicon nanostructures are biodegradable materials, what means that they self-destruct in an organism after some period of time. Besides that, in limited concentrations nanostructures are not toxic for an organism. However, hydrofluoric acid (HF), used by conventional method in order to produce silicon nanowires, is extremely toxic.

Obtaining of silicon nanowires with the help of metal-assisted etching becomes possible due to chemical etching of a silicon wafer, where metal nanoparticles (for instance, silver nanoparticles) activate etching.

Kirill Gonchar, a Junior researcher in the Low Temperature Physics and Superconductivity Department, the Faculty of Physics, at the Lomonosov Moscow State University, describes the whole scheme of nanowires elaboration. He says: "We've used a two-step method of etching. At the first stage silver nanoparticles were deposited on the surface of a silicon wafer. But this deposition didn't produce a level layer but different island regions. At the second stage the silicon wafer was etched right in the places, covered with silver. Because of this, those silicone sheet places, which were uncovered with silver, turned into nanowires. Silver nanoparticles fell into the silicone sheet. And the more etching was lasting the longer nanowires were got at the output. At the end silver was removed with the help of nitric acid."

Researchers from the Lomonosov Moscow State University have replaced dangerous and toxic hydrofluoric acid by ammonium fluoride at all stages of chemical etching. Moreover, they have studied optical properties of silicon nanowires, produced with the help of this method, and compared them with nanowires, received on the basis of conventional method, rested on hydrofluoric acid usage.

Kirill Gonchar shares, how this idea to use ammonium fluoride in nanowires synthesis has emerged. He clarifies: "The idea of ammonium fluoride application wasn't new, it was borrowed from experiments of porous silicon obtaining, which took place 20 years ago. Ammonium fluoride was also used there instead of hydrofluoric acid. There were similar projects where nanowires were produced in ammonium fluoride, however, there was no replacement at all etching stages. We've studied optical properties of the nanowires we got and proved that they don't differ much from nanowires, obtained by conventional method."

Silicon nanowires, produced by metal-assisted etching, could be used for creation of new photonic devices and silicon based sensors. Kirill Gonchar clarifies, that nanowires are promising as sensory elements of optical sensors for different substances. This happens due to, first of all, increase of Raman effect signal intensity, which is a "finger print" of a substance. And, secondly, due to sensitivity to different gases presence, for instance, oxygen (the relevant patent has been already registered).

Moreover, structures, containing silicon nanowires, could be used in antireflection coating for solar cells. While ordinary silicon reflects in visible range about 30% of incident light, there could be obtained silicon nanowires which reflect 1-2%.
-end-


Lomonosov Moscow State University

Related Nanowires Articles:

Resistance is utile: Magnetite nanowires with sharp insulating transition
A Japanese research team led by Osaka University produced Fe3O4 nanowires on 10-nm length scales by deposition on an MgO substrate.
Giving nanowires a DNA-like twist
Argonne National Laboratory played a critical role in the discovery of a DNA-like twisted crystal structure created with a germanium sulfide nanowire, also known as a 'van der Waals material.' Researchers can tailor these nanowires in many different ways -- twist periods from two to twenty micrometers, lengths up to hundreds of micrometers, and radial dimensions from several hundred nanometers to about ten micrometers.
Shell increases versatility of nanowires
Nanowires promise to make LEDs more colorful and solar cells more efficient, in addition to speeding up computers.
Scientists synthesize new nanowires to improve high-speed communication
Scientists from the Institute of Process Engineering, City University of Hong Kong and their collaborators synthesized highly crystalline ternary In0.28Ga0.72Sb nanowires to demonstrate high carrier mobility and fast IR response.
Dose of vitamin C helps gold nanowires grow
Rice University scientists discover a method to turn stubby gold nanorods into gold nanowires of impressive length.
Silver nanowires promise more comfortable smart textiles
In a paper to be published in the forthcoming issue in NANO, researchers from the Nanjing University of Posts and Telecommunications have developed a simple, scalable and low-cost capillary-driven self-assembly method to prepare flexible and stretchable conductive fibers that have applications in wearable electronics and smart fabrics.
Artificial synapses made from nanowires
Scientists from J├╝lich together with colleagues from Aachen and Turin have produced a memristive element made from nanowires that functions in much the same way as a biological nerve cell.
Nanowires could make lithium ion batteries safer
From cell phones and laptops to electric vehicles, lithium-ion batteries are the power source that fuels everyday life.
Scientists have a new way to gauge the growth of nanowires
In a new study, researchers from the US Department of Energy's Argonne and Brookhaven National Laboratories observed the formation of two kinds of defects in individual nanowires, which are smaller in diameter than a human hair.
Cleaning nanowires to get out more light
A simple chemical surface treatment improves the performance of nanowire ultraviolet light-emitting diodes.
More Nanowires News and Nanowires Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.