Nav: Home

Plasma electrons can be used to produce metallic films

May 07, 2020

Computers, mobile phones and all other electronic devices contain thousands of transistors, linked together by thin films of metal. Scientists at Linköping University, Sweden, have developed a method that can use the electrons in a plasma to produce these films.

The processors used in today's computers and phones consist of billions of tiny transistors connected by thin metallic films. Scientists at Linköping University, LiU, have now shown that it is possible to create thin films of metals by allowing the free electrons in a plasma take an active role. A plasma forms when energy is supplied that tears away electrons from the atoms and molecules in a gas, to produce an ionised gas. In our everyday life, plasmas are used in fluorescent lamps and in plasma displays. The method developed by the LiU researchers using plasma electrons to produce metallic films is described in an article in the Journal of Vacuum Science & Technology.

"We can see several exciting areas of application, such as the manufacture of processors and similar components. With our method it is no longer necessary to move the substrate on which the transistors are created backwards and forwards between the vacuum chamber and a water bath, which happens around 15 times per processor", says Henrik Pedersen, professor of inorganic chemistry in the Department of Physics, Chemistry and Biology at Linköping University.

A common method of creating thin films is to introduce molecular vapours containing the atoms that are required for the film into a vacuum chamber. There they react with each other and the surface on which the thin film is to be formed. This well-established method is known as chemical vapour deposition (CVD). In order to produce films of pure metal by CVD, a volatile precursor molecule is required that contains the metal of interest. When the precursor molecules have become absorbed onto the surface, surface chemical reactions involving another molecule are required to create a metal film. These reactions require molecules that readily donate electrons to the metal ions in the precursor molecules, such that they are reduced to metal atoms, in what is known as a "reduction reaction". The LiU scientists instead turned their attention to plasmas.

"We reasoned that what the surface chemistry reactions needed was free electrons, and these are available in a plasma. We started to experiment with allowing the precursor molecules and the metal ions to land on a surface and then attract electrons from a plasma to the surface", says Henrik Pedersen.

Researchers in inorganic chemistry and in plasma physics at IFM have collaborated and demonstrated that it is possible to create thin metallic films on a surface using the free electrons in an argon plasma discharge for the reduction reactions. In order to attract the negatively charged electrons to the surface, they applied a positive potential across it.

The study describes work with non-noble metals such as iron, cobalt and nickel, which are difficult to reduce to metal. Traditional CVD has been compelled to use powerful molecular reducing agents in these cases. Such reducing agents are difficult to manufacture, manage and control, since their tendency to donate electrons to other molecules makes them very reactive and unstable. At the same time, the molecules must be sufficiently stable to be vaporised and introduced in gaseous form into the vacuum chamber in which the metallic films are being deposited.

"What may make the method using plasma electrons better is that it removes the need to develop and manage unstable reducing agents. The development of CVD of non-noble metals is hampered due to a lack of suitable molecular reducing agents that function sufficiently well", says Henrik Pedersen.

The scientists are now continuing with measurements that will help them understand and be able to demonstrate how the chemical reactions take place on the surface where the metallic film forms. They are also investigating the optimal properties of the plasma. They would also like to test different precursor molecules to find ways of making the metallic films purer.

The research has obtained financial support from the Swedish Research Council, and has been carried out in collaboration with Daniel Lundin, guest professor at IFM.
-end-
The article: "Chemical vapor deposition of metallic film using plasma electrons as reducing agents", Hama Nadhom, Daniel Lundin, Polla Rouf and Henrik Pedersen, (2020), Journal of Vacuum Science & Technology A, Vol. 38, published online 23 March 2020, doi: 10.1116/1.5142850

Link: https://doi.org/10.1116/1.5142850

Linköping University

Related Plasma Articles:

Fighting pandemics with plasma
Scientists have long known that ionized gases can kill pathogenic bacteria, viruses, and some fungi.
Topological waves may help in understanding plasma systems
A research team has predicted the presence of 'topologically protected' electromagnetic waves that propagate on the surface of plasmas, which may help in designing new plasma systems like fusion reactors.
Plasma electrons can be used to produce metallic films
Computers, mobile phones and all other electronic devices contain thousands of transistors, linked together by thin films of metal.
Plasma-driven biocatalysis
Compared with traditional chemical methods, enzyme catalysis has numerous advantages.
How bacteria protect themselves from plasma treatment
Considering the ever-growing percentage of bacteria that are resistant to antibiotics, interest in medical use of plasma is increasing.
A breakthrough in the study of laser/plasma interactions
Researchers from Lawrence Berkeley National Laboratory and CEA Saclay have developed a particle-in-cell simulation tool that is enabling cutting-edge simulations of laser/plasma coupling mechanisms.
Researchers turn liquid metal into a plasma
For the first time, researchers at the University of Rochester's Laboratory for Laser Energetics (LLE) have found a way to turn a liquid metal into a plasma and to observe the temperature where a liquid under high-density conditions crosses over to a plasma state.
How black holes power plasma jets
Cosmic robbery powers the jets streaming from a black hole, new simulations reveal.
Give it the plasma treatment: strong adhesion without adhesives
A Japanese research team at Osaka University used plasma treatment to make fluoropolymers and silicone resin adhere without any adhesives.
Chemotherapeutic drugs and plasma proteins: Exploring new dimensions
This review provides a bird's eye view of interaction of a number of clinically important drugs currently in use that show covalent or non-covalent interaction with serum proteins.
More Plasma News and Plasma Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Sound And Silence
Sound surrounds us, from cacophony even to silence. But depending on how we hear, the world can be a different auditory experience for each of us. This hour, TED speakers explore the science of sound. Guests on the show include NPR All Things Considered host Mary Louise Kelly, neuroscientist Jim Hudspeth, writer Rebecca Knill, and sound designer Dallas Taylor.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

Kittens Kick The Giggly Blue Robot All Summer
With the recent passing of Ruth Bader Ginsburg, there's been a lot of debate about how much power the Supreme Court should really have. We think of the Supreme Court justices as all-powerful beings, issuing momentous rulings from on high. But they haven't always been so, you know, supreme. On this episode, we go all the way back to the case that, in a lot of ways, started it all.  Support Radiolab by becoming a member today at Radiolab.org/donate.