Brand new materials that are just an atom thick are helping to roll out a revolution in electronics that researchers say is as significant as the move from valves to silicon chips.
‘We have in front of us a sort of revolution,’ said Dr Maurizio Peruzzini, director of the Italian National Council for Research’s Institute for the Chemistry of OrganoMetallic Compounds (CNR ICCOM).
At the heart of this explosion in atom-scale devices could be phosphorene, the 2D version of the highly reactive element phosphorus.
Unlike graphene, which allows electric currents to pass freely across it, phosphorene has a so-called band gap – which means an electric current can be made to pass through it selectively – a critical attribute for making electronic chips.
However, the problem with phosphorene is that its strength is also its weakness – it has swathes of free electrons making it extremely responsive, but that also makes it extremely reactive, even with air and water.
‘Phosphorene is a very bad guy, from a chemical viewpoint, but the possibilities are real,’ said Dr Peruzzini, who is working on ways to make usable phosphorene as part of the PHOSFUN project, funded by the EU’s European Research Council (ERC).
His team has come up with a way to lock in the responsiveness while preventing it from reacting with everything in sight, by encasing flakes of phosphorene in large molecules known as polymers.
‘We create a composite material, a hybrid material, which at present has demonstrated to be extremely stable,’ said Dr Peruzzini.
That has opened the door for them to start adding metals – such as so-called transition metals like gold and copper that are found towards the middle of the periodic table – to make completely new materials.
These advances in making phosphorene stable and adding other metals could allow chemists to dream of a range of applications, such as creating new catalysts to draw the carbon out of factory emissions and turn waste greenhouse gases into new fuels, or developing high-yield solar panels.
They could also lead to quantum switches sensitive to the movements of subatomic particles, enabling the creation of extremely high-power computers, and sensors that can react to the presence of just a handful of atoms.
‘We are thinking about orders of magnitude of higher sensitivity than current ones,’ said Dr Peruzzini. ‘Physicists are extremely excited about the possibilities of phosphorene.’
To make the step from the chemist’s bench to the engineer’s, researchers must work out how to synthesise 2D materials in a reproducible, standardised way.
Since graphene was first isolated in 2004 by drawing a piece of sticky tape away from the graphite tip of a pencil, 2D materials normally come in the irregular flakes produced by the so-called Scotch tape method.
‘It’s likely you will discover new properties.’
Dr Ageeth Bol, Eindhoven University of Technology, the Netherlands
As a former industrial chemist working for Phillips and IBM, Dr Ageeth Bol at Eindhoven University of Technology in the Netherlands knows the kinds of standardisation needed by industry to integrate 2D materials into their industrial processes.
‘You cannot make chips for an iPhone using a piece of tape,’ said Dr Bol, who is the principal investigator of the ERC-funded ALDof 2DTMDs project. ‘You need a method of having good control of the material while fabricating it over a large area.’
The work being done by Dr Bol and Dr Peruzzini represents a fundamental step towards making 2D materials available to engineers who will start building these ultra-fast, ultra-sensitive devices.
Dr Bol is developing a technique to create sheets of a specific type of 2D material that combines transition metals with elements such as selenium or sulphur, which could be used to shrink down electronic chips.
She is creating the 2D materials using a process called atomic layer deposition, enhanced by using a cloud of charged gas known as a plasma. Her system is able to build up material layer by layer with control at the atomic scale.
The process means that fundamental physicists will be able to start experimenting on large areas of various 2D materials that are stacked on top of each other to give them as yet undreamt of new capabilities.
‘These layers will influence each other so then it’s likely you will discover new properties,’ said Dr Bol. ‘And in that way you can actually engineer materials.’
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