A material that performs wonders

A material that performs wonders

ROMA – AS Dr Mopeli Fabiane demonstrates a new material he calls graphene, you can almost sense an intense passion in his heart.
Graphene is a material that will beat your average semi-conductors in terms of flexibility, high speed in electronic devices and low cost.
This National University of Lesotho (NUL) Senior Lecturer is developing a material that is so thin, it is just one atom thick — and it is a million times thinner than your single hair, yet 200 times stronger than steel.

This time around, he is bringing another discovery, which he has just published in the prestigious Journal of Raman Spectroscopy.
“If you add just another layer, one atom thick, and make two layers, one over the other, and give them a special arrangement, you have a material that performs wonders.”
He calls it a graphene.

And he dubs it “the first truly two-dimensional material ever discovered”.
“It is one of the most difficult materials to make — making a material that is just one or two atoms thick is no picnic,” Dr Fabiane says.
“At the same time, it will rival a number of its competitors in the market for low cost, because it originates from low cost raw materials.”
The origins of this material, graphene, are just as intriguing as the material itself.

It is made of pure carbon, just like diamond or graphite, the other highly famous pure carbon cousins.
“But the beauty of graphene is that the carbon is taken from methane,” he says.
You got it right, methane, that gas you use for cooking in your home.

As the saying goes, out of the ordinary, come the most extraordinary.
For those with an inch of chemistry, methane is made of 1 carbon and 4 hydrogens (CH4).
However, Dr Fabiane is able to take methane, rip it off, and pick just what he wants, carbon atoms, letting go off the hydrogens.
He then deposits those atoms on a body such as copper foil to make graphene.
So what’s in the latest discovery by Dr Fabiane?

First look at the topic, as it appears on the Journal of Raman Spectroscopy, but don’t be intimidated, we shall try, if we can, to demystify it.
“Raman Spectroscopy and imaging of Bernal-stacked Bilayer Graphene Synthesised on Copper Foil by Chemical Vapour Deposition: Growth Dependence on Temperature.”
Let’s start here.
Graphene is not an insulator, it is not a semi-conductor, it is not even a metal.
It is a semi-metal.
It is somewhere in between metals and semiconductors.
This is how.
You probably know that atoms have electrons moving around their nuclei.
In semiconductors, those atoms can move from one level (energy level) to another by jumping over a region called a “band gap.”
As the electrons do the jumping, they either gain or lose energy depending on the direction of jumping.
For instance, electrons bound to an atom will need to jump this band gap to another level where they can start moving as electricity.
That is why insulators, with large band gaps (which electrons find hard to jump over), conduct electricity poorly, semi-conductors, with narrower gaps, are moderate conductors and metals, with little to no gaps, are good conductors.

“What makes graphene interesting is that there are regions where it has band gaps, like semi-conductors, and regions where there are no band gaps, like in metals,” Dr Fabiane says.
“That is why we call graphene a semi-metal.”

But something great happens when you take two layers of graphene and arrange them in a specified order.
And that is the heartbeat of Dr Fabaine’s unusual research.

First, remember graphene atoms are arranged in a hexagon (if you could see the arrangement with a naked eye, it would look more like a beehive).
“When we grow a two layered graphene, and arrange these layers such that half of the carbons in one hexagon in the top layer are in the middle of the hexagon in the bottom layer, the graphene layers are said to be Benarl stacked,” he says.

The genius is there, because, “in this arrangement, and contrary to most semiconductors, you can control the bilayer’s band gaps in real-time with electric fields”.
That is you can choose to have as little or as much conducting as possible by controlling the sizes of band gaps.
“It is at this point where we beat semi-conductors, whose band gaps are often stagnant,” says Dr Fabiane.
Add another fact.

Graphene layers are very high speed electrical conductors.
Since they have just one layer of atoms, they present little roadblocks on the way of moving electrons.
By now you know why they present opportunities in high speed switches, amplifiers and energy convertors.
If you have something that works better at lower cost, who wouldn’t go for that option?

Of course Dr Fabiane is not alone in this work which was started by Nobel Prize winners in the UK more than two decades ago.
He is collaborating with an equally passionate team of scientists at the University of Pretoria and the University of Pennsylvania.

Own Correspondent

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