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When you ask Professor Chennupati Jagadish to explain what he does, even he admits it’s not an easy thing to understand. He is not a materials scientist or an engineer or a physicist. But while none of these labels fits particularly well, each accounts for an aspect of his expertise.
 This is a Jagadish trait. He is a hard man to pigeonhole and his approaches to problems come from many directions. He tends to cross borders and divides between theories and disciplines — and even national boundaries, as an Indian-born Australian citizen.
There is one question that is guaranteed to solicit a strong opinion from any academic or researcher. What is more important — applied or fundamental research?
But Professor Jagadish cannot even give a simple answer to this, as his work is both. It is not that he is sitting on the fence, more that there is no fence as far as he and his research are concerned.
“The applications are there waiting, all we have to do is prove these things are possible,” he says.
These applications are in the fields of computing and communications. Talk in computing circles is of a world of superfast computers, where information moves at the speed of light, unencumbered by wires.
Jagadish and his team are developing the tiny lasers that are key to this process — cutting edge study that is a world away from his childhood, where he did his homework in the dim light of kerosene lamp.
His work today is with semiconductors, materials that, as the name suggests, fall between conductors, such as copper, and insulators, such as the rubber and plastic that coat household wires. Semiconductors are the ideal material for Professor Jagadish, as they are neither one nor the other, but both: part insulator, part conductor.
Lasers
Semiconductors are the material from which lasers are made. In lasers an electron is passed across what is called the ‘band gap’ (a divide that exists in the ‘reciprocal’ space as opposed to our rather dull ‘real’ space) within the semiconductor and it falls back across the band gap. In falling, it releases energy as a photon. Lasers work by using reflective materials to focus these photons into a beam of light.
A problem with this is that the electrons do not always do what they are supposed to do and they can get lost on their way across the band gap, so no photon is ever released. Professor Jagadish is working to minimise the chances of electrons getting lost by giving them less options.
“If you’ve got electrons going around in all three dimensions you can’t use them efficiently,” Professor Jagadish says.
“That’s why we are interested in reducing the size because you get better performance. We’re aiming for zero dimensional structures because you have such small dimensions in every direction, they emit photons efficiently.
“What we are saying is size matters in this case.”
It is for work with these tiny structures, known as quantum dots, that Professor Jagadish was recently awarded a Federation Fellowship, Australia’s most valuable publicly-funded fellowship.
"What we are saying is size matters in this case"
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Professor Jagadish is able to make quantum dots by carefully passing gases of different materials at varying rates across a heated semiconductor wafer, in a process called dissociation. Depending on the speed and quantity of each gas Professor Jagadish can make different combinations of materials.
“To really precisely control the thickness of layers we try to use a very small amount of gas and deposit it very slowly,” he explains.
The process has been refined to the point that he has been able to build up to 250 layers of different materials, with each layer only a single atom high.
Quantum dots can be made atom by atom by carefully dissociating the right mixture of gases at the right speed.
The trouble with this approach is that the dots form randomly. It is impossible to predict where the dots will be, so it is impractical to use them to store information — if you don’t know where they are, you cannot retrieve the data.
Sculpture
Some scientists argue that this approach is flawed and that rather than building the dots atom by atom from nothing in a random pattern, a ‘top down’ approach is better. The dots should be carved out like a sculpture using a process called plasma etching and electron beam lithography.
Those working from the bottom up can build dots, but not predict where they are, while the top down approach can produce ordered patterns, but in carving them out of the semiconductor they tend to damage the dots so they are no longer suitable for optoelectronic devices.
“With plasma etching, you create a lot of defects — there are missing atoms which can trap the electrons,” Professor Jagadish explains.
Professor Jagadish, as you might expect, argues that both approaches have merit and a combination is likely to yield the best results. He proposes that a top down approach can be used to make a template on which one can grow ordered arrangements of quantum dots.
“The project I proposed in my Federation Fellowship is to create ordered nanostructures on which we can create quantum dots in a periodic arrangement.
“If you know where the dot is you can do a lot more. You can store information and send one photon at a time.
“How do we do this is where the real excitement is — creating ordered nanostructures.”
Creating ordered nanostructures is not a simple matter and with electron beam lithography equipment to etch out templates costing $2 million, Professor Jagadish and his colleagues have already begun to look for alternative ways of creating templates. Their method is ingenious.
Professor Jagadish and his students make an alumina (oxidised aluminium) template by repeatedly oxidising a piece of aluminium — this process is similar to electroplating used to finish metals in the automotive industry. By repeating the process he eventually creates a lattice material: an ordered nanoscale mesh.
Gold
He then evaporates gold through the mesh onto a sheet of Gallium Arsenide, where it is deposited in an ordered arrangement.
The dissociation process is then carried out as normal, but the dissociated materials build up under the tiny spots of gold.
Professor Jagadish is hoping to be able to create what are in effect pillars of quantum dots, proving that the template-plus-bottom-up theory is workable, without the need for expensive equipment.
“Equipment doesn’t do research, people do and what I love about this research is it is not the richest labs that do well, it is the ones that use their grey matter.
“Sometimes you can get away with things, but you can only prove the concept, then you need the tools.”
"Equipment doesn’t do research, people do and what I love about this research is it is not the richest labs that do well, it is the ones that use their grey matter"
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Professor Jagadish’s excitement about his work is clear, but he emphasises that it takes teamwork to achieve results and says his role is to inspire his team of PhD students and post-doctoral researchers to find areas of research about which they can become similarly passionate.
“Research should be fun. When you are having fun, you can create your best work,” he says.
“The success of my research is due to the excellent efforts of the people I have been lucky enough to work with. My job is to inspire, motivate and guide them to achieve their full potential and pursue our exciting ideas.”
It has taken Professor Jagadish, his colleagues and their grey matter 14 years to establish ANU at the top of this field.
Nanotechnology is an area where the results may be tiny, but the funding required is enormous and the $15 million worth of equipment Professor Jagadish’s department has made, acquired and repaired is only a first step. Brains may have so far triumphed over finance, but now he hopes to draw in the investment necessary to sustain Australia’s (currently ranked number seven in the world) reputation near the top of nanotechnology tree.
Driven
“Because the rest of the world is aggressively investing and creating new initiatives we may fall behind. If we want to see Australia as a high-tech economy, we need to start investing.”
He is currently pursuing an ARC grant to establish a nanolithography facility at ANU, which will make vital equipment available to the Australian research community.
A soft-spoken man who is always ready to patiently explain his work (using the periodic table he carries in his wallet and drawing on whatever paper comes to hand), Professor Jagadish is also extraordinarily driven — someone committed to being at the top of his field.
“Philosophically, I’m one of those people who really wants to do their best. It’s up to the world to judge me,” he says.
In his work Professor Jagadish may find the answers in the middle ground, but in his ambition to establish a world centre of nanotechnology, there is no room for even a nanoscale compromise.
This is an edited extract from the forthcoming ANU Research Review. Providing in-depth profiles of some of Australia’s leading researchers, the Review will be released in April.
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