After that success I thought, "gosh, here's one material where if you add nanostructures to it you can improve its properties a lot, I wonder how else this can be used?" My area has broadened now to look at other functional oxides, not just high temperature superconductors but lots of other oxide materials that have interesting properties, such as ferroelectrics and magnetic materials. There again I could begin to realise all the fantastic property enhancements you could get out of these materials by engineering them on the nano scale.
What is particularly special about functional oxides?
What is special about them is that they have a whole range of electrical and magnetic properties, all the way from very good insulating materials that carry no current to superconductors and everything in between – such as semiconductors, ferroelectrics, magnetic materials, and ionic conductors. Manipulating the structure of these materials on a very fine scale allows you to control and enhance their properties, so you can make a better ferroelectric material or you can make a ferromagnet that operates at a higher temperature.
One big area of the research you're doing with functional oxide materials is looking at oxide interfaces. What is particularly notable about the way that oxides behave at interfaces?
We're looking at some new oxide interfaces to try to understand what is going on at the interface in terms of structural distortions, charge transfer effects, and atomic reconstruction effects. In particular we're looking at transition metal oxides - such as lanthanum manganese oxide and bismuth iron oxide - because of their multiferroic properties, which could lead to new forms of information storage and processing.
As well as looking at the properties of oxides, you're also looking at turning oxides into functional devices in their own right. What is your research in this area?
Instead of having planar interfaces in devices, we have created new vertical checkerboard structures on thin films that self assemble and don't require complex patterning to create an interesting device. These materials are very exciting because you can very carefully control the strain at the interfaces to create a whole new set of properties. For instance we've been able to make very highly tuneable microwave dielectric materials, which are useful in things like mobile phones and communication devices. It's a new paradigm in creating thin films.
As far as practical applications in terms of electronics or energy, are there any areas of your work that you think are particularly promising?
One area is in creating microactuators for MEMs – microelectro mechanical systems. We're making energy harvesting nanoferroelectric materials that do not contain lead, because at the moment the best performing materials for these applications contain lead, a toxic substance. So there's a big drive to get away from lead and find new ferroelectric materials that work with a high displacement effect above room temperature.
Where do you see your work going in the future?
Materials science is moving so fast and the field is extremely exciting at the moment, with new effects and new phenomena being discovered so quickly. As a result it's hard to predict what things will be like in five years time. What I'm doing now will keep me very busy for the next few years.
This fast pace means that there is a need to have new journals in the area. I have just become an editor of a new journal from the America Institute of Physics, called APL Materials. Sometimes it's hard to define what materials science is all about, it's very interdisciplinary, so this is my opportunity to mould the field.
Interview: Helen Jaques (© AcademiaNet)