Ultra-High-Vacuum Deposition System
The new facility has already helped them secure two research grants from the NERF and Marsden funds to develop spintronic applications.
About the Equipment:
This Ultra-High Vacuum system is designed for growing pure crystalline films of just about any material. It includes an ionising gas source to introduce nitrogen or other gases into the chamber and two evaporating crucibles for depositing metal atoms onto a substrate. These can be heated to well over a thousand degrees celsius using an electron gun or filament heaters. The substrate is mounted on a rotating holder to ensure the atoms fall evenly over the surface. The substrate can be heated up to 950ºC to encourage atoms to rearrange themselves into a perfectly ordered crystal structure. A separate load lock chamber allows you to transfer samples in and out of the main chamber within a couple of hours – a huge timesaver. Finally, an electron diffraction system, paid for by Victoria University, allows you to analyse the crystal structure of films as they grow.
As Ben explains, when it comes to researching new materials, “just about always the quality of the results is determined by the quality of the samples.” Before they can even think about applications, they need to determine the material’s native properties and to do this they need to grow beautifully pure defect-free single crystal films. In the past they were dependent on facilities in Christchurch to grow their samples. “Collaborating with the Canterbury MacDiarmid members taught us a great deal about growing and studying rare-earth nitrides,” Ben says. But having an in-house facility speeds up progress dramatically. It gives them the ability to grow up to two films a day and offers a new level of control. “There are lots of parameters to choose when you’re growing the film,” Ben explains, “like temperature and deposition rates and they all make subtle differences to the films you grow so we want to make lots of films to figure out what the best recipe is. This makes it possible to be so much more productive.” Having a constant stream of samples frees the group to get on with the physics – characterising the magnetic, electronic and structural properties of the materials and eventually developing useful applications. “I’d love to produce a magnetic memory element,” says Ben “that could be used in the computer. To sell those and make millions. We’d all benefit from that!”
Ben’s group is at the centre of a thriving international network. They have collaborators in France, the US, Australia and across New Zealand at Callaghan Innovation, Canterbury, Massey and Auckland. The ability to grow high quality films puts the group in position to become a world authority in their field, which is attracting increasing international attention. Through their strong relationships with synchrotron expert Kevin Smith from Boston University and magnetism experts from France they have set up career channels for local students and post-doctoral fellows going overseas. Without the support of the MacDiarmid Institute, Ben says that it would have been impossible to establish his group in this position. “Getting this equipment in a timely fashion has been massively important,” he says “along with support for travel and collaborations.”
Many of the materials are magnetic, and I am particularly interested in understanding the origins of the magnetic behaviour and how it affects the ability of the materials to conduct electricity.My present focus is on a class of materials called “rare-earth nitrides”, which we prepare in the form of very thin layers grown on top […]