Bulletin

Issue: September/October 2007

News

Soft X-ray option for surface physics

One of the world’s most advanced toroidal electron spectrometers is being built at La Trobe University by a team of physicists for delivery to the Australian Synchrotron next year.

The new device, funded by an ARC grant, will be used by researchers from La Trobe and the Universities of Newcastle, Sydney, Western Australia and Macquarie.

These universities have contributed $520,000 to the project in a bid to get the new Melbourne facility functioning to a highest possible level, says Professor Robert Leckey.

Otherwise, some of the best research will continue to go offshore to the Berlin Synchrotron, which has already gained one of the La Trobe machines.

Professors Robert Leckey and John Riley have been working for more than 30 years to perfect the analytical techniques that are at the heart of the $1.5 million machine.

Basically, the spectrometer uses a beam of soft X-rays to map the surface atoms of a sample. It has the advantage of being able to measure electron emissions over all angles at once. The sample is slowly rotated so that a complete picture of its surface emerges in just twenty minutes. Other spectrometers can only measure a restricted range of angles.

‘The greatest advantage of our system is that you can get the data quickly,’ says Professor Riley. ‘One of the limitations of the process is the need to keep surfaces clean in the vacuum. The faster you can get results the better.’

This is the fourth model designed and built by the physics team. T1 was built in 1980 then shipped to the original Berlin Synchrotron in 1985.

‘It worked happily and successfully there until the synchrotron was replaced by a bigger one,’ says Professor Leckey. T2 went to Nobel prize-winning scientist Professor Kai Siegbahn in Sweden and T3 was delivered in 2002 to the new Berlin facility.

This spectrometer took three years to build. It now often runs twenty-four hours a day and is used by several German research teams. La Trobe physicists have built up strong relationships with the University of Erlangen/Nürnberg and have run many experiments in Berlin.

When T4 is commissioned they will be able to do their X-ray diffraction studies of surface structure in Melbourne. The patterns that emerge are as complex and beautiful as the images in a kaleidoscope. They can only be interpreted by equally complex software.

The physics professors understate the role they have played in this important area of analytical physics. Their equipment says it all – vacuum chambers, donut shaped electrodes, an aluminium spectrometer, a bank of monitors and three computers, all on mag wheels.

The T4 is expected to open up the field of surface analysis in Australia which has until now been linked to facilities offshore. It will be one of two end stations attached to the soft X-ray beam line of the Synchrotron.