Electron Beam Annealer for UHV Triple Beam Line System
The MacDiarmid funding paid for the revamp and allowed the system to get up and running in as short a time frame as possible.
About the Instrument:
The system consists of three beam lines feeding in at different angles to a central ultra-high-vacuum chamber. The first beam line is an ion implanter to shoot an ion of any element of the periodic table into the sample. The second is an electron beam annealer, which fires rounds of electrons at the sample surface to heat it up – “It will get it up to 1400°K, where silicon atoms are like a liquid,” says Andreas. The third is an RBS beam line to analyse the structure and composition of the surface – this tells you which elements are present in the first 200 – 300 nanometres of the surface, at what concentration and what depth. The sample sits in a flexible sample holder, which can be rotated to face any of the three beam lines or even two at a time.
Andreas’s group is using the triple beam line to grow and analyse silicon ‘nano-whiskers’ that self-assemble on the surface of a silicon substrate after it is implanted with ions and heated up. Their current goal is to produce ‘spintronic’ materials – materials which allow the control of the spin of electrons as well as their charge and could dramatically increase the storage capacity and power of computers. Having access to all three beam lines within a single vacuum chamber has absolutely transformed their capability and productivity for this project. In the past they had to transfer samples from one vacuum chamber to another between each processing stage. This could take up to 24 hours and the surfaces tended to oxidise in the air during transfer, which prevented further nanostructure growth. “Now we can do an annealing study and analyse it multiple times,” says Andreas. “This is a massive, massive advancement for us. It means we can have one sample replacing a series of twenty to thirty samples and cut time by a factor of ten.” If the sample is thin enough you can heat it up from the back side and use all three beam lines at once. This opens up some ‘ultra-exciting’ new science. “The sample can be sitting at 1000ºC (almost liquid state) and be implanted and analysed at the same time…And I have no idea what will happen. We don’t know. There’s no literature you can dial up…It’s phenomenal!” The MacDiarmid Institute has funded a post-doctoral fellow to investigate and hopefully ‘demystify’ the technique of electron beam annealing. When a beam of electrons hits a surface, atoms literally hop around and rearrange themselves into new structures. Although the team have had a lot of success with the technique in the past, no-one is quite sure how or why it works. The triple beam line is a perfect tool to find out.
The triple beam-line is the only ion implanting facility in the Institute and an integral part of several current research projects at Callaghan Innovation, Massey, Victoria, Canterbury and Auckland Universities. “I think it’s for people to try out and see what they can do” Andreas says “— I’m pretty sure that once we understand it better… people will use the equipment a lot more.” The group’s spintronic nano-whiskers project has brought together researchers from across the Institute. Andreas shares a MacDiarmid funded PhD student with Richard Blaikie at Canterbury University who will be measuring the emission characteristics of the nano-whiskers. Spintronics theorist, Uli Zülicke from Victoria will be helping with theoretical understanding. Andreas believes the new capability will also be a boost to his international collaborations with groups in Australia, Korea, Germany and Singapore.