Irene Battisti worked for four years to build the 'most stable microscope in the world', a quest that paid off. According to quantum mechanics, electrons in a crystal behave like waves. Battisti's microscope yields images of these waves in unprecedented detail. This promises important insight into the physics of complex materials.
Building the most stable microscope in the world
'When I started my PhD in Leiden, I was given a choice: either you focus on building this new microscope full time, or we can accept that it will take a bit longer and let you do other research,' says Battisti. This choice wasn't hard for Battisti, who likes to work on several things at the same time. 'I chose option two, but I also started building the microscope during my very first week.'
This microscope is a Scanning Tunnelling Microscope (STM): an atomically sharp needle is scanned over the surface of a material at only nanometers distance. The electrical currents that flow through the needle yield a profile of the behaviour of electrons in that material, at a resolution of single atoms.
If that sounds relatively easy, the mechanical demands are taxing. If the needle would be the size of Mount Everest, the tip shouldn't move more than the size of a bacterium. To accommodate this hyperstability, the microscope rests on a 40-tonne concrete island built into the floor of the new Gorlaeus measurement hall, which is suspended, using springs to damp any vibrations from the outside world.
On top of that, the measurements take place at a chilly 4 degrees above absolute zero, and the setup includes a full vacuum and cooling system. The core part is made out of the material sapphire, which is extremely stiff, but also very difficult to handle. Luckily, Battisti could rely on the expertise of the Faculty's Fine Mechanical Department for help and guidance.
'Building the microscope took two and a half years,' says Battisti. In the meantime, she gained experience in researching materials on a smaller commercial STM. 'We called it Tamagotchi because it is a small and cute Japanese instrument, and we need to feed it with liquid helium twice a week,' she explains.
The research group, headed by Milan Allan, is interested in high-temperature superconductivity. Certain materials conduct electricity without any electrical resistance at low temperatures. Despite three decades of research, physicists still don't understand this phenomenon completely. Using Tamagotchi, Battisti published groundbreaking research into this phenomenon.
'We were very excited when the first images came in from the microscope we had been building for two and a half years. Astonishingly, the data was beautifully clean.’
However, the new STM, called Dome, is in a different league. 'We were very excited by the level of detail when the first images came in,' Battisti says. Quantum mechanics tells us that particles, including the electrons in a metal, are in fact waves. With Dome, these electron waves are clearly visible, reflecting off single atoms, just like the ripples in a pond reflect against rocks. 'We keep being astonished by how beautifully clean the data is,' says Battisti, 'and we believe that this microscope will lead to new discoveries in high-temperature superconductivity.'
After her thesis defence, Battisti took a job at Nearfield Instruments, a start-up close to Rotterdam that is building scanning probe microscopes for industrial application in the semiconductor industry.
'Again, I am building a scanning probe microscope. And again, there are many challenges, and I like that. But now, there are fifty people working on it, instead of only a small team of one PhD student and a few FMD engineers. The pace of work is different, and problems are solved with a more systematic approach. I liked tinkering in the lab, but I really like this, too.'
Irene Battisti (Verona, Italy, 1990) did a bachelor's in Physics in Padua, and came to the Netherlands as a master's student on the Erasmus programme. 'To be honest, it wasn't a conscious choice,’ she says, 'there were only a few options, and Leiden seemed to be the best.'
But when she arrived, Battisti really appreciated the atmosphere. 'I liked the way that research is done here, in small research groups with an informal, international culture and ample communication between groups. I was used to very formal groups with much hierarchy in Italy. So I never regretted coming to the Netherlands. Even if the weather and nature here are maybe not so nice as they are in Italy.'