Topological insulators, a relatively new class of materials, may serve as new building blocks for next-generation electronics. But until recently no materials could be fabricated, functioning as such at room temperature. And the unique properties - conducting surface states at the interface, while the bulk remains insulating – could not yet be verified experimentally in oxide materials. My work reflects the true task of the Mesa+ institution’s research, Rosa Luca Bouwmeester states. ‘In close collaboration with other groups, we were able to think, and work, out of the box in order to take research a decisive step further.’ 

Luca fabricated complex oxide materials systems herself, aiming towards the realization of an artificial topological insulator. She did this in close collaboration with the Inorganic Materials Science group. ‘Their expertise on building oxide materials, formed by pulsed laser deposition, is essential,’ Luca says.

From her master thesis project on, Luca specialised in fabricating BaBiO3 based materials systems. ‘In my PhD work I combined these with perovskite Y-Bi-O layers,’ she says. ‘These structures theoretically show the presence of a band inversion, indicating their nontrivial topology.’

Four-Probe STM

As a member of the Quantum Transport in Matter Group herself, she also collaborated closely with experts from the Physics of Interfaces and Nanomaterials (PIN). ‘To characterize the unique electronic properties, I was very lucky to use a four-probe Scanning Tunnelling Microscope,’ she says.

‘It is fascinating to actually see how nano-properties at the interface, affect the physical conducting properties in the macro world. I believe the industry should get more prepared to gain control on the micro- and nanoscale in-house, working towards future applications. In the end, millimetre-sized lab samples have to be scaled up to wafer-sized production units.’

Synchrotron in Paris

As to using topological insulators, a long path still has to be travelled, Luca explains, because of their instability in atmospheric environments. She used vacuum suitcases to transport her highly sensitive samples to the French National Synchrotron Facility in Paris.

‘Here I could perform angle-resolved photoemission spectroscopy measurements, using X-rays produced with ultra-fast electrons,’ she says. ’Due to the working relations of professor Gertjan Koster - who supervised me together with professor Alexander Brinkman - I was able to work in some narrow timeslots, staying in a hotel next to the research facilities. Here I combined exceptional working hours with some occasional sleeping and jogging activities. Also, I was privileged to work two weeks in Japan, performing synchrotron measurements as well.’

Student Years

Luca experienced the Mesa+ institution as a ‘home-base’ from her bachelor student years on.

‘The atmosphere is a safe, open and hearty one,’ she says. ‘There always is room for consultation, sharing ideas and solving problems together. I discovered how much joy doing research can bring from my bachelor thesis onwards.’

‘I especially recall guiding groups around in those days, and explain the cleanroom facilities to scholars, entrepreneurs and visitors of all kinds. It is a good thing to try and explain your own research work, in accessible language. On several occasions I got really inspired and came up with new ideas, discussing with visitors about the nano-world.’

Future

In her future work, not much room will exist for scientific research. ‘That is not to say I will leave it for good,’ Luca says.

‘After my PhD I’m going to work as a strategy consultant in an industrial and hands-on setting. I’m looking forward to this dynamic new working environment. I believe my experiences as a PhD will prove helpful. I learned to see through complex layouts, to strictly monitor the red line of work, and to carefully plan my projects. I’m looking forward to using these skills in a completely different setting.’