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Topological Insulators Interfaced with Trivial and Ferromagnetic Insulators. Selective contact and patterning of surface states.



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Anirban, Ankita Saptarshi  ORCID logo


Topological insulators (TIs) are a novel class of material which host helical surface states with exciting and unique electronic properties. They can provide insights into new physics and also pave the way for potential spintronic applications. Much work has been done to identify and characterise these surface states, but this has largely focused on exfoliated flakes and single crystals. This thesis presents work towards creating devices using topological insulators which will enable us to probe their transport properties and can lead to their integration in existing technologies. This project has developed methods of fabricating TI devices which can allow characterisation and control of topological surface states. First, different etching techniques are compared on TI films and the devices are characterised by transport measurements. Next, two types of heterostructures are investigated which allow for control and patterning of the TSS. First, the TI is interfaced with trivial insulators. These systems allow for electrostatic gating over large areas of TSS which enables us to tune the Fermi level to the Dirac point. Next, the TI is interfaced with ferromagnetic insulators. This is expected to open up an energy gap at the Dirac point due to the magnetic exchange interaction. Selective etching of these heterostructures allows us to probe regions of TI/FI and regions of TI and compare them through transport measurements. The results in this thesis provide a foundation for the fabrication of multifunctional topological insulator devices which will open the way to explore new physics of topological surface states.





Ford, Christopher


topological insulator, ferromagnetism, surface state, selective etching, nanofabrication, ferromagnetic insulator, proximity effect, topological surface state, electron transport, low temperature measurements


Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge