Masters Defense: Merlin von Soosten – University of Copenhagen

Masters Defense: Merlin von Soosten

AFM lithography and low temperautre transport of mesoscopic ring interferometers in complex oxide 2DEGs

Abstract: Complex oxide hetero structures host a 2-dimensional electron system (2DES) exhibiting a huge variety of physical phenomena. Co-existing and tunable properties promise for a rich experimental platform for electron transport measurements. This study is aimed at the exploration and fabrication of mesoscopic devices defined at this interface. The interface between the two transition metal oxides LaAlO3 and SrTiO3 (LAO and STO) has served as a model structure since the discovery of its remarkable properties in 2004. Resolution limits in device fabrication have limited experiments at mesoscopic scales, highest resolution has been achieved in 2009 where atomic force microscope (AFM)-lithography was used to create nanoscale confined circuits.

This study focuses on the comparable high mobility γAl2O3/SrTiO3 (GAO/STO) interface, and finishes with low temperature measurements of a superconducting interferometer defined by AFM-lithography. With the fabrication of oxide interfaces by pulsed laser deposition (PLD), building an AFM-lithography setup, and low temperature transport measurements, all aspects from an idea to a final working device are conducted and presented in this thesis. A visit to Jeremy Levy’s group at the University of Pittsburgh provided the necessary experimental understanding of the lithography technique, to develop a similar system locally. Low temperature measurements on a 150 nm radius ring raise questions about 1/4th magnetic flux quantization.