Leiden University Student Repository

Vermeer, Joost (2022)

STM-based Scanning SQUID Microscopy: A novel magnetic imaging technique

Master thesis | Physics (MSc)

Magnetic imaging plays an essential part in measuring magnetic sources, whether they are nanoparticles, superconductor vortices, edge currents, or something else. Current techniques either lack the necessary sensitivity and spatial resolution or are too invasive to use in many applications. Scanning SQUIDs are non-invasive and have excellent sensitivity, but operate at a large distance from the surface. By integrating a SQUID into a Scanning Tunneling Microscopy (STM) we will be able to image magnetic sources within 1 nm from the surface, increasing its sensitivity and spatial resolution. It also allows us to simultaneously gather topographic information, something no other scanning SQUID can do. To achieve this, a new production method is developed to create a SQUID on top of a sharp tip. To get a continuous superconducting connection across the surface of the tip, Molybdenum Germanium is used as a superconductor, with silver SNS junctions to prevent hysteresis. Measurements on...Show moreMagnetic imaging plays an essential part in measuring magnetic sources, whether they are nanoparticles, superconductor vortices, edge currents, or something else. Current techniques either lack the necessary sensitivity and spatial resolution or are too invasive to use in many applications. Scanning SQUIDs are non-invasive and have excellent sensitivity, but operate at a large distance from the surface. By integrating a SQUID into a Scanning Tunneling Microscopy (STM) we will be able to image magnetic sources within 1 nm from the surface, increasing its sensitivity and spatial resolution. It also allows us to simultaneously gather topographic information, something no other scanning SQUID can do. To achieve this, a new production method is developed to create a SQUID on top of a sharp tip. To get a continuous superconducting connection across the surface of the tip, Molybdenum Germanium is used as a superconductor, with silver SNS junctions to prevent hysteresis. Measurements on larger MoGe-Ag SQUIDs show that this design could achieve a theoretical spin sensitivity of 1μB/√Hz at 4.2 K, with a spatial resolution of 30 nm.Show less

Scanning SQUID

Author

Vermeer, Joost

Faculty

Faculty of Science

Specialisation

Quantum matter and optics

Supervisors

Aarts, J
Lahabi, K

ECTS Credits

24

Language

en