Superconductivity in Ge/Si core-shell nanowire quantum dots

Elferink, W. (2015) Superconductivity in Ge/Si core-shell nanowire quantum dots.

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Abstract:Superconductivity through semiconducting nanowires can open up many new possibilities in research of physics. In this project we investigate the effect of different metal contacts on tunnelling supercurrents through a semiconducting Ge/Si core-shell nanowire. The requirements for a tunnelling supercurrent through a semiconducting nanowire are transparent contacts and ballistic transport throughout the nanowire. We made multiple devices and tested aluminium, niobium, palladium and titanium as contacts in different configurations. For samples with contacts of pure niobium, pure aluminium or a stack of palladium, niobium and aluminium; we find high contact resistances and energy barriers at the contact interfaces. In a sample with contacts consisting out of 0.4 nanometers titanium, 15 nanometers palladium and 50 nanometers aluminium; we find low contact resistances and no energy barriers. These properties indicate that a layer of Ti and Pd on top of the nanowire is essential for transparent contacts in our system. With these contacts, this sample seems to meet the requirements and is a promising candidate for a tunnelling supercurrent through Ge/Si core-shell nanowires. Aside from these progressions towards our main goal we have also seen results indicating the possibility of measuring enhanced weak localization in these superconductor to nanowire to superconductor systems. The validity of these measurements needs to be verified.
Item Type:Essay (Bachelor)
Faculty:TNW: Science and Technology
Subject:33 physics
Programme:Applied Physics BSc (56962)
Link to this item:http://purl.utwente.nl/essays/67537
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