Bachelor Defence: Daniel Steffensen – University of Copenhagen

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Center for Quantum Devices > QDev/NBI Seminars/Events > 2015 > Bachelor Defence: Dani...

Bachelor Defence: Daniel Steffensen

"As-grown Suspended Carbon Nanotubes"

The work concerning the fabrication and characterization of ultra-clean suspended
as-grown single-walled carbon nanotubes (SWNT) that is the focus of my bachelor
project, and will be presented at this defence. The fabrication focused on optimizing and finding the right metal stacking, and implements these.
The contacts were variations of a sticking layer of either Ta or W with an adhesion
layer of Pt on top. The SWNTs were grown by chemical vapor deposition, followed by
characterization of these at room temperature. The energy spectra were determined
at sub-kelvin temperatures (T∼300mK) in a cryostat by confining the SWNT as
quantum dots (QDs).
The obtained devices showed Coulomb blockade (CB) and Kondo effects. Through
analysis, however, it was shown that the structures were highly irregular, suggesting
multiple interacting ill-defined QDs, most likely produced by the irregular contacts
after growth. A short outlook will be given for further development of clean SWCT devices.