Doctoral Degrees (Electrical and Electronic Engineering)
Permanent URI for this collection
Browse
Browsing Doctoral Degrees (Electrical and Electronic Engineering) by Subject "AFM nanolithography"
Now showing 1 - 1 of 1
Results Per Page
Sort Options
- ItemFabrication of Josephson junctions using AFM nanolithography(Stellenbosch : University of Stellenbosch, 2010-12) Elkaseh, Akram Abdulsalam; Perold, W. J.; Srinivasu, V. V.; University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: Planar weak link structures, such as micro-bridges, variable thickness bridges and nanobridges, have always attracted a lot of attention. Their potential to behave as real Josephson elements make them useful devices, with numerous applications. Powerful techniques, such as focused ion-beam and electron-beam lithography, were successfully used and are well understood in planar weak link structure fabrication. In this dissertation the results of an experimental study on planar weak link structures are presented. For the first time these structures have been successfully fabricated using AFM nanolithography on hard high-temperature superconducting YBCO tracks, where diamond coated silicon tips were used as a ploughing tool. Superconducting YBCO thin films were deposited on different substrates, using inverted cylindrical magnetron sputtering. The films were used to fabricate micro-bridges, variable thickness bridges and nano-bridges, by using conventional photolithography, argon ion-beam milling and AFM nanolithography. The measured I-V characteristics of the fabricated micro-bridges (width down to 1.9 µm), variable thickness bridges (thickness down to 15 nm) and nano-bridge (width down to 490 nm) showed well defined DC and AC Josephson effect characteristics. For better understanding of the behaviour of these types of weak links, critical current versus temperature measurements, and magnetic field modulation of the critical current measurements, were also performed, with the results and discussions given inside the chapters. The major challenges that were experienced in the laboratory during the fabrication processes and the operation of the fabricated devices are also discussed, with the solutions given where appropriate.