Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: High Temperature Superconductors (HTS) exhibit exceptional electrical properties that make them
attractive candidates for numerous electronic devices and applications. However, constructing
working devices can be challenging due to fabrication difficulties of these brittle ceramics. This
thesis investigates new methods to make the fabrication of high quality YBa2Cu3O7 (YBCO) thin
films easier and compatible with more materials.
We present the development of a universal add-on method that can be used in situ to improve the
quality of superconducting thin films deposited by Pulsed Laser deposition (PLD). We investigate
the in situ application of electric fields and voltage biasing to improve the thin film growth. Considering
various electrode configurations, we have developed a final electrode design that is stable
and produces reproducible results. By introducing an insulated high voltage (HV) electrode into the
chamber during deposition, the quality of the deposited thin films can be modulated depending on
the polarity of the voltage applied. Applying a positive voltage improves the film quality obtained.
Applying a negative voltage degrades the superconducting properties of the films.
A simple proof-of-concept HTS dual-mode microwave filter was designed, fabricated and tested.
Only the filter produced using our novel PLD technique displayed the correct filtering action upon
cooling to 77K. This is attributed to the thin films better superconducting properties due to our
developed technique. / AFRIKAANSE OPSOMMING: Hoë Temperatuur Supergeleiers (HTS) vertoon aantreklike elektriese eienskappe wat hulle goeie
kandidate maak vir verskeie elektroniese toepassings. Om werkende toestelle te ontwikkel kan 'n
uitdaging wees, as gevolg van die vervaardigings probleme wat bestaan vir hierdie bros keramiek materiaal.
Hierdie tesis ondersoek nuwe metodes om die vervaardiging van 'n hoë gehalte YBa2Cu3O7
(YBCO) dun films makliker en versoenbaar te maak met verskeie materiale.
Ons toon die ontwikkeling van 'n algemene metode wat maklik bygevoeg kan word om in situ die
gehalte van supergeleidende dun films, wat deur gepulseerde laser deponering (PLD) gedeponeer
is, te verbeter. Ons ondersoek die in situ toepassing van elektriese velde en spannings om die
dun film groei te verbeter. Verder oorweeg ons verskeie elektrode konfigurasies en ontwikkel 'n
finale elektrode ontwerp wat stabiel is en herhaalbare resultate produseer. Die kwaliteit van die
gedeponeerde dun films kan gemoduleer word deur die byvoeging van 'n geïsoleerde hoogspannings
(HV) elektrode tydens deponering, afhangende van die polariteit van die aangelegde spanning. 'n
Positiewe spanning verhoog die film kwaliteit, terwyl 'n negatiewe spanning die supergeleidende
eienskappe van die films verlaag.
'n Eenvoudige HTS dubbele-modus mikrogolffilter is ontwerp, vervaardig en getoets, om as toepassings
voorbeeld te dien. Slegs die filter wat geproduseer was met behulp van ons nuwe PLD
tegniek, vertoon die beste filter oordrag by 77K. Dit word toegeskryf aan die beter supergeleidende
eienskappe van die dun film, as gevolg van die toepassing van ons ontwikkelde tegniek.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/96096 |
| Date | 12 1900 |
| Creators | Hardie, Graham Lyall |
| Contributors | Perold, Willem J., Stellenbosch University. Faculty of Engineering. Department of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xviii, 137 p. : ill. |
| Rights | Stellenbosch University |
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