Establishing a process for the fabrication of high-quality HTc SQUIDs

[摘要] ENGLISH ABSTRACT:High-temperature (HTc) SQUID magnetometers are used in the biomedical field of magnetocardiography(MCG). The use of MCG enables a much earlier diagnosis of potentially dangerousconditions than the use of electrocardiography (EeG). For the use of MCG, high-qualityHTc SQUIDs are necessary. These SQUIDs can only be realised if the design and fabricationprocesses are well defined and understood. In this thesis an extensive literature review on thedesign process explains all the concepts necessary to understand and design a high-quality HTcSQUID. Then the fabrication process is redefined and characterised.The SQUIDs are fabricated with YBCO thin films on MgO substrates. The relevant stepsin the process are the pulsed laser deposition (PLD), UV lithography and argon ion milling.The characterisation of the fabrication process is based on a statistical method called Designof Experiment (DOE). This enables more information to be obtained about the fabricationprocess than before. For the PLO process the important parameters are determined and aninitial optimisation is done. During the characterisation process it is proven that the use ofozone during PLO has a positive effect on the quality of the YBCO thin film. On the PLDapparatus the substrate heater and laser-beam profile is improved. The UV lithography processis analysed and a DOE is proposed for optimisation. A temperature bath is added to the processto enable better reproducibility. An rf multicusp ion mill is built for argon-ion milling, thisdevice is tested and shown to provide the required etching capability.

[发布机构] Stellenbosch University