Transport- und Rauscheigenschaften supraleitender Quanteninterferometer aus YBa_2Cu_3O_7_-_#delta#

The transport and noise properties of direct current superconducting quantum interference devices (dc SQUIDs) made from YBa_2Cu_3O_7_-_#delta# have been studied. Since discrepancies between experimentally obtained values for signal and thermal noise compared to predictions obtained in numerical simulations are frequently observed, a detailed analysis of the parameter dependencies of the signal and noise of dc SQUIDs was carried out. Special attention was made to the regime of large thermal fluctuations where the origin of the discrepancies was suspected. Complementary, a recently developed analytical theory for dc SQUIDs operated in the presence of large thermal fluctuations was compared with both numerical simulation and experimental data. Surprisingly, a good agreement between theory and experiment was found in the limit of large thermal fluctuations. However, discrepancies were found to increase with increasing SQUID inductance. In order to compare theory and experiment, preparation of dc SQUIDs with well defined parameters is required. The according technology, i.e. patterning of pulsed laser deposited YBCO on bicrystalline substrates is briefly presented, along with a detailed study on adjustability of SQUID parameters. Special care was taken to measure the SQUID parameters as accurate as possible, the required measurement techniques being explained in detail. Several side aspects such as junction asymmetry, rf interference and low frequency noise are briefly examined. Furthermore, the effect of a damping resistance parallel to the SQUID inductance on the SQUID signal and noise has been studied. Finally, two examples of SQUID applications are presented. (orig.)126 refs.Available from TIB Hannover: RA 831(3711) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman