Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ films: Growth and applications in dc SQUIDs and microwave devices
Tl-2212 thin films were grown ex situ in a two step process on a variety of substrates, including ones with artificially introduced high angle steps. Grain boundary weak links were formed on LaAlO/sub 3/ substrates with steps and on bicrystal substrates and were employed in dc SQUIDs. The white noise level of the SQUIDs was 50/spl mu//spl Phi//sub 0///spl radic/(Hz) at 77 K. A 12.5 GHz HEMT oscillator stabilized with a Tl-2212 resonator gave 8-10 dB lower phase noise than using a gold resonator.
Thallium- and mercury-containing cuprates in electronic devices
Results on the synthesis of Tl- and Hg-based thin films featuring different numbers of planes are presented. At optimal annealing conditions of 108 K and 92 K were achieved for Tl-2212 and Tl-2201 films, respectively. Tl-2201 films can be grown with orthorhombic or tetragonal structure depending mainly on the Tl content. Bicrystal and step-edge weak links were fabricated in Tl-2212 films with ranging from 105 to 109 K. The weak links were studied and applied in dc SQUIDS. Microwave resonators with a microstrip configuration was designed and used in oscillators at 12 GHz frequency.
A coplanar transmission line high-T/sub c/ superconductive oscillator at 6.5 GHz on a single substrate
The design and construction of a planar, low-noise cryogenic oscillator operating at 6.5 GHz are presented. The oscillator has been built as a hybrid superconductive microwave integrated circuit (SMIC) on a single 10*10 mm LaAlO/sub 3/ substrate. Single-sided, coplanar line structures are used throughout the circuit with YBa/sub 2/Cu/sub 3/O/sub 7- delta / as conductor material. The oscillator was constructed around a GaAs MESFET as the active device. The complete oscillator is cooled by immersion in liquid nitrogen. An output power of 4.9 dBm was obtained. Single-sided noise power at 10 kHz offset from carrier was -90 dBc/Hz.<<ETX>>