High Performance YBCO Films
Abstract
The objective of this program is to identify suitable low loss, low dielectric constant substrates and develop and optimize deposition processes for high quality YBCO films including the necessary buffer layers. Ultimate goals are large area substrates having double-sided HTS coating with a surface resistance ten times lower than copper at 40 GHz. High quality HTS films on low dielectric constant substrates are expected to find widespread use in advanced millimeter wave components, in extending the power handling capability of microwave and millimeter wave circuitry, and in facilitating high speed computer interconnects. Sample demonstration circuits will be built toward the end of the program. We have successfully deposited a high quality YBCO film on a good low loss and low dielectric constant substrate, magnesium fluoride (e=5). With the use of two buffer layers (magnesium oxide and strontium titanate) between the YBCO and the substrate, transition temperatures of 89 deg K and transition widths of about 0.5 deg K were achieved. The critical current density Jc of 4 x 10 6 A/cm2 at 77K in zero field is among the highest reported for YBCO films. The magnesium fluoride (MgF2) substrate has a tetragonal structure with a dielectric constant of 5.2 in the plane of the substrate and 4.6 perpendicular to the substrate surface. It has a good harness (-575 Knoop) and a linear thermal expansion coefficient that closely matches YBCO and the buffer layers.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 31, 1992
- Accession Number
- ADA258481
Entities
People
- Edgar J. Denlinger
Organizations
- Sarnoff Corporation