Thermal stability of Pb-alloy Josephson junction electrode materials. III. Correlation of microstructure and strain in Pb-In-Au base electrodes

Journal Article · Fri Jan 01 04:00:00 EST 1982 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.329935· OSTI ID:5825857

Murakami, M; Serrano, C M

Upon cooling typical Pb-alloy Josephson junction devices from 300 to 4.2 K, strain is introduced into the junction electrode films due to the thermal expansion coefficient mismatch between the films and their underlying Si substrates. To reduce the probability of device failure, it is desirable for the strain to be supported elastically by the electrodes. Studies were undertaken by transmission electron microscopy and x-ray diffraction to correlate film microstructure with the elastic strain that can be supported at 4.2 K by Pb-alloy films containing Au and/or In. Grain size was confirmed to be one of the key factors that control the level of the elastic strain supported at 4.2 K when the films contained no misfit dislocations. The critical grain size (g/sub c/) (the value larger than which strain relaxation occurs upon cooling to 4.2 K) was found to be approx.0.6 ..mu..m for the Pb and Pb-alloy films prepared at 298 K by nucleating them on an ultrathin Au or oxidized In layer in a vacuum lower than 1 x 10/sup -7/ Torr. The Pb-alloy films prepared at 77 K supported more strain elastically; no strain relaxation was observed when their grain sizes were about a factor of two larger than the g/sub c/. When films contained misfit dislocations as observed at Pb/In interfaces in Pb-In and Pb-In-Au alloy films prepared at 298 K, strain relaxation by the dislocation glide was observed even though the average grain sizes were smaller than g/sub c/. No evidence was obtained that Pb/sub 3/Au and AuIn/sub 2/ intermetallic compounds observed in Pb-Au and Pb-In-Au films, respectively, control the level of elastic strain they can support at 4.2 K. However, these compounds were found to retard grain growth of the Pb-alloy films and to improve their grain size uniformity.

• Research Organization: IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598
• OSTI ID: 5825857
• Journal Information: J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 53:1; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

420201* -- Engineering-- Cryogenic Equipment & Devices
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALLOYS
COHERENT SCATTERING
COOLING
CORRELATIONS
CRYSTAL STRUCTURE
DATA
DIFFRACTION
ELECTRODES
ELECTRON MICROSCOPY
EXPANSION
EXPERIMENTAL DATA
GOLD ALLOYS
GRAIN SIZE
INDIUM ALLOYS
INFORMATION
JOSEPHSON JUNCTIONS
JUNCTIONS
LEAD ALLOYS
MEDIUM TEMPERATURE
MICROSCOPY
MICROSTRUCTURE
NUMERICAL DATA
REACTIVITY COEFFICIENTS
SCATTERING
SIZE
STABILITY
STRAINS
SUPERCONDUCTING JUNCTIONS
TEMPERATURE COEFFICIENT
TEMPERATURE EFFECTS
THERMAL EXPANSION
TRANSMISSION ELECTRON MICROSCOPY
ULTRALOW TEMPERATURE
X-RAY DIFFRACTION