Oxygen-doped Pb-In-Au films suitable for Josephson tunnel junction base electrodes
The effects of oxygen doping during film deposition on film microstructures, surface morphology, strain behavior, and electrical resistivity have been studied by using transmission and scanning electron microscopies, x-ray diffraction, and electrical resistivity measurements for 0.2-..mu..m-thick Pb and Pb-12 wt.% In-4 wt.% Au films prepared at approx.77 K. The average grain size of both types of films was found to decrease with increasing oxygen partial pressure during the film deposition: one order of magnitude smaller grains, compared with those prepared in a high vacuum (< or approx. =5 x 10/sup -8/ Torr), were obtained when the oxygen pressure was higher than 1 x 10/sup -6/ Torr. The finest average grain size obtained in the present experiments was < or approx. =15 nm, which is over 10 times smaller than the film thickness. The surfaces of both films were found to be smooth when the films were prepared at oxygen pressures below 1 x 10/sup -5/ Torr. Strain relaxation upon cooling to 4.2 K was observed for oxygen-doped Pb films, but no strain relaxation was observed for Pb-In- Au films. In addition, no hillocks were observed in oxygen-doped Pb-In-Au films cycled 300 times between 300 and 4.2 K. The electrical resistivities of Pb-In-Au films were found to increase with oxygen pressure; an increase of a factor of 10 was observed when the films were prepared at an oxygen pressure of 1 x 10/sup -5/ Torr. The thermal cyclability of large-area Josephson tunnel junctions, in which oxygen-doped Pb-In-Au films were used as the base electrodes, exhibited the lowest cycling-induced failure level ever reported for large-area Pb-alloy Josephson tunnel junctions beyond 400 thermal cycles. The number of thermal cycles to reach 5% cumulative failure increased from 1000 to 5000 cycles by introducing 5 x 10/sup -7/ Torr of oxygen during film preparation at 77 K. However, the sigma value (slope of the log normal failure distribution) becomes about three times larger.
- Research Organization:
- IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598
- OSTI ID:
- 5224005
- Journal Information:
- J. Appl. Phys.; (United States), Vol. 53:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
JOSEPHSON JUNCTIONS
SCANNING ELECTRON MICROSCOPY
TRANSMISSION ELECTRON MICROSCOPY
DOPED MATERIALS
ELECTRIC CONDUCTIVITY
EXPERIMENTAL DATA
FILMS
GOLD ALLOYS
INDIUM ALLOYS
LEAD ALLOYS
LOW TEMPERATURE
MORPHOLOGY
OXYGEN
STRAINS
SURFACES
THICKNESS
TUNNEL EFFECT
ULTRALOW TEMPERATURE
X-RAY DIFFRACTION
ALLOYS
COHERENT SCATTERING
DATA
DIFFRACTION
DIMENSIONS
ELECTRICAL PROPERTIES
ELECTRON MICROSCOPY
ELEMENTS
INFORMATION
JUNCTIONS
MATERIALS
MICROSCOPY
NONMETALS
NUMERICAL DATA
PHYSICAL PROPERTIES
SCATTERING
SUPERCONDUCTING JUNCTIONS
420201* - Engineering- Cryogenic Equipment & Devices