Study of the Ge surface segregation in superconducting sputter-deposited Nb/sub 3/Ge films using Auger electron spectroscopy

Journal Article · Thu Feb 01 00:00:00 EST 1979 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.326022· OSTI ID:6517780

Buitrago, R H; Toth, L E; Goldman, A M

Auger electron spectroscopy (AES) has been used to diagnose the nature of Ge enrichment in the top atomic layers of sputter-deposited films of superconducting Nb/sub 3/Ge. In films with high T/sub c/'s, there is a small oxygen-rich layer of 5--10 A followed by a layer about 60--70 A thick in which a pronounced Ge enrichment exists. This segregation layer is much thicker than comparable layers found in other binary alloys and this suggests that thermodynamic considerations are not the only cause of the enrichment. Beneath the layers, the Nb/sub 3/Ge film is chemically homogeneous as a function of depth with constant Nb/Ge ratio existing up to the interface with the substrate where a Nb enrichment occurs. In films with low T/sub c/'s, however, there is a smaller oxygen-rich layer and a thinner Ge-rich layer existing at the top surface. Very thin films sputter deposited under otherwise optimum conditions for producing high transition temperatures have low T/sub c/'s and an incompletely formed Ge-rich surface layer. Additional experiments have established that the Ge-rich layer forms during the sputter deposition and its thickness is a function of deposition time. The data have serious implications for the fabrication of tunneling junctions for the purposes of probing the physics of superconductivity in Nb/sub 3/Ge because the thickness of the Ge-rich layer is about the same as the coherence length. Methods to remove the Ge-rich layer without damaging the underlying film were also investigated, as was the effect of oxidation on the layer. One interesting sidelight of the interpretation of the data is that the Ge-rich layer may stabilize the growth of the high-T/sub c/ metastable phase.

• Research Organization: School of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455
• OSTI ID: 6517780
• Journal Information: J. Appl. Phys.; (United States), Vol. 50:2
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
GERMANIUM ALLOYS
SUPERCONDUCTIVITY
NIOBIUM BASE ALLOYS
TYPE-II SUPERCONDUCTORS
PHASE STUDIES
AUGER ELECTRON SPECTROSCOPY
FILMS
INTERMETALLIC COMPOUNDS
LAYERS
OXIDATION
SEGREGATION
SPUTTERING
SURFACE PROPERTIES
SURFACE TREATMENTS
SURFACES
TRANSITION TEMPERATURE
TUNNEL EFFECT
ALLOYS
CHEMICAL REACTIONS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRON SPECTROSCOPY
NIOBIUM ALLOYS
PHYSICAL PROPERTIES
SPECTROSCOPY
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
360102* - Metals & Alloys- Structure & Phase Studies
656102 - Solid State Physics- Superconductivity- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena- (-1987)