Thin, quench-condensed lead-based alloy films investigated by resistivity and superconducting tunneling measurements

Journal Article · Mon Oct 01 00:00:00 EDT 1973 · Journal of Low Temperature Physics

DOI:https://doi.org/10.1007/BF00654394· OSTI ID:4376683

Granqvist, C. G.; Claeson, T.

Quench-condensed lead-based alloy films were investigated by the superconductive tunneling method to study how structural order affects the phonon distribution, and in particular the appearance of localized impurity modes. As solute, 10 at.% of either Na, Mg, Zn, Ga, Ge, Ag, Cd, In, Sn, Sb, or Te was used. The films were condensed upon a substrate at 0.4 K and studied as deposited and after anneals to 30, 100, and 300 K. It was found that the shape of the phonon- induced tunneling structure could be used as a means to classify the state of structural order in the films. Temperatures of transformations from one state to another could be identified with those where steps occurred in curves of film resistance vs. annealing temperature. The most notable transformation was the one that took the film from an amorphous to a finely grained crystalline state. The transformation temperature scales with the melting point of the pure impurity element of the binary alloy. As the annealing temperature was increased further another temperature region was reached where the crystallites grew in size, causing notable changes in the phonon spectra. A third transformation occurred at low temperatures within the amorphous state for a few of the alloys. Localized impurity modes could be observed only in PbIn and only when the films had been annealed so that relatively large crystallites had formed. The absence of these high-frequency modes in most of the alloy films ean be explained as being due to a lack of order or solubility in the ordered state. Such arguments cannot, however, explain why no localized modes are seen in PbSn. In disordered films the phonon distribution is shifted toward lower frequencies compared to the case of a single crystal. For this type of lead-hased alloy the shift implies lower values of the superconducting transition temperature T and gap DELTA _o(0), but a higher 2 DELTA _o(0)/k_BT_c ratio. The depend ence of these values and of the tunnel resistance upon the structural slate is studied. The effect of fluctuations on the superconducting transition is noted for the thin, amorphous films.

• Research Organization: Univ. of Tech., Goteborg
• Sponsoring Organization: USDOE
• NSA Number: NSA-29-008891
• OSTI ID: 4376683
• Journal Information: Journal of Low Temperature Physics, Vol. 13, Issue 1-2; Other Information: Orig. Receipt Date: 30-JUN-74; ISSN 0022-2291
• Publisher: Plenum Press
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
*LEAD BASE ALLOYS- SUPERCONDUCTIVITY
ANNEALING
ANTIMONY ALLOYS
CADMIUM ALLOYS
FILMS
GALLIUM ALLOYS
GERMANIUM ALLOYS
INDIUM ALLOYS
MAGNESIUM ALLOYS
PHONONS
SILVER ALLOYS
TELLURIUM ALLOYS
TIN ALLOYS
TUNNEL EFFECT SODIUM ALLOYS
ZINC ALLOYS