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Proceedings Paper

Elastic Electron Tunneling Spectroscopy On Niobium/A-Silicon Oxide/Lead Junctions
Author(s): S. Celaschi; A. K. Green
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Paper Abstract

Polycrystalline Niobium/Lead junctions using barriers of partially oxidized amorphous silicon (a-Si) were investigated. The method of elastic supercRnducting tunneling spectroscopy is used for this purpose. A thin layer of Ak (10 A) is used to passivate the Nb surface against the formation of conductive Nb sub-oxides. A detailed study of the behavior of oxidized a-Si layers as the tunneling barrier is reported. The insulator is shaped as a double height barrier to account for the partially oxidized nature of the a-Si deposited layer. The average barrier heights are 15 ± 5 meV and 1.2 ± 0.2 eV for the a-Si and SiOx layers respectively. The extremely low value obtained for the effective barrier height of a-Si is associated with the high density of localized states in the mobility gap of the a-Si. The conduction is explained to be electron tunneling between localized states within the "gap". A systematic degradation of the Nb/Pb BCS tunneling characteristics with increasing a-Si thickness has been observed which correlates with deviations from the metal-insulator-metal microscopic tunneling theory. These anomalies are associated with the intrinsic properties of the unoxidized fraction of the a-Si layer.

Paper Details

Date Published: 28 June 1985
PDF: 7 pages
Proc. SPIE 0524, Spectroscopic Characterization Techniques for Semiconductor Technology II, (28 June 1985); doi: 10.1117/12.946332
Show Author Affiliations
S. Celaschi, Instituto de Fisica e Quimica de Sao Carlos (Brasil)
A. K. Green, Naval Weapons Center (United States)

Published in SPIE Proceedings Vol. 0524:
Spectroscopic Characterization Techniques for Semiconductor Technology II
Fred H. Pollak; Raphael Tsu, Editor(s)

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