28 June 1985 Elastic Electron Tunneling Spectroscopy On Niobium/A-Silicon Oxide/Lead Junctions
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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.
© (1985) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
S. Celaschi, S. Celaschi, A. K. Green, A. K. Green, } "Elastic Electron Tunneling Spectroscopy On Niobium/A-Silicon Oxide/Lead Junctions", Proc. SPIE 0524, Spectroscopic Characterization Techniques for Semiconductor Technology II, (28 June 1985); doi: 10.1117/12.946332; https://doi.org/10.1117/12.946332
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