Title :
Investigation of the tunnel barrier in Nb-based junctions prepared by sputtering and electron beam evaporation
Author :
Kohlstedt, H. ; Gundlach, K.H. ; Schneider, A.
Author_Institution :
Inst. de Radio Astron. Millimetrique, Domaine Univ., Martin d´´Heres, France
fDate :
3/1/1991 12:00:00 AM
Abstract :
Nb-based tunnel junctions prepared by DC magnetron sputtering and electron beam evaporation are compared. Tunnel barriers consisting of Nb oxide, Al oxide and Si oxide are analyzed by anodization, Auger electron, and inelastic electron tunneling spectroscopy. Results obtained from Nb2-Si oxide/Si-Nb1 and Pb/Bi-Si oxide/Si-Nb1 structures are presented. Nb and Si were deposited by electron beam evaporation and Pb/Bi from tantalum boats. Silicium oxide has a relatively low dielectric constant (∈SiO2 ≃4, ∈SiO≃6) and is thus of interest for tunnel barriers. The anodization profile of Nb2-Si oxide Si-Nb1 layers for Si thickness up to 10 nm are discussed. Pb/Bi-Si oxide/Si-Nb1 junctions showed reasonably good quality Si thickness between 0.5 and 1 nm. The presence of Si in the barrier is confirmed by the inelastic electron tunnel spectrum (d2 I/dV2 as a function of junction bias voltage V) which shows the longitudinal and transversal acoustic phonons of Si
Keywords :
niobium; sputtered coatings; superconducting junction devices; vapour deposited coatings; 0.5 to 1 nm; 10 nm; AlOx; DC magnetron sputtering; Nb-SiOx-Si-Nb; NbOx; Pb-Bi-SiOx-Si-Nb; anodization; dielectric constant; electron beam evaporation; inelastic electron tunneling spectroscopy; Bismuth; Boats; Dielectric constant; Electron beams; Magnetic analysis; Niobium; Spectroscopy; Sputtering; Tunneling; Voltage;
Journal_Title :
Magnetics, IEEE Transactions on
