Preparation Study of Bi-Sr-Ca-Cu-Oxides Superconducting Thin Films by Resistive Evaporation
A conventional vacuum system housing resistively heated sources only was used to study the evaporation conditions for Bi-Sr-Ca-Cu oxides thin film production. Thin film were prepared by sequential evaporation of CaF2, SrF2 and Bi pulverized mixture and Cu from the two separate sources. The starting materials were weighed to yield a stoichometric Bi2 Sr2 CaCu2 film of about 1μm thickness upon evaporation to completion. Well polished MgO Substrates kept at room temperature were used in this experiment.
The films were annealed in a quartz-tube furnace at 350°C for one hour for oxidation of the copper layers thus precluding any Bismuth escape, followed by 10 minutes at 725°C in flowing O2 bubbled through water for defluorination and then at Ca. 870°C for 14 hours.
Typical results, using four-point probe method reveal a Tc (R = 0) at 83K and critical current density of 103 A/cm2 at 66K.
This work presents one of the simplest vacuum deposition methods in which no thickness monitor or any other control system is required. The crucial point in the heating treatment was to overcome the problem of the Bismuth diffusing out of the film during the long annealing time at high temperature.
KeywordsCritical Current Density Copper Layer Thickness Monitor Resistive Evaporation Auger Depth Profile
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- 8.J.M. Tarascon, W.R. McKinnon, P. Barboux, D.M. Hwang, B.G. Bagley, L.H. Greene, G.W. Hull, Y. Le Page, N. Stoffel and M. Girond, Phys. Rev. B (submitted).Google Scholar