•R. Schneider, A.G. Zaitsev, J. Geerk, G. Linker und F. Ratzel
Forschungszentrum Karlsruhe, Institut für Festkörperphysik
We report on two approaches to the in-situ synthesis of superconducting
MgB2 thin films. In the first approach, Mg and B were simultaneously
sputtered from two separate planar targets. The substrate temperature Ts
was limited to a small range of 290 to 320°C.
The resulting films on sapphire substrates were c-axis textured with low
growth quality. Their transition temperature Tc reached a maximum
of 24 K with a transition width of 0.6 K. A short-time in-situ annealing
at 600°C improved Tc
to 28 K. In the second approach, the Mg sputter source was replaced by
a specially designed Mg evaporator. Due to this intense Mg source Ts
could be increased to 440°C,
and Tc of the ''as-grown'' films rose to 33 K. Short-time in-situ
annealing after the film deposition enhanced Tc to 36 K. For
these films we also measured a high critical current density of 15 MA/cm2
at 6 K.