Annealing of heavy ion irradiated Nb3Ge films

High T
c
Nb
3
Ge films prepared by coevaporation have been irradiated by 20 MeV sulfur ions at low temperatures (< 25 K). X-ray analysis showed an expansion of the Al5 lattice and an increasing degree of amorphicity, while T
c
vs. dose decreased from 22 K to 4.3 K with a slight minimum of ∼70 mK depth at
\phi t\sim 3.10^{15}
cm
^-2
before saturation. - Filmsirradiated by doses up to
\leq 1.5 \cdot 10^{15}
cm
^-2
could be annealed to the pre-irradiation T
c
. In contrast, strong irradiation led to an (X-ray-) amorphous structure, from which T
c
values of only 15-17 K could be recovered, similar to the results obtained for amorphous NbGe films condensed at LN
2
temperature. - The behaviour of the film resistivity during the heat treatment indicates that for films irradiated by low doses only lattice defects anneal, whereas for high dose damaged films recrystallization from the amorphous state occurs.