Cell parameters are: a = b = 3.9492 ? , c = 10.493 ? ,
α= β = 79.15°, γ= 60°, cell volume = 138.30 ?3.
The epitaxial growth of thin CaGe2 films with reactive
deposition epitaxy on Ge(1,1,1) substrates has been
described. The films consisted in general of a mixture
of the known trigonal rhombohedral tR6 modification
and a hexagonal hR2 modification of CaGe2 containing
two Ca and two buckled Ge layers per unit cell in
a twofold stacking sequence whose formation appears
to be favored by strain.Epitaxial layers of both polytypes
show remarkably higher crystalline quality
compared to epitaxial CaSi2 films grown on silicon
substrates. The tr-6 modification is found to be unstable
in air in contrast to the hR-2 modification.
