Calcium digermanide

Description

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.