Effect of fractal crystallization on the depositing sequence of a Pd/Ge thin film system

The behavior of fractal crystallization in a Pd/Ge thin film system of various ratios of thickness (or composition) after annealing has been investigated by transmission electron microscope. It is difficult for coevaporated Pd–Ge films to obtain fractal crystallization. The fractal structure in Pd/$a$-Ge bilayer films can form more easily than in $a$-Ge/Pd bilayer films. The fractal crystallization was restricted because of the formation of the compounds (⁠$Pd2Ge$ and PdGe) in the Pd/Ge thin film system. Growth of the fractal structure depends on the competition between the two processes of amorphous germanium (⁠$a$-Ge) crystallization and compound formation. Fractal formation can be explained by a random successive nucleation model.