EXPERIMENTAL DEMONSTRATION OF THE ROLE OF LOCAL LATENT-HEAT IN GE PATTERN-FORMATION

(Amorphous Ge)/(polycrystalline Au) bilayer thin films with different Au grain size were prepared, and the pattern formation of Ge in annealed films has been investigated. It was found that as the average Au grain size increases from 40 to 410 nm, the Ge patterns change from ramified fractals to simple tip-splitting patterns and finally to round patterns. Furthermore, our experiment proves that the fractal formation in such films is truly dominated by the local-latent-heat, and that the pattern geometry is governed by the latent-temperature field range and the lattice network formed by the grain boundaries of the underlying Au film. © 1990 The American Physical Society.