Fractal-like structures have been observed in sputter-deposited thin films of Nb${\mathrm{Ge}}_2$. These structures exhibit a striking resemblance to those produced by computer simulations of diffusion-limited aggregation using the Witten-Sander model. An effective fractal dimensionality of about 1.9 has been determined from digitized photomicrographs. Our results indicate a two-stage growth process in which an initial structure with a fractal dimensionality of about 1.7 is thickened by a subsequent growth process.

• Received 27 November 1984

DOI:https://doi.org/10.1103/PhysRevLett.54.701