Laplacian growth of amorphous carbon filaments in a non-diffusion-limited experiment.

Abstract

Ramified amorphous filaments grow by the aggregation of hydrocarbon molecules on charged specimens in a transmission electron microscope. The molecules move on deterministic trajectories and are attracted by the aggregate. Fractal, dense branching, and compact morphologies appear. Under suitable conditions, dense branching aggregates show an oscillating growth behavior. The aggregation is of the Laplacian type but not diffusion limited. The morphology of the deposit is determined by surface migration of the molecules on the aggregate. Due to the transformation of the material into amorphous carbon under electron irradiation, the morphology depends on the aggregation rate. The experiment shows that particles following simple Newtonian trajectories can form ramified objects of various morphologies by aggregation.