Study of rough growth fronts of evaporated polycrystalline gold films

Abstract

The scaling exponents of interface width and coarsening of evaporated gold films with thickness from 30 to 1800 nm were obtained from two-dimensional measurements on scanning tunneling microscopy (STM) images and are presented here. The lateral size of protrusion on the surface of the films increases with a constant scaling exponent n1/3. The interface width grows in two stages. The final stage starts at 60 nm and corresponds to a time scaling exponent of 1/3 with a constant slope morphology. Scaling exponents are compared with those from models for high thickness epitaxial growth and for polycrystalline film growth, all predict a constant slope morphology. To help the choice among the three compatible models, STM results are compared with transmission electron microscopy (TEM) images where low contrast structures can be observed on large crystalline plates. As a result it may be interpreted that the structures observed correspond either to a mound growth or to an array of columns with low grain boundaries between them. Other smaller crystalline components are observed in polycrystalline areas and can be assigned to columnar tops. The practically unimodal Gaussian distribution of local heights, indicates that the surface morphologies arising from these two bulk structural components are not very different and suggests that both morphologies are controlled by the same atomic surface diffusion phenomena.