SCANNING-TUNNELING-MICROSCOPY STUDY ON THE GROWTH MODE OF VAPOR-DEPOSITED GOLD-FILMS

The growth of gold deposits on smooth glass from the vapor phase at 30 nm-1 s-1, 298 K, and incident angle near the substrate normal covering the 30-1000 nm average film thickness (HBAR) range is investigated through scanning tunneling microscopy (STM) complemented with oxygen-adatom electro-sorption measurements. The STM images of the deposits reveal a columnar structure resulting from a mechanism involving shadowing and surface diffusion. Quantitative data are obtained directly from STM images. The height distribution N(h) of the interface obeys an N(h) is-proportional-to e(-kh) relationship. For HBAR < 500 nm, the interface thickness (xi) increases as a power law with HBAR, whereas for HBAR > 500 nm it reaches a steady state. Under the latter condition, xi depends on the STM scan length (S) as xi is-proportional-to S(alpha) with alpha close to 1/3. These results indicate that the growth process of the gold deposits results in compact nonfractal structures with self-affine fractal surfaces, as predicted by ballistic deposition models. However, the latter fail to describe some aspects of the morphology and evolution of thin vapor-deposited gold films on this substrate.