Articulo
Scanning-tunneling-microscopy study on the growth mode of vapor-deposited gold films
Autor
Herrasti, Pilar
Ocón, Pilar
Vázquez, Luis
Salvarezza, Roberto Carlos
Vara, J. M.
Arvia, Alejandro Jorge
Institución
Resumen
The growth of gold deposits on smooth glass from the vapor phase at 30 nm<sup>−1</sup> s <sup>−1</sup>, 298 K, and incident angle near the substrate normal covering the 30—1000 nm average film thickness (h¯) range is investigated through scanning tunneling microscopy (STM) complemented with oxygen-adatom electrosorption 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 <i>N(h)</i> of the interface obeys an <i>N(h)∝ e <sup>−kh</sup></i> relationship. For h¯<500 nm, the interface thickness (ξ) increases as a power law with h¯, whereas for h¯ > 500 nm it reaches a steady state. Under the latter condition, ξ depends on the STM scan length (S) as ξ∝ S<sup>α</sup> with a 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. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas Facultad de Ciencias Exactas