Portal de Periódicos da CAPES

Nucleation and growth of gold films on graphite

1975; Elsevier BV; Volume: 28; Issue: 1 Linguagem: Inglês

10.1016/0022-0248(75)90026-3

1873-5002

C.M. Wayman, T. P. Darby,

Advanced Materials Characterization Techniques

To determine the effect of substrate temperature on the nucleation and growth of gold films vapor deposited on single crystal graphite, films deposited at ≈ 1A˚/s in a vacuum of ≈ 10-9 Torr on air-cleaved substrates held at temperature ranging from room temperature to 450°C and on vacuum-cleaved substrates held at temperatures ranging from — 152 to 450°C were studied using transmission electron microscopy and diffraction. As the substrate temperature is increased from room temperature to 450°C, the particle density on air-cleaved surfaces approaches that on vacuum-cleaved substrates, the dendritic morphology characteristic of vacuum-cleaved substrates is lost, coalescence events become much more prominent, and the metal islands are more three-dimensional and geometrical. At or above a 200°C substrate temperature the particle morphology consists of a few large (500 to 1000A˚) triangular and hexagonal platelets and numerous small (200 to 500A˚) octahedral and multiply-twinned particles regardless if the substrate is air- or vacuum-cleaved. In general, the films have a [111] fiber texture with some directional alignment in the substrate surface. For films on vacuum-cleaved graphite as the temperature is decreased below room temperature, the dendrites become more clearly defined down to -52°C, but below this temperature the branches are shorter and narrower than at room temperature and the directional alignment in the substrate plane progressively deteriorates. The morphological changes occuring as the temperature increases can be explained by the more pronounced coalescence and grain growth, the greater kinetic-controlled island growth, and the lower particle densities that result. The major differences between films on air-and vacuum-cleaved substrates can be correlated with the effects of substrate temperature and cleanliness (i.e., either air- or vacuum-cleaved).