Surface diffusion of metal atoms on polymer substrates during physical vapour deposition
The surface diffusion of physical-vapour-deposited metal atoms on thermoplastic polymer substrates was investigated. In accordance with the hypothesis of the “classical” atomistic diffusion model, diffusion coefficients are derived from a Monte Carlo simulation. Because the “classical” atomistic diffusion model neglects the desorption of the metal atoms, the absolute diffusion data obtained in our investigations should only be considered as rough estimates. It is more the intention of our work to present relative values in order to correlate the metal surface diffusion on polymer substrates with their physical states (morphologies and surface dynamics). As expected, the diffusivity of metal atoms is strongly influenced by the chemical affinity (“reactivity”) between the metal atoms and the polymer substrate. Furthermore, the diffusivity strongly depends on the physical state of the polymer substrate. On polymer surfaces above the glass-transition temperature the surface diffusivity of metal atoms is 1 order of magnitude higher than the diffusivity below the glass-transition temperature.
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