Discontinuous noble metal island films are utilised as biosensors by monitoring changes in their surface plasmon resonance, which are highly sensitive to adsorbed molecules. The reproducible production of such films is therefore of great interest. We present results of in-situ spectroscopic ellipsometric (SE) monitoring of metal island film growth by pulsed filtered cathodic vacuum arc (PFCVA). Utilising optical features in the silicon oxide substrate the film thickness is accurately determined to within 0.1 nm. Accurate knowledge of the film thickness provides the necessary information to unambiguously determine the film optical constants. The use of a highly reproducible pulsed plasma source allows us to determine the material mass deposition rate, and consequently the void content of the film. The percolation threshold of the island films is determined by from the film optical constants, and compared with the vakue determined by in-situ conductivity measurements and te predictions of percolation theory.

Instability in noble metal islands, especially in the period immediately following deposition by PFCVA, complicates the production of films of stable and reproducible area coverage for use as biosensors. In-situ film resistivity measurements reveal changes in the conductivity of PFCVA deposited silver island films for periods in excess of one hour. In-situ SE reveals morphological changes in the films for a period less than 4 minutes, corresponding to an increase in film thickness. We propose that an increase in silver island height during this period, caused by particle mobility and surface energy minimization, is responsible for the short term morphological changes. Conductivity changes for periods greater than 4 minutes are attributed to slow cooling of the film combined with the negative temperature coefficient of resistance of metal islands films.

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