The surface quality of light reflective metal films on polymer substrates were experimentally examined and evaluated. The study included light optical hotstage microscopy of in-situ samples and scanning electron microscopy. Conditions for producing aluminum metal films with desirable light reflecting properties are relatively demanding. The film formation is a complex series of events which include nucleation, coalescence and crystal growth.
Surface flaws, debris or other imperfections are readily visualized with the aid of the optical or the electron microscope. Although complex methods have been developed for the examination of small surface areas with fine-featured metallic films, there was little incentive to adopt the techniques for large samples. This situation prevailed because the simple microscopic evaluations were sufficient to reveal unacceptable qualities.
Hotstage microscopy was decisive in understanding the light reflectivity of the metalized layer and the substrate's influence over the deposited film. Prior to the hot stage examination, only the thin section based knowledge supported the film evaluations. There was always the disturbing possibility that some mechanically or chemically introduced artifacts were contributing to the observed surface irregularities and distortions.
The hotstage experiments proved that the observed surface corrugations are the result of complex mechanisms which may depend on several factors. These contributing factors include the combined results or the individual interaction between substrate, base coat, residual stress and temperature. Surface corrugations reproduced with the hotstage yielded valuable informations. In some instances, the experiments, pinpointed the underlying cause and in others it indicated the role of the variables.
Bartosiewicz, L. and Kelly, C. J.
"The Dark Side of Bright Metal Coatings,"
Scanning Microscopy: Vol. 3
, Article 11.
Available at: https://digitalcommons.usu.edu/microscopy/vol3/iss3/11