In the initial stage of their growth, thin metal films deposited on dielectrics consist of individual semi-spherical islands distributed more or less randomly on the substrate. During further growth these islands increase, coalesce and form first discontinuous film with irregular objects and then semicontinuous layer. The TEM micrographs of metal films can be analysed and information about film morphology can be derived.
The forms and the spatial distribution of islands in very thin films can be described fully by standard methods of mathematical morphology as a radial distribution function or a distribution of nearest neighbours. However, the accuracy of these methods decreases rapidly with increasing film thickness -it is limited for discontinuous films with large islands of irregular form and these methods cannot be used at all for semicontinuous films.
In file contribution the standard morphological methods are tested by computer experiment, where file simulated micrographs with known parameters are processed together with experimental micrographs of Au and Ag thin films and the limits of applicability of individual algorithms are derived.
Besides the well-known morphologic,'d methods some other methods are suggested and analysed. It was found that especially the chord-length distribution method is very promising. Chord-length distribution is a complex method, which can be used both for characterisation of forms of individual objects in discontinuous metal films and for description of their distribution over the substrate. An attempt is made to extend the limits of chord-length distribution method even to semicontinuous films, where the physical meaning of derived characteristics must be yet established.
The second method, which applicability can be extended to semicontinuous films, is the covariance. For discontinuous films the covariance function brings evidence about several morphological characteristics of the film in the same moment. By its ,analysis it is possible to derive values of coverage, to calculate object radii and to characterise the regularity of the distribution of objects on the substrate. For semlcontinuous films part of this information is lost, however some new features of films can be calculated.