The optical constants of thin molybdenum layers and molybdenum/tin oxi
de cermets, produced by a batch sputtering deposition system, were det
ermined by spectroscopic ellipsometry. The geometrical structure of th
e layers and the embedded particles was analysed with an atomic force
microscope. The results were used for the investigation of a suitable
effective medium theory to describe the optical constants of cermets w
ith relatively high filling factors.