Ellipsometry study of ultra thin layers of evaporated gold

Optical properties of ultra thin (from 1 to 40 nm) films of gold evaporated on glass; and silicon were studied with the method of spectroscopic ellipsometry in both external and internal reflection configurations as well as with the UV-visible absorption spectroscopy. The results obtained showed a gradual shift of the plasmon peak from 580 nm for 1 nm thick films to more than 1000 nm for thick (40 nm) gold films. Such phenomenon can be interpreted in terms of quantum confinement of surface plasmons in gold islands. The threshold of the metal-dielectric transition was found at the film thickness between 4 and 5 nm. Thiolation of the surface of glass has resulted in a slight decrease in the effective thickness of gold layer and respective smaller blue shift of n(lambda) and k(lambda) dispersion curves, however no dramatic changes were observed in the film morphology