Particulate Au and Ag films for optical recording

Particulate films, consisting of a 3-D arrangement of ultrafine Au or Ag particles with diameters of 8-20 nm, were prepared using the gas evaporation technique. As a consequence of the low packing density of the particles, films with a thickness of ~4 microm show very low reflectivities of <3% in the wavelength range of 300-1000 nm, causing high absorption of incident light. Additionally the sintering temperature of the ultrafine particles is very low (~350 degrees C for Au). So a drastic altering of the optical properties of the particulate films is observed when irradiated by a laser. A sensitive optical recording medium with an adjustable reflectivity can be realized using a two-layer configuration with a reflector layer covered by a thin ~0.5-microm particulate Au film. Particulate Au or Ag films can also be used for photographic applications.