OPTICAL-PROPERTIES OF ULTRAROUGH SILVER FILMS ON SILICON

The optical properties of inhomogeneously grown rough silver films hav e been analyzed on the basis of reflectance measurements. Data have be en recorded within the wave number range 50 cm(-1)<lambda(-1)<50 000 c m(-1). The results are compared with compact and fairly smooth films, made from the same metal. Rough films reveal very low reflectance and high absorptivity values of nearly 1, at wave numbers >200 cm(-1). The reflectance of these films is peaking at the bulk plasma resonance hv (p) of silver at 3.87 eV. Smooth compact films. in contrast, show a pr onounced minimum at the same energy, Based on an effective medium appr oach and available literature data, the dielectric function (DF) and a bsorption coefficient have been calculated. For rough films, the real part of the DF remains positive within the whole spectral range, but i s negative for compact films below hv(p), in agreement with published data. The calculated DF of the inhomogeneously grown films fully resem bles the experimental observations. (C) 1996 American Institute of Phy sics.