Determination of size and concentration of copper nanoparticles dispersed in glasses using spectroscopic ellipsometry

For the generation of particular optical properties the melt of a commercia lly manufactured glass is doped with copper compounds. The glass obtained i s opaque black at the usual thickness and looks dark red after making it in to bulbs of incandescent lamps. It is generally assumed that copper particl es cause this colouring. A proof in a spectrophotometric way fails due to t he very high absorbance even for a sample thickness below 20 mum. It will b e shown that in these cases spectroscopic ellipsometry is a suitable method of investigation. The pseudo-optical constants of this material were determined as a function of wavelength in the range from 350 nm to 700 run by ellipsometric measure ments. They can be reproduced very well by those of a model that consists o f a roughness layer situated on a substrate of glass containing spherical c opper particles with a Gaussian size distribution with (R) over bar = 6.5 n m and sigma = 0.24 (R) over bar and a volume concentration of 2.4 x 10(-3). For this modelling the dielectric function of the roughness layer was appr oximated by Bruggeman effective-medium theory and that of the copper-contai ning glass substrate was calculated on the basis of the theory of Gans and Happel. The results were verified by transmission electron microscope inves tigations.