Sensitivity of optical methods to the homogeneity of particulate layers

For stratified layers, it was recently demonstrated that information about the structure of thin dielectric layers could be determined from scanning angle reflectometry measurements independent of any model of the interface. A measure of the deviation of the film from uniform was defined and demonstrated to be measurable. This analysis is extended here to the case of particulate layers, where we show that the same uniformity parameter can give information about the deviation of the distribution of particles on the surface from a uniform one. Preliminary optical data on moderately sized polystyrene particles, 116 nm in diameter, suggest that the closest approach of two particles on the surface is considerably greater than their diameter. This is in agreement with direct measurements of the radial distribution functions of these particles adsorbed on surfaces under similar conditions.