Relation between optical scattering, microstructure and topography of thin silver films 1: Optical scattering and topography

Discrepancies have been found between experimental measurements of angular scattering from metal films, principally silver and aluminum, and values predicted from vector scattering theory (considering roughness-only effects) using known optical factors and statistics of the surface roughness as inputs. The main discrepancy concerns the magnitude and angular variation of s-polarized backscattering measured relative to p-polarized backscattering from the same sample under the same conditions. Freshly evaporated and sputtered films have too high s-polarized backscattering levels, as compared to the p-polarized values. When the films are annealed in vacuum, the agreement with theory improves, but the films become rougher, scattering levels increase, and sizes of silver grains increase. Theoretical refinements to improve agreement with experiment are also discussed.