Effects of sample polydispersity and beam profile on ellipsometric light scattering

Ellipsometric light scattering (ELS) is shown to selectively extract the coherent scattering contribution representing the averaged properties of a particle ensemble. This property is essential for the previously reported [Erbe et al., Phys. Rev. E73, 031406 (2006)] high sensitivity of ELS to the refractive index profile at particle interfaces. Two mechanisms for coherence loss in ELS measurements are discussed: sample polydispersity and illumination by a Gaussian beam. Suitable experimental quantities for a distinction of coherent and incoherent scattering contributions are introduced. Furthermore, the application of the concepts to reflection ellipsometry at rough surfaces is discussed.