C-60 fullerene films on silicon substrates are investigated by luminescence and multi-angle-of-incidence (MAI) ellipsometry. The ultrasonic treatment decreases the integral intensity and modifies the photoluminescence spectrum shape. The optical properties of C-60 fullerene films are shown to be well described within a two-layer model, a bulk fullerene layer and a surface film. It is found that the ultrasonic treatment mainly affect the optical constants of the surface layer. The change of the film optical properties is caused by the decrease of the defect concentration due to the ultrasonic treatment. (C) 2008 Elsevier B.V. All rights reserved.