The annealing effect on the properties of silicon oxynitride (SiOxNy) thin films has been investigated. The present contribution aims to study the structural and optical properties of SiOxNy thin films deposited by plasma enhanced chemical vapor deposition in view of their application in the field of photovoltaics. Evolution of the surface morphology and increase of the optical band gap with the thermal treatment have been determined and discussed in view of the application of the film as an emitter layer in heterojunction solar cells. (C) 2016 Elsevier B.V. All rights reserved.