Post deposition annealing of IBS mixture coatings for compensation of film induced stress

In this work, the influence of using ion beam sputtered mixtures instead of pure materials and the impact of applied post deposition annealing to residual stress is investigated. Single layer pure films and mixtures of Nb2O5 / SiO2 as well as multilayer coatings are examined by the means of residual stress. High residual compressive stress was measured for all as-deposited samples. Pure and mixed monolayer samples were annealed at various temperatures and residual stress was determined after each annealing routine. Residual changes in optical constants, layer thickness and surface roughness upon annealing are examined to explain stress behavior. Obtained data was used to make optimization of high reflectivity structures with completely eliminated residual stress. The proposed method can be used to coat very thin substrates where flatness requirements are essential.