Damage morphologies and causes of laser-induced damage of thin oxide films at 248 nm

摘要

Abstract: The effect of ultraviolet laser radiation (248 nm) on dielectric thin films can be separated into intrinsic absorption of the film material, absorption at structure faults of the layer like grain boundaries or F-centers, and the absorption at inclusions of different materials. Besides this, the film substrate interface as well as the substrate material by itself can act as absorbing regions. Our investigations to the damage morphology of laser induced changes at oxide thin films show typical damage structures for the different sites, where the main part of the laser radiation was absorbed. In some cases we found surprising figures, e.g. lens formed film detachments between damage pits originating from absorbing inclusions. Together with calculations of the temperature field, which is generated by the laser pulse, the dominating damage mechanisms are estimated. At the oxide films under test, the damage is released by inclusion absorption with additional film ablation by overlapping electron avalanches. !10