Influence of the Secondary Ion Beam Source on the Laser Damage Mechanism and Stress Evolution of IBS Hafnia Layers

Abstract

Ion beam sputtered hafnia is a preferred high index coating material for laser applications. It exhibits a mostly amorphous structure and an adequate laser-induced damage (LIDT) threshold. In this work, we investigated the influence of an assisting ion source on the film stress as well as the LIDT of the sputtered hafnia layers. The stress increases with an increasing ion energy of the assisting ion beam. We identified a maximum compressive stress of 3–3.5 GPa before the film cracks, blisters, and delaminates. Different states of stress lead to different laser-induced damage thresholds and damage morphologies.

Crystallization behavior of ion beam sputtered HfO2 thin films and its effect on the laser-induced damage threshold

“…We also found an intermediate decrement of the LIDT values, which is not reported in [24] and worth further investigation. One explanation for the small Scherrersize is high stress, this according to our own experience leads to low LIDT [39]. The other possibility is a high concentration of grain boundaries, which according to Tateno et al [40] can also be a cause for reduced LIDT.…”