Reduction of interface defects in Al₂O₃/HfO₂ nanolaminates using ultrathin SiO₂ interlayers grown via plasma-enhanced atomic layer deposition

Al₂O₃/HfO₂ nanolaminates combine the advantages of both Al₂O₃ and HfO₂, showing great potential in applications such as laser coatings. However, the Al₂O₃-on-HfO₂ interface in Al₂O₃/HfO₂ nanolaminates has a relatively high defect density, which can negatively affect the overall performance of associated coatings. Ultrathin SiO₂ interlayers were added at the Al₂O₃-on-HfO₂ interface in an Al₂O₃/HfO₂ nanolaminate and an Al₂O₃-HfO₂ nanocomposite with thinner sublayers using plasma-enhanced atomic layer deposition. The experimental results show that adding SiO₂ interlayers can reduce the interface defect density and increase the laser-induced damage threshold (LIDT) of the nanolaminate and nanocomposite without significantly affecting the refractive index. When using this Al₂O₃-HfO₂-SiO₂ nanocomposite instead of HfO₂ to fabricate a plate laser beam splitter coating, the LIDT can be increased by 1.5 times. We believe that this ultrathin SiO₂ interlayer strategy may benefit other nanolaminates with high-density interface defects and contribute to enhancing the performance of high-power laser coatings.