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 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.