HfO2/SiO2 anti-reflection films for UV lasers via plasma-enhanced atomic layer deposition

Highlights: • The HfO₂/SiO₂ anti-reflection film for UV laser was presented via low-temperature PEALD. • The presented PEALD AR film shows better laser-damage resistance than conventional e-beam deposition method. • The impact of precursor exposure time on PEALD film properties were investigated. • The XPS measurement shows the impurity content of PEALD HfO₂ film is high, leading to a large absorption and low LIDT. -- Abstract: The laser-induced damage threshold (LIDT) of HfO₂/SiO₂ anti-reflection (AR) films for ultraviolet (UV) lasers was improved via low-temperature plasma-enhanced atomic layer deposition (PEALD). Focused on the chemical composition, optical absorption, surface scattering, and laser-resistance, the impact of precursor exposure time on PEALD SiO₂ film properties and growth temperature on PEALD SiO₂ and HfO₂ film properties were investigated respectively. When irradiated by UV laser, PEALD SiO₂ film exhibits a higher LIDT than the PEALD HfO₂ film, which is consistent with their less impurity content and lower absorption. A bilayer structure HfO₂/SiO₂ AR film for 355 nm laser was designed and experimentally demonstrated via PEALD growth at a temperature of 150 °C. The prepared PEALD AR film shows a reflectance < 0.2% at 355 nm as designed and better laser-damage resistance with a LIDT of 24.4 J/cm² (355 nm, 7.8 ns) than the conventional e-beam deposition method.