原子层沉积高激光损伤阈值的Al2O3/HfO2/SiO2双叠层紫外反射膜研究

Inertial confinement fusion (ICF) plays a very important role in national strategy like energy and military, but the laser-induced damage threshold (LIDT) of ultraviolet (355 nm) high reflective coating is so low that it has become a core problem to prevent ICF from moving forward. As the conventional film deposition techniques have limitation on the control of defects and electric field (E-field), the development of new advanced coating technology is expected to achieve a breakthrough. Atomic layer deposition (ALD) is able to achieve high controllability over the coating parameters (thickness, composition, structure). So this project attempt to fabricate ultraviolet high reflective coatings through ALD by taking Al2O3、HfO2 and SiO2 as the coating materials. A new structure is proposed here to use HfO2/SiO2 as the bottom stack and Al2O3/SiO2 as the top stack to realize both high reflectivity and high LIDT. The damage properties、damage mechanism and the effect of E-field on the laser-induced damage will be studied in depth. On this basis, we hope to improve the LIDT of the Al2O3/HfO2/SiO2 coating to a great extent by combining the optimization of ALD process and controlling the E-field of the film. This research will make a contribution to the improvement of laser damage properties of reflectors in ICF.

激光惯性约束核聚变（ICF）在能源、军事等国家战略上意义重大，目前紫外355nm反射膜的损伤阈值太低成为阻碍ICF发展的关键问题。常规镀膜方式在缺陷控制和电场调控上比较局限，发展新的先进镀膜技术有望取得突破性进展。原子层沉积（ALD）技术对薄膜组分、结构和厚度具有原子层级可控的优点，易于获得高质量薄膜。本项目提出利用ALD制备紫外反射膜的思路，选择阈值较高的Al2O3、HfO2和SiO2为镀膜材料，并提出“以HfO2/SiO2叠层作为底层实现高反射率，Al2O3/SiO2叠层作为顶层实现高损伤阈值”的新结构，通过研究ALD生长叠层膜的工艺参数，以期制备高质量的Al2O3/HfO2/SiO2双叠层紫外反射膜。同时将研究薄膜的损伤特性、损伤机理和电场调控方法，希望结合ALD工艺优化和电场调控大幅度提高Al2O3/HfO2/SiO2反射膜的损伤阈值。为ICF反射膜激光损伤能力的提升做出贡献。

应用在激光惯性约束核聚变（ICF）中的反射镜的损伤一直是制约ICF发展的关键，其中355nm紫外反射膜的损伤问题更是其中的焦点。常规镀膜方式在缺陷控制和电场调控上比较局限，发展新的先进镀膜技术有望取得突破性进展。原子层沉积（ALD）技术对薄膜组分、结构和厚度具有原子层级可控的优点，易于获得高质量薄膜。本项目选择阈值较高的Al2O3、HfO2和SiO2为镀膜材料，提出“以HfO2/SiO2叠层作为底层实现高反射率，Al2O3/SiO2叠层作为顶层实现高损伤阈值”的新结构，有望制备高损伤阈值的355nm反射膜。同时为了降低容易导致损伤的顶层薄膜中的缺陷，提出利用ALD制备顶层薄膜的思路。通过细致研究ALD生长Al2O3、HfO2和SiO2薄膜的工艺，获得了ALD制备高质量、低缺陷的三类薄膜材料的核心技术参数。然后结合PVD和ALD技术制备了高质量的Al2O3/HfO2/SiO2双叠层紫外反射膜。研究了双叠层反射膜的损伤特性、损伤机理和电场调控方法，发现双叠层反射膜的设计较常规反射膜在激光损伤阈值上有较大提高，同时通过降低界面电场的方法，可进一步提高反射膜的损伤阈值。本项目的研究成果可为高损伤阈值的紫外反射膜的设计提供参考，同时有助于推进对反射膜中电场作用机制的认知，为ICF反射膜激光损伤能力的提升做出贡献。