Ultraviolet optical coatings employ wide bandgap dielectric materials due to their characteristic low absorption. High-reflectivity and antireflective coatings are essential for optical devices, which can be achieved by alternately depositing two dielectrics with different refractive indices. In this research, a multilayer high-reflectivity coating has been designed for middle UV wavelengths using Al₂O₃ and AlF₃ layers on a sapphire (0001) substrate, and the initial two-layer structure has been fabricated by atomic layer deposition. The surface morphology and roughness of the coating was measured by atomic force microscopy after each deposition step. Ultraviolet spectroscopy and spectroscopic ellipsometry were used to characterize the optical performance of the single and multilayer coatings. Monochromatic x-ray photoemission spectroscopy was used to study the film composition, bonding, and impurities. A bilayer reflective coating was demonstrated, with a smooth surface (R_q < 1 nm) and peak reflectance of 25%−30% at a wavelength of 196 nm. The measured reflectance deviated from the simulations in the middle UV range, and an analysis of the AlF₃ layer prepared by plasma enhanced atomic layer deposition indicated the presence of Al-rich clusters, which were associated with the UV absorption. A thermal atomic layer deposition process for AlF₃ deposition showed reduced absorption, which could be more effective for shorter wavelength designs.

中文翻译：

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基于原子层沉积氧化铝和氟化物的多层紫外反射涂层

紫外光学涂层采用宽带隙介电材料，因为它们具有低吸收特性。高反射率和抗反射涂层对于光学器件来说是必不可少的，这可以通过交替沉积两种不同折射率的电介质来实现。在这项研究中，使用 Al ₂ O ₃和 AlF ₃为中紫外波长设计了多层高反射涂层在蓝宝石 (0001) 衬底上形成层，并且最初的两层结构是通过原子层沉积制造的。在每个沉积步骤之后，通过原子力显微镜测量涂层的表面形态和粗糙度。紫外光谱和光谱椭偏仪用于表征单层和多层涂层的光学性能。使用单色 X 射线光电子能谱来研究薄膜的组成、键合和杂质。展示了双层反射涂层，具有光滑的表面 ( R _q  < 1 nm) 和在 196 nm 波长处的峰值反射率为 25%-30%。测量的反射率偏离了中间 UV 范围内的模拟，以及 AlF ₃的分析通过等离子体增强原子层沉积制备的层表明存在富铝簇，这与紫外线吸收有关。用于 AlF ₃沉积的热原子层沉积工艺表明吸收减少，这对于较短波长的设计可能更有效。