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HfO2 film prepared by ion beam sputtering (IBS) has greater potential in low loss laser films. However, it is prone to form sub-stoichiometric and polycrystalline structure resulting in high absorption and scattering loss. Besides, the adsorption of excess oxygen atoms will produce oxygen inclusions in the surface of HfO2 during fabrication, leading to the formation of surface hole defects, thereby increasing the surface roughness. Annealing is an important method to achieve better stoichiometry, but it tends to induce crystallization or recrystallization of the film. In this paper, thin amorphous SiO2 layers were periodically added into HfO2 coatings to synthesize HfO2/SiO2 nanolaminate layers, which can effectively suppress crystallization during HfO2 growth, increase the crystallization threshold temperature during thermal annealing, eliminate hole defects on the film surface and minimize the absorption and scattering loss. We present a detailed study of the crystallization, surface topography and absorption evolution in HfO2/SiO2 nanolaminate layers as a function of sub-layer thickness and thermal annealing temperature. It was found that thinner HfO2 layers show higher threshold temperature of crystallization, so it can maintain almost zero absorption and amorphous state under high temperature annealing.
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