采用电子束蒸镀技术在氟化镁基底上制备了单层Al2O3 薄膜和含有HfO2中间层的HfO2/Al2O3双层薄膜。在空气中对所制备的薄膜进行1h600℃的退火处理。通过掠入角X 射线衍射仪(GIXRD)、场发射扫描电镜(FE-SEM)、傅里叶变换红外光谱仪(FTIR)、纳米压痕和划痕法对薄膜的微观结构、红外透过率和力学性能进行了表征。结果表明: 退火处理后HfO2/Al2O3 双层薄膜中形成了一层树枝状的新层, 这种新层的硬度大于17.5 GPa。这种高硬度的新层能够保护氟化镁基底不被划伤。从GIXRD 图谱中只能找到单斜相HfO2 的衍射峰, 而Al2O3 薄膜仍然保持非晶态。从这些结果中可以推断出HfO2 从非晶态向单斜相的转变促进了这种树枝状新层的产生, 也正是这种新层提高了保护薄膜的力学性能。

Al2O3 thin films with or without HfO2 interlayer between Al2O3 and substrate were deposited on MgF2 substrates by electron-beam evaporation technique. The as-deposited thin films were then annealed at 600 degrees C for 1 h to promote crystallization. The microstructure, IR transmittance and mechanical properties of the as-deposited and annealed samples were investigated by field emission scanning electron microscopy (FE-SEM), grazing incidence X-ray diffraction (GIXRD), Fourier Transform Infrared (FTIR) spectrometer, nanoindentation, and scratch tests, respectively. FE-SEM results show that a new branch-like layer is generated in annealed HfO2/Al2O3 double-layer thin films. The hardness of the newly formed layer is considered to be larger than 17.5 GPa. Because of the high hardness of the new layer, the MgF2 substrate can be protected from being drown out during scratch test. From GIXRD patterns, Al2O3 still remains amorphous while HfO2 interlayer transforms from amorphous to monoclinic phase after annealing process. It could be deduced that it is the phase transformation of HfO2 interlayer that promotes the formation of the harder branch-like layer.