离子源偏压对PIA-EB-Hf法制备的HfO2激光薄膜性能的影响

探究HfO₂薄膜的激光损伤特性以进一步提高激光损伤阈值(Laser Induced Damage Threshold, 简称LIDT), 对其在高功率激光系统中的广泛应用具有重要的意义。在不同的离子源偏压下, 采用等离子体辅助电子束蒸发金属铪(Hf)并充氧(O₂)进行反应沉积法制备了中心波长为1064 nm, 光学厚度为4H的HfO₂薄膜样品。测试了薄膜组分和残余应力; 根据透射谱拟合了薄膜的折射率; 通过XRD谱图和SEM表面形貌图分析了薄膜的微观结构; 对激光损伤阈值、损伤特性和机理进行了论述。结果表明: 偏压100 V时制备的薄膜具有最佳O/Hf配比; 薄膜压应力和折射率均随偏压降低而减小。薄膜内存在结晶, 激光能量在晶界缺陷处被强烈聚集和吸收, 加速了膜层的破坏, 形成由几百纳米的烧灼坑聚集而成的海绵状损伤结构。随着偏压降低, 膜结晶取向由(\stackrel{\text{?}}{1}11)晶面向(002)晶面转变, 界面能降低; 晶粒减小, 结构更均匀, 缓解了激光能量在晶界处的局部聚集与吸收, 表现出较大的激光损伤阈值。

APS Bias Voltage on Properties of HfO2 Laser Films Deposited by Reactive Plasma Ion Assisted Electron Evaporation

The anti laser HfO₂ films were deposited by reactive plasma ion assisted electron beam evaporation in low O₂-pressure with different Advanced Plasma Source (APS) bias voltages. Properties of HfO₂ film sincluding chemical composition, refractive index and residual stress were investigated. Microstructure of HfO₂ films was analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). Laser induced damage threshold (LIDT) and damage mechanisms of HfO₂ films were finally evaluated and discussed. Properties of HfO₂ films display sensitive to APS bias voltage. As the APS bias voltage decreases, the O/Hf ratio in the film increases, accompanied by decreasing refractive index and residual stress. The damage morphology of HfO₂ films appears in the form of agglomerations of craters with a few hundreds of nanometers, left by evaporation of grains ascribed to strong absorption and accumulation of laser energy at grain-boundaries. HfO₂ films with higher LIDT can be grown under lower bias voltage which benefits the achievement of uniform microstructure and the crystallization orientation from (\stackrel{\text{?}}{1}11) plane to (002) plane with low grain boundary energy and lattice defects.