离子源偏压对PIA-EB-Hf法制备的HfO2激光薄膜性能的影响

APS Bias Voltage on Properties of HfO_2 Laser Films Deposited by Reactive Plasma Ion Assisted Electron Evaporation

探究HfO_2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(O_2)进行反应沉积法制备了中心波长为1064 nm,光学厚度为4H的HfO_2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(111)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。

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 （111 ） plane to （002） plane with low grain boundary energy and lattice defects.