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 O-2-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 ((1) over bar 11) plane to (002) plane with low grain boundary energy and lattice defects.