Simulation of Laser-Induced Thermo-Mechanical Stress During Ultrafast Laser Ablation of Indium Tin Oxide with Transient Optical Properties

There is still a lack of understanding of a possible mechanical ablation mechanism and the causes of thermal degradation of thin indium tin oxide (ITO) films.A dual hyperbolic two temperature model is applied to the ultrashort pulsed laser ablation process of 100 nm indium tin oxide films.The model describes transient optical properties by taking into account the changes in the complex dielectric function due to laser excitation.The laser excitation is modelled by free electron dynamics and a nonlinear absorption coefficient for a laser pulse duration of 700 fs and a central wavelength of 1056 nm.For peak fluences F 0.35 J/cm 2 , we find that the modeled strain exceeds the yield strain in the regions where the experimental craters show signs of mechanical ablation behavior.For larger peak fluences F > 0.35 J/cm 2 the model predicts lattice temperatures T l exceeding the melting temperature T melt,ITO of indium tin oxide.The computed depth where T l T melt,ITO agrees with the measured ablation crater depths.