Numerical simulation on plasma characteristics of Ge ablated by pulse laser

In the early stage of UV excimer laser ablation of semiconductor, plasma induced by laser ablation was assumed at local thermodynamic equilibrium. One-dimension hydrodynamic model is presented for the laser ablation of Ge in a background gas (He) at 133.32 Pa and the characteristics of plasma induced by Gaussian-shaped KrF laser pulse with wavelength of 248 nm, pulse width of 17 ns, and peak power of 4×108 W/cm2. The results show that the ablated depth arrives 55 nm after laser pulse irradiation. The background gas He is gradually pushed away by the Ge vapor, forming a compression shock wave. And the maximum temperature always locates at the front of the shock wave. Spatial distribution of ionization degrees at different time shows that the first-order ionization degree of Ge always domin