Molecular Dynamics Simulations Of Femtosecond Laser Processing Of Silicon

This paper, based on the SW potential and Z layer energy model, using moleculardynamics method, simulated the process of femtosecond laser processing of silicon byprogramming.Compared with Two-temperature model and traditional energy coupling, thetwo-temperature model is suited for metallic materials. So, using traditional energycoupling method achieves the absorption, transmission and distribution of energybetween the laser and the silicon material. Using Z-layer energy model describes theprocess of energy deposition, then the laser act on the material and then bubbles. Thelower part of material’s temperature increasing proved that the processing creates heatshock and spreads down. SW potential has a suitable cutoff distance, little parametersand simple form. So, this article chooses SW potential carrying on a MD and derivationof the formula from SW potential.In the condition of FREE EMD simulation, no mass and energy exchange with theoutside world, because of conservation of mechanical energy, the total energy remainsthe same. Selecting the appropriate time step size and speed of algorithms, because itcan improve the accuracy of the system and ensure the computational efficiency is nottoo low.The processing phenomena were affected by laser characteristic parameters and thestyle of loading process. The simulation can get some results as follows: the materialwas more thicker, the energy density was more bigger; at a given pulse width, changethe energy density and the linear absorption coefficient, the linear absorption coefficienthas more bigger effect on the ablation phenomena; at given pulse with and wave length,the ablation phenomena of femtosecond lasers under two loading styles are almost samein the condition of bigger energy density, while in the condition of smaller energydensity, the processing phenomena are different. At a given energy density, because ofthe Si(111) structure’s spacing of adjacent layer are different, exist relaxationphenomenon, Si(100) structure’s ablation phenomena was more obvious.