Molecular dynamics simulation on laser ablation of metal and silicon

Ablation phenomena of material induced by laser irradiation are complicated and it is unjustifiable to analyze them theoretically with a continuum mod el. In this study, atomic behavior of copper, aluminum and silicon during l aser ablation is simulated applying molecular dynamics. Variation of atomic array and stress state of atoms during and after laser irradiation are sho wn visually. Main conclusions obtained are summarized as follows. (1) Therm al shock wave travels to interior of material with laser irradiation. Propa gation velocity of thermal shock wave is equal to elastic wave velocity. (2 ) In ablation process, mam small voids generate in the liquid phase at firs t. Then they become larger and larger, and adjacent voids combine each othe r, which develop into a relatively larger void. Finally, the vicinity of su rface bounds out forming into relatively large lumps. (3) In metal with las er irradiation of relatively high power density, molten metal whose kinetic energy is too small to evaporate becomes spherical by surface tension and deposit around the hole. On the other hand, in the case of relatively low p ower density, fusing atoms flow out from the molten pool and deposit around the hole. (4) In silicon, a part of vaporizing atoms deposits around the h ole, whose height is smaller than that in metal under the same laser irradi ating condition. The surface of generated wall of silicon is rough comparin g with metal.