The effect of target temperature on the deterioration of metal surfaces under pulsed laser irradiation

The effects of pulsed laser irradiation on preheated solid metal surfaces h ave been studied. The surface of low-melting point metals (In and Bi) is ir radiated by KrF excimer laser pulses of fluences below 400 mJ/cm(2). Evalua tion of the optical microscopic pictures of the processed metal surfaces re veals that the characteristic lateral dimension of laser-induced surface st ructures increases as the melting point is approached. The results are expl ained in terms of the lifetime of the melt pool, obtained by numerical temp erature calculations. Close to the melting point, the increased lifetime of the molten phase allows ample time for smoothing of the surface before its resolidification. (C) 2000 Elsevier Science B.V. All rights reserved.