Thin Solid Films 453 – 454 (2004) 323–327 0040-6090/04/$ - see front matter  2003 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2003.11.147 Finite element analysis of the initial stages of the laser ablation process J.C. Conde , F. Lusquinos , P. Gonzalez *, J. Serra , B. Leon , A. Dima , L. Cultrera , D. Guido , a a a, a a b b b ˜ ´ ´ A. Zocco , A. Perrone c c Dpto. Fısica Aplicada, University of Vigo, Lagoas-Marcosende 9, 36200 Vigo, Spain a ´ Physics Department, University of Lecce, via Arnesano, 73100 Lecce, Italy b University of Lecce and National Nanotechnology Laboratory of Istituto Nazionale di Fisica della Materia, 73100 Lecce, Italy c Abstract The growth of thin films by pulsed-laser deposition involves extremely complex physical processes. The study of different aspects of the basic mechanisms of the laser ablation is still in progress, with special emphasis on the modelling of the plume deflection effect and the structure formation on the irradiated surface. In this work, the initial stages of the laser ablation process have been investigated considering the surface roughness and the continuous morphological changes of the surface produced by laser irradiation. Assuming a thermal ablation model, a computational approach of the structure formation on the irradiated surface by finite elements using ANSYS (6.1) has been developed. Complementary, different ablation experiments on silicon wafers  using a XeCl excimer laser (308 nm) impinging at 458 with respect to the target were carried out. Scanning electron microscope analyses were performed to study the morphological changes of the Si surface. The validity of the model and the agreement of the numerical results are discussed.  2003 Elsevier B.V. All rights reserved. Keywords: Laser ablation; Coatings; Finite elements method 1. Introduction Since the mid-1980s the pulsed-laser ablation and deposition is a widely used technique for materials science and processing. The discovery of the excimer lasers catapulted the application and the development to the growth of thin films and multilayers with special emphasis to high-T superconducting materials. It is c based on two unique characteristics: the transfer of the stoichiometry of a multicomponent system onto the substrate and the possibility to combine gas-phase chem- istry with surface physics. The observation that all materials (metals, semiconductors and insulators) can be deposited by pulsed-laser deposition (PLD), the possibility of film oxygenation and other chemical changes, which occur in transit from the target to substrate are truly remarkable. In spite of these advantages, PLD technique still presents some drawbacks making difficult to emerge it as a technology for high-quality thin film deposition. The presence of droplets on the film surface and inhom- *Corresponding author. Tel.: q34-986-812216; fax: q34-986- 812201. E-mail address: pglez@uvigo.es (P. Gonzalez). ´ ogeneities in the grown film due to the anisotropic expansion of the plasma plume are the main restrictions of this method. The physical phenomena involved in the laser ablation process are extremely complex. Different aspects of physics and chemistry of laser ablation are still being studied with special emphasis on the light–matter inter- action and the formation and dynamic expansion of the ionized gas cloud, ablation plume, that may reach electron temperatures of thousands of degrees w1,2x. In addition, the complete understanding of the basic mech- anisms of laser ablation processes, a modelling of photo- induced interactions with solids is required. In this work, a theoretical model of the laser ablation process was developed which takes the roughness of the surface into account. The heat differential equation was solved by the finite elements method using ANSYS  (6.1) program w3x. The validity of the model and the agreement of the solutions were experimentally corroborated. 2. Statement of the problem Conventional experimental systems for the growth of thin films by pulsed-laser techniques are based on the