LASER-INDUCED FORMATION OF MICRO-ROUGH STRUCTURES

Laser induced micro-rough structures (LIMS) are a by-product of laser ablation process and are created during multiple pulse irradiation on the surface of the material. Although LIMS have been found to be delet erious for the thin film deposition process, these surfaces have wide variety of applications in synthesis of adherent coatings in thermal e xpansion mismatched systems. Earlier models, based on interference eff ects of the laser beam, to explain the evolution of LIMS, are not cons istent with the experimental results. Experiments were conducted on a wide variety of materials (e.g. SiC, alumina, YBaCuO superconductor, e tc.) to understand the mechanisms for generation of the micro-rough st ructures. A novel model was developed to explain the characteristics o f LIMS such as (i) feature orientation (ii) evolution of surface struc tures as a function of pulses, (iii) formation of LIMS within a energy window near ablation threshold and (iv) periodicity which is in indep endent of the laser wavelength and incident angle.