Surface modification of Ti-based nanocomposite multilayer structures by using laser beam irradiation

Abstract

A study of the effects of laser irradiation on the morphology and structure of Al/Ti and Ni/Ti multilayers is reported in this paper. Multilayers of Al/Ti and Ni/Ti were deposited by dc ion sputtering on Si(100) substrates in a single vacuum run. Laser processing was done by a focused Er, Yb, Cr glass laser beam at a wavelength of 1540 nm, a pulse duration of 40 ns and fluence in the range 8.5-23.8 J cm(-2). Surface changes can be summarized as follows: (i) the intensive removal of surface material with crater-like characteristics, (ii) the appearance of hydrodynamic features (such as resolidified droplets) and (iii) the sporadic appearance of cracking. Changes in the (Ni/Ti)/Si system included modification of the Si substrate with the formation of polygonal-mosaic structures and the appearance of hydrodynamic features in the form of nano-globules. The rate of ablation increased with energy density, whereas the rate of ablation for the (Ni/Ti)/Si system (similar to 11 x 10(3) mu m(3) per pulse) was higher than that for the (Al/Ti)/Si system (similar to 7 x 10(3) mu m(3) per pulse).