Generation of nanostructures in metallic surfaces using subnanosecond UV laser processing

Abstract

In this work we present the rich surface structure phenomenology that has been observed when the surface of different metals (Nb, Ni, steel) is irradiated with a subnanosecond (300 ps) UV laser, and how it affects some of their properties. The influence of different laser parameters, as the laser polarization direction, the pulse irradiance, laser scanning speed and the overlapping in the perpendicular direction, have been studied and a complete set of nanostructures have been defined. Laser treatments have been performed in air, but also in controlled atmospheres (Ar, N2) or with the surface immersed in liquids (Vaseline oil, water) observing that the generated nanostructures are different depending on the particular experimental conditions imposed. An important effort has been carried out in order to obtain homogeneous nanostructures over extended areas, using a new laser line scanning protocol. In these studies, it has been observed that not only the laser parameters affect the generated nanostructure, but some materials properties are also important. Combining laser treatments with EBSD studies it has been demonstrated that crystallography also plays an important role in the generated nanostructure, observing that the level of interaction of the laser with a particular grain has some correlation with its crystallographic order. It has ben also observed that, in depending on the properties of the materials, nanostructures can be modified by the application of external electromagnetic fields.