Laser surface texturing of Ti/Cu/Ti and Ti/Cu/Zr/Ti multilayers thin films

Abstract

In this study, the design of surface pattering with the co-existence of micrometer and nanometer features was carried out to improve the arrayed surface structures on Ti/Cu/Ti and Ti/Cu/Zr/Ti multilayer thin films by picosecond laser processing. The novel composite structure consisted of two layers of Ti and subsurface distributed Cu and Zr layers (thickness of 10 nm) were deposited by ion sputtering on Si substrate to the total thickness of 300 nm. The changes in the composition, surface morphology, and wetting properties after laser modification was monitored by Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), optical profilometry, and wettability measurements. It was found that laser irradiation can induce the melting of material with the formation of wrinkled periodic structures at the edges of the laser spots in both systems as a consequence of the hydrodynamic effects. Another interesting result was that the periodic structure in form of LSFL (low spatial frequency LIPSS) ripples was numerous but slightly pronounced in Ti/Cu/Zr/Ti, due to the presence of the Zr component as an ultra-thin subsurface layer, which most likely favored creating LIPSS. Such laser texturing has been used in the biomedical field as a method of developing surface topography, coated with oxides to potentially improve cell response via suitable surface wetting for a biological system.