Topographic, chemical and property modifications of PVD ZrCu-based thin film metallic glasses through femtosecond laser treatment
Résumé
Metallic glasses (MGs) exhibit very interesting mechanical and chemical properties due to their absence of crystalline defects and their amorphous structure. They have been studied a lot in their bulk state (BMGs), but are size limited and complex to synthesize. More recently, it was proved that PVD processes exhibit high cooling rate of the deposited atoms to allow the formation of metastable amorphous metallic phases [1]. Thus, metallic glasses are easier to obtain by PVD in thin film form than bulk ones. The synthesis of such thin films through PVD process allows a high freedom in the film chemistry composition. From pure metallic targets, the magnetron sputtering process has already shown its ability to synthesize Zr-based thin film metallic glasses (TFMGs). These films exhibited a very low surface roughness together with the absence of grain boundaries, making them suitable for a femtosecond laser treatment [2], in order to still improve their properties. The laser irradiation process modification with a great repeatability, and gives rise to localized topographic and chemical modifications at the surface of the thin film. The work proposed here considers the formation of laser induced periodic surface structures (LIPSS) at the surface of two ternary magnetron sputtered TFMGs (ZrCuAg and ZrTiAg) using femtosecond laser pulses treatment. The choice of the laser parameters leads to the formation of several surface texturations of the thin films. The characterization of these structures is made at several scales, from topographic to chemical modifications, from Atomic Force Microscopy to Electronic Microscopy (Scanning and Transmission EM). These measurements permit to better understand the interaction of ultrashort laser pulses to amorphous material like MGs. Then, some property modifications of the TFMGs induced by such laser textures are studied. Ref.: [1] C.-Y. Chuand, et al., “Mechanical properties study of a magnetron-sputtered Zr-based thin film metallic glass”, Surface and Coatings Technology, 2013 [2] M. Prudent, et al., “Initial morphology and feedback effects on laser-induced periodic nano-structuring of thin-film metallic glasses”, Nanomaterials, 2021