LIPSS formation on complex oxide thin films: the case of Yttrium Stabilized Zirconia
Résumé
Ceramic oxide materials have shown a plethora of interesting physico-chemical properties which have been useful for applications in a wide range of modern technological applications including energy harnessing and storage. Among such ceramics is the complex oxide yttrium-stabilized zirconia (YSZ) which is currently used as an electrolyte in solid oxide electrochemical cells (SOEC) for hydrogen production through high temperature electrolysis processes. For such applications, it is crucial to precisely control the electrolyte /electrode interface and eventually increase the exchange area. This can be accomplished through laser texturing of the electrolyte’s surface. Such an approach is quite attractive because of its conceptual simplicity and the possibility of scaling-up to large surfaces. Yet challenges lie in understanding and controlling the interaction of the laser beam with the surface of these oxide materials that are structurally complex, mechanically fragile and risk chemical decomposition under laser irradiation. This work deals with the investigation of the picosecond UV laser structuring of YSZ coatings with the aim of controllably forming laser induced periodic surface structures (LIPSS), via two experimental approaches. The first one consists in laser structuring of YSZ mediated through a thin film deposited on top of the YSZ material. Two thin film cases were considered: a dielectric, namely gadolinium doped ceria (GDC) thin film, as is the case in a real SOEC and a metallic gold (Au) layer. The second approach is a direct structuring of the YSZ surface under static and scanning modes. Experimental parameters, namely laser fluence (up to 700 mJ/cm2) and pulse number (10-1000 shots), were varied to determine the conditions under which LIPSS are obtained, in addition to evaluating the damage/ablation thresholds for the different configurations. In addition, the formation of micro-spikes was detected at laser fluences exceeding 600 mJ/cm2. X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS) measurements were also performed on the textured surfaces to elucidate the physical and chemical mechanisms occurring as a result of the laser irradiation. Finally, preliminary results on laser irradiation under a controlled atmosphere and in vacuum will be presented.