Synthesis of ultra-thin oxide layer in laser-treated 3× (Al/Fe)/Si multilayer structure

摘要

The conditions of ultra-thin oxide films synthesized as the Al/Fe multilayer structures after the surface treatment with femtosecond laser radiation were studied. Thin films composed of three (Al/Fe) bilayers were deposited by DC ion sputtering on (100) Si wafers to the total thickness of 410 nm. Laser irradiations were performed by 40-fs pulses of a Ti:Sapphire laser operating at 800 nm, at fluences slightly higher than the ablation threshold. The samples were characterized by Auger electron spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. Progressed intermixing of components was achieved for the irradiation with fluence of 0.43 J cm~(-2), when intermetallic phase was formed and all components were almost uniformly distributed through the entire multilayer structure. Exception is the subsurface region, to the thickness of 20 nm, where the distribution of constructive components and their oxide is changing with the distance from the surface, and this distribution depends on the applied laser fluences. An ultrathin oxide layer was formed at the surface, with the specific combination of the oxide phases, Al_2O_3 and Fe_2O_3, depending on the applied fluences. Laser-induced modification was accompanied with the ablation of the material and the creation of parallel periodic structures. These effects of laser-induced morphological features are increased with increasing laser fluences, caused by the pronounced mobility of the materials. The special morphology of the laser-assisted synthesis of mixture of Al_2O_3 and Fe_2O_3 in the form of an ultra-thin oxide layer can improve their characteristics for functional applications, as catalysts and sensors.