Laser-induced surface alloying in nanosized Ni/Ti multilayer structures

• Published in: Applied surface science Vol. 264; pp. 273 - 279
• Main Authors: Petrović, Suzana, Radak, B., Peruško, D., Pelicon, P., Kovač, J., Mitrić, M., Gaković, B., Trtica, M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-01-2013; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Diffusion; Exact sciences and technology; Laser alloying; Ni/Ti multilayer; Physics; Ripple structure; Surface segregation; Ripple structure; Ni/Ti multilayer; Diffusion; Surface segregation; Laser alloying; Multilayers; Laser radiation; Physical radiation effects; Nickel; Surface alloying
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2012.10.012

► Different multilayer (Ni/Ti) structures were modified by picoseconds Nd:YAG laser. ► Laser-induced alloying was achieved within the heat affected zone (HAZ) of the sample. ► Surface segregation of titanium was followed by formation of thin TiO2 film. ► Ripple structures on the surfaces of the 5- and 10-bilayered samples were recorded.
Laser-induced alloying effects on the composition and structure of different Ni/Ti multilayer structures were studied. Thin films composed of one, five, and ten (Ni/Ti) bilayers were deposited by DC ion sputtering on (100) Si wafers. Laser irradiations were performed by 150ps pulses of a Nd:YAG laser operating at 1064nm. The samples were characterized by Rutherford backscattering spectrometry (RBS), Auger electron spectroscopy (AES), X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). At a laser fluence of 0.9Jcm−2, interaction between Ni and Ti layers was initiated, and NiTi alloy formed in 5- and 10-bilayered samples. Progressed alloying was achieved at a laser fluence of 1.2Jcm−2. The alloy was formed mostly within the heat affected zone (HAZ) of the sample. Surface segregation of titanium was followed by formation of a 25nm thin TiO2 film on the surface of the multilayered structures. In addition, parallel periodic surface structures on the surfaces of the 5- and 10-bilayered samples were clearly recorded. Their period in the case of the 5-bilayered system (0.77μm) agrees very well with the predictions of the common theory, whereas, in the case of the 10-bilayered system, two periods of such structures are observed (1.43μm and 0.4μm), and none of them coincides with the prediction.