Probing femtosecond laser-induced heating of Ti/Sn bimetallic thin films

Abstract This study investigates the effects of femtosecond (fs) laser irradiation on the structural and surface properties of epitaxially deposited Sn/Ti bimetallic thin films. Films with 15 nm and 25 nm bimetallic layers were grown using molecular beam epitaxy (MBE) on SiO 2 /Si substrates under ultra-high vacuum conditions. Non-isothermal heating was performed using a 1030 nm fs laser with a pulse duration of 300 fs, a 40 μ m spot size, and a repetition rate of 500 kHz, raster scanned over the surface. The surface morphology after irradiation was characterised by scanning electron microscopy (SEM), revealing the formation of nanostructures such as voids and sphere-like protrusions, and laser induced periodic surface structures (LIPSS). Rutherford backscattering spectrometry (RBS) analysis indicated elemental diffusion and oxidation, with Sn migrating to form oxide layers. The extent of intermixing and structural modification increased with laser fluence, especially in sample C, leading to changes in layer thickness and composition. These results demonstrate that femtosecond laser processing can effectively modify the microstructure and surface of bimetallic thin films, offering potential fabrication pathways for tailoring material properties for advanced nanotechnological applications.