Modification of Surface Properties in Ruthenium Thin Films through Nitrogen Ion Irradiation

Abstract

Surface modification is an important strategy for tailoring the physical and chemical properties of materials for advanced technological applications. In thin films, changes in surface structure, roughness, and composition can strongly influence their functional behavior. In this work, we studied the effect of N+-ion irradiation at 20 keV energy on Ru thin films of two different thicknesses, 100 Å and 1000 Å, over a fluence range of ~1014 to 1017 ions/cm2. The main objective of this study is to investigate the evolution of the structural and wettability properties of Ru thin films of different thicknesses under increasing ion fluence. Overall, the results reveal that increasing ion fluence promotes surface roughening in both film thicknesses, which is correlated with an increase in contact angle. This indicates a clear transition from hydrophilic to hydrophobic behaviour, with the highest contact angle of ~95.54° observed at a fluence of 1017 ions/cm2. TRIM simulations reveal that for the 100 Å film, the projected ion range exceeds the film thickness, allowing interaction with the bottom substrate, whereas in the 1000 Å film, ion penetration remains largely confined within the Ru layer. GIXRD confirms fluence-dependent structural modification, including peak broadening with preferred orientation changes from Ru (101) to (002). Overall, this study demonstrates that N+-ion irradiation serves as an effective route for tuning both the surface morphology and wettability of Ru thin films, enabling controlled enhancement of hydrophobicity.