Compositional and structural studies of ion-beam modified AlN/TiN multilayers

Abstract

This paper reports on compositional and structural modifications induced in coated AlN/TiN multilayers by argon ion irradiation. The initial structure consisting of totally 30 alternate AlN (8nm thick) and TiN (9.3nm thick) layers was deposited on Si (100) wafers, by reactive sputtering. Irradiation was done with 180keV Ar+ to a high dose of 8×1016 ions/cm2, which introduces up to ∼10at.% of argon species, and generates a maximum displacement per atom of 92 for AlN and 127 for TiN, around the projected ion range (109±34nm). Characterizations were performed by Rutherford backscattering spectrometry, spatially resolved x-ray photoelectron spectroscopy, and transmission electron microscopy. The obtained results reveal that this highly immiscible and thermally stable system suffered a severe modification upon the applied ion irradiation, although it was performed at room temperature. They illustrate a thorough inter-layer mixing, atomic redistribution, structural change and phase transformation within the affected depth. The original TiN layers appear to grow in thickness, consuming the adjacent AlN layers, while retaining the fcc crystalline structure. In the mostly affected region, the interaction proceeds until all of the original AlN layers are consumed. Compositional studies with photoemission spectroscopy show that due to the ion irradiation treatment the TiN and AlN layers are transformed into Ti0.75Al0.25N and Ti0.65Al0.35N ternary compounds characterized by a better homogenized chemical form compared to non-irradiated layers. The results can be interesting towards further development of radiation tolerant materials based on immiscible ceramic nanocomposites.