Al-induced fullerene-like nanostructures in C-Al-N thin films

The role of aluminium incorporated into growing carbon nitride (CNx) films prepared by reactive dc-magnetron sputtering was investigated using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM). XPS analyses revealed the formation of Al-N bonding besides C-C and C-N bonds. With increasing Al concentrations above 11.8 at.%, a structural transformation from essentially amorphous (a-) (CNx, AlN) phase to locally ordered microstructure comprising of fullerene-like (FL-) CNx nanostructures surrounded by a-(CNx, AlN) matrices was evidenced by Raman and HRTEM. The effect of aluminium in triggering FL-CNx nanostructures was elucidated from thermodynamic considerations.