Synthesis and characterization of superhard aluminum carbonitride thin films

Oxygen-free aluminum carbonitride thin films were grown on Si (100) substrates by reactive magnetron sputtering of Al target with the gas mixture of Ar, CH4 and N2 as precursor. A complementary set of techniques including X-ray photoelectron spectroscopy, energy-dispersive X-ray spectrometry, X-ray diffraction, transmission electron microscopy and atomic force microscopy was employed for the characterization of the deposit chemistry, structure as well as morphology. Film growth proceeds along the preferred [0001] direction with the basal planes twisted because of the frustration in arranging the building blocks for aluminum carbonitrides. Under given conditions, the deposits show a declining tendency of crystallization with increasing carbon content. Strong covalent bonding and structural disorder give the film's extreme mechanical rigidity: Berkovich hardness is over 27.0 GPa for all the deposits, and an extreme value of 53.4 GPa was measured in Al47C20N33.