A Comparative Study of the Mechanical and Tribological Properties of Thin Al2O3 Coatings Fabricated by Atomic Layer Deposition and Radio Frequency Sputtering

Thin Al2O3 films (150 nm thick) are deposited by atomic layer deposition (ALD) and radio frequency sputtering on Si substrates and submitted to annealing in N-2 atmosphere at 900 degrees C for 90 min. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), nanohardness, and fretting wear measurements are used to infer the structural, morphological, mechanical, and wear properties of the as-deposited and annealed films. Results show a higher hardness for the annealed coatings, being the hardness of the annealed ALD coating the highest (18.8 GPa). The measured mechanical properties convey clear trends of stiffening and hardening associated with selected process (ALD versus sputtering) and postprocessing (annealed versus unannealed).