Mechanical and tribological properties of 100-nm thick alumina films prepared by atomic layer deposition on Si(100) substrates

The study investigates mechanical and tribological properties of alumina (Al2O3) films prepared on Si(100) substrates. The 100-nm thick films were deposited by atomic layer deposition. Nanoindentation and nano-scratch tests were performed with Berkovich and sphero-conical diamond indenters, respectively. Energy-dispersive X-ray spectroscopy and optical and scanning electron microscopy were used to analyse the surface morphology and chemical composition of the thin films. X-ray diffraction was used to characterize their crystal structure. Crystallization was found to start at 1100 degrees C after 3 hours of annealing. The hardness and tribological properties of the alumina films were influenced by the substrate in nanoindentation and nano-scratch tests. Within the relatively low load range (5-50 mN), the coefficient of friction of Si and alumina against diamond depended on the load, most likely due to a change in the elastic/plastic deformation behaviour within the Si substrate.