Mechanical properties of aluminum, zirconium, hafnium and tantalum oxides and their nanolaminates grown by atomic layer deposition

The mechanical properties of two different metal oxide nanolaminates comprised of Ta2O5 and Al2O3, HfO2 or ZrO2, grown on soda-lime glass substrate by atomic layer deposition, were investigated. Ta2O5 and Al2O3 layers were amorphous, whereas ZrO2 and HfO2 possessed crystalline structure. Thickness of single oxide layers was varied between 2.5 and 15 nm. The total thickness of the laminate structures was in the range of 160-170 nm. The hardness values of single layer oxides on glass ranged from 6.7 GPa (Ta2O5) to 9.5 GPa (Al2O3). Corresponding elastic moduli were 96 GPa and 101 GPa. The hardnesses of laminates were in the range of 6.8-7.8 GPa and elastic moduli were between 93 and 118 GPa. The results implied a correlation between mechanical properties and the relative content of constituent single oxides.