Influence of Annealing on Mechanical Behavior of Alumina-Tantala Nanolaminates

Abstract

Mechanical properties of thin films are significant for the applicability of nanodevices. Amorphous Al2O3-Ta2O5 double and triple layers were atomic layer-deposited to the thickness of 70 nm with constituent single-layer thicknesses varying from 40 to 23 nm. The sequence of layers was alternated and rapid thermal annealing (700 and 800 °C) was implemented on all deposited nanolaminates. Annealing caused changes in the microstructure of laminates dependent on their layered structure. Various shapes of crystalline grains of orthorhombic Ta2O5 were formed. Annealing at 800 °C resulted in hardening up to 16 GPa (~11 GPa prior to annealing) in double-layered laminate with top Ta2O5 and bottom Al2O3 layers, while the hardness of all other laminates remained below 15 GPa. The elastic modulus of annealed laminates depended on the sequence of layers and reached up to 169 GPa. The layered structure of the laminate had a significant influence on the mechanical behavior after annealing treatments.