Nano-indentation fracture test of Pb(Zr0.52Ti0.48)O3 ferroelectric thin films Original Research Article

In this paper, we propose an elastic groundsill beam model with piezoelectric effect considered to assess the interfacial adhesion of ferroelectrics thin films, complemented and validated by nano-indentation fracture test on Pb(Zr0.52Ti0.48)O3 (PZT) thin films. It was observed that the hardness and elastic modulus of thin films depend on the indentation depth. It was also observed from the load-indentation depth curves and atomic force microscopy (AFM) images that the fracture failure of PZT thin films induced by nano-indentations can be divided into three typical stages: no damage, bulging and spallation. The delamination of thin film systems was modeled as an interfacial crack propagation problem, with the energy release rate determined from the elastic groundsill beam model. Good agreement was observed between the indentation load and the radius of the largest imprint. For PZT thin films deposited on single Si substrate with thickness of 350 nm and 450 nm, the energy release rates per unit new crack area are in the range of 3.4~52.4 J/m2 and the phase angles are constant of 13.4°. The corresponding mode I and mode II stress intensity factors are in the range of KI=0.4–1.6MPa·m1/2 and KII=0.6–2.2MPa·m1/2.