Nanomechanical-ferroelastics behavior, and the low-temperature ferroelectric manifestation of BiMnO3 thin films

Ferroelastic-nanomechanical behavior of BiMnO3 thin films on (100) Nb-doped SrTiO3 substrate is studied at the nanoscale, for the first time using the theories of depth sensing indentation and finite element analysis. This was to understand the redirection of polarization in ferroelastic behavior using piezoelectric direct effect and applying a controlled local force by nanoindentation. The values of the nanomechanical properties Young's modulus (E), hardness (H), and Stiffness (S) were measured to be E = 142 +/- 3 GPa, H = 8 +/- 0.2 GPa, and S = 44072 +/- 45 N m(-1) respectively. Using the experimental mechanical properties, a finite element analysis was carried out to understand the relationship between the irreversible work versus depth curve and plastic-deformation evolution of the thin film-interface-substrate system, associated with the pop-in observed. Von Mises stress maps are presented to clearly illustrate the deformations, mechanical failures, and influences between the BiMnO(3 )film and the SrTiO3 Substrate. The ferroelastic range for BiMnO3 material was observed between 0 to 12 nm, and the yield strength was Y = 2.6 +/- 0.7 GPa. The ferroelectric properties through hysteresis curves were evaluated at two different temperatures of 200 K and 300 K in order to observe the effect of polarization with temperature. Providing better polarization performance at lower temperatures; P s = 9.14 +/- 0.01 ( mu C cm(-2)), P-r = 2.23 +/- 0.02 ( mu C cm(-2)) and H-c = 0.77 kV cm(-1).