Nanoscale polarisation switching and leakage currents in (Ba0.955Ca0.045)(Zr0.17Ti0.83)O3epitaxial thin films

This paper investigates the crystal structure, ferroelectric, temperature-dependent leakage current conduction mechanism and the piezoresponse force microscopy (PFM) behaviours of (Ba 0.955 Ca 0.045 ) (Zr 0.17 Ti 0.83 )O 3 –BZT–BCT ( ) films at the vicinity of the morphotropic phase boundary (MPB) of the [(1 − x ) BaZr 0.20 Ti 0.80 O 3 – x Ba 0.70 Ca 0.30 TiO 3 ] ( ) composition. Epitaxial BZT–BCT thin films were grown on conductive La 0.5 Sr 0.5 CoO 3 (LSCO) layers coated onto MgO (1 0 0) single-crystal substrates by pulsed laser deposition (PLD). High resolution x-ray diffraction (HR-XRD) reciprocal space maps (RSMs) confirmed the epitaxy with in-plane tetragonal symmetry ( c < a ), and Raman spectra also revealed a tetragonal perovskite crystalline lattice structure. Polarisation studies demonstrate that BZT–BCT films exhibit a high saturation polarisation of 148 µ C cm −2 and a high recoverable (discharged) energy-storage density of 39.11 J cm −3 at 2.08 MV cm −1 . Temperature-dependent P – E hysteresis loops resulted in a decrease in polarisation. Temperature-dependent leakage current behaviour was obtained and possible conduction mechanism is discussed. PPFM images revealed switchable ferroelectric piezoelectric contrasts after the application of a ±9 V dc voltage on the conductive tip of the piezoresponse force microscope.