Nanoscale study by piezoresponse force microscopy of relaxor 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 and 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 thin films grown on platinum and LaNiO3 electrodes

Relaxor 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (70/30 PMN-PT) and 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 (90/10 PMN-PT) thin films have been grown by RF-sputtering on platinum (Pt) and lanthanum nickelate (LaNiO3) bottom electrodes. For both electrodes, macroscopic measurements evidence lower coercive fields, remnant polarizations and piezoelectric coefficients d33 for 90/10 PMN-PT films compared to 70/30 PMN-PT films. For both compositions, coercive fields and remnant polarizations are lower for films grown on LaNiO3 compared to on Pt while piezoelectric coefficients d33 are higher. For each electrode and composition, a similar behavior is revealed for electromechanical activity at the nanoscale when measuring local piezoelectric hysteresis loops; on the other hand, the voltages required for switching the domains are the highest for 90/10 PMN-PT films grown on LaNiO3. The existence of large grain boundaries in the films grown on Pt and the presence of local random fields with polar nano-domains for the 90/10 composition could explain the differences measured in domains switching properties at the macroscale and nanoscale levels.