Roles of Nano-Domain Switching and Non-180^\circ Domains in Enhancing Local Piezoelectric Responses of Highly (100)-Oriented Pb(Zr_0.60Ti_0.40)O_3 Thin Films

Ferroelectric Pb(Zr_0.60Ti_0.40)O_3 thin films deposited on the niobium-doped SrTiO_3 and Pt (111)/Ti/SiO_2/Si substrates are fabricated by a sol-gel method. X-ray diffraction indicates that the films have a 'cube-on-cube' growth with highly (100) preferred orientation and good surface qualities. Using piezoelectric force microscopy, we investigate domain structures and butterfly amplitude loops of ferroelectric thin films. The results indicate that the film deposited on Nb:SrTiO_3 has both kinds of 180^\circ polarizations perpendicular or parallel to the surface while the film deposited on Pt/Ti/SiO_2/Si has irregular phase differences. Excellent piezoelectric polarization are observed in the films on niobium-doped SrTiO_3 with local d_33^\ast values around 45 pm/V three times more than that of the films around 13 pm/V deposited on Pt (111)/Ti/SiO_2/Si. Our findings emphasize that nano-domain switching ability and non-180^\circ domains will contribute significantly to enhance piezoelectric responses of ferroelectric thin films.