Piezoelectric response of epitaxial Pb(Zr0.2Ti0.8)O3 films measured by scanning tunneling microscopy

We report on scanning tunneling microscopy measurements of the piezoelectric response in ferroelectric heterostructures grown by off-axis rf magnetron sputtering. The samples are composed of a single-crystalline ferroelectric film of Pb(Zr0.2Ti0.8)O-3 deposited on a conducting substrate and covered with an ultrathin metallic film of gold. The high quality of the c-axis oriented ferroelectric layer is evidenced by sharp polarization hysteresis loops. By applying a voltage to the bilayer and recording the inverse piezoelectric effect with the scanning tunneling microscope, we demonstrate the ability to measure the phase response as well as the ferroelectric switching. We obtained strain-field plots with a butterfly loop shape, and a quantitative measurement of the longitudinal piezoelectric coefficient (d(33)). (C) 2000 American Institute of Physics. [S0003-6951(00)02037-4].