Manipulation of superdomains in Pb(Zr_0.2Ti_0.8)O₃ epitaxial films grown on SrTiO₃(110) substrates

Various interesting physical properties arising from manipulating strain energy terms in epitaxial films have attracted great attention. For tetragonal Pb(Zr_0.2Ti_0.8)O₃ (PZT) films, the large piezoelectric response mainly originates from the switching of 90-degree c/a domains due to the strain-relief-induced reorientation. In this study, we found a superdomain structure existing the epitaxial PZT films when grown on the (110)-oriented SrTiO₃ (STO). The in-plane strain from STO breaks the uniaxial symmetry of the tetragonal PZT film, and with suitable adjusting the strain energy, superdomains can be formed in long-range areas. We used X-ray diffraction, transmission electron microscopy, and piezoresponse force microscopy (PFM) to investigate the distortion of crystal and domain structures. The PFM images show periodic nanodomains with size about 50-80 nm in the superdomain region and indicate the coexistence of at least two distortions of the crystal. The superdomains can be effectively induced or erased by external fields. Based on systematical investigations, the mechanism to create superdomains by electric fields is concluded relating to the surface energy. This study provides basic understanding and control of this unique superdomain structure.