Compositional control of ferroelectric domain structures in heteroepitaxial PLZT thin films

The mechanism and control of ferroelectric domain formation in heteroepitaxial (Pb1-xLax)(ZryTi1-y)O-3 (PLZT) thin films grown on MgO(001) substrates have been investigated as a function of composition and temperature. Pulsed laser deposition and RF magnetron sputtering techniques were used and optimized to fabricate epitaxial thin films with varying La and/or Zr concentrations. Periodic 90 degrees domain structures were developed when the film transformed from the cubic phase to the tetragonal phase during cooling after deposition. As a result of the tetragonality of the films, the domain formation induced slightly tilted twin structures. All films were grown highly c axis oriented and the degree of c axis orientation was improved with increasing La or Zr concentration. Experimental observations of the 90 degrees domain evolution in films have been carried out in-situ and ex-situ using conventional and synchrotron X-ray diffraction and demonstrated that the most important parameter affecting the domain structure and its abundance is the transformation strain at the Curie temperature, which can be varied systematically by changing the concentration of La and/or Zr in the PLZT system.