Influence of processing conditions on the structure, composition and ferroelectric properties of sputtered PZT thin films on Ti-substrates

摘要

PZT thin (～500nm) films are synthesized on titanium (Ti) substrates by r.f. magnetron sputtering under various processing conditions. Present work aims to investigate the influence of working pressure and post-annealing temperature on the quality of the films. Phase evolution, surface morphology with local chemical composition and dielectric/ferroelectric properties of PZT films have been studied as the functions of working pressure and post-annealing temperature. A working pressure of ～0.7 Pa and a post-crystallization temperature of ～650℃ are found to be the optimum processing conditions for growing perovskite PZT films on Ti-substrates. Irrespective of processing conditions, however, all PZT films on Ti-substrates show poor electrical response. Depth dependent change in the chemical states of Pb, Zr, Ti and oxygen within the PZT films and across the PZT/Ti interfaces has also been scrutinized by XPS depth profiling. It is observed that within PZT films, Pb exists both in Pb~(2+) and Pb~0 (metallic-Pb) states. Surfaces of the PZT films are found to be enriched with a thin (～60 nm) Pb-deficient and Zr-rich pyrochlore/fluorite (Py/Fl) phase. Existence of a thin titanium oxide layer in the form of a TiCh/TiO stack has also been confirmed at the PZT/Ti interface. Processing conditions dependant structural modifications have been correlated with the dielectric and ferroelectric properties of the films.