Can lead nonstoichiometry influence ferroelectric properties of Pb(Zr,Ti)O-3 thin films?

In this letter, we report on the influence of lead content on thin-film fer roelectric properties of lead niobium zirconate titanate. These films were prepared by the sol-gel technique and deposited on (La,Sr)CoO3 electrodes. It was determined that 7% excess lead in the sol was required to obtain nom inally stoichiometric films. Lead deficiency in the film results in lead va cancies and excess lead is accommodated by forming octahedral site vacancie s. Further amounts of lead in the sol leads to second phase PbO, which then coexists with the perovskite phase. The charged vacancies are compensated by mobile holes, which can interact with domains during switching. Under ap plied field and short pulse widths, the films with larger number of holes e xhibited poor switching. Significant polarization relaxation was measured f or films with excess lead, which is attributed to interaction of ionic defe cts with domains. Our results indicate that lead excess leads to poor relia bility properties,whereas lead deficiency suppresses the polarization of th e capacitors. (C) 1999 American Institute of Physics. [S0003-6951(99)00931- 6].