Lead Excess in Pb(Zr,Ti)O₃ Thin Films Deposited by Reactive Sputtering at Low Temperatures

Pb(Zr,Ti)O ₃ thin films deposited by multi-target reactive sputtering at low substrate temperatures are characterized by a significant lead excess without a measurable second phase formation. The presence of Pb ^{4 +} sites was detected by means of the lead X-ray photoelectron spectroscopy spectra. Besides the Pb (4f _7/2 ) and Pb (4f _5/2 ) peaks of Pb ^{2 +} two smaller peaks at higher energy were obtained, which should be assigned to a higher lead valence. A disordered structure enhances the temperature dependence of the optical gap in the temperature region between two second order phase transitions at 200 and 290°C. At these temperatures, the dielectric properties exhibit a Debye-type or Maxwell-Wagner-type relaxor contribution. The ternary phase diagram of a PbTiO ₃ -PbZrO ₃ -PbPbO ₃ solution shows that about one third of the Zr-sites is occupied by Pb ^{4 +} .

Keywords:

• Ferroelectrics
• X-ray photoelectron spectroscopy
• phase diagram
• antisite point defects
• dielectric properties

PACS:

• 77.80.Bh
• 77.84.Dy
• 81.15.cd
• 82.45.Un
• 82.80.Pv

Acknowledgments

This work was supported by Grant KJB1010301 (Academy of Sciences of the Czech Republic) and 202/02/D078/A (Grant Agency of the Czech Republic), by the German Research Council (Deutsche Forschungsgemeinschaft) as part of the Research Group FOR520.