Improvement of loss factor tan δ of PZT PbTi0.75Zr0.25O3 films by O -Ion-implantation

Ion implantation into (111) PZT films was done with 150 keV O+-ions using the following doses: 5 · 1010 cm-2 and 5 · 1013cm-2. The penetration depth of the O+-ion beam (through a 150 nm top Pt-electrode) was calculated with the TRIM. SP program version TRVMC95. For 104 particles, 22% of them were calculated to pass the top Pt electrode, 1% of the 104 particles were calculated to reach a penetration depth of 150 nm in PZT. The O+-implantation led to a significant improvement (50%) of loss factor tan δ. This effect is ascribed within current theory to a decrease of oxygen vacancies (defects). Oxygen vacancies are supposed to be associated by Ti3+, Ti2+ and Ti+centers in the perovskite lattice. Evidence for a possible participation of such reduced (charged) titanium defects was obtained by luminescence spectroscopy. Therefore, PZT samples were treated with H2 to increase the concentration of reduced Tin+ (n<4) ions in the perovskite lattice by chemical treatment. The luminescence spectrum of such reduced samples showed peaks at 3.2, 2.95 and 2.8 eV (surface Ti3+, Ti2+ Ti+ centers). Furthermore, peaks at 1.87eV and 2.2 eV were observed. These near-midgap states have been ascribed to transitions from Ti3+ and Ti2+ from the bulk of PZT (3.8 eV excitation energy, T = 6K). Finally, a sharp luminescence peak at 3.34 eV (6K) is assigned as self-trapped exciton luminescence.