Effect of Pt3Pb on the permittivity and conductivity of lead zirconate titanate thin films

Abstract

The evolution and interaction of buried interfaces during the synthesis of lead zirconate titanate (PZT) ferroelectric thin film devices have been previously predicted by density functional theory modeling and observed experimentally via in–situ structural characterization. Moreover, the formation and disappearance of an intermetallic phase (Pt3Pb) during the crystallization of the film has been identified as a key process expected to affect the resulting electrical properties of the devices. To elucidate this effect, a combination of direct current (leakage current measurements) and alternating current (impedance spectroscopy) characterization techniques are used to examine the electrical properties of sol–gel–derived PZT thin films. Films with the intermetallic phase exhibit a high potential barrier at the metal–insulator interface (0.83 eV) similar to the fully crystallized films (0.81 eV) and a lower current density than the films without the intermetallic phase, as shown in the Richardson plot. Impedance measurements also revealed that the conductivity of the films with the intermetallic phase, σ = 1.9 × 10−11 S cm−1, and the real part of the relative permittivity at 10 kHz, εr′=42, are lower than the other films (fully crystallized film: σ = 3.5 × 10−10 S cm−1 εr′=566, amorphous crystallized film: σ = 4.6 × 10−11 S cm−1 εr′=121). It is shown that these electrical characterization methods can serve as non–destructive examination tools to track the evolution of secondary phases during device synthesis and fabrication.