Lead enrichment at the surface of lead zirconate titanate thin films

Compositional and Optical Gradient in Films of PbZrxTi1-xO3 (PZT) Family

“…11). The spontaneous polarization allows the cations to diffuse faster and is the reason why surface enrichment is so significant in ferroelectric films (Watts et al, 2005). The ferroelectric (FE) polarization induced electrochemically by this mechanism is in the direction observed experimentally by Impey et al, 1998, and.…”

“…Qualitative depth profile can be also analyzed by the detection of concentration gradients of the chemical elements of PZT thin films using Z contrast TEM with EDX (Ledermann et al, 2003). In the work of Watts et al, 2005, the EDX was performed on PbZr 0.52 Ti 0.48 O 3 (PZT 52/48) thin films. Compositional profiles were determined along with analysis of the state of oxidation of the lead.…”

“…The trend of n with depth presented in Fig. 9b can be caused by several reasons such as 1) residual stress in the film, 2) concentration gradients of Ti or Zr with the layer, 3) an increase in excess Pb (Aulika et al, 2009;Ledermann et al, 2003;Watts et al, 2005), 4) polarization profile that is strongly dependent on film thickness (polarization is homogeneous in the greater part of the thick film except in small regions at the film boundaries, while it is completely inhomogeneous in thin films). (Fig.…”

“…8b that the Zr/Ti ratio decreases directionally from the substrate to the surface, which is opposite to the observations, e.g., of Ledermann by TEM. However, it is known that sol-gel thin films may have higher concentrations of Pb at the surface (Impey et al, 1998;Ledermann et al, 2003;Watts et al, 2005).…”

“…An analogy may be drawn with the oxidation of metals such as Cu and Sn where the metals dif-fuse towards the reacting surface (Wagner, 1971;Cabrera and Mott, 1948). The data presented by Watts et al indicates that the pyrolysis and crystallization steps for sol-gel films result in incomplete oxidation (Watts et al, 2005). The diffusion is driven by the oxidation of Pb at the PZT/oxygen interface.…”