Figure 5. Progress transition of Ti valence states.

(a) EELS spectra of Ti-L edges for different positions in PZT film. A 2D spectrum image (22 × 63 pixels) was acquired with 3.1 nm pixel width from a rectangular region. Lateral (in plane direction) 22 spectra were summed to enhance signal-to-noise ratio. Each number indicates the distance in nm from the surface of the PZT film. (b) Multiple least-square fitting results with the 94 nm spectrum as a reference. (c) A schematic of charge (top) and electric field (bottom) distributions in paraelectric PZT film. V_O represents the concentration of doubly charged oxygen vacancy.