Structural investigations of Pt/TiOx electrode stacks for ferroelectric thin film devices

Effects of the thermal treatment and the fabrication process of Pb(Zr0.3Ti0.7)O-3 (PZT) thin films using chemical solution deposition on Pt/TiOx electrode stacks were investigated using complementary analytical techniques including atomic force microscopy (AFM), x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and grazing incidence x-ray reflectivity of synchrotron radiation. The surface and interface structures of the Pt/TiOx electrode stacks with different thermal treatments, and the PZT/Pt/TiOx sample were examined. The propagation of Pt hillocks on the bare Pt/TiOx electrode stacks upon the annealing was observed. AFM observations also revealed that the upper surface of the Pt bottom electrode under PZT thin film became rougher than that of the bare Pt electrode with the same thermal history. Global structural information including the density, surface or interface root-mean-square roughness, and thickness of each constituent layer in the samples were determined using x-ray reflectivity. A density decrease of the Pt layer upon the annealing or during the fabrication of PZT thin films was found from fitting the specular reflectivity, and further confirmed by the negative shift of the Yoneda peak of Pt in the diffuse reflectivity. The formation of Pt hillocks on the bare Pt electrodes was attributed to the compressive stress during the high-temperature annealing caused by the limited incorporation of Ti and O into the Pt layer. Roughening of the PZT/Pt interface was ascribed to the interaction between the compressive stress in Pt and the indentation by the PZT crystallization and grain growth during the annealing. (c) 2006 American Institute of Physics.