Structures and properties of (001)-oriented Pb(Zr,Ti)O 3 films on LaNiO 3 /Si(001) substrates by pulsed laser deposition
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Tae Soo Kang and Jung Ho Jeb) Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, Korea (Received 15 December 1999; accepted 28 September 2000)
In Pb(Zr0.4Ti0.6)O3(PZT) (110-nm-thick) films grown on (00l)-oriented LaNiO3 (LNO) (50-nm-thick)/Si(001) films by pulsed laser deposition, the microstructures and various structural properties of the PZT and the underlying LNO films were comparatively studied mainly using synchrotron x-ray scattering experiments. Basically, the PZT films resembled the LNO films in microstructure, crystal orientation, and mosaic distribution. The PZT films, however, showed an isotropic structural order (in- and out-of-plane coherence lengths: 18 and 14 nm) in contrast to the anisotropic order of the LNO films (in- and out-of-plane coherence lengths: 5 and 30 nm). The PZT/LNO/Si systems displayed a good hysteresis characteristic (remanent polarization, 11.8 C/cm2; coercive field, 36.1 kV/cm). We confirmed that oriented PZT films with reasonable ferroelectric properties can be successfully prepared on properly textured LNO films at a relatively low processing temperature.
I. INTRODUCTION
Thin films of Pb(ZrxTi1−x)O3 (PZT) have attracted great attention because of their potential and practical applications in a variety of functional devices.1 One of their most important applications is in the area of nonvolatile memory devices. A suitably prepared electrode layer is usually required to integrate the thin-film form of PZT into devices. As is well-known, electrode layers can affect the properties of formulated devices and, in some cases, decide their functions wholly. Until now, metal thin films including Pt have been widely used as electrodes.2 These metal electrodes, however, often cause inferior fatigue properties in PZT memory devices.3 Moreover, improper preparation of Pt films brings about hillocks, eventually resulting in short circuit in devices. Considerable efforts thus have been devoted to develop more compatible electrode layers with PZT. Oxides having a metallic conductivity have been studied as an alternative electrode to metal films. They seem more compatible with PZT than metals in chemistry and structure. Among various conducting oxides, LaNiO3 (LNO) is expected to be able to serve both as a surface
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e-mail: [email protected] e-mail: [email protected] J. Mater. Res., Vol. 15, No. 12, Dec 2000
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for growing well-oriented PZT films and as an electrode layer because it shows an n-type metallic behavior at room temperature4 and a pseudocubic perovskite structure (a ⳱ 3.84 Å),5 thereby matched well with PZT in lattice parameter and crystal symmetry. Using deposition methods such as sputtering, pulsed laser deposition (PLD), sol-gel, and spray combustion, several kinds of Pb-containing titanate films have been successfully deposited on conducting perovskite LNO electrode layers.6 –14 The deposited films differed somewhat from one another depending on the depositi
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