Structural and Ferroelectric Properties of Epitaxial PbZr 0.52 Ti 0.48 O 3 and BaTiO 3 Thin Films Prepared on SrRuO 3 /S
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Structural and Ferroelectric Properties of Epitaxial PbZr0.52Ti0.48O3 and BaTiO3 Thin Films Prepared on SrRuO3/SrTiO3(100) Substrates J. Rodríguez Contreras1, J. Schubert2, U. Poppe1, O. Trithaveesak2, K. Szot1, Ch. Buchal2, H. Kohlstedt1, and R. Waser1 1
Forschungszentrum Jülich, Institut für Festkörperforschung IFF, 52425 Jülich, Germany Forschungszentrum Jülich, Institut für Schichten und Grenzflächen ISG, 52425 Jülich, Germany 2
ABSTRACT We have prepared single crystalline epitaxial PbZr0.52Ti0.48O3 (PZT) and BaTiO3 (BTO) thin films on single crystalline epitaxial SrRuO3 (SRO) thin films grown on SrTiO3 (100) (STO) substrates. PZT and SRO thin films were grown using high-pressure on-axis sputtering and BTO using pulsed laser deposition (PLD). The film thickness ranged between 12 to 165 nm. Their excellent structural properties, surface smoothness and interface sharpness were demonstrated by X-Ray Diffraction measurements (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and Atomic Force Microscopy (AFM). Rutherford Backscattering Spectrometry and Channeling measurements (RBS/C) were used to analyze stoichiometry and crystalline quality. Ferroelectric hysteresis loops were obtained for all films of a thickness down to 12 nm showing a decrease in the remanent polarization Pr and an increase in the coercive field Ec towards thinner film thicknesses. Furthermore we have prepared tunneling junctions with a PZT or BTO barrier thickness of 3-6 nm. Reproducible bi-stable I-V-curves and bias dependence of the conductance were obtained suggesting an influence of the ferroelectric properties of the barrier material on the tunnel current. INTRODUCTION We report on PZT and BTO thin films of high crystalline quality and show the electrical behavior for different film thicknesses. In addition we show measurements performed on ultra thin (5 nm) PZT and BTO films using SRO bottom electrode and either Pt or SRO as top electrode. The dc I-V-curves exhibit tunneling characteristics at low temperatures. EXPERIMENTAL DETAILS We have deposited PZT/SRO thin films on STO (100) substrates by high-pressure on-axis sputtering [1]. BTO thin films were grown on high-pressure sputtered SRO films by PLD using on-axis geometry [2]. Stoichiometric BTO and SRO targets were used to grow stoichiometric thin films, whereas a PZT target with a lead excess of 20% was necessary to compensate the loss of this volatile component. A deposition rate of 12 nm/h, 45 nm/h and 5 nm/s (0.5 nm/puls) was achieved for PZT, SRO and BTO respectively. The optimized substrate temperature and oxygen pressure during growth were about 580°C at 3 mbar for both PZT and SRO, and 800°C at 2⋅10-3 mbar for BTO thin films. Film composition and thickness, as well as crystalline quality and structure were measured by RBS and XRD. The surface roughness was studied by AFM. C8.10.1
HRTEM was used to investigate the crystalline quality, lattice constants, and interface sharpness of ultra thin films. To measure ferroelectric hysteresis loops Pt/PZT/SRO with PZT thick
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