Preparation of PZT-YBCO Heterostructure on YSZ Coated Si by KrF Laser Ablation
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2 Kenji Ebiharal, Fumiaki Mitsugil, Tomoaki Ikegami',and Jagdish Narayan
'Department of Electrical Engineering and Graduate School of Science and Technology, University, Kurokami 2-39-1, Kumamoto 860-8555, Japan Department of Materials and Science, North Carolina State University, Raleigh, NC, USA
2Kumamoto
ABSTRACT KrF excimer laser ablation technique is used to fabricate the ferroelectric Pb(ZrxTi1,xO 3)(PZT) capacitor on Si(100) substrate. The superconducting YBa 2Cu 3OT.x(YBCO) and the colossal magnetoresistive Lao 8sro,2 MnO 3 (LSMO) thin films are used as bottom electrodes for the ferroelectric capacitive structure. The YBCO and LSMO films were studied to understand the interface problems with perovskite oxide films. The fabricated PZT/YBCO/YSZ/Si capacitor shows the ferrolectric properties of the remanent polarization of 20pC/cm 2 and the coercive field of 40 kV/cm. Post-thermal annealing improves the ferroelctric properties and the results are comparable with that of the PZT/YBCO/MgO(1 00) structure. The leakage current of the PZT capacitor is discussed. INTRODUCTION Ferroelectric nonvolatile random access memories(FeRAM) have attracted much attention from the viewpoint of their high-speed and low voltage operation, low power consumption, long-term endurance and large-scale integration. The lead zirconate titanate( Pb(Zr,Ti)0 3 :PZT) thin films have been one of the promising candidates for the FeRAM application because of their high remanent polarization and low coercive field. The direct integration of ferroelectric films
into the silicon technology without damaging the underlying semiconductor devices has been hampered due to degrading of the ferroelectric properties [I]. In fabricating the capacitor stack consisting of ferroelectrics and electrodes, the choice of bottom electrode materials is very important to avoid forming an insulating oxide at the PZT-electrode interfaces. We have studied the PZT / perovskite oxide YBa 2Cu 30 7.x(YBCO) heterostructures for the ferroelectric-superconducting devices[2-4]. The integration of these structures into high integrated silicon-based devices requires the use of buffer layer material between the bottom electrodes and the silicon substrate. YSZ buffer layer is very effective for preparing PZT/YBCO/YSZ/Si(100) structure having high-quality ferroelectric properties for a nonvolatile memory device. In this study, we report the fabrication of the ferroelectric PZT/YBCO heterostructures on YSZ-coated silicon substrate. Recently, colossal magnetoresistance (CMR) in manganese perovskite has attracted considerable attention due to its physical properties and potential applications. The CMR materials are closely latticed matched to the perovskite ferroelectrics such as PZT. We also report the preparation of Lal-,SrxMnO 3(LSMO) film needed for PZT/LSMO structure, in which LSMO is used as a bottom electrode. KrF excimer laser ablation technique was used to prepare the thin films and the heterostructures.
341 Mat. Res. Soc. Symp. Proc. Vol. 623 © 2000 Materials Research
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