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Passive Layer Formation at Ferroelectric PbTiO3/Pt Interfaces Studied by EELS

Published online by Cambridge University Press:  01 February 2011

S. J. Welz ,
L. F. Fu ,
R. Erni ,
M. Kurasawa ,
P. C. McIntyre  and
N. D. Browning
S. J. Welz
Affiliation:
Department of Chemical Engineering and Materials Science, University of California Davis, One Shields Ave., Davis, CA 95616, USA
L. F. Fu
Affiliation:
Department of Chemical Engineering and Materials Science, University of California Davis, One Shields Ave., Davis, CA 95616, USA
R. Erni
Affiliation:
Department of Chemical Engineering and Materials Science, University of California Davis, One Shields Ave., Davis, CA 95616, USA
M. Kurasawa
Affiliation:
Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA
P. C. McIntyre
Affiliation:
Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA
N. D. Browning
Affiliation:
Department of Chemical Engineering and Materials Science, University of California Davis, One Shields Ave., Davis, CA 95616, USA National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, USA
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Abstract

Polarization fatigue with repeated electric cycles in ferroelectric thin films is a major degradation problem in ferroelectric nonvolatile memories. However, the origin of this phenomenon is still not properly understood. The fatigue mechanism of a ferroelectric perovskite in a multilayer ferroelectric PbTiO3 thin film material has been investigated here using scanning transmission electron microscopy (STEM). Z-contrast images of the interfaces show that the ferroelectric PbTiO3 layer has partly decomposed into a single crystal PbTiO3 layer and an amorphous layer. Nanometer-sized precipitates are present near the Pt electrode. Electron energy-loss spectroscopy (EELS) analysis reveals that the amorphous layer is a Ti-rich phase between TiO2 and PbTiO3. The precipitates are determined to be a Pt-Pb rich crystalline phase. It is suggested that the formation of the structure-distorted intermediate layer and precipitates may be associated with the ferroelectric degradation process by acting as a passive layer in a ferroelectric capacitor. In addition, the formation of the Pt-Pb rich precipitates may cause an interruption of the consistent Pt electrode, which may result in failure of the device.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 875: Symposium O – Thin Films - Stresses and Mechanical Properties XI , 2005 , O14.3
Copyright
Copyright © Materials Research Society 2005

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