Search

The influence of Pt, tin-doped In2O3, and RuO2 electrodes on the electrical fatigue of bulk ceramic Pb(Zr,Ti)O3 (PZT) has been studied. Schottky barrier heights at the ferroelectric/electrode interfaces vary by more than one electronvolt for different electrode materials and do not depend on crystallographic orientation of the interface. Despite different barrier heights, hysteresis loops of polarization, strain, permittivity, and piezoelectric constant and the switching kinetics are identical for all electrodes. A 20% reduction in polarization after 106 bipolar cycles is observed for all the samples. In contrast to PZT thin films, the loss of remanent polarization with bipolar switching cycles does not significantly depend on the electrode material. [ABSTRACT FROM AUTHOR]

The interface formation between Ba0.6Sr0.4TiO3 and Al2O3 has been studied using photoelectron spectroscopy with in situ sample preparation. A negligible valence band discontinuity, corresponding to a ∼5.6 eV barrier for electron transport at the BST/Al2O3 interface is determined. Current-voltage measurements show that the leakage current can be significantly reduced by inserting the Al2O3 barrier layer between barium strontium titanate (BST) and Pt electrode. Different charge injection behavior depending on Al2O3 thickness is observed, which correspond well with the experimentally determined energy band diagrams. Direct tunneling from the metal electrode into the BST conduction band through the Al2O3 barrier layer is observed. [ABSTRACT FROM AUTHOR]

The various properties and electrical fatigue exhibited by the Pb(Zr,Ti)[O.sub.3] ceramics with different electrodes are analyzed. The loss of remanent polarization of the ceramics is shown to be completely independent of the electrode material.

The photoelectron spectroscopy technique is employed to explain the synthesis and the electrical properties of the (Ba,Sr)Ti[O.sub.3]/[Al.sub.2][O.sub.3] interfaces. The insertion of a barrier is shown to be extremely helpful in the reduction of the leakage current of the interfaces.

The interface formation between PbTiO3 and SrTiO3 has been studied by in situ photoelectron spectroscopy. A valence band offset of 1.1±0.1 eV, corresponding to a conduction band offset of 1.3±0.1 eV, is determined. These values are in good agreement with the band offsets estimated from measured ionization potentials of SrTiO3 and PbTiO3 surfaces. The observed band offsets are also in line with a ~1.1 eV difference in barrier heights of PbTiO3 in contact with different electrode materials as compared to barrier heights of SrTiO3 with the same electrode materials. The results indicate that the band alignment is not strongly affected by Fermi level pinning and that the barrier heights are transitive. The limits of Fermi level variation observed from a number of thin films prepared on different substrates with different conditions are the same for both materials when these are aligned following the experimentally determined band offsets. By further comparing electrical conductivities reported for SrTiO3 and PbTiO3, it is suggested that the range of Fermi level position in the bulk of these materials, which corresponds to the range of observed conductivities, is comparable to the range of Fermi level position at interfaces with different contact materials. In particular the possibly low barrier height for electron injection into SrTiO3 is consistent with the metallic conduction of donor doped or reduced SrTiO3, while barrier heights ≳1 eV for PbTiO3 are consistent with the high resistivity even at high doping concentrations. The variation of barrier heights at interfaces therefore provides access to the range of possible Fermi level positions in the interior of any, including insulating, materials, which is relevant for understanding defect properties. [ABSTRACT FROM AUTHOR]