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25 Dec 2006

Volume 89, Issue 26, Articles (26xxxx)

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Appl. Phys. Lett. 89, 263110 (2006); http://dx.doi.org/10.1063/1.2424541 (3 pages)

Ch. Deneke, U. Zschieschang, H. Klauk, and O. G. Schmidt
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Mechanism of leakage current reduction of tantalum oxide capacitors by postmetallization annealing

W. S. Lau, K. K. Khaw, Taejoon Han, and Nathan P. Sandler

Appl. Phys. Lett. 89, 262901 (2006); http://dx.doi.org/10.1063/1.2408645 (3 pages) | Cited 6 times

Online Publication Date: 26 December 2006

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In this letter, the authors will point out that defect states related to impurities or structural defects in tantalum oxide capacitors can be passivated by hydrogen during postmetallization anneal (PMA) while oxygen vacancies are enhanced by PMA such that some will observe a decrease while other may observe an increase in the leakage current after PMA. The PMA process can be tuned such that the hydrogen passivation of defect states dominates over the enhancement of oxygen vacancies, resulting in significant leakage current reduction.
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84.32.Tt Capacitors
81.65.Rv Passivation
85.40.Ls Metallization, contacts, interconnects; device isolation

Strain distribution in epitaxial SrTiO3 thin films

Z. Y. Zhai, X. S. Wu, Z. S. Jiang, J. H. Hao, J. Gao, Y. F. Cai, and Y. G. Pan

Appl. Phys. Lett. 89, 262902 (2006); http://dx.doi.org/10.1063/1.2424282 (3 pages) | Cited 10 times

Online Publication Date: 27 December 2006

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The lattice strain distributions of epitaxial SrTiO3 films deposited on LaAlO3 were investigated by in situ x-ray diffraction at the temperature range of 25–300 K, grazing incident x-ray diffraction, and high resolution x-ray diffraction. The nearly linear temperature dependence of the out-of-plane lattice constant of SrTiO3 was observed in the measured temperature range. The depth distribution of the lattice strain at room temperature for SrTiO3 films includes the surface layer, strained layer, and interface layer.
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68.60.Bs Mechanical and acoustical properties
61.66.Fn Inorganic compounds
68.55.-a Thin film structure and morphology

Structural properties of SrO thin films grown by molecular beam epitaxy on LaAlO3 substrates

O. Maksimov, V. D. Heydemann, P. Fisher, M. Skowronski, and P. A. Salvador

Appl. Phys. Lett. 89, 262903 (2006); http://dx.doi.org/10.1063/1.2424440 (3 pages) | Cited 3 times

Online Publication Date: 27 December 2006

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SrO films were grown on LaAlO3 substrates by molecular beam epitaxy and characterized using reflection high-energy electron diffraction (RHEED) and x-ray diffraction (XRD). The evolution of the RHEED pattern is discussed as a function of film thickness. 500 Å thick SrO films were relaxed and exhibited RHEED patterns indicative of an atomically smooth surface having uniform terrace heights. Films had the epitaxial relationship (001)SrO‖(001)LaAlO3; [010]SrO‖[110]LaAlO3. This 45° in-plane rotation minimizes mismatch and leads to films of high crystalline quality, as verified by Kikuchi lines in the RHEED patterns and narrow rocking curves of the (002) XRD peak.
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81.05.-t Specific materials: fabrication, treatment, testing, and analysis
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
68.35.B- Structure of clean surfaces (and surface reconstruction)

Oxygen vacancy in monoclinic HfO2: A consistent interpretation of trap assisted conduction, direct electron injection, and optical absorption experiments

Peter Broqvist and Alfredo Pasquarello

Appl. Phys. Lett. 89, 262904 (2006); http://dx.doi.org/10.1063/1.2424441 (3 pages) | Cited 63 times

Online Publication Date: 27 December 2006

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The authors calculate energy levels associated with the oxygen vacancy in monoclinic HfO2 using a hybrid density functional which accurately reproduces the experimental band gap. The most stable charge states are obtained for varying Fermi level in the HfO2 band gap. To compare with measured defect levels, they determine total energy differences specific to the considered experiment. Their results show that the oxygen vacancy can consistently account for the defect levels observed in (Poole-Frenkel-type) trap assisted conduction, direct electron injection, and optical absorption experiments.
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71.55.Ht Other nonmetals
72.20.Ht High-field and nonlinear effects
72.25.Hg Electrical injection of spin polarized carriers
61.72.J- Point defects and defect clusters

Low symmetry phase in Pb(Zr0.52Ti0.48)O3 epitaxial thin films with enhanced ferroelectric properties

Li Yan, Jiefang Li, Hu Cao, and D. Viehland

Appl. Phys. Lett. 89, 262905 (2006); http://dx.doi.org/10.1063/1.2425016 (3 pages) | Cited 10 times

Online Publication Date: 28 December 2006

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The authors report the structural and ferroelectric properties of Pb(Zr0.52Ti0.48)O3 (PZT) epitaxial thin films grown on (001), (110), and (111) SrRuO3/SrTiO3 substrates by pulsed laser deposition. A monoclinic C (Mc) phase has been found for (101) films, whereas (001) and (111) ones were tetragonal (T) and rhombohedral (R), respectively. The authors find that the ferroelectric polarization of the Mc phase is higher than that in either the T or R ones. These results are consistent with predictions (i) of epitaxial phase diagrams and (ii) that the enhanced ferroelectric properties of morphotropic phase boundary PZT are related to a low symmetry monoclinic phase.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.55.-a Thin film structure and morphology
77.22.Ej Polarization and depolarization
81.30.Dz Phase diagrams of other materials

Controlling interfacial reactions between HfO2 and Si using ultrathin Al2O3 diffusion barrier layer

Rajesh Katamreddy, Ronald Inman, Gregory Jursich, Axel Soulet, and Christos Takoudis

Appl. Phys. Lett. 89, 262906 (2006); http://dx.doi.org/10.1063/1.2425023 (3 pages) | Cited 10 times

Online Publication Date: 29 December 2006

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The authors investigated the effectiveness of atomic layer deposited (ALD) aluminum oxide barrier layer in controlling the interfacial reaction between ALD HfO2 film and Si substrate. The HfO2 was observed to form silicate and silicide at its interface with Si during 5 min postdeposition annealing in Ar at 800 and 1000 °C. A 0.5-nm-thick Al2O3 barrier layer was found to control interfacial reactions between HfO2 and Si during annealing at 800 °C, but not at 1000 °C, whereas a 1.5-nm-thick barrier of Al2O3 was needed to prevent interfacial reaction up to an annealing temperature of 1000 °C.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.Fx Diffusion; interface formation
68.55.A- Nucleation and growth
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
61.72.Cc Kinetics of defect formation and annealing

Domain reversal and relaxation in LiNbO3 single crystals studied by piezoresponse force microscope

Yi Kan, Xiaomei Lu, Xiumei Wu, and Jinsong Zhu

Appl. Phys. Lett. 89, 262907 (2006); http://dx.doi.org/10.1063/1.2425034 (3 pages) | Cited 13 times

Online Publication Date: 29 December 2006

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The LiNbO3 crystal was polarized and characterized by the piezoresponse force mode of scanning probe microscope. By using the Kolmogorov-Avrami-Ishibashi [Izv. Akad. Nauk, USSR: Ser. Math. 3, 355 (1937) ; J. Chem. Phys. 8, 212 (1940) ; J. Phys. Soc. Jpn. 63, 1031 (1994) ; 63, 1601 (1994) ] theory to analyze the relaxation process after domain switching, it was found that (1) the percent of final switched domains after poling increased with the enhancing poling voltage, (2) the nucleation time was a constant to a certain sample, (3) the dimension of domain growth decreased with the enhancing poling voltage, and (4) the relaxation time had a maximum at a medial voltage. The corresponding mechanism for domain switching was discussed, which is hopefully useful for domain engineering.
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77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
77.22.Gm Dielectric loss and relaxation

Deaging of heat-treated iron-doped lead zirconate titanate ceramics

T. Granzow, E. Suvaci, H. Kungl, and M. J. Hoffmann

Appl. Phys. Lett. 89, 262908 (2006); http://dx.doi.org/10.1063/1.2425035 (3 pages) | Cited 7 times

Online Publication Date: 29 December 2006

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Doping strongly influences the properties of ferroelectric perovskite materials. One striking difference between donor- and acceptor-doped materials is the transition from “soft” to “hard” ferroelectric behavior. The physical reasons for this phenomenon are still unclear. The authors present measurements of the ferroelectric hysteresis and deaging behavior of iron-doped lead zirconate titanate after adjusting the defect structure by heat treatment in an oxygen-depleted atmosphere. Contrary to expectations, the introduction of extra oxygen vacancies makes the material “softer.” This effect, which is discussed based on a model of defect dipoles, sheds new light on the unsolved problem of hardening and aging.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
81.40.Gh Other heat and thermomechanical treatments
61.72.J- Point defects and defect clusters
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