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18 Jun 2007

Volume 90, Issue 25, Articles (25xxxx)

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Appl. Phys. Lett. 90, 253101 (2007); http://dx.doi.org/10.1063/1.2749418 (3 pages)

G. D. Dice, M. J. Brett, D. Wang, and J. M. Buriak
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Electroclinic effect in a chiral smectic C siloxane material

J. N. Jang, A. B. Davey, and W. A. Crossland

Appl. Phys. Lett. 90, 252901 (2007); http://dx.doi.org/10.1063/1.2749860 (3 pages)

Online Publication Date: 18 June 2007

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The authors have proposed that the electroclinic effect can explain the mechanism of layer rotation in the chiral smectic C phase. In this work, they investigate the soft mode in the chiral smectic C phase with three different experiments: dielectric permittivity measurements, light transmission measurements, and direct tilt angle measurements. They could clearly identify the electroclinic effect in the chiral smectic C phase in the experiments, which was very small compared to that of the SmA* phase.
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77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
61.30.-v Liquid crystals
77.22.Ch Permittivity (dielectric function)
77.80.-e Ferroelectricity and antiferroelectricity

Dielectric and thermal evidence of phase transitions in the system of (1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 crystals

Haixia Wang, Xiaomin Pan, Di Lin, Haosu Luo, Zhiwen Yin, and Brahim Elouadi

Appl. Phys. Lett. 90, 252902 (2007); http://dx.doi.org/10.1063/1.2710077 (3 pages) | Cited 4 times

Online Publication Date: 19 June 2007

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Dielectric permittivity, differential scanning calorimetry nonisothermal measurements, and hysteresis loops were performed for oriented (1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 unpoled crystals. Two distinguished branches were obtained where spontaneous ferroelectric to relaxor or ferroelectric phase transition was observed within the peculiar relaxor to normal ferroelectric region. The percolating polar region induced by the addition of PbTiO3 tends to gradually develop comparable ferroelectric order changing slightly with temperature from the nonpolar matrix, associated with a weak first or first order phase transition. Small frequency dispersion due to relaxor polarization at or below transition temperature TFE-R or FE indicated the changes of ferroelectric multidomain and polar nanoregion in this disordered system.
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77.80.B- Phase transitions and Curie point
77.80.Dj Domain structure; hysteresis
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
64.70.K- Solid-solid transitions

Multiferroic properties and dielectric relaxation of BiFeO3/Bi3.25La0.75Ti3O12 double-layered thin films

Fengzhen Huang, Xiaomei Lu, Weiwei Lin, Wei Cai, Xiumei Wu, Yi Kan, Hai Sang, and Jinsong Zhu

Appl. Phys. Lett. 90, 252903 (2007); http://dx.doi.org/10.1063/1.2749873 (3 pages) | Cited 23 times

Online Publication Date: 19 June 2007

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BiFeO3 (BFO)/Bi3.25La0.75Ti3O12 (BLT) films were prepared on (111) Pt/Ti/SiO2/Si substrates via metal organic decomposition method. The multiferroic and dielectric properties of the films were studied. It was found that the ferroelectric polarization and dielectric constant of the films were enhanced by introducing BLT as a barrier layer between BFO and Pt bottom electrode, while the ferromagnetism of BFO was not influenced. More interestingly, the films showed dielectric relaxor behavior, and the possible causes of which were discussed.
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77.55.-g Dielectric thin films
75.80.+q Magnetomechanical effects, magnetostriction
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation

GaAs metal-oxide-semiconductor device with HfO2/TaN gate stack and thermal nitridation surface passivation

Fei Gao, S. J. Lee, D. Z. Chi, S. Balakumar, and D.-L. Kwong

Appl. Phys. Lett. 90, 252904 (2007); http://dx.doi.org/10.1063/1.2749840 (3 pages) | Cited 23 times

Online Publication Date: 19 June 2007

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Oxides induced Fermi level pinning at the interface between the GaAs and high-k gate dielectric is a major obstacle for developing high performance GaAs metal-oxide-semiconductor (MOS) devices. In this letter, thermal nitridation treatment on GaAs surface prior to the high-k deposition is proposed to solve the issue of interface pinning. It is found that an optimized nitride layer formed during the thermal nitridation surface treatment can effectively suppress the oxides formation and minimize the Fermi level pinning at the interface between the GaAs and HfO2. By using thermal nitridation treatment and in situ metal-organic chemical vapor deposition HfO2 as high-k gate dielectric, GaAs MOS capacitor with improved capacitance-voltage characteristics and reduced gate leakage current is achieved.
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85.30.Tv Field effect devices
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
84.32.Tt Capacitors

Characterization of ferroelectric domains in morphotropic potassium sodium niobate with scanning probe microscopy

Ralf-Peter Herber, Gerold A. Schneider, Susanne Wagner, and Michael J. Hoffmann

Appl. Phys. Lett. 90, 252905 (2007); http://dx.doi.org/10.1063/1.2750395 (3 pages) | Cited 21 times

Online Publication Date: 19 June 2007

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Lead-free piezoceramic potassium sodium niobate in its morphotropic composition was synthesized with abnormal grain growth. Ferroelectric domain patterns were imaged with piezoresponse force microscopy. Analysis of the domain structure at the morphotropic phase boundary revealed a coexistence of tetragonal and orthorhombic polarized domains in a single grain.
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77.80.Dj Domain structure; hysteresis
68.37.-d Microscopy of surfaces, interfaces, and thin films

Ferroelectric size effects in multiferroic BiFeO3 thin films

Y. H. Chu, T. Zhao, M. P. Cruz, Q. Zhan, P. L. Yang, L. W. Martin, M. Huijben, C. H. Yang, F. Zavaliche, H. Zheng, and R. Ramesh

Appl. Phys. Lett. 90, 252906 (2007); http://dx.doi.org/10.1063/1.2750524 (3 pages) | Cited 54 times

Online Publication Date: 20 June 2007

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Ferroelectric size effects in multiferroic BiFeO3 have been studied using a host of complementary measurements. The structure of such epitaxial films has been investigated using atomic force microscopy, transmission electron microscopy, and x-ray diffraction. The crystal structure of the films has been identified as a monoclinic phase, which suggests that the polarization direction is close to ⟨111⟩. Such behavior has also been confirmed by piezoforce microscopy measurements. That also reveals that the ferroelectricity is down to at least 2 nm.
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68.55.-a Thin film structure and morphology
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
77.65.-j Piezoelectricity and electromechanical effects

AgNbO3: A lead-free material with large polarization and electromechanical response

Desheng Fu, Makoto Endo, Hiroki Taniguchi, Tomoyasu Taniyama, and Mitsuru Itoh

Appl. Phys. Lett. 90, 252907 (2007); http://dx.doi.org/10.1063/1.2751136 (3 pages) | Cited 30 times

Online Publication Date: 20 June 2007

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Polarization measurements reveal that AgNbO3 has an extremely large polarization, which can reach a value of 52 μC/cm2 in polycrystals. Experiments also show that the large internal atom distortion in AgNbO3 is also strongly coupled to the electric field, indicating that high piezoelectric performance can be realized in AgNbO3 system. This finding opens the way to designing a new class of lead-free, high-performance piezoelectric materials based on AgNbO3.
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77.22.Ej Polarization and depolarization
77.65.-j Piezoelectricity and electromechanical effects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity

Pairing of cation vacancies and gap-state creation in TiO2 and HfO2

Hyo-Shin Ahn, Seungwu Han, and Cheol Seong Hwang

Appl. Phys. Lett. 90, 252908 (2007); http://dx.doi.org/10.1063/1.2749858 (3 pages) | Cited 3 times

Online Publication Date: 21 June 2007

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Based on the first-principles calculations, the authors study defect-defect interactions between cation vacancies in rutile TiO2 and monoclinic HfO2. It is found that vacancies are greatly stabilized at small separations because of a large reconstruction of nearby oxygen atoms that have two broken bonds. As a result, O–O bonds resembling O2 or O3 molecules are formed near the divacancy site. The defect levels originated from antibonding states of O p orbitals are identified within the energy gap, which can affect leakage currents and the density of trapped charges of oxides substantially.
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61.72.J- Point defects and defect clusters
71.55.Ht Other nonmetals

Magnitude of the intrinsic electrocaloric effect in ferroelectric perovskite thin films at high electric fields

G. Akcay, S. P. Alpay, J. V. Mantese, and G. A. Rossetti, Jr.

Appl. Phys. Lett. 90, 252909 (2007); http://dx.doi.org/10.1063/1.2750546 (3 pages) | Cited 53 times

Online Publication Date: 22 June 2007

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Monodomain contributions to the electrocaloric effect in mechanically free (bulk) and laterally clamped (thin film) BaTiO3 are computed using a thermodynamic analysis. The authors show that the intrinsic electrocaloric coefficient at electric fields sufficient to destroy the discontinuous ferroelectric phase transition results in an adiabatic temperature change of 8 K that agrees closely with the giant value of 12 K recently observed experimentally for lead zirconate titanate thin films [ A. S. Mischenko et al., Science 311, 1270 (2006) ]. Perfect lateral clamping transforms the discontinuous transition into a continuous transition, which decreases the magnitude of the electrocaloric effect by 20% but reduces its sensitivity to temperature.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.70.+a Pyroelectric and electrocaloric effects
77.80.B- Phase transitions and Curie point

Phase diagrams of single-domain ferroelectric-dielectric superlattices

F. A. Urtiev, V. G. Kukhar, and N. A. Pertsev

Appl. Phys. Lett. 90, 252910 (2007); http://dx.doi.org/10.1063/1.2751134 (3 pages) | Cited 13 times

Online Publication Date: 22 June 2007

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Using the thermodynamic theory, the authors developed misfit strain-temperature phase diagrams of single-domain ferroelectric-dielectric superlattices grown on cubic substrates. Owing to internal electric fields appearing in such multilayers, the superlattice diagrams are expected to be very different from phase maps of homogeneous ferroelectric films. The calculations show, however, that this electrostatic effect does not change relative positions of phase transition lines. It only shifts the diagram as a whole along the line separating stability ranges of paraelectric phase and in-plane polarization state. The magnitude of this shift is governed by the capacitance of dielectric layer and the thickness of ferroelectric one.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.30.Dz Phase diagrams of other materials
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ej Polarization and depolarization
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