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28 Apr 2008

Volume 92, Issue 17, Articles (17xxxx)

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Appl. Phys. Lett. 92, 173301 (2008); http://dx.doi.org/10.1063/1.2912822 (3 pages)

Takeo Minari, Masataka Kano, Tetsuhiko Miyadera, Sui-Dong Wang, Yoshinobu Aoyagi, Mari Seto, Takashi Nemoto, Seiji Isoda, and Kazuhito Tsukagoshi
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Re-entrant type relaxor behavior in (1−x)BaTiO3–xBiScO3 solid solution

Hai Yan Guo, Chao Lei, and Zuo-Guang Ye

Appl. Phys. Lett. 92, 172901 (2008); http://dx.doi.org/10.1063/1.2913208 (3 pages) | Cited 10 times

Online Publication Date: 28 April 2008

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The solid solution of (1−x)BaTiO3–xBiScO3 was synthesized by solid state reaction and its dielectric properties were studied by impedance spectroscopy. A dielectric anomaly was found in the temperature ranges of −30–13 °C and −60–20 °C for 0.95BaTiO3–0.05BiScO3 and 0.90BaTiO3–0.10BiScO3, respectively. The frequency dependence of the anomaly exhibits dielectric relaxation satisfying the Vogel–Fulcher law, indicating relaxorlike behavior. The relaxor state in the (1−x)BaTiO3–xBiScO3 solid solution occurs after the ferroelectric phase transition upon cooling, indicating a re-entering phenomenon. Piezoresponse force microscopic studies show that the domain wall density decreases with the addition of BiScO3. The substitution of BiScO3 also results in some no-phase-contrast areas in the domain structure image, which grow with the increasing BiScO3 amount. Decent piezoelectric hysteresis loops were obtained in these areas. The correlation between the peculiar domain structure and relaxor behavior suggests that the no-phase-contrast areas are characteristics of the domain structure of the re-entering relaxor system.
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77.80.B- Phase transitions and Curie point
77.22.Gm Dielectric loss and relaxation
77.80.Dj Domain structure; hysteresis
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Polarization switching kinetics at the nanoscale in ferroelectric copolymer Langmuir–Blodgett films

R. V. Gaynutdinov, O. A. Lysova, A. L. Tolstikhina, S. G. Yudin, V. M. Fridkin, and Stephen Ducharme

Appl. Phys. Lett. 92, 172902 (2008); http://dx.doi.org/10.1063/1.2916707 (3 pages) | Cited 16 times

Online Publication Date: 28 April 2008

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The polarization switching kinetics of ferroelectric Langmuir–Blodgett films of vinylidene fluoride-trifluoroethylene copolymer were investigated by piezoresponse force microscopy with a resolution of 100 nm. The switching time in response to a localized voltage pulse exhibits an exponential dependence on reciprocal voltage, which is consistent with nucleation-limited switching dynamics.
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82.35.Jk Copolymers, phase transitions, structure
68.55.am Polymers and organics
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials

Dielectric constant boost in amorphous sesquioxides

Pietro Delugas, Vincenzo Fiorentini, and Alessio Filippetti

Appl. Phys. Lett. 92, 172903 (2008); http://dx.doi.org/10.1063/1.2917797 (3 pages) | Cited 6 times

Online Publication Date: 28 April 2008

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High-κ dielectrics for insulating layers are a current key ingredient of microelectronics. X2O3 sesquioxide compounds are among the candidates. Here, we show for a typical material of this class, Sc2O3, that the relatively modest dielectric constant of its crystalline phase is enhanced in the amorphous phase by over 40% (from ∼ 15 to ∼ 22). This is due to the disorder-induced activation of low frequency cation-related modes which are inactive or inefficient in the crystal and by the conservation of effective dynamical charges (a measure of atomic polarizability). The analysis employs density-functional energy-force and perturbation-theory calculations of the dielectric response of amorphous samples generated by pair-potential molecular dynamics.
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77.22.Ch Permittivity (dielectric function)

1 nm equivalent oxide thickness in Ga2O3(Gd2O3)/In0.2Ga0.8As metal-oxide-semiconductor capacitors

K. H. Shiu, T. H. Chiang, P. Chang, L. T. Tung, M. Hong, J. Kwo, and W. Tsai

Appl. Phys. Lett. 92, 172904 (2008); http://dx.doi.org/10.1063/1.2918835 (3 pages) | Cited 17 times

Online Publication Date: 30 April 2008

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An equivalent oxide thickness about 1 nm for Ga2O3(Gd2O3) (GGO) on In0.2Ga0.8As has been achieved by employing a thin in situ deposited 3 nm thick Al2O3 protection layer. The dual gate oxide stacks of the Al2O3/GGO (33, 20, 10, 8.5, and 4.5 nm)/In0.2Ga0.8As/GaAs metal-oxide-semiconductor (MOS) capacitors remain amorphous after rapid thermal annealing up to 800–850 °C, accompanied with atomically sharp smooth oxide/semiconductor interfaces. Well behaved capacitance-voltage (C-V) curves of the MOS diodes have shown sharp transition from depletion to accumulation with small flatband voltage (1.1 V for Au metal gate and 0.1 V for Al), and weak frequency dispersion (1.5%–5.4%) between 10 and 500 kHz at accumulation capacitance. Low leakage current densities [3.1×10−5 and 2.5×10−9 A/cm2 at V = Vfb+1 V for Al2O3(3 nm)/GGO(4.5 and 8.5 nm)], a high dielectric constant around 14–16 of GGO for all tested thicknesses, and a low interfacial density of states (Dit) in the low 1011 cm−2 eV−1 have also been accomplished.
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85.30.Kk Junction diodes
84.32.Tt Capacitors

Piezoelectric properties of lithium modified silver niobate perovskite single crystals

Desheng Fu, Makoto Endo, Hiroki Taniguchi, Tomoyasu Taniyama, Shin-ya Koshihara, and Mitsuru Itoh

Appl. Phys. Lett. 92, 172905 (2008); http://dx.doi.org/10.1063/1.2918837 (3 pages) | Cited 13 times

Online Publication Date: 30 April 2008

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We report the growth and the piezoelectric properties of lead-free perovskite single crystals of Ag1−xLixNbO3. It possesses a rhombohedral structure with high ferroelectric phase transition (Tc = 548 K for x = 0.086) and large spontaneous polarization (Ps ∼ 40 μC/cm2 for x = 0.062) along the 〈111〉c direction of pseudocubic perovskite structure for x>0.05–0.06. High quasistatic d33 ∼ 210 pC/N and low dielectric constant have lead to a very large value of piezoelectric voltage constant g33 ∼ 53.9×10−3 Vm/N for the 〈001〉c-cut crystal of this simple perovskite. It has been shown that Li substitution might enhance the piezoelectric coefficient of the crystal. The excellent piezo-/ferroelectricity of this system are considered to be facilitated by the strong polarization nature of both Ag and Li in the perovskite structure. Our findings may stimulate further interests in the development of lead-free piezoelectrics.
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77.65.Bn Piezoelectric and electrostrictive constants
77.80.B- Phase transitions and Curie point
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization

GeOx interface layer reduction upon Al-gate deposition on a HfO2/GeOx/Ge(001) stack

Sylvie Rangan, Eric Bersch, Robert Allen Bartynski, Eric Garfunkel, and Elio Vescovo

Appl. Phys. Lett. 92, 172906 (2008); http://dx.doi.org/10.1063/1.2917480 (3 pages) | Cited 5 times

Online Publication Date: 30 April 2008

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The metallization of HfO2/Ge by Al at room temperature was studied using photoemission and inverse photoemission. Upon deposition, Al reduces the GeOx interfacial layer between Ge and HfO2, and a thin Al2O3 layer is formed at the Al/HfO2 interface. The band alignment across the Al/HfO2/Ge stacks is also addressed.
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79.60.Jv Interfaces; heterostructures; nanostructures
78.70.-g Interactions of particles and radiation with matter
77.55.-g Dielectric thin films
73.20.At Surface states, band structure, electron density of states
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Choosing the best geometries for the linear characterization of lossy piezoceramics: Study of the thickness-poled shear plate

L. Pardo, F. Montero de Espinosa, A. García, and K. Brebøl

Appl. Phys. Lett. 92, 172907 (2008); http://dx.doi.org/10.1063/1.2911731 (3 pages)

Online Publication Date: 1 May 2008

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Resonance modes of a thickness-poled piezoceramic shear plate are studied. When determining material properties from impedance measurements, it is required to obtain an uncoupled shear resonance. The shear resonance, which is electrically excited, results to a series of plate resonances, which is mechanically excited by this, when frequencies match. Thus, the condition of a high aspect ratio of the plate is not valid to eliminate coupling. Instead, the thickness (t) and lateral dimensions (L,w) of the plate must be tailored for each material. This approach was tested for a commercial piezoceramic and plates amenable for characterization obtained for aspect ratios below L:t = 15:1 (L = w).
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Theory of small-signal ac response of a dielectric liquid containing two groups of ions

G. Barbero, F. Batalioto, and A. M. Figueiredo Neto

Appl. Phys. Lett. 92, 172908 (2008); http://dx.doi.org/10.1063/1.2908044 (3 pages) | Cited 4 times

Online Publication Date: 1 May 2008

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The analysis of Macdonald for electrolytes is generalized to the case in which two groups of ions are present. We assume that the electrolyte can be considered as a dispersion of ions in a dielectric liquid, and that the ionic recombination can be neglected. We present the differential equations governing the ionic redistribution when the liquid is subjected to an external electric field, describing the simultaneous diffusion of the two groups of ions in the presence of their own space charge fields. We investigate the influence of the ions on the impedance spectroscopy of an electrolytic cell. In the analysis, we assume that each group of ions have equal mobility, the electrodes perfectly block and that the adsorption phenomena can be neglected. In this framework, it is shown that the real part of the electrical impedance of the cell has a frequency dependence presenting two plateaux, related to a type of ambipolar and free diffusion coefficients. The importance of the considered problem on the ionic characterization performed by means of the impedance spectroscopy technique was discussed.
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77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
66.10.C- Diffusion and thermal diffusion
66.10.Ed Ionic conduction
82.45.Gj Electrolytes
82.45.Fk Electrodes
77.22.Jp Dielectric breakdown and space-charge effects

Chemical nature of colossal dielectric constant of CaCu3Ti4O12 thin film by pulsed laser deposition

Guochu Deng, Nicolas Xanthopoulos, and Paul Muralt

Appl. Phys. Lett. 92, 172909 (2008); http://dx.doi.org/10.1063/1.2919076 (3 pages) | Cited 19 times

Online Publication Date: 1 May 2008

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Epitaxial CaCu3Ti4O12 thin films grown by pulsed laser deposition were studied in the as-deposited and oxygen annealed state. The first one exhibited the usual transition from dielectric to colossal dielectric behavior upon increasing the temperature to above 100 K. This transition disappeared after annealing at 900 °C in air. The two states significantly differ in their x-ray photoelectron spectra. The state of colossal dielectric constant corresponds to a bulk material with considerable amounts of Cu+ and Ti3+, combined with Cu species enrichment at the surface. The annealed state exhibited a nearly stoichiometric composition with no Cu+ and Ti3+. The previously observed p-type conduction in the as-deposited state is thus related to oxygen vacancies compensated by the point defects of Cu+ and Ti3+.
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77.22.Ch Permittivity (dielectric function)
81.15.Fg Pulsed laser ablation deposition
79.60.Dp Adsorbed layers and thin films
81.40.Gh Other heat and thermomechanical treatments
61.72.jd Vacancies
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Growth evolution and decay properties of the abnormally switched domains in LiNbO3 crystals

Yi Kan, Huifeng Bo, Xiaomei Lu, Wei Cai, Yunfei Liu, and Jinsong Zhu

Appl. Phys. Lett. 92, 172910 (2008); http://dx.doi.org/10.1063/1.2919733 (3 pages) | Cited 5 times

Online Publication Date: 1 May 2008

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Direct domain writing is carried out in single-crystalline stoichiometric LiNbO3 crystals using a scanning probe microscope. The abnormally switched domains with polarization antiparallel to the poling field are observed, and their growth and decay processes are systematically studied. The radius of these domains is proportional to the pulse magnitude while it remains constant as the pulse width varies. These abnormal domains quickly decay, the lifetime of which is linear with the poling pulse magnitude while it stretched exponentially increases with the increasing pulse width. The experimental results are carefully discussed in relation to the reported charge injection model.
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77.80.Dj Domain structure; hysteresis
77.80.Fm Switching phenomena
68.37.Ps Atomic force microscopy (AFM)

Local structural view on the polarization rotation in relaxor ferroelectric (1−x)Pb(Zn1/3Nb2/3)O3–xPbTiO3

I.-K. Jeong, J. K. Lee, and R. H. Heffner

Appl. Phys. Lett. 92, 172911 (2008); http://dx.doi.org/10.1063/1.2919070 (3 pages) | Cited 10 times

Online Publication Date: 2 May 2008

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We performed comprehensive structural studies on local ionic displacements and medium-range ordering across a series of phase transitions in (1−x)Pb(Zn1/3Nb2/3)O3–xPbTiO3 (PZN-xPT) at 15 K by using neutron pair-distribution-function (PDF) and Rietveld analyses. PDF spectra clearly demonstrate that all phases of PZN-xPT have nearly identical ionic pair correlations on a length scale of ξ ∼ 15 Å. At longer pair distances, however, PZN-xPT exhibits different pair correlations. This local- and medium-range structural information provides direct evidence that local polarizations do not rotate with long-range phase transitions, and an order-disorder type ordering of polar nanoregions determines the long-range polarization rotations in PZN-xPT.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ej Polarization and depolarization
64.70.K- Solid-solid transitions

Ru doping induced quantum paraelectricity in ferroelectric Sr0.9Ba0.1TiO3

T. Wei, Y. J. Guo, P. W. Wang, D. P. Yu, K. F. Wang, C. L. Lu, and J.-M. Liu

Appl. Phys. Lett. 92, 172912 (2008); http://dx.doi.org/10.1063/1.2913017 (3 pages) | Cited 4 times

Online Publication Date: 2 May 2008

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We investigate the effect of Ru doping on the dielectric and ferroelectric behaviors of polycrystalline Sr0.9Ba0.1TiO3. It is observed that the Ru doping significantly suppresses the ferroelectric mode, as evidenced by the Raman spectroscopy at various temperatures. The enhanced quantum fluctuation associated with the incorporation of Ru4+ at B site is demonstrated, which transforms Sr0.9Ba0.1TiO3 from the ferroelectric state into a typical quantum paraelectric state.
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77.80.B- Phase transitions and Curie point
61.72.up Other materials
78.30.Hv Other nonmetallic inorganics
77.22.Ch Permittivity (dielectric function)
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