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5 May 2008

Volume 92, Issue 18, Articles (18xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 92, 182104 (2008); http://dx.doi.org/10.1063/1.2917705 (3 pages)

Jiang Chen, Yibin Hu, Ke Xia, and Zhongshui Ma
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Anomalous photocurrent in self-assembled InAs/GaAs quantum dots

A. F. G. Monte, Fanyao Qu, and M. Hopkinson

Appl. Phys. Lett. 92, 182102 (2008); http://dx.doi.org/10.1063/1.2920763 (3 pages) | Cited 1 time

Online Publication Date: 5 May 2008

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Carrier dynamics in self-assembled InAs/GaAs quantum dots (QDs) is studied by photoluminescence (PL) and its complementary photocurrent (PC) spectroscopy. We found that carrier capture from the GaAs barriers, radiative recombination in InAs quantum dots, and tunneling among vertical QDs are very sensitive to applied bias voltage. An unusual behavior, by which the PL intensity presents steplike bias voltage dependence, has been observed. It is also consistently manifested in bias voltage dependent PC signals. We attribute this anomalous behavior to the interplay between the coupling of lateral QDs and tunneling among vertical ones.
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73.63.Kv Quantum dots
73.40.Gk Tunneling
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
72.40.+w Photoconduction and photovoltaic effects
81.16.Dn Self-assembly

Current-induced magnetization excitation in a pseudo-spin-valve with in-plane anisotropy

Jie Guo, Mansoor Bin Abdul Jalil, and Seng Ghee Tan

Appl. Phys. Lett. 92, 182103 (2008); http://dx.doi.org/10.1063/1.2919734 (3 pages) | Cited 2 times

Online Publication Date: 6 May 2008

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We study the magnetization dynamics of a pseudo-spin-valve structure with in-plane anisotropy, which is induced by the passage of a perpendicular-to-plane spin-polarized current. The magnetization dynamics is described by a modified Landau–Lifshitz–Gilbert (LLG) equation, which incorporates two spin torque terms. The simulation results reveal two magnetization excitation modes: (a) complete magnetization reversal and (b) persistent spin precession. The existence of these dual modes may be explained in terms of the competition between the four terms of the modified LLG equation. Our results give indications to the optimal operating conditions for current-induced magnetization dynamics for possible device applications.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
75.40.Mg Numerical simulation studies
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.47.-m Magnetotransport phenomena; materials for magnetotransport

Achievement of sensing single spin with the aid of Kondo resonance in quantum dot connected to ferromagnetic electrodes

Jiang Chen, Yibin Hu, Ke Xia, and Zhongshui Ma

Appl. Phys. Lett. 92, 182104 (2008); http://dx.doi.org/10.1063/1.2917705 (3 pages)

Online Publication Date: 7 May 2008

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We theoretically propose the detection of spin states of magnetic atom or molecule in proximity to a quantum dot by the Kondo effect with ferromagnetic electrodes, which can be switched in parallel or antiparallel alignments. The relative orientation of spin to the magnetization of electrode can be evidentially tracked from the spin splitting in Kondo peak of differential conductance. The experimental realization is discussed.
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75.30.Mb Valence fluctuation, Kondo lattice, and heavy-fermion phenomena
75.50.-y Studies of specific magnetic materials
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.25.-b Spin polarized transport
73.21.La Quantum dots

Enhanced Seebeck coefficient in EuTe/PbTe [100] short-period superlattices

Akihiro Ishida, Daoshe Cao, Sinsuke Morioka, Martin Veis, Yoku Inoue, and Takuji Kita

Appl. Phys. Lett. 92, 182105 (2008); http://dx.doi.org/10.1063/1.2917482 (3 pages) | Cited 9 times

Online Publication Date: 9 May 2008

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Theoretical and experimental studies on Seebeck effect in EuTe/PbTe superlattices were performed. Theoretical calculations, which take into account temperature dependent band gap, nonparabolicity, and anisotropy of effective masses in the PbTe conduction band, were performed in the framework of Boltzmann equation in which enhancement of Seebeck coefficient in EuTe/PbTe short-period superlattices grown in [100] direction was predicted. The EuTe/PbTe short-period superlattices with few monolayers EuTe were prepared on KCl (100) substrate and an enhanced Seebeck coefficient was observed in these superlattices as expected by theoretical calculations.
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72.20.Pa Thermoelectric and thermomagnetic effects
73.63.Hs Quantum wells
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.21.Cd Superlattices

Stress-induced morphology and fine-line stability enhancement of NiSi on poly-SiGe with a buffer polycrystalline silicon interlayer

Chi-Chang Wu, Wen-Fa Wu, Fu-Hsiang Ko, Hsin-Chiang You, and Wen-Luh Yang

Appl. Phys. Lett. 92, 182106 (2008); http://dx.doi.org/10.1063/1.2920202 (3 pages)

Online Publication Date: 9 May 2008

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The thermal and morphological stability of NiSi is enhanced by inserting a polycrystalline (poly-Si) buffer layer between the Ni and poly-SiGe films. NiSi films formed on poly-Si/poly-SiGe stack layers possessed continuous, smooth structures after annealing at 500–850 °C. Moreover, nickel germanosilicide [Ni(Si, Ge)] lines formed on the poly-SiGe exhibited a fine-line effect, i.e., the sheet resistance increased upon decreasing the linewidth, whereas the sheet resistance of NiSi lines formed on the poly-Si/poly-SiGe stack layers remained less than 5 Ω/square. A model for the stress-confined grain growth and recrystallization is proposed to explain the improved properties of the poly-Si-buffered film.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.Cc Kinetics of defect formation and annealing
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

A visible light-sensitive tungsten carbide/tungsten trioxde composite photocatalyst

Young-ho Kim, Hiroshi Irie, and Kazuhito Hashimoto

Appl. Phys. Lett. 92, 182107 (2008); http://dx.doi.org/10.1063/1.2924276 (3 pages) | Cited 10 times

Online Publication Date: 9 May 2008

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A photocatalyst composed of tungsten carbide (WC) and tungsten oxide (WO3) has been prepared by the mechanical mixing of each powder. Its photocatalytic activity was evaluated by the gaseous isopropyl alcohol decomposition process. The photocatalyst showed high visible light photocatalytic activity with a quantum efficiency of 3.2% for 400–530 nm light. The photocatalytic mechanism was explained by means of enhanced oxygen reduction reaction due to WC, which may serve as a multielectron reduction catalyst, as well as the photogeneration of holes in the valence band of WO3.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.50.Hp Processes caused by visible and UV light
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Giant carrier mobility in single crystals of FeSb2

Rongwei Hu, V. F. Mitrović, and C. Petrovic

Appl. Phys. Lett. 92, 182108 (2008); http://dx.doi.org/10.1063/1.2926662 (3 pages) | Cited 18 times

Online Publication Date: 9 May 2008

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We report the giant carrier mobility in single crystals of FeSb2. Nonlinear field dependence of Hall resistivity is well described with the two-carrier model. Maximum mobility values in high mobility band reach ∼ 105 cm2/V s at 8 K and are ∼ 102 cm2/V s at the room temperature. Our results point to a class of materials with promising potential for applications in solid state electronics.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.80.Jc Other crystalline inorganic semiconductors
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Pp Magnetic semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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Photoelectric response of Schottky barrier in La0.7Ca0.3MnO3/Nb:SrTiO3 heterojunctions

Z. Luo, J. Gao, A. B. Djurišić, C. T. Yip, and G. B. Zhang

Appl. Phys. Lett. 92, 182501 (2008); http://dx.doi.org/10.1063/1.2920765 (3 pages) | Cited 14 times

Online Publication Date: 6 May 2008

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Heterojunctions composed of La0.7Ca0.3MnO3 and 0.05 wt % Nb-doped SrTiO3 were fabricated using pulse laser deposition. The current-voltage characteristics of such heterojunctions can be described by tunneling with an effective Schottky barrier. These junctions showed significant response to ultraviolet and visible light. Band-to-band and internal photoemission were characterized by photoelectric experiments. A quantum efficiency of about 86% was observed at an incident energy of ∼ 3.95 eV, which corresponds to the band-to-band excitation of electrons in Nb:SrTiO3. From the internal photoemission, the height of Schottky barrier was determined as 1.64 eV.
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72.40.+w Photoconduction and photovoltaic effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling
78.55.Hx Other solid inorganic materials
81.15.Fg Pulsed laser ablation deposition

Antiferromagnetic interlayer exchange coupling between Fe3O4 layers across a nonmagnetic MgO dielectric layer

Han-Chun Wu, S. K. Arora, O. N. Mryasov, and I. V. Shvets

Appl. Phys. Lett. 92, 182502 (2008); http://dx.doi.org/10.1063/1.2919081 (3 pages) | Cited 14 times

Online Publication Date: 7 May 2008

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We have investigated the interlayer exchange coupling between the epitaxial spinel Fe3O4 layers across an insulating nonmagnetic MgO spacer. The epitaxial structure used for these investigations was Fe3O4 (10 nm)/MgO (0.8–3 nm)/Fe3O4 (10 nm)/NiO (15 nm) multilayers grown on MgO (100) substrates. We find that the two Fe3O4 layers are antiferromagnetic coupled through the MgO spacer when the MgO thickness is less than 1.5 nm. Furthermore, ab initio calculation of IEC for Fe/MgO/Fe indicates the importance of electrode states, in particular, partial oxidation of the ferromagnetic electrodes.
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75.30.Et Exchange and superexchange interactions
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
71.15.-m Methods of electronic structure calculations
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Ee Antiferromagnetics

Magnetic coupling between rare-earth and iron atoms in the La1−xRxFe11.5Si1.5 (R = Ce, Pr, and Nd) intermetallics

L. Jia, J. R. Sun, J. Shen, Q. Y. Dong, F. X. Hu, T. Y. Zhao, and B. G. Shen

Appl. Phys. Lett. 92, 182503 (2008); http://dx.doi.org/10.1063/1.2921781 (3 pages) | Cited 7 times

Online Publication Date: 7 May 2008

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A systematic investigation on the effect of R doping, particularly the magnetic coupling between R and Fe, has been performed for the La1−xRxFe11.5Si1.5 intermetallics (R = Ce, Pr, and Nd). A magnetic interaction comparable to that between Fe atoms is found between the R and Fe atoms, which causes an enhancement of the Curie temperature up to ∼ 11% when ∼ 30% of the La atoms are replaced by R. The R–Fe coupling is further found to be strongly dependent of the species of the rare earths. It monotonically grows as R sweeps from Ce to Nd. This could be a consequence of the lanthanide contraction, which causes an enhancement of the intra-atomic magnetic coupling.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
61.72.up Other materials

An easy mechanical way to create ferromagnetic defective ZnO

K. Potzger, Shengqiang Zhou, J. Grenzer, M. Helm, and J. Fassbender

Appl. Phys. Lett. 92, 182504 (2008); http://dx.doi.org/10.1063/1.2921782 (3 pages) | Cited 25 times

Online Publication Date: 7 May 2008

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We present an experiment for the creation of unconventional ferromagnetism in pure ZnO powder by application of mechanical force. The ferromagnetism is related to flakelike structures in planar compressed pieces of the powder with easy axis in the plane. It is associated with defect creation and disappears upon annealing in oxygen. Besides cluster formation, such defects might be one of the nonintrinsic origins of ferromagnetism in transition metal doped ZnO.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
61.72.J- Point defects and defect clusters

Room-temperature-photoinduced magnetism and spin-electronic functions of spinel ferrite with a spin-cluster structure

Teruo Kanki, Yasushi Hotta, Naoki Asakawa, Munetoshi Seki, Hitoshi Tabata, and Tomoji Kawai

Appl. Phys. Lett. 92, 182505 (2008); http://dx.doi.org/10.1063/1.2896609 (3 pages) | Cited 1 time

Online Publication Date: 8 May 2008

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Room-temperature-photoinduced magnetization (PIM) was observed in spinel ferrite Al0.2Ru0.8Fe2O4 thin films with a spin-cluster-glass structure. Additionally, the films exhibited significant properties as spintronic materials, showing a low saturation magnetization under 0.6μB/unit cell and good conductivity with a high spin polarized electron level of over 75%. A combination of high-temperature PIM and the electronic properties associated with spintronics would generate an area of research and development that utilize the degrees of freedom offered by optical systems in the field of spintronics.
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68.55.-a Thin film structure and morphology
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
61.43.Fs Glasses

Large magnetocaloric effect in Sm0.52Sr0.48MnO3 in low magnetic field

P. Sarkar, P. Mandal, and P. Choudhury

Appl. Phys. Lett. 92, 182506 (2008); http://dx.doi.org/10.1063/1.2919732 (3 pages) | Cited 15 times

Online Publication Date: 8 May 2008

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This letter reports on the magnetocaloric properties of Sm0.52Sr0.48MnO3 single crystal. A magnetic field of only 1 T yields a change in the magnetic entropy by 5.9 J/(kg K) at TC ( = 124 K), which is higher than those observed in several other perovskite manganites and rare earth alloys of comparable TC. This change originates from a sharp magnetization jump, associated with a first-order metamagnetic transition. Such a large change in entropy at a low magnetic field makes this material useful for magnetic refrigeration.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Abnormal phase transition and magnetic properties in Cu, Fe co-doped In2O3 nanocrystals

Dewei Chu, Yu-Ping Zeng, and Dongliang Jiang

Appl. Phys. Lett. 92, 182507 (2008); http://dx.doi.org/10.1063/1.2920818 (3 pages) | Cited 8 times

Online Publication Date: 8 May 2008

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Fe, Cu co-doped In2O3 nanocrystals were synthesized by a coprecipitation method. Phase analyses revealed that Fe ions have high solubility (up to 15.4 at. %) in the In2O3 matrix, while the Cu ions strongly restrain In2O3 phase transition from cubic to hexagonal. Raman spectroscopy shows that by adding Cu ions, the defect concentration increases. The samples show no evidence of ferromagnetism by additional Cu doping, indicating that Cu content might be a key point to realize room temperature ferromagnetism in Fe doped In2O3.
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64.70.Nd Structural transitions in nanoscale materials
81.07.Bc Nanocrystalline materials
81.30.Dz Phase diagrams of other materials
81.30.Mh Solid-phase precipitation
61.72.up Other materials
75.50.Dd Nonmetallic ferromagnetic materials

Characterization of strain-induced martensite phase in austenitic stainless steel using a magnetic minor-loop scaling relation

Satoru Kobayashi, Atsushi Saito, Seiki Takahashi, Yasuhiro Kamada, and Hiroaki Kikuchi

Appl. Phys. Lett. 92, 182508 (2008); http://dx.doi.org/10.1063/1.2924305 (3 pages) | Cited 4 times

Online Publication Date: 8 May 2008

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We propose a combined magnetic method using a scaling power-law rule and initial permeability in magnetic minor hysteresis loops for characterization of ferromagnetic α′ martensites in austenitic stainless steel. The scaling power law between the hysteresis loss and remanence is universal, being independent of volume fraction of strain-induced α′ martensites. A coefficient of the power law largely decreases with volume fraction, while the initial permeability linearly increases, reflecting a change in the morphology and quantity of martensites, respectively. The present method is highly effective for integrity assessment of austenitic stainless steels because of the sensitivity and extremely low measurement field.
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81.05.Bx Metals, semimetals, and alloys
81.30.Kf Martensitic transformations
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
64.70.kd Metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetism and clustering in Cu doped ZnO

Dan Huang, Yu-Jun Zhao, Di-Hu Chen, and Yuan-Zhi Shao

Appl. Phys. Lett. 92, 182509 (2008); http://dx.doi.org/10.1063/1.2920572 (3 pages) | Cited 22 times

Online Publication Date: 9 May 2008

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The influence of defect charge state on the magnetism of Cu doped ZnO as well as the Cu defects clustering have been investigated by the first-principles calculations. We demonstrate that p-type ZnO:Cu could have ferromagnetic (FM) property, but n-type ZnO:Cu would not have local magnetic moment. Furthermore, the neutral substitutive Cu defects are found to be favorable in clustering, which maintains the FM ordering.
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75.20.Hr Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions
71.55.Gs II-VI semiconductors
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials

Hydrostatic pressure effect on archetypal Sm0.52Sr0.48MnO3 single crystal

K. Mydeen, P. Sarkar, P. Mandal, A. Murugeswari, C. Q. Jin, and S. Arumugam

Appl. Phys. Lett. 92, 182510 (2008); http://dx.doi.org/10.1063/1.2920762 (3 pages) | Cited 10 times

Online Publication Date: 9 May 2008

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The effect of hydrostatic pressure (P) on the c-axis electrical resistivity (ρc) and ferromagnetic (FM) transition temperature (TC) of Sm0.52Sr0.48MnO3 single crystal has been investigated. At P = 0, the strong hysteretic nature of metal-insulator transition (MIT) and the abrupt decrease of ρc by several orders just below TC suggest that the FM transition is discontinuous in nature. The application of pressure strongly decreases ρc, shifts MIT to higher temperature at the rate of 19 K/GPa, and suppresses the hysteresis width. The nature of the FM phase transition would change from discontinuous to continuous at around P = 2.5 GPa.
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62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
72.60.+g Mixed conductivity and conductivity transitions
75.50.Dd Nonmetallic ferromagnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

The crossover from the vortex glass to the Bose glass in nanostructured YBa2Cu3O7−x films

Tomoya Horide, Kaname Matsumoto, Paolo Mele, Ataru Ichinose, Ryusuke Kita, Masashi Mukaida, Yutaka Yoshida, and Shigeru Horii

Appl. Phys. Lett. 92, 182511 (2008); http://dx.doi.org/10.1063/1.2924770 (3 pages) | Cited 8 times

Online Publication Date: 9 May 2008

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The glass-liquid transitions of quantized vortices were studied to understand the vortex behavior in YBa2Cu3O7−x films. We systematically controlled the pinning strength, spatial distribution, and shape of disorders by engineering of nanoinclusions in YBa2Cu3O7−x films. In these disorder systems, we observed the crossover between the vortex glass (VG) and the Bose glass (BG). The increase in pinning strength and ordering of isotropic disorders do not change the critical exponents and the conversion between the BG and the VG is triggered only by the anisotropy of pinning centers.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
64.70.D- Solid-liquid transitions
64.70.P- Glass transitions of specific systems
74.78.Na Mesoscopic and nanoscale systems
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Low strain sensitivity of the dielectric property of pyrochlore Bi–Zn–Nb–O films

Hiroshi Funakubo, Shingo Okaura, Muneyasu Suzuki, Hiroshi Uchida, Seiichiro Koda, Rikyu Ikariyama, and Tomoaki Yamada

Appl. Phys. Lett. 92, 182901 (2008); http://dx.doi.org/10.1063/1.2919723 (3 pages) | Cited 5 times

Online Publication Date: 5 May 2008

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Thermal strain sensitivity of the dielectric property was investigated for (111)-textured polycrystalline Bi–Zn–Nb–O films. Cubic pyrochlore films with similar crystallinity and the degree of the orientation were obtained on various substrates, and their 111 lattice spacing monotonously increased with the increasing thermal expansion coefficient of the substrates. The dielectric constant at 0 kV/cm and its tunability were almost independent of the residual strain, unlike highly sensitive (Ba0.5Sr0.5)TiO3 films. This strain independent characteristic of the dielectric property of pyrochlore Bi–Zn–Nb–O film is a big advantage in actual applications.
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77.22.Ch Permittivity (dielectric function)
65.40.De Thermal expansion; thermomechanical effects

Strain effects and thickness dependence of ferroelectric properties in epitaxial BiFeO3 thin films

Hua Ma, Lang Chen, Junling Wang, J. Ma, and F. Boey

Appl. Phys. Lett. 92, 182902 (2008); http://dx.doi.org/10.1063/1.2920192 (3 pages) | Cited 14 times

Online Publication Date: 6 May 2008

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A “misfit strain-temperature” phase diagram for BiFeO3 thin film was constructed based on the Landau–Devonshire theory with the mechanical substrate effect. It is found that the polarization instabilities result in the formation of the monoclinic phases in BiFeO3 thin films. The effective substrate lattice parameter has been introduced to calculate the film thickness dependence of the polarization and the dielectric constants. The theoretical results are in agreement with the experimental data for the thickness dependence of ferroelectric properties of the BiFeO3 epitaxial thin films on SrTiO3 and Si substrates.
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77.65.Ly Strain-induced piezoelectric fields
77.80.B- Phase transitions and Curie point
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films

Room temperature giant dielectric tunability effect in bulk LuFe2O4

Chang-Hui Li, Xiang-Qun Zhang, Zhao-Hua Cheng, and Young Sun

Appl. Phys. Lett. 92, 182903 (2008); http://dx.doi.org/10.1063/1.2920775 (3 pages) | Cited 26 times

Online Publication Date: 6 May 2008

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We report the extreme sensitivity of dielectric permittivity to applied dc bias electric field in bulk LuFe2O4. A small bias field of 50 V/cm can greatly reduce the dielectric permittivity in the vicinity of room temperature, which is in strong contrast to conventional ferroelectric materials where a large electric field of the order of tens of kV/cm is required. This giant dielectric tunability effect within a broad temperature interval around room temperature is very promising for tunable device applications. The possible origins of this giant effect are discussed.
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77.22.Ch Permittivity (dielectric function)

A method to measure the electric charge injected/extracted at the metal-dielectric interface

Eugen R. Neagu

Appl. Phys. Lett. 92, 182904 (2008); http://dx.doi.org/10.1063/1.2909658 (3 pages)

Online Publication Date: 7 May 2008

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A method was proposed to determine the sign and the value of the electric charge injected/extracted at the metal-dielectric interface. The method is based on the modification of the external electric field of a dielectric when electric charge is injected/extracted onto its surface. The lowest surface charge density measured in the presented experiments was around 1.8×10−6 C m−2. The method is insensitive to the orientational polarization. The charge carriers injection/extraction process takes place no matter if there is a conduction current through the sample.
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73.40.Ns Metal-nonmetal contacts
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Giant strain in lead-free (Bi0.5Na0.5)TiO3-based single crystals

Shunsuke Teranishi, Muneyasu Suzuki, Yuji Noguchi, Masaru Miyayama, Chikako Moriyoshi, Yoshihiro Kuroiwa, Katsunori Tawa, and Shigeo Mori

Appl. Phys. Lett. 92, 182905 (2008); http://dx.doi.org/10.1063/1.2920767 (3 pages) | Cited 27 times

Online Publication Date: 7 May 2008

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A giant electric-field-induced strain of 0.87% is reported for tetragonal (Bi0.5Na0.5)TiO3-(Bi0.5K0.5)TiO3-BaTiO3 single crystals along the [100]cubic direction, which is six times as large as that of Pb(Zr0.52Ti0.48)O3 ceramics. In situ x-ray diffraction measurements and transmission electron microscope observations show that the giant strain mainly originates from switching of nanosized 90° domains. Strain measurements indicate that the strain caused by the 90° domain switching is reversible for both unipolar and bipolar electric-field applications. The reversibility of the 90° domain switching can be explained by the interaction between the spontaneous polarization and the defect dipole composed of A-site vacancy and oxygen vacancy.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.Bn Piezoelectric and electrostrictive constants
77.80.Dj Domain structure; hysteresis
61.72.jd Vacancies

Microwave dielectric properties of graded barium strontium titanate films

M. W. Cole, C. V. Weiss, E. Ngo, S. Hirsch, L. A. Coryell, and S. P. Alpay

Appl. Phys. Lett. 92, 182906 (2008); http://dx.doi.org/10.1063/1.2919080 (3 pages) | Cited 29 times

Online Publication Date: 8 May 2008

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Compositionally graded barium strontium titanate (BaxSr1−xTiO3 or BST) multilayers (5 mol % MgO doped and undoped) were prepared via metallo-organic solution deposition on Pt–Si substrates and characterized electrically at 0.5, 5, and 10 GHz. For the undoped BST multilayers, the small-signal dielectric response, tunability, and the loss tangent at 10 GHz were 261, 25% at 1778 kV/cm, and 0.078, respectively. On the other hand, the Mg-doped BST multilayers displayed a significant improvement in the loss characteristics at 10 GHz (0.039) but the dielectric response and its tunability were lower (189 and 15%, respectively, at 1778 kV/cm).
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
68.65.Ac Multilayers
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
77.22.Gm Dielectric loss and relaxation

Localized electrical characterization of the giant permittivity effect in CaCu3Ti4O12 ceramics

Patrick Fiorenza, Raffaella Lo Nigro, Corrado Bongiorno, Vito Raineri, Matthew C. Ferarrelli, Derek C. Sinclair, and Anthony R. West

Appl. Phys. Lett. 92, 182907 (2008); http://dx.doi.org/10.1063/1.2919095 (3 pages) | Cited 20 times

Online Publication Date: 8 May 2008

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Nanoscale imaging of the electrical properties of CaCu3Ti4O12 ceramics has been performed using scanning impedance microscopy. Two kinds of electrical inhomogeneity are detected, namely, depletion layers at grain boundaries and calcium titanate inclusions, both of which are more resistive than the bulk of the grains. Energy filtered transmission electron microscopy was used to estimate the chemical composition of the inclusions.
Show PACS
77.22.Ch Permittivity (dielectric function)
72.80.Sk Insulators
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.72.Mm Grain and twin boundaries
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