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19 Jan 2009

Volume 94, Issue 3, Articles (03xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 94, 032101 (2009); http://dx.doi.org/10.1063/1.3070238 (3 pages)

Philip Shemella and Saroj K. Nayak
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Announcement: Chinese, Japanese, and Korean characters available for author names

Mark M. Cassar

Appl. Phys. Lett. 94, 030201 (2009); http://dx.doi.org/10.1063/1.3077644 (1 page)

Online Publication Date: 21 January 2009

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Abstract Unavailable
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01.60.+q Biographies, tributes, personal notes, and obituaries
01.10.Cr Announcements, news, and awards
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Mark M. Cassar

Appl. Phys. Lett. 94, 030202 (2009); http://dx.doi.org/10.1063/1.3078199 (1 page)

Online Publication Date: 21 January 2009

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01.60.+q Biographies, tributes, personal notes, and obituaries
01.10.Cr Announcements, news, and awards
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Whispering gallery mode biosensor operated in the stimulated emission regime

Alexandre Francois and Michael Himmelhaus

Appl. Phys. Lett. 94, 031101 (2009); http://dx.doi.org/10.1063/1.3059573 (3 pages) | Cited 17 times

Online Publication Date: 20 January 2009

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Whispering gallery modes (WGMs) are generated in fluorescent polymer microparticles in phosphate buffered saline (PBS) above the threshold for stimulated emission and compared to their characteristics below threshold. The WGM microresonators show an eightfold improvement of their signal-to-noise ratio and a threefold increase in their quality factor when operated above threshold. In an investigation on the benefits for biochemical sensing, a real-time adsorption kinetics of bovine serum albumin in PBS is monitored and compared with those kinetics acquired by means of a WGM microresonator operated below threshold as well as by surface plasmon resonance (SPR).
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87.85.fk Biosensors
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Bloch gain in quantum cascade lasers at high temperature

Tobias Gresch, Romain Terazzi, Jérôme Faist, and Marcella Giovannini

Appl. Phys. Lett. 94, 031102 (2009); http://dx.doi.org/10.1063/1.3072343 (3 pages) | Cited 1 time

Online Publication Date: 20 January 2009

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We performed multisection cavity gain measurements at high temperature with quantum cascade lasers that are based on a single quantum well active region and work in a low-inversion regime. A modal gain coefficient g = 3.7±0.9 cm kA−1 at 330 K is found for the sample with the lowest population inversion. We show that the weak dependence of the threshold current and the high values of the associated T0 parameter between 260 and 360 K are accompanied by a gain coefficient that depends weakly on temperature.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Nano-Ag:polymeric composite material for ultrafast photonic crystal all-optical switching

Xiaoyong Hu, Ping Jiang, Cheng Xin, Hong Yang, and Qihuang Gong

Appl. Phys. Lett. 94, 031103 (2009); http://dx.doi.org/10.1063/1.3073712 (3 pages) | Cited 24 times

Online Publication Date: 21 January 2009

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We report a nanocomposite material possessing large nonlinear optical coefficients and fast response simultaneously, which is made of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] doped with Ag nanoparticles. Under resonant excitation of the polymer matrix and Ag nanoparticles, the value of the nonlinear susceptibility reaches the order of 10−6 esu. A nonlinear response time of 35 ps is achieved due to the energy transfer from organic molecules to Ag nanoparticles. An ultrafast photonic crystal all-optical switching with an ultralow pump intensity of 0.2 MW/cm2 is realized.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
42.70.Qs Photonic bandgap materials
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.47.J- Ultrafast spectroscopy (<1 psec)
61.72.up Other materials
42.65.An Optical susceptibility, hyperpolarizability

The importance of Fabry–Pérot resonance and the role of shielding in subwavelength imaging performance of multiwire endoscopes

Atiqur Rahman, Pavel A. Belov, Mário G. Silveirinha, Constantin R. Simovski, Yang Hao, and Clive Parini

Appl. Phys. Lett. 94, 031104 (2009); http://dx.doi.org/10.1063/1.3073714 (3 pages) | Cited 7 times

Online Publication Date: 22 January 2009

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Multiwire endoscopes may enable the manipulation of the electromagnetic field in the subwavelength scale. Recently, two different configurations of such devices have been proposed. Here, we compare the imaging performance of the imaging device introduced by Belov et al. [Phys. Rev. B 73, 033108 (2006)] and by Silveirinha et al. [Phys. Rev. B 75, 035108 (2007)] with the shielded multiwire endoscope described by Shvets et al. [Phys. Rev. Lett. 99, 053903 (2007)] . It is demonstrated that the performance of the latter may be strongly affected by the presence of a metallic shield around the endoscope and by poor matching between the endoscope and free space. Our results show that the metallic shield is completely unnecessary and emphasize the importance of tuning the length of the wires according to the Fabry–Pérot resonance condition, as proposed by Belov et al. [Phys. Rev. B 73, 033108 (2006)] .
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87.63.L- Visual imaging
87.85.-d Biomedical engineering

Raman gain in niobium-phosphate glasses

L. Sirleto, M. G. Donato, G. Messina, S. Santangelo, A. A. Lipovskii, D. K. Tagantsev, S. Pelli, and G. C. Righini

Appl. Phys. Lett. 94, 031105 (2009); http://dx.doi.org/10.1063/1.3072354 (3 pages) | Cited 3 times

Online Publication Date: 23 January 2009

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In this paper, niobium-phosphate glasses doped with rare earths (Er and Sm) are investigated by Raman scattering. The goal of Raman characterization is twofold: (a) to perform a fine structural characterization of the synthesized glasses and (b) to measure the Raman gain coefficient of the samples and to compare it with fused silica. The results reveal the presence of NbO6 octahedra and Nb–O–P–Nb–O mixed chains. A broadening of bandwidth and a significant enhancement ( ∼ 24 times) in gain coefficient G with respect to conventional silica glasses are also demonstrated.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
61.43.Fs Glasses

λ ∼ 3.1 μm room temperature InGaAs/AlAsSb/InP quantum cascade lasers

S. Y. Zhang, D. G. Revin, J. W. Cockburn, K. Kennedy, A. B. Krysa, and M. Hopkinson

Appl. Phys. Lett. 94, 031106 (2009); http://dx.doi.org/10.1063/1.3073865 (3 pages) | Cited 23 times

Online Publication Date: 23 January 2009

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Strain compensated In0.67Ga0.33As/AlAs0.8Sb0.2/InP quantum cascade lasers emitting at wavelengths near 3.1 μm at room temperature have been demonstrated. The lasers operate in pulsed mode with threshold current density of 3.6 kA/cm2 at 80 K and 19.2 kA/cm2 at 295 K. The peak optical power for an as-cleaved 3 mm long and 10 μm wide ridge device exceeds 1 W per facet at 80 K and is around 8 mW at 295 K. The observed laser performance suggests that room temperature operation for these lasers remains possible beyond the predicted threshold for Γ-L intervalley scattering of electrons in the upper laser levels.
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42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.55.Px Semiconductor lasers; laser diodes
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Secondary electron emission from MgO protective layer by Auger neutralization of ions

Han S. Uhm, Eun H. Choi, and Guang S. Cho

Appl. Phys. Lett. 94, 031501 (2009); http://dx.doi.org/10.1063/1.3073983 (3 pages) | Cited 4 times

Online Publication Date: 23 January 2009

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A theoretical model of the secondary electron emission yield (γ) from a MgO layer is developed based on the Auger neutralization of ions, resulting in an analytical expression of γ in terms of the ionization energy Ei for the density of states in the valence band, being an exponentially decaying function of the energy deviation from the band characteristic energy of 7.88 eV. The analytical expression recovers the previously known empirical formulation of γ ∼ (Ei−2φ) for the work function φ. Results of the theoretical model agree well with the measured data in terms of the data trend.
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79.20.Hx Electron impact: secondary emission
79.20.Fv Electron impact: Auger emission
73.30.+y Surface double layers, Schottky barriers, and work functions
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Optical constants of graphene layers in the visible range

M. Bruna and S. Borini

Appl. Phys. Lett. 94, 031901 (2009); http://dx.doi.org/10.1063/1.3073717 (3 pages) | Cited 30 times

Online Publication Date: 21 January 2009

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We show that the optical constants of graphene in the visible range can be estimated by means of a very simple procedure involving their consistence with universal optical conductivity and experimentally measured optical spectra, within the framework of Fresnel coefficients calculation. The obtained complex refractive index allows for accurate prediction of the optical behavior of graphene in the visible range, from the two-dimensional limit (single atomically thick graphene layer) to the bulk limit (graphite). Therefore, it may result very useful for quantitative optical analysis of graphene layers and graphitic structures in general.
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78.66.Tr Fullerenes and related materials
81.07.Bc Nanocrystalline materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Size-dependent thermal diffusivity of multilayered thin films deposited on substrates characterized by transient grating technique

Heng-yi Ju, Shu-yi Zhang, Zhe Li, Xiu-ji Shui, and Pao-kuang Kuo

Appl. Phys. Lett. 94, 031902 (2009); http://dx.doi.org/10.1063/1.3067903 (3 pages)

Online Publication Date: 22 January 2009

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The thermal diffusivities of bilayered thin films with nanoscaled thickness deposited on substrates are characterized by nanosecond transient grating method. Based on the transient grating experiment, two-dimensional thermal diffusivity model and eigenfunction expansion method are used to calculate the thermal fields in the trilayered structures. By fitting the theoretical calculations to the experimental data of a series of trilayered structures Al/ZnO/Si with different thicknesses of ZnO films, the thermal diffusivities of the Al and ZnO films can be evaluated simultaneously. The results show that the thermal diffusivities of the ZnO films are size dependent and increase with thickness of the films.
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68.65.Ac Multilayers
66.30.Xj Thermal diffusivity
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.jd Thickness

Contactless electroreflectance of GaInNAsSb/GaNAs/GaAs quantum wells emitting at 1.5–1.65 μm: Broadening of the fundamental transition

R. Kudrawiec, P. Poloczek, J. Misiewicz, H. P. Bae, T. Sarmiento, S. R. Bank, H. B. Yuen, M. A. Wistey, and James S. Harris, Jr.

Appl. Phys. Lett. 94, 031903 (2009); http://dx.doi.org/10.1063/1.3073718 (3 pages) | Cited 1 time

Online Publication Date: 22 January 2009

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Contactless electroreflectance (CER) has been applied to study the broadening of the fundamental transition for GaInNAsSb/GaNAs/GaAs quantum wells (QWs) obtained at various growth and annealing conditions. It has been observed that CER resonances are about 50% narrower for QWs grown at lower group V fluxes and annealed at lower temperatures (660–720 °C) and longer time (30–60 min) than those previously considered optimal ( ∼ 760 °C and ∼ 60 s). The long annealing can be partially realized in situ during (and/or after) the growth of the upper part of the laser structure instead the ex situ short-time annealing, where the laser structure can unintentionally be overannealed very easily.
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78.20.Jq Electro-optical effects
68.65.Fg Quantum wells
78.67.De Quantum wells
81.40.Gh Other heat and thermomechanical treatments
42.55.Px Semiconductor lasers; laser diodes
81.07.St Quantum wells

Mechanical heterogeneity and mechanism of plasticity in metallic glasses

J. G. Wang, D. Q. Zhao, M. X. Pan, C. H. Shek, and W. H. Wang

Appl. Phys. Lett. 94, 031904 (2009); http://dx.doi.org/10.1063/1.3073985 (3 pages) | Cited 15 times

Online Publication Date: 22 January 2009

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The mechanical heterogeneity is quantified based on the spatial nanohardness distributions in three bulk metallic glasses with different plasticities. It is found that the metallic glass with high mechanical heterogeneity is more plastic. We propose that the appropriate mechanical heterogeneity makes the metallic glasses meliorate their plasticity by increasing inelastic strained area and promoting energy dissipation.
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81.40.Lm Deformation, plasticity, and creep
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.fq Plasticity and superplasticity
62.20.Qp Friction, tribology, and hardness

Multilayer structure with gradual increasing porosity for dye-sensitized solar cells

Zhipeng Tian, Hanmin Tian, Xiangyan Wang, Shikui Yuan, Jiyuan Zhang, Xiaobo Zhang, Tao Yu, and Zhigang Zou

Appl. Phys. Lett. 94, 031905 (2009); http://dx.doi.org/10.1063/1.3073834 (3 pages) | Cited 8 times

Online Publication Date: 23 January 2009

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Multilayer structure was prepared in a dye-sensitized solar cell work electrode by enlarging the porosity in each layer being coated on the fluorine-doped tin oxide transparent conducting glass from bottom to top. The multilayer structure exhibits an improved light scattering character, which resulted in better light harvesting of the cell. An obvious improvement in short circuit current is obtained. I-V characteristic measurement indicates an improved efficiency by 13% as compared to homogeneous pore-size samples. Diffuse reflectance spectra, scanning electron microscope images, and porosity measurements demonstrate that larger porosity is the cause of enhanced light scattering.
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84.60.Jt Photoelectric conversion
68.65.Ac Multilayers

In situ x-ray investigation of freestanding nanoscale Cu–Nb multilayers under tensile load

C. C. Aydıner, D. W. Brown, N. A. Mara, J. Almer, and A. Misra

Appl. Phys. Lett. 94, 031906 (2009); http://dx.doi.org/10.1063/1.3074374 (3 pages) | Cited 8 times

Online Publication Date: 23 January 2009

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The yield behavior in a freestanding sputter-deposited Cu/Nb multilayer with 30 nm nominal individual layer thickness has been investigated with in situ synchrotron x-ray diffraction during tensile loading. A pronounced elastic-plastic transition is observed with the fraction of plastically yielded grains increasing gradually with strain. Near synchronous yielding is observed in the Cu and Nb grains. The gradual progression in yield behavior is interpreted in terms of residual stresses, and elastic and plastic anisotropy.
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68.60.Bs Mechanical and acoustical properties
68.65.Ac Multilayers
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Electronic structure and band-gap modulation of graphene via substrate surface chemistry

Philip Shemella and Saroj K. Nayak

Appl. Phys. Lett. 94, 032101 (2009); http://dx.doi.org/10.1063/1.3070238 (3 pages) | Cited 27 times

Online Publication Date: 20 January 2009

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We have studied the electronic structure of graphene deposited on a SiO2 surface using density functional methods. The band structure of the graphene monolayer strongly depends on surface characteristics of the underlying SiO2 surface; for an oxygen-terminated surface, the monolayer exhibits a finite energy band gap while the band gap is closed when the oxygen atoms on the substrate are passivated with hydrogen atoms. We find that at least a graphene bilayer is required for a near zero energy gap when deposited on a substrate without H-passivation. Our results are discussed in the light of recent experiments.
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71.20.Tx Fullerenes and related materials; intercalation compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
61.48.-c Structure of fullerenes and related hollow and planar molecular structures

Spin injection studies into GaAs quantum wells in the presence of confined electrons

M. Yasar, R. Mallory, A. Petrou, A. T. Hanbicki, G. Kioseoglou, C. H. Li, O. M. J. van’t Erve, and B. T. Jonker

Appl. Phys. Lett. 94, 032102 (2009); http://dx.doi.org/10.1063/1.3073752 (3 pages) | Cited 3 times

Online Publication Date: 23 January 2009

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We compare the electroluminescence spectra (spectral composition and polarization characteristics) of two types of Fe-based AlGaAs/GaAs n-i-p spin light emitting diodes (spin LEDs). In type A spin LEDs the GaAs quantum well (QW) does not contain any confined carriers, while in type B LEDs the GaAs QW is occupied by confined electrons generated by excess n-type doping in the AlGaAs(n) barrier. Type B LEDs show a significantly smaller circular polarization at the e1h1 feature than type A devices. Other differences include the presence of the e1ℓ1 exciton as well as excitonic phonon replicas in type B LEDs. Possible mechanisms for these differences are discussed.
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85.60.Jb Light-emitting devices
72.25.Dc Spin polarized transport in semiconductors
71.35.-y Excitons and related phenomena
78.60.Fi Electroluminescence
61.72.uj III-V and II-VI semiconductors
73.63.Hs Quantum wells
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Voltage control of in-plane magnetic anisotropy in ultrathin Fe/n-GaAs(001) Schottky junctions

K. Ohta, T. Maruyama, T. Nozaki, M. Shiraishi, T. Shinjo, Y. Suzuki, S.-S. Ha, C.-Y. You, and W. Van Roy

Appl. Phys. Lett. 94, 032501 (2009); http://dx.doi.org/10.1063/1.3072344 (3 pages) | Cited 6 times

Online Publication Date: 20 January 2009

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We report on the realization of voltage control of in-plane magnetic anisotropy at room temperature in ultrathin Fe/n-GaAs(001) Schottky junctions. Clear voltage-induced changes in magnetic anisotropy were observed in a Kerr ellipticity hysteresis loop using a lock-in modulation technique. The maximum change reached 4.5% of the saturation ellipticity under the application of a sinusoidal voltage signal of 1 V peak-to-peak in an Fe layer with a thickness of 0.64 nm. These results reveal the feasibility of controlling the in-plane magnetization process by the use of a perpendicular electric field. This can be a useful technique in ultralow power magnetization switching.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Spin injection in silicon at zero magnetic field

L. Grenet, M. Jamet, P. Noé, V. Calvo, J.-M. Hartmann, L. E. Nistor, B. Rodmacq, S. Auffret, P. Warin, and Y. Samson

Appl. Phys. Lett. 94, 032502 (2009); http://dx.doi.org/10.1063/1.3064135 (3 pages) | Cited 13 times

Online Publication Date: 20 January 2009

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In this letter, we show efficient electrical spin injection into a SiGe based p-i-n light emitting diode from the remanent state of a perpendicularly magnetized ferromagnetic contact. Electron spin injection is carried out through an alumina tunnel barrier from a Co/Pt thin film exhibiting a strong out-of-plane anisotropy. The electron spin polarization is then analyzed through the circular polarization of emitted light. All the light polarization measurements are performed without an external applied magnetic field, i.e., in remanent magnetic states. The light polarization as a function of the magnetic field closely traces the out-of-plane magnetization of the Co/Pt injector. We could achieve a circular polarization degree of the emitted light of 3% at 5 K. Moreover this light polarization remains almost constant at least up to 200 K.
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85.60.Jb Light-emitting devices
85.30.Kk Junction diodes

Patterned medium for heat assisted magnetic recording

Kürşat Şendur and William Challener

Appl. Phys. Lett. 94, 032503 (2009); http://dx.doi.org/10.1063/1.3073049 (3 pages) | Cited 4 times

Online Publication Date: 21 January 2009

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Heat assisted magnetic recording (HAMR) is a potential solution to extend the limits of conventional magnetic recording. In HAMR, the heating of the recording medium is achieved with a near-field optical transducer. Although the literature suggests novel transducers, there is little consideration of the optical and thermal aspects of the magnetic medium. In this letter we suggest a recording medium that provides a significant enhancement in optical absorption and localized heating. The thermal profiles of the proposed medium and the conventional medium are compared using finite element method solutions of Maxwell’s and the heat transfer equations.
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85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
07.07.Mp Transducers

Probing magnetic configurations in Co/Cu multilayered nanowires

Jared Wong, Peter Greene, Randy K. Dumas, and Kai Liu

Appl. Phys. Lett. 94, 032504 (2009); http://dx.doi.org/10.1063/1.3073740 (3 pages) | Cited 5 times

Online Publication Date: 21 January 2009

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Magnetic configurations in heterostructures are often difficult to probe when the magnetic entities are buried inside. In this study we have captured magnetic and magnetoresistance “fingerprints” of Co nanodisks embedded in Co/Cu multilayered nanowires using a first-order reversal curve method. In 200 nm diameter nanowires, the magnetic configurations can be tuned by adjusting the Co nanodisk aspect ratio. Nanowires with the thinnest Co nanodisks exhibit single domain behavior, while those with thicker Co reverse via a vortex state. A superposition of giant and anisotropic magnetoresistance is observed, which corresponds to the different magnetic configurations of the Co nanodisks.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
75.75.-c Magnetic properties of nanostructures
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.65.Ac Multilayers
75.60.Jk Magnetization reversal mechanisms

Model for spin coupling disorder effects on the susceptibility of antiferromagnetic nanochains

C. M. Chaves, Thereza Paiva, J. d’Albuquerque e Castro, and Belita Koiller

Appl. Phys. Lett. 94, 032505 (2009); http://dx.doi.org/10.1063/1.3072361 (3 pages)

Online Publication Date: 22 January 2009

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The temperature dependence of the static magnetic susceptibility of exchange-disordered antiferromagnetic Heisenberg spin-1/2 finite chains with an odd number of spins is investigated as a function of size and type of disorder in the exchange coupling. Two models for the exchange disorder distribution are considered. At sufficiently low temperatures each chain behaves like an isolated spin-1/2 particle. As the size of the chains increases, this analogy is lost and the chains evolve into the thermodynamic limit behavior. The present study provides a simple criterion, based on susceptibility measurements, to establish when odd-sized chains effectively simulate a single spin-1/2 particle.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.10.Jm Quantized spin models, including quantum spin frustration
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Ee Antiferromagnetics
75.30.Et Exchange and superexchange interactions

Successive antiferromagnetic phase transitions in α-MnS probed by the exchange bias effect

Xi Chen, Andreas Hochstrat, Pavel Borisov, and Wolfgang Kleemann

Appl. Phys. Lett. 94, 032506 (2009); http://dx.doi.org/10.1063/1.3073045 (3 pages) | Cited 2 times

Online Publication Date: 23 January 2009

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The temperature dependence of the exchange bias of the heterolayer structure α-MnS(111)/Fe(1.5 nm)/Pt(3 nm) is investigated. It arises below Tc1 = 152 K due to the antiferromagnetic (AF) type-II spin structure of α-MnS and maximizes at Tc2 = 129 K, below which it vanishes steplike in parallel with a sudden increase in the coercive field of the Fe layer. These features are consistent with a spin reorientation transition at Tc2 probably into an AF multi-k spin order rather than with an activated domain conformation transition.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Vv High coercivity materials
75.60.Ch Domain walls and domain structure
75.50.Ee Antiferromagnetics
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Monoclinic MC phase in (001) field cooled BaTiO3 single crystals

Hu Cao, Christopher P. Devreugd, Wenwei Ge, Jiefang Li, D. Viehland, Haosu Luo, and Xiangyong Zhao

Appl. Phys. Lett. 94, 032901 (2009); http://dx.doi.org/10.1063/1.3073716 (3 pages) | Cited 6 times

Online Publication Date: 22 January 2009

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We report here the finding of a new phase in BaTiO3 single crystals. High precision x-ray diffraction investigations of (001) field cooled crystals have shown the presence of a monoclinic MC phase for temperatures below 300 K. This MC phase is shown to be stable upon removal of the electric field. The results demonstrate the presence of structurally bridging low symmetry phases that lie between tetragonal and rhombohedral ones in this classic perovskite system: indicating a means to achieve high piezoelectricity in Pb-free systems via domain engineering.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
77.65.-j Piezoelectricity and electromechanical effects
61.66.Fn Inorganic compounds

Piezoelectric properties and stabilities of CuO-modified Ba(Ti,Zr)O3 ceramics

P. Zheng, J. L. Zhang, S. F. Shao, Y. Q. Tan, and C. L. Wang

Appl. Phys. Lett. 94, 032902 (2009); http://dx.doi.org/10.1063/1.3072347 (3 pages) | Cited 12 times

Online Publication Date: 22 January 2009

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Due to the orthorhombic-tetragonal polymorphic phase transition near room temperature, undesirable large temperature dependence of piezoelectric properties is observed over common usage temperature range in BaTiO3 ceramics with high d33 values. Whereas shifting the phase transition temperature upward by partially substituting Ti with Zr is effective in reducing the piezoelectric temperature dependence, serious long-term degradation occurs. However, it is found that this could be overcome by incorporating a small amount of CuO additive. CuO-modified Ba(Ti0.9625Zr0.0375)O3 ceramics possess excellent piezoelectric properties of d33 = 300 pC/N, kp = 0.493, and k33 = 0.651 with tan δ = 0.011, and its kp remains larger than 0.40 in the broad temperature range from −43 to 73 °C and is almost constant between −25 and 55 °C. The results indicate that CuO-modified Ba(Ti,Zr)O3 ceramics are a promising low-cost lead-free material for practical applications.
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77.65.-j Piezoelectricity and electromechanical effects
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.K- Solid-solid transitions
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
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