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2 Feb 2009

Volume 94, Issue 5, Articles (05xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 94, 059901 (2009); http://dx.doi.org/10.1063/1.3086725 (3 pages)

Yuta Tsukada, Tsuyoshi Honma, and Takayuki Komatsu
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Quantitative strain-field measurement of 1:1 B-site cation ordered domains and antiphase boundaries in Pb(Sc1/2Ta1/2)O3 ceramics by high-resolution transmission electron microscopy

Cheuk W. Tai (戴卓偉) and Y. Lereah

Appl. Phys. Lett. 94, 051908 (2009); http://dx.doi.org/10.1063/1.3079412 (3 pages) | Cited 1 time

Online Publication Date: 6 February 2009

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Quantitative strain measurements of the 1:1 B-site cation ordered domains, antiphase boundaries, and dislocations in a highly ordered Pb(Sc1/2Ta1/2)O3 ceramic have been carried out by high-resolution transmission electron microscopy and geometric phase analysis. A phase shift of π between two adjacent ordered domains across an antiphase boundary is determined unambiguously. The maximum in-plane strain and lattice rotation induced by a dislocation are 9.5% and 5.4°, respectively. In a defect-free antiphase boundary, the maximum in-plane strain and lattice rotation are 1.8% and 0.9°, respectively. The strain mainly concentrates inside the antiphase boundary.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Magnetic field effect on premartensitic transition in Ni–Mn–Ga alloys

J. M. Barandiaran, V. A. Chernenko, P. Lazpita, J. Gutiérrez, I. Orue, J. Feuchtwanger, and S. Besseghini

Appl. Phys. Lett. 94, 051909 (2009); http://dx.doi.org/10.1063/1.3079677 (3 pages) | Cited 8 times

Online Publication Date: 6 February 2009

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Extensive measurements of the temperature dependencies of resistivity under constant magnetic fields made it possible to clarify the premartensitic transition sensitivity to applied magnetic field up to 14 T in polycrystalline and monocrystalline Ni–Mn–Ga alloys with compositions close to the stoichiometric one. A low-field minimum on the transition temperature versus magnetic field curves is found in both alloys. This minimum is attributed to the magnetic anisotropy contribution to the Clausius–Clapeyron relationship, which describes the premartensitic transition. This contribution is confirmed by magnetization loops measurements.
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81.30.Kf Martensitic transformations
75.50.Cc Other ferromagnetic metals and alloys
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
61.66.Bi Elemental solids
61.66.Dk Alloys
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Determination of MgO/AlN heterojunction band offsets by x-ray photoelectron spectroscopy

A. L. Yang, H. P. Song, X. L. Liu, H. Y. Wei, Y. Guo, G. L. Zheng, C. M. Jiao, S. Y. Yang, Q. S. Zhu, and Z. G. Wang

Appl. Phys. Lett. 94, 052101 (2009); http://dx.doi.org/10.1063/1.3075060 (3 pages) | Cited 11 times

Online Publication Date: 2 February 2009

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MgO is a promising gate dielectric and surface passivation film for GaN/AlGaN transistors, but little is known of the band offsets in the MgO/AlN system. X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band (ΔEv) of MgO/AlN heterostructures. A value of ΔEv = 0.22±0.08 eV was obtained. Given the experimental band gap of 7.83 eV for MgO, a type-I heterojunction with a conduction band offset of ∼ 1.45 eV is found. The accurate determination of the valence and conduction band offsets is important for use of III-N alloys based electronic devices.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.60.Jv Interfaces; heterostructures; nanostructures
71.20.Nr Semiconductor compounds
81.65.Rv Passivation
85.30.Tv Field effect devices

Compensation and carrier trapping in indium-doped CdTe: Contributions from an important near-mid-gap donor

V. Babentsov, J. Franc, and R. B. James

Appl. Phys. Lett. 94, 052102 (2009); http://dx.doi.org/10.1063/1.3073738 (3 pages) | Cited 7 times

Online Publication Date: 3 February 2009

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We report on the recharging of the neutral state of a deep-donor layer that increases the efficiency of charge collection in detector-grade CdTe:In. Measurements with photoinduced current transient spectroscopy and thermoelectric effect spectroscopy revealed positively charged energy level at EC−0.65 eV. Photoluminescence measurements identified this level being responsible for the 0.68 eV emission band. Its positive charge is converted into a neutral one by the upward displacement of Fermi level. We discuss the nature of this deep defect based on the latest ab initio calculations.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.72.uj III-V and II-VI semiconductors
72.80.Ey III-V and II-VI semiconductors
78.55.Et II-VI semiconductors
71.20.Nr Semiconductor compounds
72.20.Pa Thermoelectric and thermomagnetic effects

Landau level spectrum in a two-dimensional hole gas in C-doped (100) GaAs/Al0.4Ga0.6As square quantum well

Z. Q. Yuan, R. R. Du, M. J. Manfra, L. N. Pfeiffer, and K. W. West

Appl. Phys. Lett. 94, 052103 (2009); http://dx.doi.org/10.1063/1.3077147 (3 pages) | Cited 3 times

Online Publication Date: 3 February 2009

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We study the Landau level spectrum of a two-dimensional hole gas in carbon δ-doped (100) GaAs/Al0.4Ga0.6As square quantum well (width of 15 nm) by means of microwave cyclotron resonance (CR) and tilted field magnetotransport. Only one type of hole, with an effective mass of 0.4me, was detected in CR. By analyzing the spin-splitting level coincident conditions at B ∼ 1 T, we find that the effective g-factor is large enough to cause Landau level crossing even in zero tilt, and the product of gm∗ increases with total magnetic field.
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73.21.Fg Quantum wells
71.70.Di Landau levels
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
72.20.My Galvanomagnetic and other magnetotransport effects
73.63.Hs Quantum wells

Metallic conductivity and the role of copper in ZnO/Cu/ZnO thin films for flexible electronics

K. Sivaramakrishnan and T. L. Alford

Appl. Phys. Lett. 94, 052104 (2009); http://dx.doi.org/10.1063/1.3077184 (3 pages) | Cited 22 times

Online Publication Date: 3 February 2009

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ZnO/Cu/ZnO multilayer structures are obtained with the highest conductivity of dielectric-metal-dielectric films reported in literature with a carrier concentration of 1.2×1022 cm−3 and resistivity of 6.9×10−5 Ω-cm at the optimum copper layer thickness. The peak transmittance, photopic averaged transmittance, and Haacke figure of merit are 88%, 75%, and 8.7×10−3 Ω−1, respectively. The conduction mechanism involves metal to oxide carrier injection prior to the formation of a continuous metal conduction pathway. Optical transmission is elucidated in terms of copper’s absorption due to d-band to Fermi surface transitions at short wavelengths and reflectance combined with scattering losses at long wavelengths.
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73.40.Vz Semiconductor-metal-semiconductor structures
73.20.At Surface states, band structure, electron density of states

Electronic transport and colossal electroresistance in SrTiO3:Nb-based Schottky junctions

D. S. Shang, J. R. Sun, L. Shi, J. Wang, Z. H. Wang, and B. G. Shen

Appl. Phys. Lett. 94, 052105 (2009); http://dx.doi.org/10.1063/1.3077615 (3 pages) | Cited 15 times

Online Publication Date: 3 February 2009

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Current-voltage characteristics and colossal electroresistance (CER) have been experimentally investigated in the temperature range from 293 to 454 K for the Schottky junctions Au/SrTiO3:0.5 wt % Nb and Au/SrTiO3:0.05 wt % Nb. Both junctions show electron tunneling-dominated transport behavior. Postannealing of SrTiO3:0.05 wt % Nb in oxygen atmosphere causes a transition of the transport behavior from electron tunneling to thermionic emission. The CER effect appears in the junctions with the transport behavior dominated by electron tunneling and greatly weakens when thermionic emission prevails after postannealing. This result reveals the presence of a close relation between CER and electron tunneling.
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73.40.Ns Metal-nonmetal contacts
75.47.Gk Colossal magnetoresistance
73.40.Gk Tunneling
79.40.+z Thermionic emission
73.30.+y Surface double layers, Schottky barriers, and work functions
81.40.Gh Other heat and thermomechanical treatments

Energy-band parameters of atomic layer deposited Al2O3 and HfO2 on InxGa1−xAs

M. L. Huang, Y. C. Chang, Y. H. Chang, T. D. Lin, J. Kwo, and M. Hong

Appl. Phys. Lett. 94, 052106 (2009); http://dx.doi.org/10.1063/1.3078399 (3 pages) | Cited 13 times

Online Publication Date: 3 February 2009

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X-ray photoelectron spectroscopy (XPS) combined with reflection electron energy loss spectroscopy (REELS) were used to determine the energy-band parameters, valence-band offsets ΔEV, conduction-band offsets ΔEC, and energy-band gaps Eg, of the atomic layer deposited (ALD) Al2O3 and HfO2 on InxGa1−xAs (x = 0, 0.15, 0.25, and 0.53). Using REELS, Eg values of the ALD-Al2O3 and –HfO2 were estimated to be 6.77 and 5.56±0.05 eV, respectively. The ΔEV’s were determined by measuring the core level to valence band maximum binding energy difference from the XPS spectra. The ΔEC’s were then extracted from ΔEV’s and the energy-band gaps of the oxides and InxGa1−xAs, and are in good agreement with those estimated from the Fowler–Nordheim tunneling. The ΔEC’s and ΔEV’s are larger than 1.5 and 2.5 eV, respectively, for all the ALD-oxide/InxGa1−xAs samples.
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71.20.Ps Other inorganic compounds
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling
79.60.Bm Clean metal, semiconductor, and insulator surfaces
77.55.-g Dielectric thin films
79.20.Uv Electron energy loss spectroscopy
71.20.Nr Semiconductor compounds

Multiple conduction paths in boron δ-doped diamond structures

Niall Tumilty, Joseph Welch, Haitao Ye, Richard S. Balmer, Christopher Wort, Richard Lang, and Richard B. Jackman

Appl. Phys. Lett. 94, 052107 (2009); http://dx.doi.org/10.1063/1.3075860 (3 pages) | Cited 4 times

Online Publication Date: 4 February 2009

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Impedance spectroscopy has been used to investigate conductivity within boron-doped diamond in an intrinsic/delta-doped/intrinsic (i-δ-i) multilayer structure. For a 5 nm thick delta layer, three conduction pathways are observed, which can be assigned to transport within the delta layer and to two differing conduction paths in the i-layers adjoining the delta layer. For transport in the i-layers, thermal trapping/detrapping processes can be observed, and only at the highest temperature investigated (673 K) can transport due to a single conduction process be seen. Impedance spectroscopy is an ideal nondestructive tool for investigating the electrical characteristics of complex diamond structures.
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73.63.-b Electronic transport in nanoscale materials and structures

Anisotropic transport in quantum waveguides due to the spin-orbit interactions

Miao Wang, Kai Chang, and K. S. Chan

Appl. Phys. Lett. 94, 052108 (2009); http://dx.doi.org/10.1063/1.3079400 (3 pages) | Cited 5 times

Online Publication Date: 6 February 2009

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We theoretically investigate the charge transport in the quantum waveguides in the presence of the Rashba spin-orbit interaction and the Dresselhaus spin-orbit interaction. We find that the interplay between the Rashba spin-orbit interaction and Dresselhaus spin-orbit interaction can induce a symmetry breaking and consequently leads to the anisotropic charge transport in the quantum waveguides, the conductance through the quantum waveguides depends sensitively on the crystallographic orientations of the quantum waveguides. The anisotropy of the charge transport can even survive in the presence of disorder effect in realistic systems.
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71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.23.-b Electronic transport in mesoscopic systems
73.63.-b Electronic transport in nanoscale materials and structures

Evaluation of GaN substrates grown in supercritical basic ammonia

Makoto Saito, Hisashi Yamada, Kenji Iso, Hitoshi Sato, Hirohiko Hirasawa, Derrick S. Kamber, Tadao Hashimoto, Steven P. DenBaars, James S. Speck, and Shuji Nakamura

Appl. Phys. Lett. 94, 052109 (2009); http://dx.doi.org/10.1063/1.3079813 (3 pages) | Cited 1 time

Online Publication Date: 6 February 2009

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GaN crystals grown by the basic ammonothermal method were investigated for their use as substrates for device regrowth. X-ray diffraction analysis indicated that the substrates contained multiple grains while secondary ion mass spectroscopy (SIMS) revealed a high concentration of hydrogen, oxygen, and sodium. Despite these drawbacks, the emission from the light emitting diode structures grown by metal organic chemical vapor deposition on both the c-plane and m-plane epitaxial wafers was demonstrated. The SIMS depth profiles showed that the diffusion of the alkali metal from the substrate into the epitaxial film was small, especially in the m-direction.
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68.55.ag Semiconductors
68.55.Nq Composition and phase identification
81.05.Ea III-V semiconductors
81.10.Dn Growth from solutions
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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Multibits magnetic recording using a ferromagnetic element with shifted vortex core position

Hong-Guang Piao, Dede Djuhana, Suhk-Kun Oh, Seong-Cho Yu, and Dong-Hyun Kim

Appl. Phys. Lett. 94, 052501 (2009); http://dx.doi.org/10.1063/1.3077024 (3 pages) | Cited 3 times

Online Publication Date: 3 February 2009

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We suggest a patterned ferromagnetic multibits element for an ultrahigh density magnetic recording media. The pattern is composed of a circular ferromagnetic disk in contact to four needle-shaped sharp equilateral triangles. By using micromagnetic simulation, we found that a spin configuration of circular ferromagnetic disk is modified with position of magnetic vortex core shifted from the center by selecting a specific combination of spin states of four needles. We explore the possibility of multibits recording by shifting magnetic vortex core position in the ferromagnetic element.
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85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)

Coercivity of ledge-type L10-FePt/Fe nanocomposites with perpendicular magnetization

D. Goll and A. Breitling

Appl. Phys. Lett. 94, 052502 (2009); http://dx.doi.org/10.1063/1.3078286 (3 pages) | Cited 27 times

Online Publication Date: 3 February 2009

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Exchange-coupled ledge-type L10-FePt/Fe composite systems with out-of-plane anisotropy composed of nanostructured L10-FePt films covered by Fe are prepared to analyze the influence of the soft magnetic layer thickness on the magnetic properties. By the soft magnetic layer thickness dFe the coercivity can be tailored according to a 1/dFe1.38 relation. This result can be used to realize recording media with coercivities in the range which are afforded by conventional write heads.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Tt Fine-particle systems; nanocrystalline materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions
75.75.-c Magnetic properties of nanostructures
75.50.Ss Magnetic recording materials
75.30.Gw Magnetic anisotropy

Balancing interlayer dipolar interactions in multilevel patterned media with out-of-plane magnetic anisotropy

V. Baltz, B. Rodmacq, A. Bollero, J. Ferré, S. Landis, and B. Dieny

Appl. Phys. Lett. 94, 052503 (2009); http://dx.doi.org/10.1063/1.3078523 (3 pages) | Cited 9 times

Online Publication Date: 4 February 2009

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Nanostructures consisting of a stack of two magnetic multilayers with out-of-plane anisotropy and distinct coercivities hold great promises in spintronics devices. Yet their miniaturization leads to interlayer dipolar coupling, which results in detrimental asymmetrical behaviors of magnetization reversal or even in the loss of intermediate antiparallel configuration. In this letter, we take advantage of Ruderman–Kittel–Kasuya–Yosida interactions in order to compensate for this coupling and restore symmetry. The study has been performed on an array of square dots of 200 nm lateral size, each dot consisting of two [Co/Pt] multilayers antiferromagnetically coupled through a thin Ru spacer.
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75.30.Gw Magnetic anisotropy
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Jk Magnetization reversal mechanisms
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Ss Magnetic recording materials
75.30.Et Exchange and superexchange interactions

Interfacial defects controlled electrical and magnetotransport in Co/ZnO nanocomposites

C. Y. Hsu, J. C. A. Huang, Y. H. Lee, S. F. Chen, C. P. Liu, S. J. Sun, and Yonhua Tzeng

Appl. Phys. Lett. 94, 052504 (2009); http://dx.doi.org/10.1063/1.3077312 (3 pages) | Cited 2 times

Online Publication Date: 6 February 2009

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This work demonstrates, by frequency-dependent electrical measurements, significant variation associated with interfacial defects in Co/ZnO nanocomposites (NCs) for electrical and magnetic transport. Radio-frequency impedance measurements showed that heat treatment in an ultrahigh vacuum (UHV) increased interfacial defect density. Interfacial defects-assisted transport reduced the magnetoresistance (MR) ratio from 5.04% for the as-grown sample to 0.17% following heat treatment in UHV. The evolution of the onset frequency of power-law dispersion conductivity revealed that the increase in the interfacial defect density in Co/ZnO NCs upon heat treatment was consistent with the change in MR.
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72.20.My Galvanomagnetic and other magnetotransport effects

Local thermal bistability in MgB2 microwave coplanar resonators: Opposite jumpwise response to weak-link switching and to vortex avalanches

G. Ghigo, R. Gerbaldo, L. Gozzelino, F. Laviano, G. Lopardo, E. Monticone, C. Portesi, and E. Mezzetti

Appl. Phys. Lett. 94, 052505 (2009); http://dx.doi.org/10.1063/1.3079335 (3 pages) | Cited 3 times

Online Publication Date: 6 February 2009

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We report on specific nonlinear features in the response of microwave coplanar resonators obtained from magnesium diboride thin films. Different jumpwise behaviors observed in the resonance curves are found to be generated by either weak-link switching or vortex avalanches. Both mechanisms can be explained in terms of local-heating-induced thermal bistability, but they result in opposite effects, i.e., opposite signs in the abrupt variations of the quality factor and of the resonance frequency, due to the rf-current distribution. The weak-link-switching response shows promising characteristics (jumpwise signal, bistability, and hysteresis) for applications of MgB2 films in nonlinear devices.
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85.25.-j Superconducting devices
84.40.Az Waveguides, transmission lines, striplines
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Ferroelectric properties of Pb(Zr,Ti)O3 thin films until 40 GHz

E. Defaÿ, T. Lacrevaz, T. T. Vo, V. Sbrugnera, C. Bermond, M. Aïd, and B. Fléchet

Appl. Phys. Lett. 94, 052901 (2009); http://dx.doi.org/10.1063/1.3072348 (3 pages) | Cited 2 times

Online Publication Date: 2 February 2009

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The radio frequency characterization of Cu/TiN/Pb(Zr,Ti)O3 stack on glass is performed using coplanar transmission lines. A dielectric relaxation is evidenced around 10 GHz by the correlated decrease in the dielectric constant K together with the dielectric losses increase versus frequency. This phenomenon is attributed to domain wall relaxation. The ferroelectric nature of Pb(Zr,Ti)O3 (PZT) thin films is observed until 40 GHz with a hysteresis curve of K versus dc bias. The high K value (K ∼ 1200) combined with a high tunability ( ∼ 35%) and moderate losses ( ∼ 1%) suggest that PZT films could be well suited for tunable devices for frequencies lower than 5 GHz.
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77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ch Permittivity (dielectric function)
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

The effect of stress on the dielectric and tunable properties of barium stannate titanate thin films

Sannian Song, Jiwei Zhai, Lina Gao, and Xi Yao

Appl. Phys. Lett. 94, 052902 (2009); http://dx.doi.org/10.1063/1.3073743 (3 pages) | Cited 7 times

Online Publication Date: 2 February 2009

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Ba(Sn0.15Ti0.85)O3 thin films were grown on the LaNiO3 buffered LaAlO3, SrTiO3, MgO, and Al2O3 single crystal substrates, respectively. These substrates provide a systematic change in the stress while maintaining the same film microstructure. The stress in the thin film induces an obvious change in the dielectric behavior. The reduction in the ferroelectric transition temperature with increasing biaxial tensile stress is attributed to the suppression of in-plane polarization due to the small lateral grain size in the films. The in-plane tensile stress in this study reduces the unit cell along electric field in the parallel plate capacitor structure and decreases the tunability.
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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
77.65.Ly Strain-induced piezoelectric fields
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization

Phonon anomalies in Pb1−xLax(Zr0.9Ti0.1)O3 ceramics

E. Buixaderas, I. Gregora, S. Kamba, P. Kužel, and I. Reaney

Appl. Phys. Lett. 94, 052903 (2009); http://dx.doi.org/10.1063/1.3077019 (3 pages) | Cited 2 times

Online Publication Date: 3 February 2009

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The lattice dynamics of Pb1−xLax(Zr0.9Ti0.1)O3 (PLZT X/90/10) with X = 0, 2, 4, 10% of La was studied by means of Far Infrared, Raman and terahertz spectroscopies in the temperature range of 20–800 K. Infrared active soft phonons with anomalies near the paraelectric-ferroelectric phase transition were found for all the samples. Some Raman active phonons show anomalies ∼ 200 K below TC, due to another phase transition to a ferroelectric state with doubled unit cell. Samples with higher La content (X = 4,10) display nonclassical phonon softening described by ω2 = a(T−TC)γ with γ = 2/3.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.30.Hv Other nonmetallic inorganics
77.80.B- Phase transitions and Curie point
78.70.Gq Microwave and radio-frequency interactions

Phase transitions and the temperature dependence of the dielectric properties in tetragonally strained barium strontium titanate films

L. M. B. Alldredge, Wontae Chang, Steven W. Kirchoefer, and Jeffrey M. Pond

Appl. Phys. Lett. 94, 052904 (2009); http://dx.doi.org/10.1063/1.3079093 (3 pages) | Cited 5 times

Online Publication Date: 5 February 2009

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The dielectric properties of sputter-deposited Ba1−xSrxTiO3 (BST) thin films on (001) MgO substrates with in-plane or out-of-plane tetragonal lattice structure distortions were characterized as a function of temperature. A temperature-dependent interpolation calibration technique was developed for increased efficiency of the microwave measurements. The BST films showed significant differences in the ferroelectric phase transition due to lattice distortions with a strong temperature dependence of the in-plane dielectric behavior for films under tensile strain and a weak temperature dependence for films under compressive strain. The experimental data agreed well with theoretical modeling of the BST film strain effect based on Devonshire’s theory.
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77.80.B- Phase transitions and Curie point
77.55.-g Dielectric thin films
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
77.22.Ch Permittivity (dielectric function)
81.15.Cd Deposition by sputtering
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Measuring the relative permittivity of polyetherimide/(Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 composites from 10 kHz to 12 GHz

Cheng-Fu Yang, Chia-Ching Wu, Ying-Chung Chen, and Chean-Cheng Su

Appl. Phys. Lett. 94, 052905 (2009); http://dx.doi.org/10.1063/1.3078285 (3 pages) | Cited 3 times

Online Publication Date: 6 February 2009

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The relative permittivity of polyetherimide-(Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 (PEI-BSTZ) composites is measured from 10 kHz to 1 MHz using plate method. As the content of BSTZ filler is less than 18 vol %, the experimental values are fitted to the values predicted by Lichtenecker equation. As the content is more than 18 vol %, the measured relative permittivity of PEI-BSTZ composites is higher than the predicted values. The relative permittivity of PEI-BSTZ composites is measured at 1–12 GHz using “square cavity resonator” method. Measured at gigahertz, the relative permittivity of PEI-BSTZ composites is almost unchanged.
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77.22.Ch Permittivity (dielectric function)

Domain structure of (100)/(001)-oriented epitaxial PbTiO3 thick films with various volume fraction of (001) orientation grown by metal organic chemical vapor deposition

Satoru Utsugi, Takashi Fujisawa, Rikyu Ikariyama, Shintaro Yasui, Hiroshi Nakaki, Tomoaki Yamada, Mutsuo Ishikawa, Masaaki Matsushima, Hitoshi Morioka, and Hiroshi Funakubo

Appl. Phys. Lett. 94, 052906 (2009); http://dx.doi.org/10.1063/1.3078400 (3 pages) | Cited 9 times

Online Publication Date: 6 February 2009

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(100)/(001)-oriented epitaxial PbTiO3 films thicker than 1 μm were grown on various types of substrates by chemical vapor deposition. The domain structures of these films with different volume fractions of (001) were investigated. Domain structures, consisting of (100)/(001)-oriented domains, were observed regardless of the type of substrate. However, the tilting angles of the a- and c-domains from the surface normal linearly changed with the volume fraction of the (001) orientation. These results suggest that the volume fraction of the (001) orientation is crucial in identifying the domain structure of PbTiO3 thick films.
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77.80.Dj Domain structure; hysteresis
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.at Other materials
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Fast discharge speed in poly(vinylidene fluoride) graft copolymer dielectric films achieved by confined ferroelectricity

Fangxiao Guan, Zhongzhe Yuan, Essay W. Shu, and Lei Zhu

Appl. Phys. Lett. 94, 052907 (2009); http://dx.doi.org/10.1063/1.3079332 (3 pages) | Cited 15 times

Online Publication Date: 6 February 2009

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Although a high electric energy density was recently reported for defect-modified poly(vinylidene fluoride) (PVDF) copolymers at millisecond discharge, they usually deliver less energy at a high pulse rate. In this letter, a low loss polystyrene (PS) was grafted as side chains onto the P(VDF-chlorotrifluoroethylene) main chain. After PVDF crystallization, dielectric PS side chains were segregated to the crystalline-amorphous interface, forming a finite confinement layer for ferroelectric PVDF crystals. We speculated that less space charge was induced during electric poling because of the nanoscale confinement effect. Consequently, a fast discharge speed and a relatively high energy density were achieved.
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77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ej Polarization and depolarization
77.22.Jp Dielectric breakdown and space-charge effects
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Effects of thermal annealing on the emission properties of type-II InAs/GaAsSb quantum dots

Yu-An Liao, Wei-Ting Hsu, Pei-Chin Chiu, Jen-Inn Chyi, and Wen-Hao Chang

Appl. Phys. Lett. 94, 053101 (2009); http://dx.doi.org/10.1063/1.3062979 (3 pages) | Cited 12 times

Online Publication Date: 2 February 2009

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We report the effects of thermal annealing on the emission properties of type-II InAs quantum dots (QDs) covered by a thin GaAs1−xSbx layer. Apart from large blueshifts and a pronounced narrowing of the QD emission peak, the annealing induced alloy intermixing also leads to enhanced radiative recombination rates and reduced localized states in the GaAsSb layer. Evidences of the evolution from type-II to type-I band alignments are obtained from time-resolved and power-dependent photoluminescence measurements. We demonstrate that postgrowth thermal annealing can be used to tailor the band alignment, the wave function overlaps, and hence the recombination dynamics in the InAs/GaAsSb type-II QDs.
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78.67.Hc Quantum dots
61.72.Cc Kinetics of defect formation and annealing
73.20.Fz Weak or Anderson localization
78.47.jd Time resolved luminescence
73.21.La Quantum dots
78.55.Cr III-V semiconductors

Planar hybrid superlattices by compression of rolled-up nanomembranes

T. Zander, Ch. Deneke, A. Malachias, Ch. Mickel, T. H. Metzger, and O. G. Schmidt

Appl. Phys. Lett. 94, 053102 (2009); http://dx.doi.org/10.1063/1.3074449 (3 pages) | Cited 4 times

Online Publication Date: 2 February 2009

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Hybrid metal/semiconductor superlattices are obtained by the controlled compression of rolled-up metal/semiconductor nanomembranes. The planar superlattice maintains the crystalline quality of the semiconductor and the polycrystalline texture of the metal, allowing the integration of these materials into a multilayer system that cannot be produced by any direct deposition procedure. The superlattice consists of two symmetrically inverted multilayer stacks splitted by a metallic mirror plane. Additional intensity peaks in x-ray reflectivity confirm the periodic structure created by the roll up and compression of nanomembranes.
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68.65.Cd Superlattices
73.40.Ns Metal-nonmetal contacts
61.46.-w Structure of nanoscale materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
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