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1 Sep 2008

Volume 93, Issue 9, Articles (09xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 93, 091901 (2008); http://dx.doi.org/10.1063/1.2976330 (3 pages)

Fang-Fang Ren, M. B. Yu, J. D. Ye, Q. Chen, S. T. Tan, G. Q. Lo, and D. L. Kwong
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The α−γ−ε triple point of iron investigated by high pressure–high temperature neutron scattering

S. Klotz, Y. Le Godec, Th. Strässle, and U. Stuhr

Appl. Phys. Lett. 93, 091904 (2008); http://dx.doi.org/10.1063/1.2976128 (3 pages) | Cited 6 times

Online Publication Date: 3 September 2008

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We present high pressure–high temperature diffraction data in the 0–10 GPa and 300–1000 K range of all three main iron phases. The refinements of the diffraction patterns give molar volumes to high precision and show that the α−γ−ε triple point is located at 8.2±0.1 GPa and 678 K. These values are significantly lower than currently admitted (10.4 GPa/740 K), but are consistent with reported in situ x-ray diffraction data obtained in multianvil presses. These measurements have been made possible by the use of a high P/T cell which uses metallic toroidal gaskets and which suffers from less absorption, gives clean diffraction patterns, and shows better pressure performance than other setups.
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64.70.-p Specific phase transitions
81.40.Vw Pressure treatment
64.60.Kw Multicritical points
62.50.-p High-pressure effects in solids and liquids

A yellow-emitting Ce3+ phosphor, La1−xCexSr2AlO5, for white light-emitting diodes

Won Bin Im, Young-Il Kim, Natalie N. Fellows, Hisashi Masui, G. A. Hirata, Steven P. DenBaars, and Ram Seshadri

Appl. Phys. Lett. 93, 091905 (2008); http://dx.doi.org/10.1063/1.2976138 (3 pages) | Cited 44 times

Online Publication Date: 3 September 2008

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A yellow-emitting phosphor, La1−xCex3+Sr2AlO5, is reported that displays a peak in the excitation at 450 nm and a peak in the emission at 556 nm. When this phosphor is pumped by a blue InGaN light-emitting diode (λmax = 450 nm) we obtain white light with color rendering index (Ra) between 81 and 85 and color temperatures between 4200 and 5500 K, suggesting that this material is competitive as a blue-pumped yellow phosphors.
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78.55.Hx Other solid inorganic materials
85.60.Jb Light-emitting devices
61.66.Fn Inorganic compounds

Magnetic field-induced reverse transformation in B2-type NiCoMnAl shape memory alloys

R. Kainuma, W. Ito, R. Y. Umetsu, K. Oikawa, and K. Ishida

Appl. Phys. Lett. 93, 091906 (2008); http://dx.doi.org/10.1063/1.2965811 (3 pages) | Cited 29 times

Online Publication Date: 4 September 2008

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Effects of the addition of Co to the NiMnAl alloy on the martensitic and magnetic properties were investigated. The magnetic properties of the parent (P) phase drastically changed from paramagnetic to ferromagnetic, while the magnetization in the martensite (M) phase slightly decreased with increasing Co composition. Consequently, in the Ni40Co10Mn33Al17 alloy with the B2 ordered structure, the martensitic transformation from a ferromagnetic P to a weak magnetic M phase was obtained. The martensitic transformation temperatures in this alloy decreased by about 30 K with the application of a magnetic field of 7 T and a metamagnetic phase transformation was confirmed.
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81.30.Kf Martensitic transformations
64.70.kd Metals and alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Transformation from molecular to polymeric nitrogen at high pressures and temperatures: In situ x-ray diffraction study

I. A. Trojan, M. I. Eremets, S. A. Medvedev, A. G. Gavriliuk, and V. B. Prakapenka

Appl. Phys. Lett. 93, 091907 (2008); http://dx.doi.org/10.1063/1.2975375 (3 pages) | Cited 1 time

Online Publication Date: 4 September 2008

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We studied the mechanism of the structural transformation of molecular nitrogen to atomic single-bonded nitrogen with a cubic gauche (cg-N) crystal structure using x-ray diffraction in situ at a pressure of ∼ 140 GPa and temperatures up to 2000 K in a diamond anvil cell. The anvils, with a toroidal shape, allowed us to drastically increase the volume of the sample, reduce the acquisition time of the diffraction pattern, and improve the quality of the Raman spectra. Molecular nitrogen transforms to the cg-N phase through an intermediate disordered state. The Raman spectra are in good agreement with recent theoretical calculations.
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64.70.kt Molecular crystals
62.50.-p High-pressure effects in solids and liquids
61.66.Bi Elemental solids
78.30.Am Elemental semiconductors and insulators
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Theory of grain boundary diffusion induced by the Kirkendall effect

Hui-Chia Yu, A. Van der Ven, and K. Thornton

Appl. Phys. Lett. 93, 091908 (2008); http://dx.doi.org/10.1063/1.2978161 (3 pages) | Cited 10 times

Online Publication Date: 5 September 2008

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A set of coupled diffusion equations is numerically solved to demonstrate that grain boundary diffusion is significantly enhanced when diffusing atomic species have dissimilar atomic hop frequencies in the bulk. The model is based on a rigorous treatment of two-component substitutional diffusion where vacancies are treated as an additional species. By examining the concentration fields and the eigenvalues of the diffusivity matrix, the origin of the enhanced grain boundary diffusion is explained in terms of the Kirkendall effect.
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61.72.Mm Grain and twin boundaries
66.30.Lw Diffusion of other defects
61.72.jd Vacancies
66.30.Ny Chemical interdiffusion; diffusion barriers

Improved performance of Schottky diodes on pendeoepitaxial gallium nitride

T. Zheleva, M. Derenge, D. Ewing, P. Shah, K. Jones, U. Lee, and L. Robins

Appl. Phys. Lett. 93, 091909 (2008); http://dx.doi.org/10.1063/1.2978404 (3 pages) | Cited 4 times

Online Publication Date: 5 September 2008

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We designed experiments to investigate the role of dislocation density on the performance of Schottky diodes fabricated on a GaN material grown conventionally and by pendeo-epitaxy. Devices of varying geometries were fabricated on low defect density GaN regions grown selectively via pendeo-epitaxy. In addition, corresponding devices were fabricated on the conventional GaN material with a high density of dislocations. Schottky diodes fabricated on pendeo-material showed nearly two orders of magnitude lower leakage current and displayed improved ideality factor, while diodes built on a conventional material displayed nonideal characteristics.
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85.30.Kk Junction diodes
71.55.Eq III-V semiconductors
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Strain effect and channel length dependence of bias temperature instability on complementary metal-oxide-semiconductor field effect transistors with high-k/SiO2 gate stacks

J. C. Liao, Y. K. Fang, Y. T. Hou, C. L. Hung, P. F. Hsu, K. C. Lin, K. T. Huang, T. L. Lee, and M. S. Liang

Appl. Phys. Lett. 93, 092101 (2008); http://dx.doi.org/10.1063/1.2967442 (3 pages) | Cited 1 time

Online Publication Date: 2 September 2008

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The strain effect and channel length dependence of bias temperature instability on dual metal gate complementary metal-oxide-semiconductor field enhanced transistors with HfSiON dielectric were studied in detail. For channel length larger than 0.1 μm, both positive and negative bias temperature instabilities (PBTI and NBTI) were not affected by the tensile strain obviously. As the channel scaling down to less than 0.1 μm, the degradation after PBTI stress was still not influenced by the strain, however, the NBTI degradation was enhanced significantly. In addition, the dependence of BTI on channel length was extensively investigated under constant voltage and field stress.
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85.30.Tv Field effect devices

Polarization of defect related optical transitions in chalcopyrites

Katja Hönes, Michael Eickenberg, Susanne Siebentritt, and Clas Persson

Appl. Phys. Lett. 93, 092102 (2008); http://dx.doi.org/10.1063/1.2974085 (3 pages) | Cited 4 times

Online Publication Date: 3 September 2008

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We investigate the symmetry of shallow acceptors in Cu chalcopyrites by polarization dependent photoluminescence measurements and density functional calculations. We determine the influence of the band symmetry versus the site symmetry. The polarization of the emitted or absorbed light is parallel to the c-axis in the case of CuGaSe2 and perpendicular to the c-axis in the case of CuInSe2. The symmetry of the defects depends in each case on the symmetry of the topmost band. Neither does the site symmetry affect the defect symmetry nor do the defects change the symmetry of the band.
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78.66.Nk Insulators
61.72.jd Vacancies
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
78.55.Hx Other solid inorganic materials

Improved effective mass theory for silicon nanostructures

K. Nehari, M. Lannoo, F. Michelini, N. Cavassilas, M. Bescond, and J. L. Autran

Appl. Phys. Lett. 93, 092103 (2008); http://dx.doi.org/10.1063/1.2978196 (3 pages) | Cited 2 times

Online Publication Date: 4 September 2008

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Effective mass theory is known to fail for nanostructures of indirect band gap materials such as silicon. We show that this situation can be remedied by going beyond the conventional second order expansion in the wave vector k. The method including fourth order terms is developed for the conduction band of silicon and applied to the 〈100〉-oriented wells, wires, and dots. The energy minima, their shift in k-space, as well as the variation in the effective mass with size are fully predicted from analytical equations containing only bulk parameters. This approach opens the way for accurate simulations of realistic quantum devices avoiding heavy calculations.
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73.21.Fg Quantum wells
73.21.Hb Quantum wires
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.21.La Quantum dots

Asymmetric transport in asymmetric T-shaped graphene nanoribbons

Yuan Ping Chen, Yue E. Xie, L. Z. Sun, and Jianxin Zhong

Appl. Phys. Lett. 93, 092104 (2008); http://dx.doi.org/10.1063/1.2978246 (3 pages) | Cited 18 times

Online Publication Date: 4 September 2008

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We propose an asymmetric T-shaped graphene nanoribbon (TGNR) that shows peculiar transport properties. In the vicinity of the Fermi level, the electron transmissions from the vertical graphene nanoribbon (GNR) to the two ends of the horizontal GNR are highly asymmetric. The electrons mostly transmit to one horizontal arm while are blocked by the other one. It is originated from the local asymmetric couplings between the intersection of the junction and the two horizontal arms. The asymmetric transport is very robust, even the T-shaped junction has a large size. Thus the asymmetric TGNR can be served as important components of nanocircuits.
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73.61.Wp Fullerenes and related materials
71.20.Tx Fullerenes and related materials; intercalation compounds
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Thick YBa2Cu3O7−x+BaSnO3 films with enhanced critical current density at high magnetic fields

C. V. Varanasi, J. Burke, H. Wang, J. H. Lee, and P. N. Barnes

Appl. Phys. Lett. 93, 092501 (2008); http://dx.doi.org/10.1063/1.2976683 (3 pages) | Cited 8 times

Online Publication Date: 2 September 2008

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The thickness dependence was studied for the critical current density (Jc) of YBa2Cu3O7−x(YBCO)+BaSnO3 (BSO) nanocomposite films. These films showed a significantly reduced decline of the Jc with thickness, especially at high magnetic fields. For example, a 2 μm thick YBCO+BSO film had a Jc ∼ 3×105 A/cm2 at 5 T as compared to a typical Jc of 2.4×103 A/cm2 at 5 T for a 300 nm thick YBCO film. The thick YBCO+BSO films maintained high Tc (>88 K) and had a high density (2.5×1011/cm2) of continuous BSO nanocolumns that likely contributed for the observed Jc enhancements.
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74.25.Sv Critical currents
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures

Spin polarization tuning in Mn5−xFexGe3

A. Stroppa, G. Kresse, and A. Continenza

Appl. Phys. Lett. 93, 092502 (2008); http://dx.doi.org/10.1063/1.2977469 (3 pages) | Cited 3 times

Online Publication Date: 2 September 2008

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Experimentally, the intermetallic compound Mn4FeGe3 has been recently shown to exhibit enhanced magnetic properties and spin polarization compared to the Mn5Ge3 parent compound. The present ab initio study focuses on the effect of Fe substitution on the electronic and magnetic properties of the compound. Our calculations reveal that the changes on the Fermi surface of the doped compound are remarkable, and provide explanations for the enhanced spin polarization observed. Finally, we show that it is indeed possible to tune the degree of spin polarization upon Fe doping, thus making the Mn5−xFexGe3 intermetallic alloy very promising for future spintronic applications.
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72.25.Ba Spin polarized transport in metals
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
75.30.Cr Saturation moments and magnetic susceptibilities
71.15.-m Methods of electronic structure calculations
61.72.up Other materials
75.50.Bb Fe and its alloys

Magnetic phase transition in Zn1−xMnxO doped by nitrogen

Sh. U. Yuldashev, Kh. T. Igamberdiev, T. W. Kang, V. O. Pelenovich, and A. G. Shashkov

Appl. Phys. Lett. 93, 092503 (2008); http://dx.doi.org/10.1063/1.2969411 (3 pages) | Cited 4 times

Online Publication Date: 2 September 2008

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The specific heat measurement was used to study the magnetic phase transition in Zn0.95Mn0.05O. The magnetization dependencies on the magnetic field, M(H) curve, and on the temperature, M(T) curve measured by superconducting quantum interference device, indicate the ferromagnetic-paramagnetic phase transition in Zn0.95Mn0.05O doped by nitrogen has a Curie temperature of about 80 K. The temperature dependence of the specific heat reveals a pronounced λ shaped peak at 75 K for the nitrogen-doped sample. Such dependencies indicate a well defined second-order phase transition in this sample.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.20.Ck Nonmetals
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Reduction in critical current density for spin torque transfer switching with composite free layer

Cheng-Tyng Yen, Wei-Chuan Chen, Ding-Yeong Wang, Yuan-Jen Lee, Chih-Ta Shen, Shan-Yi Yang, Ching-Hsiang Tsai, Chien-Chung Hung, Kuei-Hung Shen, Ming-Jinn Tsai, and Ming-Jer Kao

Appl. Phys. Lett. 93, 092504 (2008); http://dx.doi.org/10.1063/1.2978097 (3 pages) | Cited 17 times

Online Publication Date: 3 September 2008

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A composite free layer (CFL) consisting of a soft layer and a hard layer exchange coupled in parallel is proposed. The experimental results showed that the critical current density (Jc) can be reduced from 7.05×106 A/cm2 of strong coupled CoFeB(12.5 Å)/Ru(4 Å)/NiFe(17.5 Å) CFL to 2.65×106 A/cm2 of weak coupled CoFeB(12.5 Å)/Ru(15 Å)/NiFe(17.5 Å) CFL. The macrospin simulations showed that the soft layer of CFL can assist the hard layer of CFL to switch at a lower Jc. These results suggest that by using CFL, it is possible to reduce the Jc of spin torque transfer switching without compromising the thermal stability.
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74.25.Sv Critical currents
75.50.Bb Fe and its alloys
72.25.Mk Spin transport through interfaces
75.50.Ww Permanent magnets
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Solid phase epitaxy of ferrimagnetic Y3Fe5O12 garnet thin films

Y. Krockenberger, H. Matsui, T. Hasegawa, M. Kawasaki, and Y. Tokura

Appl. Phys. Lett. 93, 092505 (2008); http://dx.doi.org/10.1063/1.2976747 (3 pages) | Cited 3 times

Online Publication Date: 3 September 2008

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Epitaxial Y3Fe5O12 thin films were grown on (111) Gd3Ga5O12 substrates by pulsed laser deposition and subsequent annealing above 1270 K. The as-grown films deposited at temperatures below 1070 K were amorphous and the absence of trivalent iron ions has been verified by electron spin resonance spectroscopy. The ex situ annealing above 1270 K in oxygen atmosphere converted the films into epitaxial ones with ferrimagnetic properties. The higher temperature annealing up to 1670 K enabled the higher TC and the shorter lattice constant approaching those of bulk, while the saturation magnetization stayed at 2μB/f.u. at 300 K. Slightly expanded lattice constants and reduced saturation magnetization values may originate from oxygen deficient crystal structures. Nonetheless, the epitaxial films preserved a fairly smooth surface with a root mean square roughness below 2 nm.
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81.15.Np Solid phase epitaxy; growth from solid phases
75.50.Gg Ferrimagnetics
81.40.Gh Other heat and thermomechanical treatments
81.15.Fg Pulsed laser ablation deposition
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
76.30.Lh Other ions and impurities

Magnetic and magneto-optical properties of Fe-doped SrTiO3 films

Hyun-Suk Kim, Lei Bi, G. F. Dionne, and C. A. Ross

Appl. Phys. Lett. 93, 092506 (2008); http://dx.doi.org/10.1063/1.2977963 (3 pages) | Cited 17 times

Online Publication Date: 4 September 2008

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Epitaxial films of magnetically doped SrTi1−xFexO3 (x ⩽ 0.5) were grown on (001) LaAlO3 substrates by pulsed laser deposition. Structural and magnetic studies indicate that the observed ferromagnetism is intrinsic rather than from an impurity phase. The higher transparency with Fe doping is attributed to charge compensation resulting from hole doping by Fe incorporation into the SrTiO3 lattice. SrTi0.6Fe0.4O3 has a reasonably high Faraday rotation of 0.078 deg/μm accompanied by low optical loss (0.07 dB/μm), which makes it a promising candidate for integrated waveguide isolator applications.
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75.70.Ak Magnetic properties of monolayers and thin films
78.20.Ls Magneto-optical effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
75.50.Dd Nonmetallic ferromagnetic materials
81.15.Fg Pulsed laser ablation deposition

Fluid-flow characterization with nuclear spins without magnetic resonance

C. W. Crawford, Shoujun Xu, Eric J. Siegel, Dmitry Budker, and Alexander Pines

Appl. Phys. Lett. 93, 092507 (2008); http://dx.doi.org/10.1063/1.2977773 (3 pages) | Cited 2 times

Online Publication Date: 5 September 2008

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A technique for noninvasive monitoring of flow inside metallic enclosures using laser-based atomic magnetometry is introduced. The analyte is labeled via nuclear magnetization by magnets, thereby combining the polarization and encoding steps. No radiofrequency or audiofrequency pulses are involved. We demonstrate detection of flow inside an aluminum pipe with an inner diameter of 4.9 mm that has a constriction with a diameter of 1.6 mm and a length of 6.4 mm. The results agree with a model of spin density and relaxation indicating that our technique allows for fast, quantitative, and noninvasive diagnostics of flow with potential applications discussed below.
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07.55.-w Magnetic instruments and components
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
47.80.-v Instrumentation and measurement methods in fluid dynamics
47.60.Dx Flows in ducts and channels
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Determining the static dielectric permittivity of ion conducting materials when obscured by electrode polarization

Johan Gråsjö, Ken Welch, and Maria Strømme

Appl. Phys. Lett. 93, 092901 (2008); http://dx.doi.org/10.1063/1.2977861 (3 pages) | Cited 2 times

Online Publication Date: 2 September 2008

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A method is derived for the determination of the static dielectric permittivity of ion conducting materials when this parameter is obscured by electrode polarization in as-recorded low frequency dielectric spectra. The method requires permittivity measurements at two different electrode separations, and is applicable when the electric fields created by charge separation near the electrode surfaces do not induce nonlinear effects in the frequency region where electrode polarization begins to affect the dielectric response. The performance of the method is illustrated by the analysis of an ion conducting cellulose gel biosynthesized by the Acetobacter. xylinum bacterium. The method opens up possibilities to obtain more detailed information about dynamic processes in ion conducting materials from dielectric spectroscopy.
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77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization
82.70.Gg Gels and sols

Thermal conductivity of perovskite ferroelectrics

Makoto Tachibana, Taras Kolodiazhnyi, and Eiji Takayama-Muromachi

Appl. Phys. Lett. 93, 092902 (2008); http://dx.doi.org/10.1063/1.2978072 (3 pages) | Cited 6 times

Online Publication Date: 2 September 2008

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Thermal conductivities of BaTiO3, PbTiO3, KNbO3, KTaO3, NaNbO3, and Pb(Mg1/3Nb2/3)O3 (PMN) single crystals have been measured from 2 to 390 K. Pronounced jumps are found at structural transitions in BaTiO3 and KNbO3. A low-temperature anomaly from soft optical phonons is observed in KTaO3. For PMN and NaNbO3, glasslike behavior is observed in both the thermal conductivity and heat capacity measurements. We associate the glasslike behavior in NaNbO3 with the phase separation phenomena reported in recent studies.
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66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.
77.80.B- Phase transitions and Curie point
65.40.Ba Heat capacity
61.43.Fs Glasses

Piezoelectric K0.5Na0.5NbO3 thick films derived from polyvinylpyrrolidone-modified chemical solution deposition

Lingyan Wang, Kui Yao, and Wei Ren

Appl. Phys. Lett. 93, 092903 (2008); http://dx.doi.org/10.1063/1.2978160 (3 pages) | Cited 38 times

Online Publication Date: 3 September 2008

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Lead-free K0.5Na0.5NbO3 (KNN) ferroelectric films with enhanced thickness of 3.5 μm were prepared by a polyvinylpyrrolidone-modified chemical solution deposition method. A single perovskite phase with a dense morphology and (100) orientation was obtained at relatively low annealing temperature of 600 °C. A large effective piezoelectric coefficient d33, of 61 pm/V was demonstrated at 100 kHz without considering the substrate clamping effect. A well-saturated polarization hysteresis loop was obtained with a high remnant polarization Pr of 16.4 μC/cm2. These results showed that KNN is a promising lead-free piezoelectric film candidate, and that crystallizing the film at low processing temperature to obtain (100) orientation and dense morphology is critical to achieving excellent ferroelectric and piezoelectric properties.
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81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.40.Gh Other heat and thermomechanical treatments
77.80.Dj Domain structure; hysteresis
77.65.-j Piezoelectricity and electromechanical effects
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity

Piezoelectric properties of low-temperature sintered Li-modified (Na, K)NbO3 lead-free ceramics

Ke Wang, Jing-Feng Li, and Nan Liu

Appl. Phys. Lett. 93, 092904 (2008); http://dx.doi.org/10.1063/1.2977551 (3 pages) | Cited 32 times

Online Publication Date: 4 September 2008

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LiNbO3-doped (Na, K)NbO3 lead-free piezoceramics were prepared by conventional sintering at a temperature as low as 950 °C using excess Na2O additives. The crystal structure changed from orthorhombic to tetragonal with increasing LiNbO3 amount since the phase transition temperature TO−T shifted downward. In the region of two-phase coexistence, enhanced piezoelectric constant d33 (280 pC/N) and electromechanical coupling factor kp (48.3%) with a high Curie temperature TC (475 °C) were obtained in the nominal composition 0.92(Na0.535K0.48)NbO3–0.08LiNbO3. Our results open up the way to low-temperature sintering of (Na, K)NbO3-based lead-free piezoceramics with high performance.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
61.66.Fn Inorganic compounds
64.70.K- Solid-solid transitions
77.22.Ch Permittivity (dielectric function)

Influence of ferroelectricity on the photoelectric effect of LiNbO3

S. Dunn and D. Tiwari

Appl. Phys. Lett. 93, 092905 (2008); http://dx.doi.org/10.1063/1.2978195 (3 pages) | Cited 14 times

Online Publication Date: 5 September 2008

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A comparison between domain dependent photochemical and photoelectric cation reduction in LiNbO3 is presented. The reduction in photoelectric threshold for LiNbO3 due to the depolarization field allows UV irradiation to produce free electrons that can participate in photochemical reduction in silver nitrate. This is in addition to domain directed photophysics, where influences on the space charge layer due to the internal dipole of a ferroelectric determine the carrier at the surface. We show that the interaction of photoelectric and domain dependent influences is observed in LiNbO3 due to the low electron affinity ( ∼ 1–1.5 eV) and band bending (0.3–0.8 eV).
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
72.40.+w Photoconduction and photovoltaic effects
77.22.Ej Polarization and depolarization
77.22.Jp Dielectric breakdown and space-charge effects
77.80.Dj Domain structure; hysteresis
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Silver diffusion bonding and layer transfer of lithium niobate to silicon

Kenneth Diest, Melissa J. Archer, Jennifer A. Dionne, Young-Bae Park, Matthew J. Czubakowski, and Harry A. Atwater

Appl. Phys. Lett. 93, 092906 (2008); http://dx.doi.org/10.1063/1.2976560 (3 pages) | Cited 5 times

Online Publication Date: 5 September 2008

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A diffusion bonding method has been developed that enables layer transfer of single crystal lithium niobate thin films to silicon substrates. A silver film was deposited onto both the silicon and lithium niobate surfaces prior to bonding, and upon heating, a diffusion bond was formed. Transmission electron microscopy confirms the interface evolution via diffusion bonding which combines interfacial diffusion, power law creep, and growth of (111) silver grains to replace the as-bonded interface by a single polycrystalline silver film. The transferred film composition was the same as bulk lithium niobate.
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68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers

X-ray photoelectron spectroscopy energy band alignment of spin-on CoTiO3 high-k dielectric prepared by sol-gel spin coating method

Kuo-Hsing Kao, Shiow-Huey Chuang, Woei-Cherng Wu, Tien-Sheng Chao, Jian-Hao Chen, Ming-Wen Ma, Reui-Hong Gao, and Michael Y. Chiang

Appl. Phys. Lett. 93, 092907 (2008); http://dx.doi.org/10.1063/1.2978231 (2 pages)

Online Publication Date: 5 September 2008

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The characteristics of CoTiO3 high-k dielectric prepared by sol-gel spin coating method had been demonstrated. High electrical permittivity (k ∼ 40.2) of CoTiO3 dielectric was extracted via the transmission electron microscopy image and capacitance-voltage curves. In addition, the valence band offset between thermal SiO2 and spin-on CoTiO3 was about 4.0 eV, which was detected by x-ray photoelectron spectroscopy. The band gaps of thermal SiO2 and spin-on CoTiO3 were 9.0 and 2.2 eV, respectively. Energy band alignment of spin-on CoTiO3 directly with SiO2 and indirectly with Si was determined in this work.
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77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Evolution of electric field amplitude dependent scaling behaviors in ferroelectric films over a broad temperature range

J. Yang, X. J. Meng, M. R. Shen, C. Gao, J. L. Sun, and J. H. Chu

Appl. Phys. Lett. 93, 092908 (2008); http://dx.doi.org/10.1063/1.2978329 (3 pages) | Cited 6 times

Online Publication Date: 5 September 2008

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Show Abstract
The evolution of the electric field amplitude (V0) dependent scaling of dynamic hysteresis area (A∝V0α) with the temperature in Mn doped (Pb,Sr)TiO3 film was analyzed. α exhibited different values under three temperature regions, where (1) the intrinsic ferroelectric domain nucleation, growth, and reversal, (2) the competition between the polar nanoregions and mobile defects, and (3) the Joule loss during long range movement of oxygen vacancies were demonstrated. This study provides a quantitative criterion to distinguish the intrinsic ferroelectric hysteresis from artificial one.
Show PACS
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
61.72.jd Vacancies
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