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23 Mar 2009

Volume 94, Issue 12, Articles (12xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 94, 122502 (2009); http://dx.doi.org/10.1063/1.3100783 (3 pages)

Junhua Wang, Yisheng Shi, Juexian Cao, and Ruqian Wu
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The conical shape filament growth model in unipolar resistance switching of TiO2 thin film

Kyung Min Kim and Cheol Seong Hwang

Appl. Phys. Lett. 94, 122109 (2009); http://dx.doi.org/10.1063/1.3108088 (3 pages) | Cited 43 times

Online Publication Date: 26 March 2009

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This study examined the relationship between the conducting filament resistance and reset voltage during the resistance switching of TiO2 thin films assuming a filament with a conical shape. There was a critical resistance ( ∼ 20 Ω) of the set state above and below which the filament responded differently in response to the current. Maintaining a higher set state resistance was more beneficial in achieving a more uniform reset voltage. This filament model coincides well with the localized switching behavior and the recently microscopically observed filament shape.
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68.55.ag Semiconductors
73.61.Le Other inorganic semiconductors

Direct imaging of GaN p-n junction by cross-sectional scanning photoelectron microscopy and spectroscopy

Cheng-Tai Kuo (郭承泰), Hong-Mao Lee (李弘貿), Hung-Wei Shiu (許紘瑋), Chia-Hao Chen (陳家浩), and Shangjr Gwo (果尚志)

Appl. Phys. Lett. 94, 122110 (2009); http://dx.doi.org/10.1063/1.3109778 (3 pages) | Cited 3 times

Online Publication Date: 27 March 2009

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We demonstrate that formation of p-n junction in gallium nitride (GaN) can be directly visualized on cleavage surfaces in a cross-sectional geometry, where the focused synchrotron radiation (soft x-ray) images the different doping layers on the nonpolar a-plane surface perpendicular to the polar growth direction. In contrast to the as-grown GaN polar surface, the in situ cleaved GaN a-plane surface is shown by using photoelectron spectroscopy to be under the flatband conditions. This unique surface property opens up the way to image and identify p-n junctions in III-nitride semiconductors.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
61.72.uj III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.-j Plasma applications

Effects of edge passivation by hydrogen on electronic structure of armchair graphene nanoribbon and band gap engineering

Y. H. Lu, R. Q. Wu, L. Shen, M. Yang, Z. D. Sha, Y. Q. Cai, P. M. He, and Y. P. Feng

Appl. Phys. Lett. 94, 122111 (2009); http://dx.doi.org/10.1063/1.3103551 (3 pages) | Cited 21 times

Online Publication Date: 27 March 2009

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We investigated effects of hydrogen passivation of edges of armchair graphene nanoribbons (AGNRs) on their electronic properties using first-principles method. The calculated band gaps of the AGNRs vary continually over a range of 1.6 eV as a function of a percentage of sp3-like bonds at the edges. This provides a simple way for band gap engineering of graphene as the relative stability of sp2 and sp3-like bonds at the edges of the AGNRs depends on the chemical potential of hydrogen gas, and the composition of the sp2 and sp3-like bonds at the edges of the AGNRs can be easily controlled experimentally via temperature and pressure of H2 gas.
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81.65.Rv Passivation
73.22.-f Electronic structure of nanoscale materials and related systems
71.15.-m Methods of electronic structure calculations

Vacancy phonon scattering in thermoelectric In2Te3–InSb solid solutions

Yanzhong Pei and Donald T. Morelli

Appl. Phys. Lett. 94, 122112 (2009); http://dx.doi.org/10.1063/1.3109788 (3 pages) | Cited 8 times

Online Publication Date: 27 March 2009

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Solid solution formation is a common and effective approach to reduce the lattice thermal conductivity for thermoelectric materials because of additional phonon scattering by point defects due to mass and strain fluctuations. This scattering is maximal for vacancies. In this paper we present an example of the strong effect of phonon-vacancy scattering for the InSb–In2Te3 system. The measured transport properties show a reduction by more than an order of magnitude of the lattice thermal conductivity. Further efforts are also made on optimization for thermoelectric applications through doping. Our results indicate that these solid solutions are a prospective new-type thermoelectric material.
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72.20.Pa Thermoelectric and thermomagnetic effects
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
63.20.kp Phonon-defect interactions
66.70.Df Metals, alloys, and semiconductors
61.72.jd Vacancies
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Transmission electron microscopy study on the crystallization and boron distribution of CoFeB/MgO/CoFeB magnetic tunnel junctions with various capping layers

Toyoo Miyajima, Takahiro Ibusuki, Shinjiro Umehara, Masashige Sato, Shin Eguchi, Mineharu Tsukada, and Yuji Kataoka

Appl. Phys. Lett. 94, 122501 (2009); http://dx.doi.org/10.1063/1.3106624 (3 pages) | Cited 25 times

Online Publication Date: 23 March 2009

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High-resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS) were used to study the microstructural properties of CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) with various capping layers. Crystallization of CoFeB layers was strongly dependent on the capping materials, and was affected by B diffusion. With NiFe-cap MTJs, CoFeB crystallized from the cap interface and formed a fcc structure; on the other hand, with Ta- and Ti-cap MTJs, CoFeB crystallized from the MgO interface and formed a bcc structure. EELS analysis showed that B mainly diffused to the capping layers and rarely to the MgO layers with increasing temperature. With Ti-cap MTJs, B diffusion caused hcp-Ti crystals to form an amorphous structure and CoFeB crystallized at lower temperature.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.37.Og High-resolution transmission electron microscopy (HRTEM)
66.30.H- Self-diffusion and ionic conduction in nonmetals
64.70.K- Solid-solid transitions
79.20.Uv Electron energy loss spectroscopy
68.65.Ac Multilayers

Magnetization and magnetic anisotropy of metallophthalocyanine molecules from the first principles calculations

Junhua Wang, Yisheng Shi, Juexian Cao, and Ruqian Wu

Appl. Phys. Lett. 94, 122502 (2009); http://dx.doi.org/10.1063/1.3100783 (3 pages) | Cited 3 times

Online Publication Date: 23 March 2009

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Using the full potential linearized augmented plane wave method, we explored the magnetic anisotropy energies of metallophthalocyanine molecules with Mn, Fe, Co, and Ni. Their spin magnetic moments can be expressed as 8−nμB (n = 5,6,7,8 for Mn, Fe, Co, and Ni). Interestingly, Mn-phthalocyanine has a large orbital magnetic moment of 0.19μB and a sizable magnetic anisotropy energy of 2.72 meV useable for applications.
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75.30.Gw Magnetic anisotropy
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Xx Molecular magnets

Epitaxial Mn2.5Ga thin films with giant perpendicular magnetic anisotropy for spintronic devices

Feng Wu, Shigemi Mizukami, Daisuke Watanabe, Hiroshi Naganuma, Mikihiko Oogane, Yasuo Ando, and Terunobu Miyazaki

Appl. Phys. Lett. 94, 122503 (2009); http://dx.doi.org/10.1063/1.3108085 (3 pages) | Cited 31 times

Online Publication Date: 24 March 2009

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We report on epitaxial growth and magnetic properties of Mn2.5Ga thin films, which were deposited on Cr/MgO single crystal substrates by magnetron sputtering. X-ray diffraction results revealed the epitaxial relationships as Mn2.5Ga(001)[100]∥Cr(001)[110]∥MgO(001)[100]. The presence of (002) and (011) superlattice peaks indicates that the films were crystallized into DO22 ordered structures. The perpendicular magnetic anisotropy (PMA) properties were found to be related to the extent of DO22 chemical ordering. A giant PMA (Kueff = 1.2×107 erg/cm3) and low saturation magnetization (Ms = 250 emu/cm3) can be obtained for the film with highest chemical ordering parameter (S = 0.8).
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75.70.Ak Magnetic properties of monolayers and thin films
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
81.15.Cd Deposition by sputtering
75.30.Gw Magnetic anisotropy

Half-metallicity and Gilbert damping constant in Co2FexMn1−xSi Heusler alloys depending on the film composition

Takahide Kubota, Sumito Tsunegi, Mikihiko Oogane, Shigemi Mizukami, Terunobu Miyazaki, Hiroshi Naganuma, and Yasuo Ando

Appl. Phys. Lett. 94, 122504 (2009); http://dx.doi.org/10.1063/1.3105982 (3 pages) | Cited 20 times

Online Publication Date: 24 March 2009

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Transport properties in magnetic tunnel junctions (MTJs) with Co2FexMn1−xSi (CFMS, x = 0–1.0)/Al–O/Co75Fe25 structure and Gilbert damping constant in the epitaxial CFMS films were investigated. The tunnel magnetoresistance ratio is as high as 75% in MTJs with x = 0.6 at room temperature. The Gilbert damping constant is minimal at x = 0.4. Relations between half-metallicity and the Gilbert damping constant in CFMS films were examined, revealing that the damping constant is small in half-metallic CFMS films.
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75.70.Ak Magnetic properties of monolayers and thin films
75.47.Np Metals and alloys
72.25.-b Spin polarized transport
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Magnetic semiconducting diode of p-Ge1−xMnx/n-Ge layers on silicon substrate

S. Majumdar, A. K. Das, and S. K. Ray

Appl. Phys. Lett. 94, 122505 (2009); http://dx.doi.org/10.1063/1.3097235 (3 pages) | Cited 5 times

Online Publication Date: 24 March 2009

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We have synthesized Ge-based magnetic diode composed of a Mn-doped Ge film grown on lightly As-doped Ge on silicon substrate. p-Ge1−xMnx/n-Ge heterostructure behaves like a conventional diode under forward and reverse biases and works like a spin valve below Curie temperature ( ∼ 50 K) under zero (B = 0) and nonzero (B = 300 mT) magnetic fields at forward bias (+2 V). A hysteretic behavior of p-n junction current with small coercive magnetic field implies the nonvolatility of the diode. Thus, a single element of p-Ge1−xMnx/n-Ge on silicon substrate deserves nonvolatility, rectification, and spin-valve-like functionality.
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85.30.Kk Junction diodes
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Enhancement of synchronized vortex lattice motion in hybrid magnetic/amorphous superconducting nanostructures

D. Perez de Lara, A. A. Alija, E. M. Gonzalez, J. I. Martin, M. Velez, J. M. Colino, J. V. Anguita, and J. L. Vicent

Appl. Phys. Lett. 94, 122506 (2009); http://dx.doi.org/10.1063/1.3103560 (3 pages) | Cited 1 time

Online Publication Date: 25 March 2009

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Superconducting a-Mo3Si and Nb films have been grown on arrays of Ni nanodots. We have studied the vortex lattice dynamics close to critical temperatures. Different vortex lattice configurations are obtained with the same array unit cell. These different vortex lattices occur at matching conditions between the vortex lattice and the array unit cell. The interplay between the random intrinsic pinning of the superconducting films and the periodic pinning of the array govern the vortex lattice configurations. Different vortex lattice configurations and enhancement of synchronized vortex lattice motion are obtained by increasing the periodic pinning strength and decreasing the random pinning strength.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)

Enhanced magnetic properties of FeCo ribbons nanocrystallized in magnetic field

P. Marín and A. Hernando

Appl. Phys. Lett. 94, 122507 (2009); http://dx.doi.org/10.1063/1.3091401 (3 pages) | Cited 7 times

Online Publication Date: 25 March 2009

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Tailoring the structure of nanocrystalline microstructures is an important step toward controlled design of novel nanostructured materials and devices. We demonstrate how the nanocrystalline microstructure of Co-rich ribbons can be tuned by annealing under magnetic field. The intensity of the field allows controlling different degrees of order at annealing temperatures corresponding to the first stages of the nanocrystallization process. The energy barrier for nucleation is directionally affected by the applied field. The influence of grains assembling on exchange coupling between grains has been analyzed by means of magnetic domains observation and magnetic characterization by means of a hysteresis loop.
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75.75.-c Magnetic properties of nanostructures
75.60.Nt Magnetic annealing and temperature-hysteresis effects
75.30.Et Exchange and superexchange interactions
75.60.Ch Domain walls and domain structure
75.50.Bb Fe and its alloys
75.50.Tt Fine-particle systems; nanocrystalline materials

Reduction of the spin-torque critical current by partially canceling the free layer demagnetization field

Luqiao Liu, Takahiro Moriyama, D. C. Ralph, and R. A. Buhrman

Appl. Phys. Lett. 94, 122508 (2009); http://dx.doi.org/10.1063/1.3107262 (3 pages) | Cited 21 times

Online Publication Date: 26 March 2009

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We significantly reduce the critical current Ic0 for the onset of spin torque switching of the free layer in nanometer-scale in-plane magnetized spin valves by partially cancelling its intrinsic demagnetization field through the utilization of Co/Ni multilayer free layers. The out-of-plane magnetic anisotropy arising from the Co/Ni interfaces reduces the effective demagnetization field (Heff) while not significantly affecting the thermal stability of the free layer. A zero-thermal-fluctuation critical current density Jc0 ∼ 2×106 A/cm2 is determined through both current ramp rate and nanosecond pulse measurements, and comparisons with large Heff control samples confirm that this strategy is efficient in substantially decreasing Ic0.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.-d Domain effects, magnetization curves, and hysteresis
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Gw Magnetic anisotropy

Magnetization reversal dominated by domain wall pinning in FePt based spin valves

A. P. Mihai, J. P. Attané, L. Vila, C. Beigné, J. C. Pillet, and A. Marty

Appl. Phys. Lett. 94, 122509 (2009); http://dx.doi.org/10.1063/1.3106605 (3 pages) | Cited 6 times

Online Publication Date: 27 March 2009

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In this paper, we study FePt/NM/FePt//MgO (NM = Pt or Pd) spin valves with perpendicular magnetization deposited by molecular beam epitaxy. Using extraordinary Hall effect and magnetoresistance, we show that the electrodes can be of different coercivities and magnetically decoupled, with current-in-plane magnetoresistances up to 0.8% at room temperature. Finally, using magnetic force microscopy observations, we prove that the different coercivities of the electrodes are controlled by different magnetization reversals and domain-wall pinning, thus allowing the obtaining of an antiparallel state.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.Np Metals and alloys
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
73.61.At Metal and metallic alloys
75.47.De Giant magnetoresistance
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.60.Jk Magnetization reversal mechanisms

Enhanced spin injection and detection in spin valves with integrated tunnel barriers

Andreas Vogel, Jeannette Wulfhorst, and Guido Meier

Appl. Phys. Lett. 94, 122510 (2009); http://dx.doi.org/10.1063/1.3109787 (3 pages) | Cited 13 times

Online Publication Date: 27 March 2009

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We study the spin-dependent transport in lateral spin-valve devices with aluminum oxide tunnel barriers at the interfaces between NiFe electrodes and an interconnecting Al strip. Different total conductivities per cross-sectional area are achieved by varying the oxygen pressure, the oxidation time, and the thickness of the oxidized aluminum layer. The experimental data are consistent with our theoretical description including spin diffusion, spin relaxation, and tunnel barriers at the interfaces between electrodes and aluminum strip. With decreasing tunnel conductance the amplitude of the nonlocal spin-valve effect increases by two orders of magnitude up to saturation.
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72.25.Hg Electrical injection of spin polarized carriers
72.25.Rb Spin relaxation and scattering
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)

Reduction in critical current of current induced switching in an inhomogeneous nanomagnet

M. C. Wu, A. Aziz, M. Ali, C. H. Marrows, B. J. Hickey, Z. H. Barber, and M. G. Blamire

Appl. Phys. Lett. 94, 122511 (2009); http://dx.doi.org/10.1063/1.3109790 (3 pages) | Cited 1 time

Online Publication Date: 27 March 2009

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We report low current-density switching of pseudospin valve nanopillars fabricated by a three-dimensional focused ion beam lithography. Simulations using the Landau–Liftshitz–Gilbert equation with Slonczewski spin transfer torque term demonstrate that magnetostatic coupling combined with an in-plane applied field results in a strongly inhomogeneous magnetization, which is close to the point of switching in both parallel and antiparallel configurations and so significantly reduced switching currents are possible.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
75.50.Tt Fine-particle systems; nanocrystalline materials
81.07.Bc Nanocrystalline materials
81.16.Nd Micro- and nanolithography
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
85.35.-p Nanoelectronic devices

Qubit dispersive readout scheme with a microstrip superconducting quantum interference device amplifier

S. Michotte

Appl. Phys. Lett. 94, 122512 (2009); http://dx.doi.org/10.1063/1.3109793 (3 pages) | Cited 2 times

Online Publication Date: 27 March 2009

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A flux qubit readout scheme involving a dispersive technique coupled to a microstrip superconducting quantum interference device (SQUID) amplifier has been tested experimentally. Thanks to the almost quantum limited noise of this amplifier at low temperature, this readout device is very promising for a design with actual qubits. Its proof of principle and low noise performance have been tested by simulating the qubit presence by applying a tiny flux change in the input SQUID. The resonant frequency of the amplifier is adjusted in situ with a varactor diode to approach the frequency of the tank circuit. Two operating modes (crossing or anticrossing regime) were identified.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
85.30.Kk Junction diodes
84.40.-x Radiowave and microwave (including millimeter wave) technology
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Charge-transition levels of oxygen vacancy as the origin of device instability in HfO2 gate stacks through quasiparticle energy calculations

Eun-Ae Choi and K. J. Chang

Appl. Phys. Lett. 94, 122901 (2009); http://dx.doi.org/10.1063/1.3106643 (3 pages) | Cited 17 times

Online Publication Date: 23 March 2009

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We perform quasiparticle energy calculations to study the charge-transition levels of oxygen vacancy (VO) in HfO2. The negative-U property of VO can explain flat band voltage shifts and threshold voltage (Vth) instability in hafnium based devices. In p+ Si gate electrode, the Fermi level pinning varies by up to 0.55 eV, in good agreement with the measured values. Depending on gate bias, VO traps electrons or holes from the Si channel, causing the Vth instability. It is suggested that short time-scale charge trapping/detrapping is due to metastable VO−1 centers, whereas stable VO−2 centers dominate long time-scale instability.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.Tv Field effect devices
61.72.jd Vacancies
61.72.jn Color centers

In situ investigation of the stability field and relaxation behavior of nanodomain structures in morphotropic Pb[Zr1−xTix]O3 under variations in electric field and temperature

Kristin A. Schönau, Michael Knapp, Mario Maglione, and Hartmut Fuess

Appl. Phys. Lett. 94, 122902 (2009); http://dx.doi.org/10.1063/1.3098073 (3 pages) | Cited 3 times

Online Publication Date: 23 March 2009

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The stability field of nanodomain structures recently discovered at the morphotropic phase boundary of undoped lead zirconate titanate [ Schönau et al., Phys. Rev. B 75, 184117 (2007) ] has been investigated with respect to temperature and electric field. Under electric field for distinct compositions, such as PbZr0.535Ti0.465O3, the starting domain structure of tetragonal microdomains and nanodomains is reversibly alternated into rhombohedral microdomains at high voltage. We now show that this material exhibits a dielectric relaxation directly below the formation temperature of nanodomain structures, correlated either to a high domain wall density or to polar nanoregions with activation energies in the range observed for relaxor ferroelectrics.
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77.80.Dj Domain structure; hysteresis
61.46.-w Structure of nanoscale materials
77.22.Gm Dielectric loss and relaxation
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Colossal dielectric constant up to gigahertz at room temperature

S. Krohns, P. Lunkenheimer, Ch. Kant, A. V. Pronin, H. B. Brom, A. A. Nugroho, M. Diantoro, and A. Loidl

Appl. Phys. Lett. 94, 122903 (2009); http://dx.doi.org/10.1063/1.3105993 (3 pages) | Cited 24 times

Online Publication Date: 23 March 2009

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The applicability of recently discovered materials with extremely high (“colossal”) dielectric constants, required for future electronics, suffers from the fact that their dielectric constant ε′ only is huge in a limited frequency range below about 1 MHz. In the present report, we show that the dielectric properties of a charge-ordered nickelate, La15/8Sr1/8NiO4, surpass those of other materials. Especially, ε′ retains its colossal magnitude of >10 000 well into the gigahertz range.
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77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation

Temperature- and field-dependent leakage current of epitaxial YMnO3/GaN heterostructure

H. Wu, J. Yuan, T. Peng, Y. Pan, T. Han, and C. Liu

Appl. Phys. Lett. 94, 122904 (2009); http://dx.doi.org/10.1063/1.3106635 (3 pages) | Cited 8 times

Online Publication Date: 24 March 2009

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Epitaxial ferroelectric YMnO3 (YMO) thin films were fabricated on (0001) GaN substrates by pulsed laser deposition followed by rapid thermal annealing. The temperature and field dependence of the leakage current of YMO/GaN interface was studied in a temperature range from 150 to 300 K and for an applied voltage up to 10 V. In a low temperature region from 180 to 220 K, the YMO/GaN interface acted as a Schottky barrier with a height of 0.27 eV for a field below 1.4 MV/cm, while the leakage mechanism was governed by the Fowler–Nordheim tunneling for a field above 1.4 MV/cm. Moreover, a space-charge-limited-current behavior was observed in a high field for a temperature above 270 K, while an Ohmic behavior was observed in a low field. In comparison, the dominant leakage mechanism of In/YMO interface was an Ohmic behavior in the whole measured voltage and temperature ranges.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
81.15.Fg Pulsed laser ablation deposition
73.30.+y Surface double layers, Schottky barriers, and work functions

Systematic study on work-function-shift in metal/Hf-based high-k gate stacks

Yuki Kita, Shinichi Yoshida, Takuji Hosoi, Takayoshi Shimura, Kenji Shiraishi, Yasuo Nara, Keisaku Yamada, and Heiji Watanabe

Appl. Phys. Lett. 94, 122905 (2009); http://dx.doi.org/10.1063/1.3103314 (3 pages) | Cited 1 time

Online Publication Date: 24 March 2009

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Change in the work function (WF) of the gate electrode material caused by the contact with Hf-based high-k gate dielectrics was investigated by means of the flat-band voltage (Vfb) shift in capacitance-voltage curves, and the interface dipole, which modifies the WF, was characterized by x-ray photoelectron spectroscopy. We observed a negative Vfb shift and corresponding interface dipole, which suggest the formation of oxygen vacancy (VO) in the Hf-based oxides. In contrast, we observed an opposite (positive) Vfb shift and interface dipole when Au electrodes were formed on cleaned Hf-based dielectrics. This indicates that Au–Hf bond hybridization at the Au/HfSiON interface also causes effective WF modulation, as theoretically predicted by Shiraishi et al. ( Tech. - Dig. Int. Electron Devices Meet. 2005, 43 ).
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
79.60.Jv Interfaces; heterostructures; nanostructures
61.72.jd Vacancies

Ultralow dielectric losses in pyrochlore films of the PbO–MgO–Nb2O5–TiO2 system

X. H. Zhu, E. Defaÿ, A. Suhm, E. Fribourg-blanc, and M. Aïd

Appl. Phys. Lett. 94, 122906 (2009); http://dx.doi.org/10.1063/1.3106107 (3 pages) | Cited 5 times

Online Publication Date: 25 March 2009

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(1−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMNT) (with x = 0.1) thin films were prepared on Pt-coated silicon substrates by radio-frequency magnetron sputtering and postdeposition annealing method. A well-crystallized pyrochlore phase structure, which started to nucleate and grow at 450–500 °C, was formed in the PMNT thin films. These pyrochlore-structured PMNT thin films show ultralow dielectric losses with a typical loss tangent as low as 0.001, accompanied by a relatively high dielectric constant (εr = 176). Such an extremely low dielectric loss, having never been obtained in thin films of perovskite PMNT, is probably ascribed to the specific structural feature of pyrochlore phase, chemically different from its perovskite counterpart, and ascribed to the avoidance of the polar domain-related losses.
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77.55.-g Dielectric thin films
77.22.Gm Dielectric loss and relaxation
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
81.40.Gh Other heat and thermomechanical treatments
77.22.Ch Permittivity (dielectric function)

Metal-oxide-semiconductor capacitors with erbium oxide dielectrics on In0.53Ga0.47As channels

Yoontae Hwang, Mark A. Wistey, Joël Cagnon, Roman Engel-Herbert, and Susanne Stemmer

Appl. Phys. Lett. 94, 122907 (2009); http://dx.doi.org/10.1063/1.3106618 (3 pages) | Cited 4 times

Online Publication Date: 26 March 2009

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Erbium oxide dielectrics with a thickness of ∼ 6 nm were fabricated in situ on In0.53Ga0.47As channels. Leakage current and capacitance densities were characterized as a function of applied voltage using metal-oxide-semiconductor capacitors with two different top electrode materials, Pt and Al. Leakage current densities were less than 10−3 A/cm2 at gate voltages up to ±2 V. The capacitance densities were lower with the Al electrode, which was attributed to a low-permittivity aluminum oxide layer at the electrode interface. The capacitors with the Pt electrode showed a pronounced increase in the capacitance in the depletion region at frequencies as high as 1 MHz, which was not observed for the Al electrode. Possible origins of the differences in the capacitance-voltage characteristics with Pt and Al electrodes are discussed.
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84.32.Tt Capacitors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.55.-g Dielectric thin films

Domain growth dynamics in single-domain-like BiFeO3 thin films

Y. C. Chen (陳宜君), Q. R. Lin (林其叡), and Y. H. Chu (朱英豪)

Appl. Phys. Lett. 94, 122908 (2009); http://dx.doi.org/10.1063/1.3109779 (3 pages) | Cited 12 times

Online Publication Date: 26 March 2009

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We present a quantitative study of 180° domain wall motion in epitaxial BiFeO3 (111) films, which can be treated as a nearly ideal single-domain environment. The domains were dynamically written by applying voltage pulses and examined by the piezoresponse force microscope technique. A transition of domain growth behaviors from the activated type to the nonactivated type was observed when increasing the pulse voltages. The obtained activation field was close to the ideally thermodynamic switching field of BiFeO3. The asymmetry of activated fields showed the preference of the downward polarization in the BiFeO3/SrRuO3 films.
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75.80.+q Magnetomechanical effects, magnetostriction
75.70.Kw Domain structure (including magnetic bubbles and vortices)
65.40.G- Other thermodynamical quantities
77.80.Dj Domain structure; hysteresis
75.50.Ee Antiferromagnetics

High piezoelectricity of Pb(Zr,Ti)O3-based ternary compound thin films on silicon substrates

Tao Zhang, Kiyotaka Wasa, Shu-yi Zhang, Zhao-jiang Chen, Feng-mei Zhou, Zhong-ning Zhang, and Yue-tao Yang

Appl. Phys. Lett. 94, 122909 (2009); http://dx.doi.org/10.1063/1.3103553 (3 pages) | Cited 3 times

Online Publication Date: 27 March 2009

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Pb(Zr,Ti)O3 (PZT)-based ternary compound thin films, 0.06PMnN-0.94PZT(50/50) (PMnN-PZT), are deposited on Si-based heterostructures by rf magnetron sputtering system. The intrinsic PZT(50/50) thin films are also deposited on the same kind of substrates for comparison. The PMnN-PZT thin films show the similar polycrystalline structures as those of PZT with highly (111) oriented perovskite phase. The PMnN-PZT thin films show excellent piezoelectricity and ferroelectricity which are distinctly better than those of PZT thin films prepared with the same deposition conditions. Besides, the cantilevers of PMnN-PZT thin films on the heterostructure substrates also exhibit higher sensitivities than the PZT thin film cantilevers.
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77.55.-g Dielectric thin films
77.65.-j Piezoelectricity and electromechanical effects
77.80.-e Ferroelectricity and antiferroelectricity
81.15.Cd Deposition by sputtering
68.55.aj Insulators
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