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11 Aug 2008

Volume 93, Issue 6, Articles (06xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 93, 062101 (2008); http://dx.doi.org/10.1063/1.2968206 (3 pages)

K. Shibata and K. Hirakawa
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Contactless electroreflectance of GaN bulk crystals grown by ammonothermal method and GaN epilayers grown on these crystals

R. Kudrawiec, J. Misiewicz, M. Rudziński, and M. Zając

Appl. Phys. Lett. 93, 061910 (2008); http://dx.doi.org/10.1063/1.2972030 (3 pages) | Cited 7 times

Online Publication Date: 15 August 2008

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Room temperature contactless electroreflectance (CER) spectroscopy has been applied to study the energy gap, optical quality, and band bending for n-type and semi-insulating GaN crystals grown by ammonothermal method. Broad CER resonances typical of band-to-band absorption with opposite phases, which indicates opposite band bendings, have been clearly observed for the two types of GaN crystals. In addition, GaN epilayers have been grown by metalorganic chemical vapor deposition on these crystals and characterized by CER spectroscopy. Very narrow CER resonances ( ∼ 15 meV), typical of high quality material, have been observed for these epilayers. It confirms the excellent usefulness of ammonothermal GaN substrates for GaN homoepitaxy.
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78.20.Jq Electro-optical effects
78.66.Fd III-V semiconductors
71.20.Nr Semiconductor compounds

Electron injection assisted phase transition in a nano-Au-VO2 junction

Gang Xu, C.-M. Huang, Masato Tazawa, Ping Jin, D.-M. Chen, and L. Miao

Appl. Phys. Lett. 93, 061911 (2008); http://dx.doi.org/10.1063/1.2972106 (3 pages) | Cited 8 times

Online Publication Date: 15 August 2008

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The semiconductor-metal transition of vanadium dioxide (VO2) thin films epitaxially grown on C-plane sapphire is studied by depositing Au nanoparticles onto the thermochromic films forming a metal-semiconductor contact, namely, a nano-Au-VO2 junction. It reveals that Au nanoparticles have a marked effect on the reduction in the phase transition temperature of VO2. A process of electron injection in which electrons flow from Au to VO2 due to the lower work function of the metal is believed to be the mechanism. The result may support the Mott–Hubbard phase transition model for VO2.
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71.30.+h Metal-insulator transitions and other electronic transitions

The amorphous origin and the nucleation of intermetallic compounds formed at the interface during the soldering of Sn–3.0Ag–0.5Cu on a Cu substrate

Chien-Cheng Pan, Chang-Ho Yu, and Kwang-Lung Lin

Appl. Phys. Lett. 93, 061912 (2008); http://dx.doi.org/10.1063/1.2973148 (3 pages) | Cited 11 times

Online Publication Date: 15 August 2008

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A short time reflow of 15 s at 250 °C, followed by a liquid nitrogen quench, of the Sn–3Ag–0.5Cu solder on a Cu substrate gave rise to a three-layer interfacial structure. In addition to the commonly known η-Cu6Sn5/ε-Cu3Sn layers, an amorphous layer with a thickness of less than 50 nm exists between the Cu substrate and the thin ε-Cu3Sn layer. Nanocrystalline ε-Cu3Sn cells, revealed by transmission electron microscopy (TEM), as fine as 10 nm were detected within the amorphous region. The results of TEM analysis suggest that the nucleation of interfacial intermetallic compound ε-Cu3Sn occurs within the amorphous layer.
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81.20.Vj Joining; welding

Fast crystallization of chalcogenide glass for rewritable memories

Zhimei Sun, Jian Zhou, Andreas Blomqvist, Börje Johansson, and Rajeev Ahuja

Appl. Phys. Lett. 93, 061913 (2008); http://dx.doi.org/10.1063/1.2967742 (3 pages) | Cited 14 times

Online Publication Date: 15 August 2008

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By ab initio molecular dynamics simulations, we unraveled the unique network structure of amorphous Ge1Sb2Te4, which shows high rank of ordering and mostly consists of distorted defective octahedrons with a small portion of distorted tetrahedrons. The phase transition from amorphous to cubic Ge1Sb2Te4 would be mainly a process of angle rearrangements of tetrahedrons to octahedrons and vice versa.
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61.43.Fs Glasses
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
71.15.-m Methods of electronic structure calculations
64.70.kj Glasses
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High Kondo temperature (TK ∼ 80 K) in self-assembled InAs quantum dots laterally coupled to nanogap electrodes

K. Shibata and K. Hirakawa

Appl. Phys. Lett. 93, 062101 (2008); http://dx.doi.org/10.1063/1.2968206 (3 pages) | Cited 7 times

Online Publication Date: 11 August 2008

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We have fabricated single electron tunneling structures by forming nanogap metallic electrodes directly upon single self-assembled InAs quantum dots (QDs). The fabricated samples exhibited clear Coulomb blockade effects. Furthermore, a clear Kondo effect was observed when strong coupling between the electrodes and the QDs was realized using a large QD with a diameter of ∼ 100 nm. From the temperature dependence of the linear conductance at the Kondo valley, the Kondo temperature TK was determined to be ∼ 81 K. This is the highest TK ever reported for artificial quantum nanostructures.
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73.40.Ns Metal-nonmetal contacts
73.23.Hk Coulomb blockade; single-electron tunneling
72.15.Qm Scattering mechanisms and Kondo effect
73.63.Kv Quantum dots

Investigation of local electrical properties of coincidence-site-lattice boundaries in location-controlled silicon islands using scanning capacitance microscopy

Nobuyuki Matsuki, Ryoichi Ishihara, Alessando Baiano, and Kees Beenakker

Appl. Phys. Lett. 93, 062102 (2008); http://dx.doi.org/10.1063/1.2968663 (3 pages) | Cited 10 times

Online Publication Date: 11 August 2008

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We used scanning capacitance microscopy (SCM) to investigate the electrical activity of grain boundaries consisting of random and coincidence-site-lattice (CSL) boundaries in location-controlled silicon islands, which were fabricated using the μ-Czochralski process with an excimer laser. The SCM results suggest that the electrical activity of the {122}∑9 CSL boundary is much smaller than that of a random boundary, and the {111}∑3 CSL boundary is negligible. This is consistent with previous theoretical predictions and experimental results for thin-film transistors.
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73.61.Cw Elemental semiconductors
61.72.Mm Grain and twin boundaries
81.10.Fq Growth from melts; zone melting and refining

The use of doping spikes in GaN Gunn diodes

R. F. Macpherson and G. M. Dunn

Appl. Phys. Lett. 93, 062103 (2008); http://dx.doi.org/10.1063/1.2969779 (2 pages) | Cited 5 times

Online Publication Date: 11 August 2008

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The possibility of circumventing the difficulties of fine doping control in GaN Gunn diode devices by the substitution of a fully depleted p-type doping spike for the doping notch used to promote domain formation is explored using a Monte Carlo model. The p-type doping spike is a commonly used structure, but its potential use in GaN has not been previously evaluated. The results for a functional doping spike are compared, favorably, to those for a physically reasonable doping notch.
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84.40.Dc Microwave circuits
85.30.Fg Bulk semiconductor and conductivity oscillation devices (including Hall effect devices, space-charge-limited devices, and Gunn effect devices)
02.70.Uu Applications of Monte Carlo methods
61.72.uj III-V and II-VI semiconductors

Driving Weiss oscillations to zero resistance states by microwave Radiation

J. Iñarrea and G. Platero

Appl. Phys. Lett. 93, 062104 (2008); http://dx.doi.org/10.1063/1.2969796 (3 pages) | Cited 10 times

Online Publication Date: 11 August 2008

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We present a theoretical model to study the effect of microwave radiation on Weiss oscillations. In our proposal Weiss oscillations, produced by a spatial periodic potential, are modulated by microwave radiation due to an interference effect between both, space and time-dependent, potentials. The final magnetoresistance depends mainly on the spatial period of the spatial potential and the frequency of radiation. Depending on the values of these parameters, we predict that Weiss oscillations can reach zero resistance states. On the other hand, these dissipationless transport states, created just by radiation, can be destroyed by the presence of a space-dependent potential.
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61.80.-x Physical radiation effects, radiation damage
73.21.Cd Superlattices
73.43.Qt Magnetoresistance

Modified permittivity observed in bulk gallium arsenide and gallium phosphide samples at 50 K using the whispering gallery mode method

John G. Hartnett, David Mouneyrac, Jean-Michel Le Floch, Jerzy Krupka, Michael E. Tobar, and D. Cros

Appl. Phys. Lett. 93, 062105 (2008); http://dx.doi.org/10.1063/1.2969905 (3 pages) | Cited 4 times

Online Publication Date: 11 August 2008

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Whispering gallery modes in bulk cylindrical gallium arsenide and gallium phosphide samples have been examined both in darkness and under white light at 50 K. In both samples we observed change in permittivity under light and dark conditions. This results from a change in the polarization state of the semiconductor, which is consistent with a free electron-hole creation/recombination process. The permittivity of the semiconductor is modified by free photocarriers in the surface layers of the sample which is the region sampled by whispering gallery modes.
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77.22.Ch Permittivity (dielectric function)
72.80.Ey III-V and II-VI semiconductors
77.22.Ej Polarization and depolarization
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.40.+w Photoconduction and photovoltaic effects

Resonant tunneling through double-bended graphene nanoribbons

Z. Z. Zhang, Kai Chang, and K. S. Chan

Appl. Phys. Lett. 93, 062106 (2008); http://dx.doi.org/10.1063/1.2970957 (3 pages) | Cited 16 times

Online Publication Date: 12 August 2008

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We investigate theoretically resonant tunneling through double-bended graphene nanoribbon (GNR) structures, i.e., armchair-edged GNRs (AGNRs) in between two semi-infinite zigzag GNR leads. Our numerical results demonstrate that the resonant tunneling can be tuned dramatically by the Fermi energy and the length and/or widths of the AGNR for both the metallic and semiconductorlike AGNRs. The structure can also be use to control the valley polarization of the tunneling currents and could be useful for potential application in valleytronics devices.
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73.40.Gk Tunneling
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.22.-f Electronic structure of nanoscale materials and related systems

Study on interfacial properties of InGaAs and GaAs integrated with chemical-vapor-deposited high-k gate dielectrics using x-ray photoelectron spectroscopy

H. J. Oh, J. Q. Lin, S. J. Lee, G. K. Dalapati, A. Sridhara, D. Z. Chi, S. J. Chua, G. Q. Lo, and D. L. Kwong

Appl. Phys. Lett. 93, 062107 (2008); http://dx.doi.org/10.1063/1.2968293 (3 pages) | Cited 8 times

Online Publication Date: 14 August 2008

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Interfacial reaction study using x-ray photoelectron spectroscopy was carried out for metal-organic chemical-vapor-deposited HfO2 and HfAlO gate dielectrics on p-In0.53Ga0.47As layer as compared to the cases of p-GaAs substrate. The results show that the alloying of GaAs with InAs (In0.53Ga0.47As) in the III-V channel layer and the alloying HfO2 with Al2O3 in the high-k dielectric can be an effective way to improve the interface quality due to their significant suppression effects on native oxides formation, especially arsenic oxide which causes Fermi level pinning on the high-k/III-V channel interface during the fabrication processes. Transmission electron microscopy result and the electrical characteristics of HfAlO/p-In0.53Ga0.47As capacitors further validate the x-ray photoelectron spectroscopy observations.
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68.55.ag Semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
79.60.Jv Interfaces; heterostructures; nanostructures
77.55.-g Dielectric thin films
71.20.Nr Semiconductor compounds

Stability of B–H and B–D complexes in diamond under electron beam excitation

J. Barjon, A. Mehdaoui, F. Jomard, J. Chevallier, C. Mer, M. Nesladek, P. Bergonzo, J. Pernot, F. Omnès, and A. Deneuville

Appl. Phys. Lett. 93, 062108 (2008); http://dx.doi.org/10.1063/1.2965115 (3 pages) | Cited 8 times

Online Publication Date: 14 August 2008

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The substitution of hydrogen by deuterium is generally known to increase the stability of the defect passivation in semiconductors, occasionally giving rise to giant isotope effects. In this work, the stability under an electron beam irradiation of boron-hydrogen and boron-deuterium pairs in diamond are compared. The dissociation kinetics was followed in situ by cathodoluminescence spectroscopy. Surprisingly, B–H complexes are more stable than B–D complexes under electron beam at low temperature ( ∼ 100 K), with a dissociation rate about twice smaller. These experimental results are coherent with a dissociation mechanism involving a cumulative vibrational excitation of the complexes.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.65.Rv Passivation
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
61.82.Fk Semiconductors
78.66.Db Elemental semiconductors and insulators
78.60.Hk Cathodoluminescence, ionoluminescence

Separation of bulk and surface electron transport in metamorphic InAs layers using quantitative mobility spectrum analysis

Y. Lin, A. R. Arehart, A. M. Carlin, and S. A. Ringel

Appl. Phys. Lett. 93, 062109 (2008); http://dx.doi.org/10.1063/1.2970045 (3 pages) | Cited 4 times

Online Publication Date: 14 August 2008

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Electron transport in low dislocation density, strain-relaxed InAs layers grown on metamorphic InAsyP1−y/InP substrates by molecular beam epitaxy was characterized using quantitative mobility spectrum analysis (QMSA) of Hall effect measurements. QMSA applied to systematically varied metamorphic InAs samples reveals high bulk electron mobilities of ∼ 20 000 cm2/V s at 300 K at a Si doping concentration of 1×1017 cm−3, simultaneously with a separate population of much slower electrons having an average mobility of ∼ 2400 cm2/V s due to parallel conduction within the InAs surface electron accumulation layer. Measurements made on higher doped samples reveal only a single electron population participating in transport due to lowered surface band bending that reduces surface accumulation of electrons in conjunction with the high conductivity of the high mobility metamorphic InAs bulk that overwhelms any remaining surface conductivity in the Hall effect measurements.
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73.61.Ey III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.25.+i Surface conductivity and carrier phenomena
61.72.U- Doping and impurity implantation
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.ag Semiconductors

High thermoelectric efficiency in lanthanum doped Yb14MnSb11

Eric S. Toberer, Shawna R. Brown, Teruyuki Ikeda, Susan M. Kauzlarich, and G. Jeffrey Snyder

Appl. Phys. Lett. 93, 062110 (2008); http://dx.doi.org/10.1063/1.2970089 (3 pages) | Cited 25 times

Online Publication Date: 15 August 2008

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Lanthanum doping of the high-temperature p-type thermoelectric material Yb14MnSb11 enhances the figure of merit (zT) through carrier concentration tuning. This is achieved by substituting La3+ on the Yb2+ site to reduce the free hole concentration as expected from the change in valence. The high-temperature transport properties (Seebeck coefficient, electrical resistivity, Hall mobility, and thermal conductivity) of Yb13.6La0.4MnSb11 are explained by the change in carrier concentration using a simple rigid parabolic band model, similar to that found in Yb14Mn1−xAlxSb11. Together, use of these two dopant sites enables the partial decoupling of electronic and structural properties in Yb14MnSb11-based materials.
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72.15.Jf Thermoelectric and thermomagnetic effects
61.72.up Other materials
61.66.Dk Alloys
72.15.Gd Galvanomagnetic and other magnetotransport effects
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys

A study of metal-oxide-semiconductor capacitors on GaAs, In0.53Ga0.47As, InAs, and InSb substrates using a germanium interfacial passivation layer

Hyoung-Sub Kim, I. Ok, M. Zhang, F. Zhu, S. Park, J. Yum, H. Zhao, Jack C. Lee, Prashant Majhi, N. Goel, W. Tsai, C. K. Gaspe, and M. B. Santos

Appl. Phys. Lett. 93, 062111 (2008); http://dx.doi.org/10.1063/1.2972107 (3 pages) | Cited 12 times

Online Publication Date: 15 August 2008

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In this letter, we present electrical characteristics of HfO2-based metal-oxide-semiconductor capacitors (MOSCAPs) on n- and p-type GaAs, In0.53Ga0.47As, InAs, and InSb substrates, along with the effect of a thin germanium interfacial passivation layer. We found that MOSCAPs on all n-type substrates showed good C-V characteristics with small frequency dispersion (<10% and <200 mV). However, MOSCAPs on p-type GaAs and In0.53Ga0.47As substrates exhibited poor C-V characteristics implying severe Fermi level pinning, as has also been seen for p-type InP substrate. On the other hand, MOSCAPs on p-type InAs and InSb substrates, known as smaller bandgap materials, showed good C-V characteristics. We also present plausible mechanism for Fermi level pinning and interface characteristics.
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84.32.Tt Capacitors

Morphological and chemical optimization of ex situ NH4F (40%) conditioned Si(111)-(1×1):H

M. Lublow, T. Stempel, K. Skorupska, A. G. Muñoz, M. Kanis, and H. J. Lewerenz

Appl. Phys. Lett. 93, 062112 (2008); http://dx.doi.org/10.1063/1.2972142 (3 pages) | Cited 7 times

Online Publication Date: 15 August 2008

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Synchrotron radiation photoelectron spectroscopy was employed to investigate the chemical state of Si(111) surfaces upon anisotropic etching in concentrated NH4F solution. Minute amounts of oxidized silicon were detected and attributed to the fast Si–H–OH formation at atomic steps. Combining in situ optical and scanning probe techniques, consecutive chemical treatments were developed to achieve optimized morphological and chemical surface properties. Native oxides and a stressed SiO2/Si layer are removed by a two-step NH4F treatment leading to a terraced surface without triangular etch pits; subsequently, silicon in the Si1+/2+/3+ valence states is dissolved by HF (50%) while the surface topography is preserved.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.65.Cf Surface cleaning, etching, patterning
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Magnetization dependence on dynamic strain in ferromagnetic shape memory Ni–Mn–Ga

N. N. Sarawate and M. J. Dapino

Appl. Phys. Lett. 93, 062501 (2008); http://dx.doi.org/10.1063/1.2969799 (3 pages) | Cited 4 times

Online Publication Date: 11 August 2008

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The characterization of commercial Ni–Mn–Ga for use as a dynamic deformation sensor is addressed. The flux density is experimentally determined as a function of cyclic strain loading at frequencies from 0.2 to 160 Hz. With increasing frequency, the stress versus strain response remains almost unchanged whereas the flux density versus strain response shows increasing hysteresis. This behavior indicates that twin-variant reorientation occurs in concert with the mechanical loading, whereas the rotation of magnetization vectors occurs with a delay as the loading frequency increases. The increasing magnetization hysteresis must be considered when utilizing the material in dynamic sensing applications.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Cc Other ferromagnetic metals and alloys
81.40.Lm Deformation, plasticity, and creep
62.20.fg Shape-memory effect; yield stress; superelasticity
75.80.+q Magnetomechanical effects, magnetostriction

Nanocrystalline glass-coated FeNiMoB microwires

E. Komova, M. Varga, R. Varga, P. Vojtanik, J. Bednarcik, J. Kovac, M. Provencio, and M. Vazquez

Appl. Phys. Lett. 93, 062502 (2008); http://dx.doi.org/10.1063/1.2969057 (3 pages) | Cited 6 times

Online Publication Date: 12 August 2008

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The evolution of the structure of glass-coated Fe40Ni38Mo4B16 amorphous microwire with thermal treatments and its interplay with magnetism has been studied. As shown by x-ray diffraction, a primary crystallization process resulted into formation of γ-(Fe,Ni) nanocrystallites embedded in a residual amorphous matrix. The evolution of the saturation magnetization and the switching field after different thermal treatment was studied. Amorphous glass-coated microwires based on FeNi exhibit magnetic bistability even in the nanocrystalline state. This is explained by the high magnetoelastic anisotropy, which is also responsible for magnetic hardening after annealing at the temperatures above 670 K.
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64.70.K- Solid-solid transitions
64.70.Nd Structural transitions in nanoscale materials
74.25.Ha Magnetic properties including vortex structures and related phenomena
75.80.+q Magnetomechanical effects, magnetostriction
81.40.Gh Other heat and thermomechanical treatments

Magnetic order by C-ion implantation into Mn5Si3 and Mn5Ge3 and its lateral modification

C. Sürgers, K. Potzger, T. Strache, W. Möller, G. Fischer, N. Joshi, and H. v. Löhneysen

Appl. Phys. Lett. 93, 062503 (2008); http://dx.doi.org/10.1063/1.2969403 (3 pages) | Cited 11 times

Online Publication Date: 12 August 2008

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Ferromagnetic Mn5Si3C0.8 and Mn5Ge3C0.8 films with Curie temperatures TC well above room temperature are obtained by 12C+-ion implantation in antiferromagnetic Mn5Si3 or ferromagnetic Mn5Ge3. Patterning of the films with a gold mesh serving as a stencil mask during implantation allows a lateral modification of magnetic order creating ferromagnetic regions of Mn5Si3C0.8 which are embedded in antiferromagnetic Mn5Si3. This provides a procedure for the fabrication of magnetoelectronic hybrid devices comprised of different magnetic phases.
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75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Ee Antiferromagnetics
61.72.up Other materials

Persistent current in coils made out of second generation high temperature superconductor wire.

George A. Levin, Paul N. Barnes, John Murphy, Lyle Brunke, J. David Long, John Horwath, and Zafer Turgut

Appl. Phys. Lett. 93, 062504 (2008); http://dx.doi.org/10.1063/1.2969798 (3 pages) | Cited 2 times

Online Publication Date: 13 August 2008

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We report the results of an experimental study of a persistent coil made out of YBa2Cu3O7−δ coated conductors. The magnitude of the persistent current and the rate of decay were investigated. Two distinct modes of relaxation are evident—one is flux creep and the other, which is much faster, is of less obvious origin. Our conclusion is that the persistent current in such a coil can be large enough and decay slowly enough so that coated conductors can be used to make persistent coils for variety of applications.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
84.71.Ba Superconducting magnets; magnetic levitation devices

On the origin of ferromagnetism in CeO2 nanocubes

M. Y. Ge, H. Wang, E. Z. Liu, J. F. Liu, J. Z. Jiang, Y. K. Li, Z. A. Xu, and H. Y. Li

Appl. Phys. Lett. 93, 062505 (2008); http://dx.doi.org/10.1063/1.2972118 (3 pages) | Cited 23 times

Online Publication Date: 14 August 2008

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Magnetic behaviors of pure CeO2 nanoparticles and nanocubes have been investigated both experimentally and theoretically. It is found that monodisperse CeO2 nanocubes with an average size of 5.3 nm do show ferromagnetic behavior at ambient temperature with a saturation magnetization of about 5.7 memu/g and coercive force of about 69 Oe. First-principles calculations reveal that oxygen vacancies in pure CeO2 cause spin polarization of f electrons for Ce ions surrounding oxygen vacancies, resulting in net magnetic moment for pure CeO2 samples. One oxygen vacancy at surface can induce more magnetic moments than those induced by one oxygen vacancy in bulk. The results obtained here provide evidence that pure CeO2 sample with oxygen vacancies can indeed have magnetic behavior. This study will stimulate more investigations for understanding the origin of ferromagnetic TM-doped CeO2 (TM = 3d transition metals) in a particular case and TM-doped semiconductor oxides in general at ambient temperature.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Cr Saturation moments and magnetic susceptibilities

Strong nanopore pinning enhances Jc in YBa2Cu3O7−δ films

J. Z. Wu, R. L. S. Emergo, X. Wang, G. Xu, T. J. Haugan, and P. N. Barnes

Appl. Phys. Lett. 93, 062506 (2008); http://dx.doi.org/10.1063/1.2970965 (3 pages) | Cited 7 times

Online Publication Date: 15 August 2008

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Transport critical current density (Jc) has been studied in YBa2Cu3O7−δ (YBCO) thin films doped with nanopores as pins on magnetic vortices. The density of the nanopores in the range of 5±3 pores/μm2 corresponds to an accommodation field Hm ∼ 4.1–16.6 mT. High Jc up to 8.3 MA/cm2 has been observed on these porous YBCO films at 77 K and self-field. A close correlation between Jc and the magnetic pinning potential of the nanopores has been demonstrated below Hm, suggesting that nanopores are strong pins on the magnetic vortices.
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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)
74.72.-h Cuprate superconductors
74.25.Sv Critical currents
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Lu2O3/Al2O3 gate dielectrics for germanium metal-oxide-semiconductor devices

P. Darmawan, M. Y. Chan, T. Zhang, Y. Setiawan, H. L. Seng, T. K. Chan, T. Osipowicz, and P. S. Lee

Appl. Phys. Lett. 93, 062901 (2008); http://dx.doi.org/10.1063/1.2970036 (3 pages) | Cited 5 times

Online Publication Date: 13 August 2008

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Effect of Ge out diffusion into Lu2O3/Al2O3 high-k dielectric stack was investigated. Increasing Ge signal intensity with increasing annealing temperature was observed, which suggests that there may be excessive Ge incorporation into the high-k film. The electrical measurement shows an improvement of the k value with annealing temperature, as well as an increasing trend in the leakage current density suggesting degradation in electrical performance due to Ge incorporation. Our work suggests that 8.8 at. % of Ge in the film is excessive and result in degradation of the electrical performance of the device due to the increased leakage current.
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77.55.-g Dielectric thin films
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Multiferroic BiMnO3 thin films with double SrTiO3 buffer layers

J. Y. Son and Y.-H. Shin

Appl. Phys. Lett. 93, 062902 (2008); http://dx.doi.org/10.1063/1.2970038 (3 pages) | Cited 9 times

Online Publication Date: 13 August 2008

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High quality BiMnO3 thin films with double SrTiO3 buffer layers were fabricated on Pt/Ti/SiO2/Si and SrTiO3 substrates, in which SrTiO3 buffer layers were used to reduce leakage current in BiMnO3 thin films. The SrTiO3 buffer layers had a thickness of about 5 nm obtained from the fitting of ellipsometer data, which gave the remarkable enhancement in leakage current. BiMnO3 thin films exhibited the ferromagnetic transition with the Curie temperature of about 105 K. The Pt/SrTiO3/BiMnO3/SrTiO3/Pt and SrRuO3/SrTiO3/BiMnO3/SrTiO3/SrRuO3 capacitors showed good ferroelectric properties with the remanent polarization of about 9 and 16 μC/cm2, respectively.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Cc Other ferromagnetic metals and alloys
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.)
77.80.B- Phase transitions and Curie point
84.32.Tt Capacitors

Spontaneous nanoclustering of ZrO2 in atomic layer deposited LayZr1−yOx thin films

K. B. Jinesh, W. F. A. Besling, E. Tois, J. H. Klootwijk, R. Wolters, W. Dekkers, M. Kaiser, F. Bakker, M. Tuominen, and F. Roozeboom

Appl. Phys. Lett. 93, 062903 (2008); http://dx.doi.org/10.1063/1.2971032 (3 pages) | Cited 7 times

Online Publication Date: 14 August 2008

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Show Abstract
During atomic layer deposition of homogeneous LayZr1−yOx thin films spontaneous segregation of ZrO2 nanocrystals that are embedded in an amorphous La2O3 matrix takes place. This occurs if the Zr content in the LayZr1−yOx film rises above 30%, i.e., if the pulse ratio between the lanthanum precursor and the zirconium precursor is larger than four. X-ray diffraction analysis shows that the ZrO2 nanocrystals are in the tetragonal phase, which is the most stable configuration of this material with the highest dielectric permittivity. These nanocrystal-embedded thin films exhibit higher dielectric constants as the Zr content increases.
Show PACS
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.30.Mh Solid-phase precipitation
64.75.St Phase separation and segregation in thin films
68.55.aj Insulators
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
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