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18 Oct 2004

Volume 85, Issue 16, pp. 3343-3639

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 3570 (2004); http://dx.doi.org/10.1063/1.1807953 (2 pages)

X. N. Zhang, C. R. Li, Z. Zhang, and Z. X. Cao
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Spin injection from Fe3Si into GaAs

A. Kawaharazuka, M. Ramsteiner, J. Herfort, H.-P. Schönherr, H. Kostial, and K. H. Ploog

Appl. Phys. Lett. 85, 3492 (2004); http://dx.doi.org/10.1063/1.1807014 (3 pages) | Cited 30 times

Online Publication Date: 22 October 2004

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We demonstrate room-temperature spin injection from the epitaxially grown ferromagnetic metal Fe3Si into the semiconductor GaAs. The injection efficiency is comparable to values previously obtained for the Fe∕GaAs and MnAs∕GaAs hybrid systems using the emission of similar (In,Ga)As∕GaAs light-emitting diodes for the detection of spin polarization. The temperature dependence of the detected polarization is explained by taking into account spin relaxation inside the semiconductor device.
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85.60.Jb Light-emitting devices
72.25.Dc Spin polarized transport in semiconductors
72.25.Mk Spin transport through interfaces
73.61.Ey III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth

Graphitic features on SiC surface following oxidation and etching using surface enhanced Raman spectroscopy

Weijie Lu, L. C. Feldman, Y. Song, S. Dhar, W. E. Collins, W. C. Mitchel, and J. R. Williams

Appl. Phys. Lett. 85, 3495 (2004); http://dx.doi.org/10.1063/1.1804610 (3 pages) | Cited 18 times

Online Publication Date: 22 October 2004

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Graphitic features are detected on 4H-SiC surface following oxidation and etching using surface enhanced Raman spectroscopy (SERS). The electronic state of the carbon is sp2 on both the Si- and C-faces of 4H-SiC. The structures of the “carbon clusters” consist of two-dimensional graphitic flakes less than 2 nm and one-dimensional polyenes. The degree of graphitization on the C-face SiC is higher than those on the Si-face SiC. This study provides experimental evidence for “carbon clusters” existing on SiC surfaces following oxidation at atmospheric pressure and demonstrates that SERS is an effective technique to probe low concentration species on the SiC surface.
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81.65.Mq Oxidation
78.30.Hv Other nonmetallic inorganics
81.65.Cf Surface cleaning, etching, patterning
73.20.At Surface states, band structure, electron density of states
81.05.Hd Other semiconductors
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Highly coercive electrodeposited FePt films by postannealing in hydrogen

K. Leistner, J. Thomas, H. Schlörb, M. Weisheit, L. Schultz, and S. Fähler

Appl. Phys. Lett. 85, 3498 (2004); http://dx.doi.org/10.1063/1.1807958 (3 pages) | Cited 26 times

Online Publication Date: 22 October 2004

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The properties of electrodeposited films subsequently annealed in H2 are reported and compared with those of vacuum-annealed samples. Annealing in hydrogen reduces the oxygen content incorporated during electrodeposition, resulting in significantly higher magnetization values. Phase formation is enhanced by hydrogen and L10 ordering starts at temperatures as low as 350°C. In addition, grain growth is hindered. These effects contribute to the high coercivity of 1.1 T achieved after annealing at 600°C in H2.
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75.50.Bb Fe and its alloys
75.50.Ww Permanent magnets
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
68.55.A- Nucleation and growth
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Gh Other heat and thermomechanical treatments
81.15.Pq Electrodeposition, electroplating

Spin-dependent boundary resistance in the lateral spin-valve structure

T. Kimura, J. Hamrle, Y. Otani, K. Tsukagoshi, and Y. Aoyagi

Appl. Phys. Lett. 85, 3501 (2004); http://dx.doi.org/10.1063/1.1805698 (3 pages) | Cited 39 times

Online Publication Date: 22 October 2004

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We report the detection of clear spin-valve signal without any spurious magnetoresistive signal in a lateral spin-valve structure consisting of Cu∕Ni−Fe ohmic junction using local current injection. The obtained spin-valve signal is much larger than that of the nonlocal spin-valve configuration because of the efficient spin accumulation. The local current injection experiments with different probe configurations proved that the spin-valve signal is caused by the spin-dependent boundary resistance at the interface between the ferromagnetic voltage probe and the spin-polarized nonmagnetic wire.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
72.15.Gd Galvanomagnetic and other magnetotransport effects
72.25.Hg Electrical injection of spin polarized carriers
73.40.Cg Contact resistance, contact potential
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.25.Mk Spin transport through interfaces
75.50.Bb Fe and its alloys

Direct observation and analysis of nanoscale precipitates in (Sm,Eu,Gd)Ba2Cu3Oy

M. Muralidhar, N. Sakai, M. Jirsa, N. Koshizuka, and M. Murakami

Appl. Phys. Lett. 85, 3504 (2004); http://dx.doi.org/10.1063/1.1805709 (3 pages) | Cited 12 times

Online Publication Date: 22 October 2004

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We employed atomic-resolution high-angle annular dark-field scanning transmission electron microscope to characterize the chemical composition and nature of the nanoparticles dispersed in melt-processed (Sm0.33Eu0.33Gd0.33)Ba2Cu3Oy superconductor. We found two types of stable nanometer-scale particles, small LRE-Ba2CuZrOy and (LRE,Zr)BaCuOy (LRE=Sm,Eu,Gd) ones, in the 10–60 nm range, and larger particles of Gd2BaCuO5 “Gd-211,” around 100 nm in size. A substantial increase of critical current density was observed up to 90 K. Experimental data were interpreted in terms of additive pinning by “large” defects and a point-like disorder. The nanosized particles open a new horizon for production of bulk high-Tc superconducting magnets.
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74.72.-h Cuprate superconductors
74.25.Sv Critical currents
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
68.37.Lp Transmission electron microscopy (TEM)

A model for asymmetric giant magnetoimpedance in field-annealed amorphous ribbons

N. A. Buznikov, CheolGi Kim, Chong-Oh Kim, and Seok-Soo Yoon

Appl. Phys. Lett. 85, 3507 (2004); http://dx.doi.org/10.1063/1.1806565 (3 pages) | Cited 10 times

Online Publication Date: 22 October 2004

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A phenomenological model for the asymmetric giant magnetoimpedance (GMI) in field-annealed amorphous ribbons is developed. The effect of a surface crystalline layer on the GMI response is described in terms of an effective bias field appearing due to a coupling between the crystalline layer and amorphous phase. It is shown that the presence of the bias field changes drastically the GMI profile. At low frequencies, the domain-walls motion leads to a steplike change in the GMI response. At high frequencies, the domain-walls motion is damped, and the GMI profile exhibits asymmetric two-peak behavior. The calculated dependences are shown to be in a qualitative agreement with results of experimental studies of the asymmetric GMI in field-annealed Co-based amorphous ribbons.
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75.50.Kj Amorphous and quasicrystalline magnetic materials
75.50.Cc Other ferromagnetic metals and alloys
75.47.De Giant magnetoresistance
61.43.Bn Structural modeling: serial-addition models, computer simulation
61.43.Dq Amorphous semiconductors, metals, and alloys
75.60.Ch Domain walls and domain structure
81.40.Gh Other heat and thermomechanical treatments
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.40.Mg Numerical simulation studies

Experimental study of the influence of edge roughness on magnetization switching in Permalloy nanostructures

M. T. Bryan, D. Atkinson, and R. P. Cowburn

Appl. Phys. Lett. 85, 3510 (2004); http://dx.doi.org/10.1063/1.1806566 (3 pages) | Cited 24 times

Online Publication Date: 22 October 2004

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Rectangular Permalloy nanostructures with different edge roughness, but the same average width, were fabricated by controlled variations in the exposure conditions of an electron-beam lithography process. The average widths that were studied ranged from 200 to 640 nm. Structures were characterized individually using magneto-optical Kerr effect single-structure nanomagnetometry and scanning electron microscopy on the same structure. Increased edge roughness caused increased coercivity, except for 200-nm-wide structures. Large edge roughness doubled the coercivity of wide (>600 nm) structures. The coercivity of nominally identical structures (same roughness amplitude) differed by up to 20 Oe, suggesting that the specific edge profile influences magnetic switching.
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75.50.Bb Fe and its alloys
75.50.Vv High coercivity materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.07.Bc Nanocrystalline materials
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.46.-w Structure of nanoscale materials
78.20.Ls Magneto-optical effects
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.16.Nd Micro- and nanolithography

Effects of high-intensity ultrasound on Bi2Sr2CaCu2O8+x superconductor

Tanya Prozorov, Brett McCarty, Zhihua Cai, Ruslan Prozorov, and Kenneth S. Suslick

Appl. Phys. Lett. 85, 3513 (2004); http://dx.doi.org/10.1063/1.1808500 (3 pages) | Cited 8 times

Online Publication Date: 22 October 2004

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Slurries of powdered Bi2Sr2CaCu2O8+x (BSCCO-2212) superconductor in high-boiling alkanes were irradiated with intense ultrasound. Significant enhancements of magnetic irreversibility as well as transport critical current are reported. The effects are dependent on the concentration of the slurry and are optimal for 1.5 wt % slurry loading. Electron microscopy shows that ultrasonic treatment leads to a change in grain morphology and intergrain welding. The observed enhancement of superconducting properties is consistent with the limitations in critical currents in BSCCO superconductor being due to intergrain coupling rather than intragrain pinning strength.
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74.72.-h Cuprate superconductors
74.70.Dd Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.)
74.81.Bd Granular, melt-textured, amorphous, and composite superconductors
74.25.Sv Critical currents
68.35.B- Structure of clean surfaces (and surface reconstruction)
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.F- Transport properties
74.62.Yb Other effects
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
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Spontaneous polarization change with Zr∕(Zr+Ti) ratios in perfectly polar-axis-orientated epitaxial tetragonal Pb(Zr,Ti)O3 films

Hitoshi Morioka, Shintaro Yokoyama, Takahiro Oikawa, Hiroshi Funakubo, and Keisuke Saito

Appl. Phys. Lett. 85, 3516 (2004); http://dx.doi.org/10.1063/1.1795357 (3 pages) | Cited 27 times

Online Publication Date: 22 October 2004

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Epitaxial Pb(Zr,Ti)O3 (PZT) films 50 and 250 nm thick with the Zr∕(Zr+Ti) ratio from 0.13 to 0.65 were grown on (100)cSrRuO3∕∕(100)SrTiO3 substrates at 540 °C by pulsed-metalorganic chemical vapor deposition. The crystal orientation, lattice parameter, axial angle, and relative volume fraction of constituent domains were determined by high-resolution x-ray diffraction reciprocal space mapping. We grew (100) and∕or (001)-oriented epitaxial PZT films for the whole Zr∕(Zr+Ti) ratio. A tetragonal single phase was obtained for the Zr∕(Zr+Ti) ratio ranging from 0.13 to 0.54 and 0.19 to 0.45 with the 50 and 250 nm thick films, respectively, while mixed phases of a tetragonal and rhombohedral from 0.45 to 0.60 for the 250 nm thick films was obtained. For the films consisting of a tetragonal single phase, lattice parameters of a- and c-axes and their ratio (c∕a) were almost the same as the reported data for the PZT powder, suggesting a small amount of residual strain in them. In addition, perfectly polar-axis (c-axis)-oriented tetragonal films were obtained for the 50 nm thick films, while an ∼70% c-axis-orientation for the 250 nm thick ones was obtained. Polarization–electric-field hysteresis loops with a good square shape were observed for all films. Also, spontaneous polarization (Ps) values that were directly measured for the 50 nm thick films and estimated for the 250 nm thick films taking into account the volume fraction of the polar-axis-orientated domain were closely in line with the Zr∕(Zr+Ti) ratio, and they decreased as the ratio increased. The square of the estimated Ps was found to be proportional to the crystal distortion, c∕a−1. These results are essential not only for understanding the origin of the large Ps of PZT but for the property design of the ferroelectric devices using PZT.
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77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

High piezoelectric response in polar-axis-oriented CaBi4Ti4O15 ferroelectric thin films

Desheng Fu, Kazuyuki Suzuki, and Kazumi Kato

Appl. Phys. Lett. 85, 3519 (2004); http://dx.doi.org/10.1063/1.1807010 (3 pages) | Cited 10 times

Online Publication Date: 22 October 2004

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We report on the piezoelectric properties of polar-axis-oriented CaBi4Ti4O15 films detected by atomic force microscope (AFM). The sol-gel-derived films onto Pt foil show excellent switching properties, and can be uniformly polarized over large areas with a conductive AFM tip. The films have an extremely high piezoelectric coefficient of d33, and a value of 180 pm∕V has been detected. These results indicate that the oriented bismuth-layered films can be used as the lead-free piezoelectrics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.65.Bn Piezoelectric and electrostrictive constants
77.80.Dj Domain structure; hysteresis
77.22.Ej Polarization and depolarization
77.80.Fm Switching phenomena
68.37.Ps Atomic force microscopy (AFM)
68.55.A- Nucleation and growth

Ba0.5Sr0.5TiO3–Bi1.5Zn1.0Nb1.5O7 composite thin films with promising microwave dielectric properties for microwave device applications

L. Yan, L. B. Kong, L. F. Chen, K. B. Chong, C. Y. Tan, and C. K. Ong

Appl. Phys. Lett. 85, 3522 (2004); http://dx.doi.org/10.1063/1.1785861 (3 pages) | Cited 14 times

Online Publication Date: 22 October 2004

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Crack-free, dense, and uniform Ba0.5Sr0.5TiO3(BST)–Bi1.5Zn1.0Nb1.5O7(BZN) composite thin films were deposited on (100) LaAlO3, (100) SrTiO3, and (100) MgO substrates via a pulsed laser deposition, using a combined target of BST and BZN ceramics. Phase composition and microstructure of the BST-BZN thin films were characterized by x-ray diffraction and scanning electron microscopy. The films, on LAO, STO, and MgO substrates, showed zero-field microwave (∼7.7 GHz) dielectric constants of 471, 435, and 401, dielectric loss tangents of 0.0048, 0.0043, and 0.0037, and dielectric tunabilities of 6.2%, 6.0%, and 5.7% at ∼8.1 kV∕cm, respectively. The good physical and electrical properties of the BST–BZN composite thin films make them promising candidates for microwave device applications.
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81.15.Fg Pulsed laser ablation deposition
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.55.-g Dielectric thin films
61.66.Bi Elemental solids
61.66.Dk Alloys
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation

The characteristics of hole trapping in HfO2∕SiO2 gate dielectrics with TiN gate electrode

Wen-Tai Lu, Po-Ching Lin, Tiao-Yuan Huang, Chao-Hsin Chien, Ming-Jui Yang, Ing-Jyi Huang, and Peer Lehnen

Appl. Phys. Lett. 85, 3525 (2004); http://dx.doi.org/10.1063/1.1808228 (3 pages) | Cited 15 times

Online Publication Date: 22 October 2004

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The characteristics of charge trapping during constant voltage stress in an n-type metal–oxide–semiconductor capacitor with HfO2∕SiO2 gate stack and TiN gate electrode were studied. We found that the dominant charge trapping mechanism in the high-k gate stack is hole trapping rather than electron trapping. This behavior can be well described by the distributed capture cross-section model. In particular, the flatband voltage shift (ΔVfb) is mainly caused by the trap filling instead of the trap creation [Zafar et al., J. Appl. Phys. 93, 9298 (2003)]. The dominant hole trapping can be ascribed to a higher probability for hole tunneling from the substrate, compared to electron tunneling from the gate, due to a shorter tunneling path over the barrier for holes due to the work function of the TiN gate electrode.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.32.Tt Capacitors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Ferroelectric nanomesa formation from polymer Langmuir–Blodgett films

Mengjun Bai and Stephen Ducharme

Appl. Phys. Lett. 85, 3528 (2004); http://dx.doi.org/10.1063/1.1808251 (3 pages) | Cited 21 times

Online Publication Date: 22 October 2004

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We report the fabrication and characterization of nanoscale ferroelectric structures consisting of disk-shaped nanomesas averaging 8.7±0.4 nm in height and 95±22 nm in diameter, and nanowells 9.8±3.3 nm in depth and 128±37 nm in diameter, formed from Langmuir–Blodgett films of vinylidene fluoride copolymers after annealing in the paraelectric phase. The nanomesas retain the ferroelectric properties of the bulk material and so may be suitable for use in high-density nonvolatile random-access memories, acoustic transducer arrays, or infrared imaging arrays. The nanomesa and nanowell patterns may provide useful templates for nanoscale molding or contact-printing.
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77.84.Jd Polymers; organic compounds
81.07.Bc Nanocrystalline materials
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
68.55.A- Nucleation and growth
77.80.B- Phase transitions and Curie point
77.80.Dj Domain structure; hysteresis
77.70.+a Pyroelectric and electrocaloric effects
81.40.Gh Other heat and thermomechanical treatments
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Phonon-polaritons in quasiperiodic piezoelectric superlattices

Xue-jin Zhang, Yan-qing Lu, Yong-yuan Zhu, Yan-feng Chen, and Shi-ning Zhu

Appl. Phys. Lett. 85, 3531 (2004); http://dx.doi.org/10.1063/1.1803939 (3 pages) | Cited 11 times

Online Publication Date: 22 October 2004

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Phonon-polaritons are studied both theoretically and experimentally in a one-dimensional two-component generalized quasiperiodic piezoelectric superlattice. The experimental observation of phonon-polaritons through dielectric abnormality is carried out at the microwave region. Some potential applications are discussed.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
77.65.Bn Piezoelectric and electrostrictive constants
77.80.Dj Domain structure; hysteresis

A strong magnetoelectric voltage gain effect in magnetostrictive-piezoelectric composite

Shuxiang Dong, J. F. Li, D. Viehland, J. Cheng, and L. E. Cross

Appl. Phys. Lett. 85, 3534 (2004); http://dx.doi.org/10.1063/1.1786631 (3 pages) | Cited 60 times

Online Publication Date: 22 October 2004

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A magnetoelectric laminate composite consisting of magnetostrictive Terfenol-D (Tb1–xDyxFe2–y) and piezoelectric Pb(Zr,Ti)O3 layers has an extremely high voltage gain effect of ≈300 at its resonant state, offering potential for high-voltage miniature transformer applications.
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75.80.+q Magnetomechanical effects, magnetostriction
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.65.-j Piezoelectricity and electromechanical effects
84.30.Jc Power electronics; power supply circuits
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
77.84.Lf Composite materials

Using the surface spontaneous depolarization field of ferroelectrics to direct the assembly of virus particles

Steve Dunn, Dave Cullen, Estefania Abad-Garcia, Cristina Bertoni, Richard Carter, Dave Howorth, and Roger W. Whatmore

Appl. Phys. Lett. 85, 3537 (2004); http://dx.doi.org/10.1063/1.1797535 (3 pages) | Cited 22 times

Online Publication Date: 22 October 2004

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Tobacco mosaic virus (TMV) particles have been assembled at predetermined locations on the surface of a ferroelectric thin film with the composition PbZr0.3Ti0.7O3. The domain structure, hence the surface depolarization field for the ferroelectric associated with the bending of the ferroelectric band structure, was modified at length scales of around 2 μm. A suspension of TMV particles was deposited onto the surface of the ferroelectric over the region where domain modification had been performed. SPM images (intermittent contact) revealed that the virus particles were attracted to regions of the surface that had either been positively modified or were nominally neutral. Regions of modified negative surface charge effectively repelled the virus particles.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.22.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis
85.65.+h Molecular electronic devices
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
82.70.Kj Emulsions and suspensions

Hydrogen and deuterium incorporation and transport in hafnium-based dielectric films on silicon

R. P. Pezzi, L. Miotti, K. P. Bastos, G. V. Soares, C. Driemeier, I. J. R. Baumvol, P. Punchaipetch, G. Pant, B. E. Gnade, R. M. Wallace, A. Rotondaro, J. M. Visokay, J. J. Chambers, and L. Colombo

Appl. Phys. Lett. 85, 3540 (2004); http://dx.doi.org/10.1063/1.1801682 (3 pages) | Cited 10 times

Online Publication Date: 22 October 2004

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Hydrogen and deuterium incorporation into nitrided and non-nitrided hafnium silicate films on Si during thermal annealing in 1H- and 2H-containing atmospheres was investigated. 1H profiling was accessed by means of nuclear resonant reaction profiling, whereas 2H incorporation was quantified by nuclear reaction analysis. The effects of preannealing in different atmospheres and temperatures were determined, as well as the losses of 1H and 2H from these structures during postannealing in vacuum. The results reveal a rather uniform depth distribution of incorporated 1H, in striking contrast with previous studies on hydrogen in silicon oxide and oxynitrides and hafnium oxide films on Si. These results are discussed in terms of the defects present in each one of the structures studied here.
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77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
76.60.-k Nuclear magnetic resonance and relaxation
81.15.Cd Deposition by sputtering
82.30.-b Specific chemical reactions; reaction mechanisms
81.40.Gh Other heat and thermomechanical treatments

Field-effect transistors with LaAlO3 and LaAlOxNy gate dielectrics deposited by laser molecular-beam epitaxy

X. B. Lu, H. B. Lu, Z. H. Chen, X. Zhang, R. Huang, H. W. Zhou, X. P. Wang, B. Y. Nguyen, C. Z. Wang, W. F. Xiang, M. He, and B. L. Cheng

Appl. Phys. Lett. 85, 3543 (2004); http://dx.doi.org/10.1063/1.1806547 (3 pages) | Cited 15 times

Online Publication Date: 22 October 2004

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High permittivity LaAlO3 (LAO) and LaAlOxNy (LAON) thin films have been deposited directly on a Si(100) substrate using a laser molecular-beam epitaxy technique. Metal–oxide–silicon field-effect transistors (MOSFETs) are fabricated using such LAO and LAON thin films as gate dielectrics and well-behaved transistor characteristics have been observed. High-resolution transmission electron microscopy observations indicate that LAO thin films can remain amorphous structure even after annealing at 1000°C. The small equivalent oxide thickness (EOT) of 17 math is achieved for 75 math LAO film with an effective dielectric constant of 17.2±1 for the whole gate stack. Furthermore, a smaller EOT, larger drive current, and lower subthreshold slope have been observed for devices with the LAON thin film. For all the devices, the gate leakage currents are at least two orders of magnitude lower than that of the same electrical thickness SiO2. Reasonable subthreshold slopes of 248 and 181 mV∕dec were obtained for MOSFETs with LAO and LAON films, respectively.
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85.30.Tv Field effect devices
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Lp Transmission electron microscopy (TEM)
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Hysteretic behavior of the charge injection in single silicon nanoparticles

H. Diesinger, T. Mélin, D. Deresmes, D. Stiévenard, and T. Baron

Appl. Phys. Lett. 85, 3546 (2004); http://dx.doi.org/10.1063/1.1808889 (3 pages) | Cited 7 times

Online Publication Date: 22 October 2004

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Charge injection in individual silicon nanoparticles has been investigated by electric force microscopy (EFM). Stored charges injected from the EFM tip have been counted using a quantitative method. Injection kinetics reveals the setting-up of an equilibrium regime. Equilibrium charge–voltage characteristics are analyzed, and display an overall linear behavior corresponding to successive tunneling through the nonequivalent tip–nanoparticle and nanoparticle–substrate oxide barriers. A hysteretic behavior is observed in the equilibrium charge–voltage characteristics, and attributed to a secondary charge injection process associated with the nanoparticle oxide surface.
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73.63.Bd Nanocrystalline materials
73.40.Gk Tunneling

Interface effect on thermal conductivity of carbon nanotube composites

Ce-Wen Nan, Gang Liu, Yuanhua Lin, and Ming Li

Appl. Phys. Lett. 85, 3549 (2004); http://dx.doi.org/10.1063/1.1808874 (3 pages) | Cited 144 times

Online Publication Date: 22 October 2004

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A simple formula for the thermal conductivity enhancement in carbon nanotube composites is presented by incorporating the interface thermal resistance with an effective medium approach. This model well describes the thermal conductivity enhancement observed recently in nanotube suspensions. In particular, this simple formula predicts that a large interface thermal resistance across the nanotube-matrix interface causes a significant degradation in the thermal conductivity enhancement, even for the case with ultrahigh intrinsic thermal conductivity and aspect ratio of the carbon nanotubes embedded.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Electrochemical nanopatterning of Ag on solid-state ionic conductor RbAg4I5 using atomic force microscopy

Minhwan Lee, Ryan O’Hayre, Fritz B. Prinz, and Turgut M. Gür

Appl. Phys. Lett. 85, 3552 (2004); http://dx.doi.org/10.1063/1.1807964 (3 pages) | Cited 20 times

Online Publication Date: 22 October 2004

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This report introduces an electrochemical nanopatterning technique performed under ambient conditions without involving a liquid vessel or probe-to-sample material transfer. Patterning is accomplished by solid-state electrochemical nanodeposition of Ag clusters on the surface of the solid ionic conductor RbAg4I5 using an atomic force microscopy probe. Application of negative voltage pulses on the probe relative to an Ag film counter electrode on an RbAg4I5 sample induces nanometer-sized Ag deposition on the ion conductor around the probe. The patterned Ag particles are 0.5–70 nm high and 20–700 nm in diameter. The effect of the amplitude and duration of bias voltage on the size and shape of deposited Ag clusters is also shown.
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81.16.Nd Micro- and nanolithography
82.45.Fk Electrodes
61.46.-w Structure of nanoscale materials
68.55.-a Thin film structure and morphology
68.37.Ps Atomic force microscopy (AFM)

Size effect on Young’s modulus of thin chromium cantilevers

S. G. Nilsson, X. Borrisé, and L. Montelius

Appl. Phys. Lett. 85, 3555 (2004); http://dx.doi.org/10.1063/1.1807945 (3 pages) | Cited 39 times

Online Publication Date: 22 October 2004

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Thin chromium cantilevers with sub-100 nm thickness have been characterized by an atomic force microscope operating in contact mode. A continuous determination of the local mechanical properties at all lengths was accomplished by applying force along the length of the cantilevers. The result show a decrease of the Young’s modulus as the cantilevers get thinner.
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68.37.Ps Atomic force microscopy (AFM)
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Multiple layer local oxidation for fabricating semiconductor nanostructures

M. Sigrist, A. Fuhrer, T. Ihn, K. Ensslin, D. C. Driscoll, and A. C. Gossard

Appl. Phys. Lett. 85, 3558 (2004); http://dx.doi.org/10.1063/1.1809273 (3 pages) | Cited 2 times

Online Publication Date: 22 October 2004

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Coupled semiconductor nanostructures with a high degree of tunability are fabricated using local oxidation with a scanning force microscope. Direct oxidation of the GaAs surface of a Ga[Al]As heterostructure containing a shallow two-dimensional electron gas is combined with the local oxidation of a thin titanium film evaporated on top. A four-terminal quantum dot and a double quantum dot system with integrated charge readout are realized. The structures are tunable via in-plane gates formed by isolated regions in the electron gas and by mutually isolated regions of the Ti film acting as top gates. Coulomb blockade experiments demonstrate the high quality of this fabrication process.
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81.07.Ta Quantum dots
81.16.Nd Micro- and nanolithography
68.65.Hb Quantum dots (patterned in quantum wells)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.65.Mq Oxidation
68.37.Ps Atomic force microscopy (AFM)
73.23.Hk Coulomb blockade; single-electron tunneling

Bond length contraction in Au nanocrystals formed by ion implantation into thin SiO2

P. Kluth, B. Johannessen, V. Giraud, A. Cheung, C. J. Glover, G. de M. Azevedo, G. J. Foran, and M. C. Ridgway

Appl. Phys. Lett. 85, 3561 (2004); http://dx.doi.org/10.1063/1.1803619 (3 pages) | Cited 18 times

Online Publication Date: 22 October 2004

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Au nanocrystals (NCs) fabricated by ion implantation into thin SiO2 and annealing were investigated by means of extended x-ray absorption fine structure (EXAFS) spectroscopy and transmission electron microscopy. A bond length contraction was observed and can be explained by surface tension effects in a simple liquid-drop model. Such results are consistent with previous reports on nonembedded NCs implying a negligible influence of the SiO2 matrix. Cumulant analysis of the EXAFS data suggests surface reconstruction or relaxation involving a further shortened bond length. A deviation from the octahedral closed shell structure is apparent for NCs of size 25 math.
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81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
78.70.Dm X-ray absorption spectra
61.80.Jh Ion radiation effects
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.up Other materials

Formation of highly transmissive liquid metal contacts to carbon nanotubes

Mehdi M. Yazdanpanah, S. Chakraborty, S. A. Harfenist, R. W. Cohn, and B. W. Alphenaar

Appl. Phys. Lett. 85, 3564 (2004); http://dx.doi.org/10.1063/1.1807946 (3 pages) | Cited 5 times

Online Publication Date: 22 October 2004

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We have developed a method to produce liquid metal contacts to carbon nanotubes that allows direct measurement of the influence of the contact on the nanotube conductance. Gallium is deposited onto standard gold nanotube contacts, where it gradually spreads to coat the contact region. The two-terminal multiwall nanotube conductance increases by as much as 1.2e2∕h during the transition from gold to gallium contacts, and approaches 2e2∕h at room temperature, with a current density of 2×108 A∕cm2. Surprisingly, the conductance is independent of the contact area or contact separation, providing evidence that transport is ballistic in multiwall nanotubes.
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85.35.Kt Nanotube devices
73.40.Ns Metal-nonmetal contacts
73.63.Rt Nanoscale contacts
73.23.Ad Ballistic transport
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