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9 Jul 2001

Volume 79, Issue 2, pp. 145-277

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Ti/Al/Pt/Au and Al ohmic contacts on Si-substrated GaN

Z. M. Zhao, R. L. Jiang, P. Chen, D. J. Xi, H. Q. Yu, B. Shen, R. Zhang, Y. Shi, S. L. Gu, and Y. D. Zheng

Appl. Phys. Lett. 79, 218 (2001); http://dx.doi.org/10.1063/1.1385189 (3 pages) | Cited 8 times

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Al and Ti/Al/Pt/Au ohmic contacts on GaN epitaxial layers were studied. The epilayers were grown on Si (111) substrates by low-pressure metalorganic chemical vapor deposition. Al/GaN contacts achieved a minimum contact resistivity of 7.5×10−3 Ω cm2 after annealing in N2 ambient at 450 °C for 3 min. Further annealing degraded the contacts. Ti/Al/Pt/Au and GaN contacts achieved a minimum contact resistivity of 8.4×10−5 Ω cm2 after annealing in N2 at 650 °C for 20 s. The Ti/Al/Pt/Au contacts on GaN showed a better thermal stability than Al/GaN contacts. After annealing at 600 °C for 30 min. they were still ohmic contacts. The mechanisms for ohmic contact formation of Ti/Al/Pt/Au contacts were also analyzed. © 2001 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
61.72.Cc Kinetics of defect formation and annealing
73.40.Cg Contact resistance, contact potential

Epitaxy of InAs quantum dots on self-organized two-dimensional InAs islands by atmospheric pressure metalorganic chemical vapor deposition

T. S. Yeoh, C. P. Liu, R. B. Swint, A. E. Huber, S. D. Roh, C. Y. Woo, K. E. Lee, and J. J. Coleman

Appl. Phys. Lett. 79, 221 (2001); http://dx.doi.org/10.1063/1.1379981 (3 pages) | Cited 16 times

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Fully coherent InAs quantum dots and InAs quantum dots grown on self-organized two-dimensional (2D) islands by atmospheric pressure metalorganic chemical vapor deposition are investigated. The significantly lower critical thickness window of between 1 and 2.0 monolayers for fully coherent dots is attributed to the suppression of a segregated indium floating layer. An InAs quantum dot density of 4.7×1010 cm−2 was achieved on GaAs, and a highly localized InAs quantum dot density of over 5×1012 cm−2 was achieved on 2D InAs islands. © 2001 American Institute of Physics.
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81.07.Ta Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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Magnetically soft, high-moment, high-resistivity thin films using discontinuous metal/native oxide multilayers

G. S. D. Beach, A. E. Berkowitz, F. T. Parker, and David J. Smith

Appl. Phys. Lett. 79, 224 (2001); http://dx.doi.org/10.1063/1.1383998 (3 pages) | Cited 17 times

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Multilayers consisting of discontinuous metal layers with native oxide surfaces have been fabricated using CoxFe100−x alloys ranging in composition from pure Co to pure Fe. For the Fe-containing compositions, the composites are magnetically soft with resistivities in the range of 100 to 2000 μΩ cm. Mössbauer spectroscopy indicates a magnetically ordered Fe-oxide component, and the magnetic moment of the oxide phase for pure Fe/native oxide multilayers has been determined. © 2001 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.63.-b Electronic transport in nanoscale materials and structures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Cr Saturation moments and magnetic susceptibilities
68.65.Ac Multilayers
75.50.Bb Fe and its alloys
76.80.+y Mössbauer effect; other γ-ray spectroscopy

Superconducting MgB2 thin films by pulsed laser deposition

S. R. Shinde, S. B. Ogale, R. L. Greene, T. Venkatesan, P. C. Canfield, S. L. Bud’ko, G. Lapertot, and C. Petrovic

Appl. Phys. Lett. 79, 227 (2001); http://dx.doi.org/10.1063/1.1385186 (3 pages) | Cited 46 times

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Growth of MgB2 thin films by pulsed laser deposition is examined under ex situ and in situ processing conditions. For the ex situ process, boron films grown by pulsed laser deposition were annealed at 900 °C with excess Mg. For the in situ process, different approaches involving ablation from a stoichiometric target under different growth conditions, as well as multilayer deposition involving interposed Mg layers were examined and analyzed. Magnetic measurements on ex situ processed films show Tc of ∼39 K, while the current best in situ films show a susceptibility transition at ∼22 K. © 2001 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
74.78.-w Superconducting films and low-dimensional structures
74.10.+v Occurrence, potential candidates
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.25.Ha Magnetic properties including vortex structures and related phenomena

Large transport critical currents in unsintered MgB2 superconducting tapes

Giovanni Grasso, Andrea Malagoli, Carlo Ferdeghini, Scilla Roncallo, Valeria Braccini, Antonio S. Siri, and Maria R. Cimberle

Appl. Phys. Lett. 79, 230 (2001); http://dx.doi.org/10.1063/1.1384905 (3 pages) | Cited 181 times

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The powder-in-tube process has been employed to fabricate tape-like conductors with a strong metallic sheath and based on the newly discovered MgB2 superconducting phase. Long superconducting tapes have been prepared by packing reacted MgB2 powders inside pure Ag, Cu, and Ni tubes which are then cold worked by drawing and rolling. Such tapes have shown transport properties as good as bulk MgB2 samples sintered in high pressure and high temperature conditions. At 4.2 K, the highest critical current density of 105 A/cm2 has been achieved on nickel-sheathed single-filament conductors. A direct correlation between the sheath tensile strength and the critical current of the unsintered tape has been observed. © 2001 American Institute of Physics.
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84.71.Mn Superconducting wires, fibers, and tapes
74.25.Sv Critical currents
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
74.72.-h Cuprate superconductors
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.05.Mh Cermets, ceramic and refractory composites

Magnetotransport in manganite trilayer junctions grown by 90° off-axis sputtering

J. S. Noh, T. K. Nath, C. B. Eom, J. Z. Sun, W. Tian, and X. Q. Pan

Appl. Phys. Lett. 79, 233 (2001); http://dx.doi.org/10.1063/1.1383276 (3 pages) | Cited 19 times

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We report magnetotransport studies on La0.67Sr0.33MnO3/SrTiO3/La0.67Sr0.33MnO3 trilayer junctions, fabricated using 90° off-axis sputtering. Films were grown on both (001) (LaAlO3)0.3–(Sr2AlTaO6)0.7 and (110) NdGaO3 substrates. The sputtered trilayers show improved junction resistance uniformity over those made using pulsed laser deposition. Cross-sectional transmission electron microscopy and atomic force microscopy studies confirm smooth interfaces and a uniform barrier. Magnetoresistances up to ∼100% are observed for junctions on (001) (LaAlO3)0.3–(Sr2AlTaO6)0.7 with a 30 Å barrier at 13 K and around 100 Oe. Junction magnetoresistance versus magnetic field behavior is more stable, indicating improved transport and magnetic homogeneity across the junction. © 2001 American Institute of Physics.
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75.47.De Giant magnetoresistance
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.Gk Colossal magnetoresistance
68.37.Lp Transmission electron microscopy (TEM)
68.37.Ps Atomic force microscopy (AFM)
68.35.Ct Interface structure and roughness
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Scaling on hysteresis dispersion in ferroelectric systems

J.-M. Liu, H. L. W. Chan, C. L. Choy, Y. Y. Zhu, S. N. Zhu, Z. G. Liu, and N. B. Ming

Appl. Phys. Lett. 79, 236 (2001); http://dx.doi.org/10.1063/1.1384894 (3 pages) | Cited 40 times

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The hysteresis area as a function of frequency of the time-varying external electric field—hysteresis dispersion—for ferroelectric Pb(Zr0.52Ti0.48)O3 is measured, and the Monte-Carlo simulation on the hysteresis dispersion for a model ferroelectric lattice is performed too. We demonstrate the scaling behavior of the single-peaked hysteresis dispersion for the two ferroelectric systems, predicting a unique effective characteristic time for the domain reversal. This characteristic time shows an inversely linear dependence on the field amplitude as long as the amplitude is high enough that the reversible domain rotation response is negligible. © 2001 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Effect of acceptor and donor dopants on polarization components of lead zirconate titanate thin films

S. B. Majumder, B. Roy, R. S. Katiyar, and S. B. Krupanidhi

Appl. Phys. Lett. 79, 239 (2001); http://dx.doi.org/10.1063/1.1383057 (3 pages) | Cited 15 times

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We have compared the magnitudes of reversible and irreversible polarization components of sol–gel-derived Nd3+- and Fe3+-doped PZT (53/47) thin films on platinized silicon substrates. Beyond the switching field, it was found that the reversible component of the polarization remains almost constant both for donor- (Nd3+) and acceptor- (Fe3+) doped PZT films. The irreversible polarization component reduces with the increase in Nd3+ content, whereas it increases until 3 at. % Fe3+-doped PZT thin films. The dielectric behavior of these films at subswitching fields was analyzed in terms of Rayleigh law. The inverse of the Raleigh coefficient (υ) was considered as a measure of the obstacle for the domain-wall motion. In the case of Fe-doped PZT, the inverse of the Raleigh coefficient (υ) shows a declining linearity with Fe content, which may be found exactly opposite to that observed for Nd-doped PZT. The observed results are explained in terms of the nature of the defect-domain-wall interaction of acceptor-and-donor-doped PZT thin films. Studies indicated that in the case of Fe-doped PZT films, the possible defect interaction initiates only above 2 at. % and it was found to be much lower in magnitude in comparison with the Nd doping. © 2001 American Institute of Physics.
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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.Fm Switching phenomena
77.80.Dj Domain structure; hysteresis

Polarization imprint and size effects in mesoscopic ferroelectric structures

M. Alexe, C. Harnagea, D. Hesse, and U. Gösele

Appl. Phys. Lett. 79, 242 (2001); http://dx.doi.org/10.1063/1.1385184 (3 pages) | Cited 77 times

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Piezoresponse scanning force microscopy measurements performed on lead zirconate titanate mesoscopic structures revealed a negative shift of the initial piezoelectric hysteresis loop. The shift is dependent on the size of the structure and is most probably due to the pinning of ferroelectric domains at the free lateral surface and ferroelectric–electrode interface. Considering a simple model, the thickness of the pinned domain layers is found to be about 15 and 70 nm at the ferroelectric–electrode interface and lateral free surface, respectively. © 2001 American Institute of Physics.
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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
77.65.-j Piezoelectricity and electromechanical effects

Electrical characteristics of ZrOxNy prepared by NH3 annealing of ZrO2

Sanghun Jeon, Chel-Jong Choi, Tae-Yeon Seong, and Hyunsang Hwang

Appl. Phys. Lett. 79, 245 (2001); http://dx.doi.org/10.1063/1.1385347 (3 pages) | Cited 52 times

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The electrical characteristics of ZrOxNy prepared by NH3 annealing of ZrO2 were investigated for use in metal–oxide–semiconductor gate dielectric applications. Compared with conventional ZrO2, ZrOxNy exhibits excellent electrical characteristics such as high accumulation capacitance, low leakage current density, and superior thermal stability. Based on high resolution transmission electron microscope analysis of both ZrO2 and ZrOxNy samples which had been annealed at 800 °C for 5 min, the ZrO2 exhibited a polycrystalline state but the ZrOxNy was amorphous in structure. In addition, the thickness of ZrOxNy was thinner than that of ZrO2. The improvement in electrical characteristics can be explained by the better thermal stability and lower rate of oxidation of ZrOxNy. © 2001 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
61.72.Cc Kinetics of defect formation and annealing
68.60.Dv Thermal stability; thermal effects
85.30.Tv Field effect devices
68.55.-a Thin film structure and morphology

Electrophoretic deposition of pure and MgO-modified Ba0.6Sr0.4TiO3 thick films for tunable microwave devices

E. Ngo, P. C. Joshi, M. W. Cole, and C. W. Hubbard

Appl. Phys. Lett. 79, 248 (2001); http://dx.doi.org/10.1063/1.1384899 (3 pages) | Cited 53 times

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We report on the structural, dielectric, and optical properties of barium strontium titanate–magnesium oxide composite (BST-MgO) thick films fabricated by the electrophoretic deposition technique. The structure and morphology of the films were analyzed by x-ray diffraction and scanning electron microscopy, respectively. The films were optically characterized via FT-Raman spectroscopy. The dielectric measurements were conducted on metal–insulator–metal capacitors using platinum as the top and bottom electrodes. The typical small signal dielectric constants of Ba0.60Sr0.40TiO3 and Ba0.60Sr0.40TiO3–20 wt % MgO thick films, measured at an applied frequency of 1 MHz, were 603 and 327, respectively. The corresponding values of dissipation factor were 0.029 and 0.002, respectively. A high dielectric tunability of 17.3% was obtained for Ba0.60Sr0.40TiO3 thick films at an applied electric field of 20 kV/cm. The dielectric properties of the present thick films were comparable to those of the bulk ceramics; suggesting their suitability for high-frequency wide-band voltage-tunable device applications.
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85.40.Xx Hybrid microelectronics; thick films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
84.40.Lj Microwave integrated electronics
81.05.Mh Cermets, ceramic and refractory composites

Dielectric and ferroelectric properties of SrBi4Ti4O15 single crystals

Hiroshi Irie and Masaru Miyayama

Appl. Phys. Lett. 79, 251 (2001); http://dx.doi.org/10.1063/1.1384480 (3 pages) | Cited 57 times

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SrBi4Ti4O15 single crystals were grown, and their dielectric and ferroelectric properties were investigated along the a(b) axis and c axis, separately. The dielectric permittivity at 1 MHz was 1900 along the a(b) axis at the Curie temperature of 520 °C. This value was ten times higher than that along the c axis. With respect to the ferroelectricity, the saturated remanent polarization was 29 μC/cm2 and the saturated coercive field was 26 kV/cm along the a(b) axis under an electric field of 59 kV/cm, and ferroelectricity was not observed along the c axis. © 2001 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis
77.80.B- Phase transitions and Curie point
77.22.Ej Polarization and depolarization
77.22.Gm Dielectric loss and relaxation

Effects of strain on the dielectric properties of tunable dielectric SrTiO3 thin films

S. Hyun and K. Char

Appl. Phys. Lett. 79, 254 (2001); http://dx.doi.org/10.1063/1.1384893 (3 pages) | Cited 48 times

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We fabricated an epitaxial Au/SrTiO3(001)/SrRuO3 (or CaRuO3)(001)/SrTiO3 (or LaAlO3)(001) heterostructure to investigate the effect of the strain on the epitaxial tunable dielectric thin films. SrTiO3 thin films showed very different dielectric properties depending on the bottom electrode with an opposite lattice mismatch. The SrTiO3 thin films grown on the CaRuO3 bottom electrodes showed nearly a two times larger tunability than that on SrRuO3. We think this is due to the different strain on the SrTiO3 thin films. The tensile strain along the applied electric field in the parallel plate capacitor enhances the dielectric constant and the tunability, while the compressive strain decreases them. We believe this is consistent with the hardening of the soft mode phonon due to the compressive strain. © 2001 American Institute of Physics.
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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.Ch Permittivity (dielectric function)
68.60.Bs Mechanical and acoustical properties
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Large area dense nanoscale patterning of arbitrary surfaces

Miri Park, P. M. Chaikin, Richard A. Register, and Douglas H. Adamson

Appl. Phys. Lett. 79, 257 (2001); http://dx.doi.org/10.1063/1.1378046 (3 pages) | Cited 71 times

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We demonstrate a large-area fabrication of hexagonally ordered metal dot arrays with an area density of ∼ 1011/cm2. We produced 20 nm dots with a 40 nm period by combining block copolymer nanolithography and a trilayer resist technique. A self-assembled spherical-phase block copolymer top layer spontaneously generated the pattern, acting as a template. The pattern was first transferred to a silicon nitride middle layer by reactive ion etch, producing holes. The nitride layer was then used as a mask to further etch into a polyimide bottom layer. The metal dots were produced by an electron beam evaporation followed by a lift-off process. Our method provides a viable route for highly dense nanoscale patterning of different materials on arbitrary surfaces. © 2001 American Institute of Physics.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Electric field-induced carbon nanotube junction formation

G. W. Ho, A. T. S. Wee, and J. Lin

Appl. Phys. Lett. 79, 260 (2001); http://dx.doi.org/10.1063/1.1383279 (3 pages) | Cited 27 times

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We present experimental evidence of nanojunction structures explicitly observed after application of high electric fields on multiwall carbon nanotube arrays. The electric field as well as thermal effects result in carbon–carbon bond breaking and redeposition leading to nanojunction formation. The growth mechanism of the nanojunction is believed to be open-ended topological defect growth in which carbon atoms at two adjacent nanotube tips chemically react and fuse forming an array of nanojunctions. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.De Nanotubes

Influence of the wetting-layer growth kinetics on the size and shape of Ge self-assembled quantum dots on Si(001)

H. J. Kim and Y. H. Xie

Appl. Phys. Lett. 79, 263 (2001); http://dx.doi.org/10.1063/1.1383274 (3 pages) | Cited 10 times

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The growth temperature of the wetting layer is used as the key variable in the study of a series of Ge self-assembled quantum dots on Si(001) substrates. A relaxed SiGe buffer layer is used for most of the samples as a means of maintaining the density of Ge dots. Ge dots are in the shapes of pyramids, domes, and superdomes, similar to those reported in the literature. A significant difference in the fraction of pyramids is observed between samples with wetting layers grown at low (280 °C) and high (650 °C) temperatures. This difference is in turn dependent on the total amount of Ge deposited or equivalently, the average size of dots. These observations point to the presence of Si during the initial stage of Ge dot formation and that the fraction of pyramids as well as the critical size for the transition from pyramids to domes are influenced by the presence of Si. © 2001 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots
81.05.Cy Elemental semiconductors
81.16.Dn Self-assembly
68.55.-a Thin film structure and morphology

Ballistic switching and rectification in single wall carbon nanotube Y junctions

Antonis N. Andriotis, Madhu Menon, Deepak Srivastava, and Leonid Chernozatonskii

Appl. Phys. Lett. 79, 266 (2001); http://dx.doi.org/10.1063/1.1385194 (3 pages) | Cited 38 times

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Transport properties of various semiconducting zig-zag carbon nanotube Y junctions are studied for the investigations of rectification and switching. Our results indicate that such junctions, when symmetric, can support both ballistic rectification and/or the ballistic switching operating modes. Although structural symmetry of the Y junction is found to be a necessary condition for rectification, it may not be sufficient in all cases. © 2001 American Institute of Physics.
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73.63.Fg Nanotubes
73.40.Ei Rectification
73.23.Ad Ballistic transport
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.35.Kt Nanotube devices

Drastic change of phase interference by small diffusion of heavy-mass electrode atoms in carbon nanotubes and phase switching device

Junji Haruyama, Izumi Takesue, and Tetsuro Hasegawa

Appl. Phys. Lett. 79, 269 (2001); http://dx.doi.org/10.1063/1.1385183 (3 pages) | Cited 4 times

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We slightly diffuse atoms of electrode materials into one end of multiwalled carbon nanotubes (MWNTs), grown using nanoporous alumina membranes. Diffusion of the light-mass materials (carbon and aluminum) lead to weak localization in Altshuler–Aronov–Spivak oscillation, consistent with past reports. In contrast, we find that diffusion of heavy-mass materials (gold and platinum) at the volume ratio of only about 5% change this weak localization to antilocalization. It is understood by a drastic change of the phase interference caused by the injection of spin-flipped electrons due to spin–orbit interaction in the diffusion region, in the entire part of the MWNTs. We also propose an electron-wave phase switching circuit using this effect. © 2001 American Institute of Physics.
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73.63.Fg Nanotubes
85.35.Kt Nanotube devices
73.23.-b Electronic transport in mesoscopic systems
85.35.Ds Quantum interference devices
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
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Fine tuning work function of indium tin oxide by surface molecular design: Enhanced hole injection in organic electroluminescent devices

Chimed Ganzorig, Kwang-Joo Kwak, Kazuto Yagi, and Masamichi Fujihira

Appl. Phys. Lett. 79, 272 (2001); http://dx.doi.org/10.1063/1.1384896 (3 pages) | Cited 86 times

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Characteristics of electroluminescent (EL) devices were improved dramatically using indium tin oxide (ITO) chemically modified with H-, Cl-, and CF3-terminated benzoyl chlorides. By the use of reactive –COCl groups, ITO surfaces were modified quickly and the work function of the modified ITO was changed widely depending upon the permanent dipole moments introduced in the para- position of benzoyl chloride. We also compared the performance of the EL devices with ITO modified with different binding groups (–SO2Cl, –COCl, and –PO2Cl2) of p-chlorobenzene derivatives. Finally, we examined the correlation between the change in the work function and the performance of the EL devices by the chemical modification and found that the enormous increase in ITO work function up to 0.9 eV is possible using phenylphosphoryl dichloride with a CF3-terminal group in the para-position. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
81.65.-b Surface treatments
73.30.+y Surface double layers, Schottky barriers, and work functions
81.05.Hd Other semiconductors
85.60.Bt Optoelectronic device characterization, design, and modeling
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Metal-insulator-vacuum type electron emission from N-containing chemical vapor deposited diamond

Ken Okano, Takatoshi Yamada, Atsuhito Sawabe, Satoshi Koizumi, Junji Itoh, and Gehan A. J. Amaratunga

Appl. Phys. Lett. 79, 275 (2001); http://dx.doi.org/10.1063/1.1385341 (3 pages) | Cited 24 times

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This letter presents a clear explanation of the electron emission mechanism of the high-resistivity N-doped diamond cathode. Due to the very low barrier to emission of electrons from the N-doped diamond conduction band into vacuum, electrons in the conduction band of diamond can establish an appreciable leakage current at very low anode voltage. When such a current starts to flow, there is a field which is developed across the diamond bulk. This field is observed as an increase in the electric field at the back contact, causing the injected tunneling current increases exponentially. This process leads to the low threshold emission from the high resistivity N-doped diamond cathode. © 2001 American Institute of Physics.
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81.05.U- Carbon/carbon-based materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
79.70.+q Field emission, ionization, evaporation, and desorption
85.45.Db Field emitters and arrays, cold electron emitters
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