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5 Feb 2001

Volume 78, Issue 6, pp. 685-846

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Significant enhancement of photoconductivity in truly two-component and chemically hybridized CdS-poly(N-vinylcarbazole) nanocomposites

C. L. Yang, J. N. Wang, W. K. Ge, S. H. Wang, J. X. Cheng, X. Y. Li, Y. J. Yan, and S. H. Yang

Appl. Phys. Lett. 78, 760 (2001); http://dx.doi.org/10.1063/1.1345826 (3 pages) | Cited 14 times

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Chemically hybridized CdS-poly(N-vinylcarbazole) (PVK) nanocomposites with different molar ratios of CdS to PVK were prepared. A variety of techniques including optical absorption, photoluminescence (PL), photocurrent spectroscopy, and time-resolved PL were employed to investigate the properties of CdS–PVK nanocomposites. A significant enhancement of photoconductivity was observed in CdS–PVK nanocomposites as compared to pure PVK and CdS/PVK nanoblends. We interpret this result as the improved interface quality between CdS and PVK in CdS–PVK nanocomposites, which facilitates fast interfacial carrier transfer and thus increases the charge generation efficiency. © 2001 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
72.80.Tm Composite materials
78.55.-m Photoluminescence, properties and materials
78.40.-q Absorption and reflection spectra: visible and ultraviolet
78.47.-p Spectroscopy of solid state dynamics

Voltage induced photoluminescence quenching in porous silicon revisited

M. R. Reshotko and I. Balberg

Appl. Phys. Lett. 78, 763 (2001); http://dx.doi.org/10.1063/1.1345837 (3 pages) | Cited 5 times

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We have reexamined the features of the voltage induced quenching of the photoluminescence in solid state structures in which the active material is porous silicon. By comparing the increase of the quenching due to the increase of temperature or bias with the corresponding increase in the electrical transport and phototransport, we conclude that this effect is not a field-enhanced carrier-separation effect, as suggested previously. Rather, this is a thermal effect, which is very pronounced, due to the inefficient cooling in the open, coral-like structure of luminescent porous silicon. © 2001 American Institute of Physics.
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78.55.Mb Porous materials
78.55.Ap Elemental semiconductors
78.20.Jq Electro-optical effects
78.66.Db Elemental semiconductors and insulators
73.61.Cw Elemental semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.50.Fq High-field and nonlinear effects

Second-harmonic generation from silicon nanocrystals embedded in SiO2

Y. Jiang, P. T. Wilson, M. C. Downer, C. W. White, and S. P. Withrow

Appl. Phys. Lett. 78, 766 (2001); http://dx.doi.org/10.1063/1.1345825 (3 pages) | Cited 32 times

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We present observations of optical second-harmonic generation (SHG) from silicon nanocrystals embedded in SiO2. SHG sensitivity to Si/SiO2 interface states, charge on the nanocrystals, and particle density gradients is demonstrated. SHG is proven to be a powerful noncontact nondestructive diagnosis tool for characterization of Si-nanocrystal-based devices and materials. © 2001 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
73.20.-r Electron states at surfaces and interfaces
78.40.Fy Semiconductors
73.22.-f Electronic structure of nanoscale materials and related systems

Highly doped thin-channel GaN-metal–semiconductor field-effect transistors

R. Gaska, M. S. Shur, X. Hu, J. W. Yang, A. Tarakji, G. Simin, A. Khan, J. Deng, T. Werner, S. Rumyantsev, and N. Pala

Appl. Phys. Lett. 78, 769 (2001); http://dx.doi.org/10.1063/1.1344577 (3 pages) | Cited 11 times

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We report on the influence of the channel doping on dc, high frequency, and noise performance of GaN metal–semiconductor field-effect transistors (MESFETs) grown on sapphire substrates. The devices with the channel thicknesses from 50 to 70 nm and doping levels up to 1.5×1018 cm−3 were investigated. An increase in the channel doping results in the improved dc characteristics, higher cutoff, and maximum oscillation frequencies, and reduced low frequency and microwave noise. The obtained results demonstrate that the dc and microwave performance characteristics of short-channel GaN MESFETs may be comparable to those for conventional AlGaN/GaN heterostructure FETs. © 2001 American Institute of Physics.
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85.30.Tv Field effect devices
84.40.-x Radiowave and microwave (including millimeter wave) technology
85.30.De Semiconductor-device characterization, design, and modeling
61.72.uj III-V and II-VI semiconductors

Dislocation reduction in GaN grown by hydride vapor phase epitaxy via growth interruption modulation

Wei Zhang, Stephan Roesel, Helder R. Alves, Dirk Meister, Wilhelm Kriegseis, Detlev M. Hofmann, Bruno K. Meyer, Till Riemann, Peter Veit, Juergen Blaesing, Alois Krost, and Juergen Christen

Appl. Phys. Lett. 78, 772 (2001); http://dx.doi.org/10.1063/1.1344224 (3 pages) | Cited 6 times

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Thick GaN layers have been deposited on c-Al2O3 (0001) substrates using hydride vapor phase epitaxy by modulating the growth process via switching on/off GaN growth. Cathodoluminescence and transmission electron microscopy images of the cross-sectional structure show that there are separated multilayers structure in the GaN films. The dislocations density decreases from 1010 cm−2 in the initial layer to 109–108 cm−2 in the subsequently grown layer and then to 107 cm−2 in the top layer. This shows that the interruption of the growth process is helpful for suppression of structural defects. X-ray diffraction and photoluminescence measurements also demonstrate the high quality of the GaN films. © 2001 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Cr III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
78.60.Hk Cathodoluminescence, ionoluminescence

T-shaped ballistic spin filter

A. A. Kiselev and K. W. Kim

Appl. Phys. Lett. 78, 775 (2001); http://dx.doi.org/10.1063/1.1347023 (3 pages) | Cited 96 times

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We propose a semiconductor structure that can filter electron spin without using external magnetic fields. The structure consists of a T-shaped quasi-one-dimensional channel and an electrode placed near the channel intersection to control the spin-orbit interaction for electrons. Our calculations demonstrate that the proposed device can redirect electrons with opposite spins from an unpolarized source to left and right output leads, respectively, and, thus, serve as a spin filter. When the incident electron energy is in resonance with the quasilocalized zero-dimensional states at the intersection, polarization of the transmitted fluxes approaches 100%. © 2001 American Institute of Physics.
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85.35.Ds Quantum interference devices
85.30.De Semiconductor-device characterization, design, and modeling
73.20.Fz Weak or Anderson localization
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Validity of the Stoner–Wohlfarth model in hysteretic giant magnetoimpedance of annealed amorphous materials

Cheol Gi Kim, Seok Soo Yoon, Kil Jae Jang, and Chong-Oh Kim

Appl. Phys. Lett. 78, 778 (2001); http://dx.doi.org/10.1063/1.1345799 (3 pages) | Cited 10 times

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The hysteretic characteristics of giant magnetoimpedance (GMI) profiles have been measured in Co-based amorphous ribbon with various anisotropy angles θk, and they have been analyzed by using the Stoner–Wohlfarth model. A two-peak behavior with a dip near zero field is revealed in the measured GMI profile at 10 MHz, irrespective of θk. The negligible hysteresis of the field for the dip is in close agreement with that calculated assuming a magnetization jump from a metastable to a stable state. However, the hysteretic asymmetries for the increasing and decreasing fields in the samples with the angle range of 20° ⩽ θk<60° are well described by a divergence in the calculation without a magnetization jump. The asymmetry for the sample with θk ≥ 60° may also be due to the divergence. But the two peak of the measured profiles, which are due to the anisotropy distribution in the actual materials, are different from the calculated profiles, which have a single peak near zero field. This indicates that the Stoner–Wohlfarth model adequately describes a hysteretic asymmetry of GMI profiles for the anisotropy angle in the range of 20° ⩽ θk<60° at a frequency of 10 MHz in amorphous ribbons. © 2001 American Institute of Physics.
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75.50.Kj Amorphous and quasicrystalline magnetic materials
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy

Cationic ordering control of magnetization in Sr2FeMoO6 double perovskite

Ll. Balcells, J. Navarro, M. Bibes, A. Roig, B. Martínez, and J. Fontcuberta

Appl. Phys. Lett. 78, 781 (2001); http://dx.doi.org/10.1063/1.1346624 (3 pages) | Cited 167 times

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The role of the synthesis conditions on the cationic Fe/Mo ordering in Sr2FeMoO6 double perovskite is addressed. It is shown that this ordering can be controlled and varied systematically. The Fe/Mo ordering has a profound impact on the saturation magnetization of the material. Using the appropriate synthesis protocol a value of 3.7 μB has been obtained. Mössbauer analysis reveals the existence of two distinguishable Fe sites and a charge density at the Fem+ ions significantly larger than 3d5 suggesting a Fe contribution to the spin-down conduction band. The implications of these findings for the synthesis of Sr2FeMoO6 having optimal magnetoresistance response are discussed. © 2001 American Institute of Physics.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
72.20.My Galvanomagnetic and other magnetotransport effects
76.80.+y Mössbauer effect; other γ-ray spectroscopy
71.20.Ps Other inorganic compounds

Magnetic block array for patterned magnetic media

Kazuyuki Koike, Hideo Matsuyama, Yoshiyuki Hirayama, Kiwamu Tanahashi, Takashi Kanemura, Osamu Kitakami, and Yutaka Shimada

Appl. Phys. Lett. 78, 784 (2001); http://dx.doi.org/10.1063/1.1345804 (3 pages) | Cited 24 times

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We have fabricated a magnetic rectangular block array of 130 Gblock/in.2 with a block-size-to-period ratio of 0.85 by using focused ion beam lithography. Each block has perpendicular crystal magnetic anisotropy and a single domain structure. Its advantage as patterned media is discussed in conjunction with thermal stability in recorded magnetization, reading signal, and area density. © 2001 American Institute of Physics.
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75.50.Ss Magnetic recording materials
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films

Efficient modified “walk on spheres” algorithm for the linearized Poisson–Bolzmann equation

Chi-Ok Hwang and Michael Mascagni

Appl. Phys. Lett. 78, 787 (2001); http://dx.doi.org/10.1063/1.1345817 (3 pages) | Cited 3 times

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A discrete random walk method on grids was proposed and used to solve the linearized Poisson–Boltzmann equation (LPBE) [R. Ettelaie, J. Chem. Phys. 103, 3657 (1995)]. Here, we present an efficient grid-free random walk method. Based on a modified “walk on spheres” algorithm [B. S. Elepov and G. A. Mihailov, Sov. Math. Dokl. 14, 1276 (1973)] for the LPBE, this Monte Carlo algorithm uses a survival probability distribution function for the random walker in a continuous and free diffusion region. This simulation method is illustrated by computing four analytically solvable problems. In all cases, excellent agreement is observed. © 2001 American Institute of Physics.
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05.60.Cd Classical transport
02.60.Lj Ordinary and partial differential equations; boundary value problems
02.50.Ng Distribution theory and Monte Carlo studies

All Ya–Ba–Cu–O c-axis trilayer interface-engineered Josephson junctions

B. H. Moeckly

Appl. Phys. Lett. 78, 790 (2001); http://dx.doi.org/10.1063/1.1345821 (3 pages) | Cited 9 times

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We demonstrate the fabrication of c-axis YBCO trilayer Josephson junctions incorporating an engineered interface as the barrier layer. These devices display resistively shunted junction-like I–V characteristics with IcRn products >1 mV at 4.2 K and ∼100 μV at 60 K. © 2001 American Institute of Physics.
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74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
85.25.Cp Josephson devices
74.50.+r Tunneling phenomena; Josephson effects
74.72.-h Cuprate superconductors
74.25.Sv Critical currents
81.65.Cf Surface cleaning, etching, patterning
68.35.Ct Interface structure and roughness
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Infrared optical properties of LaNiO3–platinized silicon and PbZrχTi1−χO3–LaNiO3–platinized silicon heterostructures

J. Yu, Z. M. Huang, X. J. Meng, J. L. Sun, J. H. Chu, and D. Y. Tang

Appl. Phys. Lett. 78, 793 (2001); http://dx.doi.org/10.1063/1.1347403 (3 pages) | Cited 7 times

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Using infrared spectroscopic ellipsometry, the optical constants of LaNiO3 thin films on Pt(111)–Ti–SiO2–Si substrates are obtained in the 2.5–12.6 μm range, in which the infrared optical constants decrease when the annealing temperature increases from 600 to 650 °C. At the same time, the infrared optical properties of PbZrχTi1−χO3(PZT) thin films with χ = 0.3 and 0.5 on LaNiO3–Pt–Ti–SiO2–Si substrates are simultaneously studied with respect to annealing temperatures. The infrared optical properties are associated closely with the grain size and crystallographic orientation of the films induced by annealing temperature, combined by the particular substrate. For the Ni–PZT–LaNiO3–Pt multilayer heterostructures, the infrared absorptance better than 99% can be achieved for PZT pyroelectric thin film infrared microsensors. © 2001 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Nk Insulators
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing
85.60.Gz Photodetectors (including infrared and CCD detectors)

Local probing of the polarization state in thin Pb(ZrTi)O3 films during polarization reversal

E. D. Mishina, N. E. Sherstyuk, E. Ph. Pevtsov, K. A. Vorotilov, A. S. Sigov, M. P. Moret, S. A. Rössinger, P. K. Larsen, and Th. Rasing

Appl. Phys. Lett. 78, 796 (2001); http://dx.doi.org/10.1063/1.1329332 (3 pages) | Cited 10 times

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The polarization state of a thin Pb(ZrTi)O3 film is probed by optical second-harmonic generation (SHG) while applying an external voltage (a sine wave). A hysteresis in the SHG intensity is observed that corresponds to the dielectric hysteresis and is analyzed using a phenomenological relation between the SHG intensity and the dielectric polarization. Based on this model, the polarization state of the film during polarization reversal is mapped. © 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.Ej Polarization and depolarization
77.80.Dj Domain structure; hysteresis
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Nk Insulators

Domain structures and planar defects in SrBi2Ta2O9 single crystals observed by transmission electron microscopy

Xinhua Zhu, Jianmin Zhu, Shunhua Zhou, Qi Li, Zhiguo Liu, and Naiben Ming

Appl. Phys. Lett. 78, 799 (2001); http://dx.doi.org/10.1063/1.1347383 (3 pages) | Cited 4 times

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In this work, the domain structures and structural planar defects in SrBi2Ta2O9 (SBT) single crystals with (001) orientation were investigated by transmission electron microscopy. The 90° domain walls are identified by the 90° rotation relationship of the electron diffraction pattern about the [001] zone axis, and which exhibit irregular configurations. Antiphase boundaries (APBs) in SBT single crystals are also observed, which exhibit ribbon-like morphologies. Fourfold vertices formed by four APBs meeting together are observed as predominant singularities, and are explained by a four-state clock model, in which the four states are considered as the TaO6 octahedra tilting left, right, forward, or backward along the crystallographic directions. Some threefold vertices are also observed since both threefold and fourfold vertices are energetically allowed in the present model. © 2001 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
61.72.Nn Stacking faults and other planar or extended defects
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Interparticle coupling effects in nanofabricated substrates for surface-enhanced Raman scattering

L. Gunnarsson, E. J. Bjerneld, H. Xu, S. Petronis, B. Kasemo, and M. Käll

Appl. Phys. Lett. 78, 802 (2001); http://dx.doi.org/10.1063/1.1344225 (3 pages) | Cited 136 times

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Surface-enhanced Raman scattering (SERS) substrates, consisting of arrays of electromagnetically coupled Ag nanoparticles on Si, were manufactured by electron-beam lithography. Substrate Raman efficiency, evaluated from the relative SERS intensities of the adsorbates rhodamine 6G and thiophenol, was found to increase rapidly with decreasing interparticle separation, signaling the importance of strong interparticle coupling effects in SERS. The observed SERS efficiency variation can be qualitatively explained in terms of electrostatic models of coupled metal structures. © 2001 American Institute of Physics.
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78.30.Jw Organic compounds, polymers
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.16.Nd Micro- and nanolithography
78.68.+m Optical properties of surfaces
78.30.Er Solid metals and alloys
81.07.Bc Nanocrystalline materials
68.43.Fg Adsorbate structure (binding sites, geometry)

Quantum dot and hole formation in sputter erosion

B. Kahng, H. Jeong, and A.-L. Barabási

Appl. Phys. Lett. 78, 805 (2001); http://dx.doi.org/10.1063/1.1343468 (3 pages) | Cited 59 times

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Recently, it was experimentally demonstrated that sputtering under normal incidence leads to the formation of spatially ordered uniform nanoscale islands or holes. Here, we show that these nanostructures have inherently nonlinear origin, first appearing when the nonlinear terms start to dominate the surface dynamics. Depending on the sign of the nonlinear terms, determined by the shape of the collision cascade, the surface can develop regular islands or holes with identical dynamical features, and while the size of these nanostructures is independent of flux and temperature, it can be modified by tuning the ion energy. © 2001 American Institute of Physics.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials

Fermi electron wave packet interference images on carbon nanotubes at room temperature

A. Hassanien, M. Tokumoto, P. Umek, D. Mihailovic, and A. Mrzel

Appl. Phys. Lett. 78, 808 (2001); http://dx.doi.org/10.1063/1.1345803 (3 pages) | Cited 12 times

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We report on the structure and electronic properties of single wall carbon nanotubes tips with atomically spatial resolution. Scanning tunneling microscopy shows topographic images of closed tips with a variety of geometrical structure; these include round, conical, as well as tips with a messy shape. Standing wave pattern of the charge density is observed at the tube cap which is formed due to constructive interference between the electronic states and its reflection on the nanotube tips. Atomically resolved images show asymmetry in the charge density that decay out within 6 nm away from the cap. These distinctive tip states do not exist elsewhere on the tube and are related to the presence of topological defects at tube ends. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Conductance of polymer nanowires fabricated by a combined electrodeposition and mechanical break junction method

H. X. He, C. Z. Li, and N. J. Tao

Appl. Phys. Lett. 78, 811 (2001); http://dx.doi.org/10.1063/1.1335551 (3 pages) | Cited 65 times

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We electrochemically deposit conducting polymer to bridge two closely placed electrodes, and then form a polymer nanowire by stretching the polymer bridge with the electrodes. During stretching, the conductance increases initially as the polymer chains are aligned in parallel, and then decreases in a stepwise fashion, due to abrupt changes in the nanowire thickness. We study the current–voltage (I–V) characteristics of the nanowire as a function of its electrochemical potential in an analogous fashion to the control of the gate voltage in semiconductor devices. Depending on the potential, the I–V curves vary from ohmic to rectifying characteristics. © 2001 American Institute of Physics.
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73.63.Nm Quantum wires
81.07.Nb Molecular nanostructures
81.15.Pq Electrodeposition, electroplating
73.61.Ph Polymers; organic compounds
61.41.+e Polymers, elastomers, and plastics
82.35.Cd Conducting polymers
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Full-band simulation of indirect phonon assisted tunneling in a silicon tunnel diode with delta-doped contacts

Cristian Rivas, Roger Lake, Gerhard Klimeck, William R. Frensley, Massimo V. Fischetti, Phillip E. Thompson, Sean L. Rommel, and Paul R. Berger

Appl. Phys. Lett. 78, 814 (2001); http://dx.doi.org/10.1063/1.1343500 (3 pages) | Cited 24 times

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Full-band simulations of indirect, phonon assisted, interband tunneling are used to calculate the current–voltage response of a low-temperature molecular-beam-epitaxy-grown silicon tunnel diode with delta-doped contacts. Electron confinement in the contacts results in weak structure in the current–voltage characteristic. The structure is lost when finite lifetime effects are included. The approach uses the nonequilibrium Green function formalism in a second-neighbor sp3s∗ planar orbital basis. © 2001 American Institute of Physics.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.30.De Semiconductor-device characterization, design, and modeling
73.61.Cw Elemental semiconductors

Band-edge luminescence in quaternary AlInGaN light-emitting diodes

M. Shatalov, A. Chitnis, V. Adivarahan, A. Lunev, J. Zhang, J. W. Yang, Q. Fareed, G. Simin, A. Zakheim, M. Asif Khan, R. Gaska, and M. S. Shur

Appl. Phys. Lett. 78, 817 (2001); http://dx.doi.org/10.1063/1.1343493 (3 pages) | Cited 19 times

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Operation of InGaN multiple-quantum-well (MQW) light-emitting diodes (LEDs) with quaternary AlInGaN barriers at room and elevated temperatures is reported. The devices outperform conventional GaN/InGaN MQW LEDs, especially at high pump currents. From the measurements of quantum efficiency and total emitted power under dc and pulsed pumping, we show the emission mechanism for quaternary barrier MQWs to be predominantly linked to band-to-band transitions. This is in contrast to localized state emission observed for conventional InGaN/InGaN and GaN/InGaN LEDs. The band-to-band recombination with an increased quantum-well depth improves the high-current performance of the quaternary barrier MQW LEDs, making them attractive for high-power solid-state lighting applications. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Quantitative metrology study of Cu/SiO2 interconnect structures using fluorescence x-ray microscopy

Guangyong Xu, X. Su, C. B. Stagarescu, D. E. Eastman, B. Lai, Z. Cai, I. C. Noyan, and C.-K. Hu

Appl. Phys. Lett. 78, 820 (2001); http://dx.doi.org/10.1063/1.1339996 (3 pages) | Cited 6 times

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We demonstrate the capability of fluorescence x-ray microscopy with a 0.25 μm beam for in situ measurements of Cu-wiring interconnects of submicron dimensions. We are able to measure submicron line widths, lengths, and thicknesses of both Cu and W structures, and a Ta liner in the test vehicle, to the absolute accuracy of 0.03 μm, and a relative accuracy of ∼4% in lateral dimensions, and ∼10% in heights. The shape of a buried electromigration void was also determined. This nanoscale nondestructive characterization technique promises to be powerful for a variety of materials systems. © 2001 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
07.85.Tt X-ray microscopes

Lateral AlxGa1−xN power rectifiers with 9.7 kV reverse breakdown voltage

A. P. Zhang, J. W. Johnson, F. Ren, J. Han, A. Y. Polyakov, N. B. Smirnov, A. V. Govorkov, J. M. Redwing, K. P. Lee, and S. J. Pearton

Appl. Phys. Lett. 78, 823 (2001); http://dx.doi.org/10.1063/1.1346622 (3 pages) | Cited 34 times

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AlxGa1−xN (x = 0–0.25) Schottky rectifiers were fabricated in a lateral geometry employing p+-implanted guard rings and rectifying contact overlap onto an SiO2 passivation layer. The reverse breakdown voltage (VB) increased with the spacing between Schottky and ohmic metal contacts, reaching 9700 V for Al0.25Ga0.75N and 6350 V for GaN, respectively, for 100 μm gap spacing. Assuming lateral depletion, these values correspond to breakdown field strengths of ⩽ 9.67×105 V cm−1, which is roughly a factor of 20 lower than the theoretical maximum in bulk GaN. The figure of merit (VB)2/RON, where RON is the on-state resistance, was in the range 94–268 MW cm−2 for all the devices. © 2001 American Institute of Physics.
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85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables

Self-repair of ordered pattern of nanometer dimensions based on self-compensation properties of anodic porous alumina

Hideki Masuda, Masato Yotsuya, Mari Asano, Kazuyuki Nishio, Masashi Nakao, Atsushi Yokoo, and Toshiaki Tamamura

Appl. Phys. Lett. 78, 826 (2001); http://dx.doi.org/10.1063/1.1344575 (3 pages) | Cited 44 times

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The self-repair of an ordered pattern of nanometer dimensions based on the self-compensation properties of anodic porous alumina is demonstrated. In a pretextured pattern formed on Al using the nanoindentation process with an array of convexes, the deficiency sites of the pattern were found to be compensated automatically during the anodization. Combining the self-compensation properties of the pore configuration of the anodic porous alumina with the preparation of a replica of the compensated porous structure allowed us to develop a process which has the capability of self-repairing the imperfections in the starting pattern. It was confirmed that deficiencies in the starting pattern could be repaired automatically in the Ni pattern regenerated using the self-compensated anodic porous alumina as a template. © 2001 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
81.16.Dn Self-assembly
81.05.Rm Porous materials; granular materials
61.43.Gt Powders, porous materials
81.65.-b Surface treatments
82.45.-h Electrochemistry and electrophoresis
68.35.Gy Mechanical properties; surface strains
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Self-assembled Fe nanowires using organometallic chemical vapor deposition and CaF2 masks on stepped Si(111)

J.-L. Lin, D. Y. Petrovykh, A. Kirakosian, H. Rauscher, F. J. Himpsel, and P. A. Dowben

Appl. Phys. Lett. 78, 829 (2001); http://dx.doi.org/10.1063/1.1345830 (3 pages) | Cited 37 times

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Linear arrays of 3 nm wide Fe stripes with 15 nm spacing are fabricated by self-assembly. They are formed by photolysis of ferrocene that is selectively adsorbed between CaF2 stripes. An ultraviolet nitrogen laser removes the organic ligands from ferrocene. Arrays of CaF2 stripes serve as masks, which are self-assembled on a stepped Si(111) surface. Scanning tunneling microscopy is used to investigate the surface morphology during growth. A generalization of this method to other wire materials is discussed. © 2001 American Institute of Physics.
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81.16.Dn Self-assembly
81.07.Vb Quantum wires
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
75.75.-c Magnetic properties of nanostructures
68.65.La Quantum wires (patterned in quantum wells)
68.43.Mn Adsorption kinetics
82.50.Hp Processes caused by visible and UV light
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Bundle structure and sliding of single-walled carbon nanotubes observed by frictional-force microscopy

K. Miura, M. Ishikawa, R. Kitanishi, M. Yoshimura, K. Ueda, Y. Tatsumi, and N. Minami

Appl. Phys. Lett. 78, 832 (2001); http://dx.doi.org/10.1063/1.1334359 (3 pages) | Cited 8 times

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The bundle structure and the sliding of single-walled carbon nanotubes (SWNTs) have been observed by frictional-force microscopy. The diameter of the nanotube and the nearest distance between any two nanotubes were estimated to be 1.4 and 0.3 nm, respectively. The frictional force required to move SWNTs on a KCl(001) surface and its energy dissipation were estimated to be 11 nN and 0.75×10−16 J, respectively. © 2001 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
62.20.Qp Friction, tribology, and hardness
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