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8 Jun 2009

Volume 94, Issue 23, Articles (23xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 94, 233101 (2009); http://dx.doi.org/10.1063/1.3148782 (3 pages)

E. Moyen, M. Macé, G. Agnus, A. Fleurence, T. Maroutian, F. Houzé, A. Stupakiewicz, L. Masson, B. Bartenlian, W. Wulfhekel, P. Beauvillain, and M. Hanbücken
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Laser triggered single streamer in a pin-to-pin coplanar dielectric barrier discharge

P. F. Ambrico, M. Ambrico, M. Šimek, A. Colaianni, G. Dilecce, and S. De Benedictis

Appl. Phys. Lett. 94, 231501 (2009); http://dx.doi.org/10.1063/1.3152284 (3 pages) | Cited 1 time

Online Publication Date: 9 June 2009

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The effect of laser light interaction with alumina surface of a single filament coplanar dielectric barrier discharge has been investigated. It has been found that for laser photon energy lower than the pure alumina photoelectron emission threshold, the laser beam was effective in triggering single streamer discharge below regular ignition voltage threshold. This work demonstrates that triggering of the filamentary discharge occurs due to the laser induced extraction of electrons originally trapped by the plasma radiation at the dielectric surface; the trap energy levels lower than the dielectric band gap explain the easier electron detrapping due to incident laser photons.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.38.Dx Laser light absorption in plasmas (collisional, parametric, etc.)
52.80.-s Electric discharges

High-energy negative ion beam obtained from pulsed inductively coupled plasma for charge-free etching process

O. V. Vozniy and G. Y. Yeom

Appl. Phys. Lett. 94, 231502 (2009); http://dx.doi.org/10.1063/1.3152763 (3 pages) | Cited 5 times

Online Publication Date: 9 June 2009

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Negative ions in conventional inductively coupled plasma are often more chemically active than positive ions (for example, in CF4 or SF6 plasmas), but inconveniently they are trapped inside the sheath and cannot be used for high-energy surface etching in sources with a grid-type acceleration system. In this work we describe a method of positive and negative ion extraction that allows the energy and flux of oppositely charged particles to be varied independently. Then by scattering the ions off from a metal surface, it is possible to form a high-energy beam of neutrals from the negative ions by using the low-energy positive component of the beam current for better charge compensation.
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52.50.Gj Plasma heating by particle beams
52.77.Bn Etching and cleaning
52.40.Kh Plasma sheaths
41.75.Cn Negative-ion beams

N2(A3Σu+) time evolution in N2 atmospheric pressure surface dielectric barrier discharge driven by ac voltage under modulated regime

P. F. Ambrico, M. Šimek, G. Dilecce, and S. De Benedictis

Appl. Phys. Lett. 94, 231503 (2009); http://dx.doi.org/10.1063/1.3152770 (3 pages) | Cited 2 times

Online Publication Date: 9 June 2009

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The relaxation of N2(A3Σu+) metastable in N2 ac (5 KHz and 7 KVpp) surface dielectric barrier discharge driven under pulse modulated regime, TON = 5 ms and TOFF = 20 ms, at atmospheric pressure has been investigated. N2(A) has been detected by optical-optical double resonance laser induced fluorescence in a space layer (space afterglow) at 1 mm above the discharge electrode. The time evolution clearly shows that in the space afterglow layer N2(A) builds up and decay in millisecond time scale and does not vary in the voltage cycle.
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52.80.Hc Glow; corona
76.70.Hb Optically detected magnetic resonance (ODMR)
78.55.-m Photoluminescence, properties and materials

Temporal behavior of cold atmospheric plasma jet

A. Shashurin, M. N. Shneider, A. Dogariu, R. B. Miles, and M. Keidar

Appl. Phys. Lett. 94, 231504 (2009); http://dx.doi.org/10.1063/1.3153143 (3 pages) | Cited 29 times

Online Publication Date: 11 June 2009

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Temporally resolved evolution of parameters in atmospheric plasma jet is studied by means of microwave scattering, fast photographing, and measuring of jet currents. It is observed that streamer (“plasma bullet”) propagating along with gas flow is generated immediately after the breakdown. It is demonstrated that an afterglow plasma column remains on the way of streamer passing. Lifetime of the afterglow plasma column is 3–5 μs, which is longer than that of the streamer.
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52.75.-d Plasma devices
52.80.Hc Glow; corona
52.70.Gw Radio-frequency and microwave measurements
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Control of phase transition in quasi-one-dimensional atomic wires by electron doping

Hyungjoon Shim, Sang-Yong Yu, Woosang Lee, Ja-Yong Koo, and Geunseop Lee

Appl. Phys. Lett. 94, 231901 (2009); http://dx.doi.org/10.1063/1.3143719 (3 pages) | Cited 7 times

Online Publication Date: 8 June 2009

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We report on the controlled change in the phase transition in In atomic chains on a Si(111) surface by introducing Na as impurity atoms. The Na-induced changes in the transition temperature (Tc) from a metallic room-temperature 4×1 structure into an insulating low-temperature 8×2 structure were determined by using low-energy electron diffraction. The Tc decreased almost linearly when the amount of deposited Na atoms was increased. The decrease in Tc with the increase in the amount of adsorbed Na atoms is suggested to be due to the doping of electrons from adsorbate to the substrate.
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71.30.+h Metal-insulator transitions and other electronic transitions
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Twin formation during the growth of InP on SrTiO3

J. Cheng, L. Largeau, G. Patriarche, P. Regreny, G. Hollinger, and G. Saint-Girons

Appl. Phys. Lett. 94, 231902 (2009); http://dx.doi.org/10.1063/1.3151826 (3 pages) | Cited 6 times

Online Publication Date: 8 June 2009

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The epitaxial growth of InP on (001)-oriented SrTiO3 (STO) is analyzed, and evidence is shown of the formation of twins during the early stages of the growth. A detailed crystallographic description of these twins is presented, and the origin of their formation is discussed. The elevated interface energy characteristic of the InP/STO system, combined with the initial three-dimensional growth of the semiconductor and with the existence of a commensurate heterointerface between STO and the twinned InP variant are identified as the main causes of twin formation during the growth of this highly heterogeneous epitaxial system.
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81.05.Ea III-V semiconductors
68.55.ag Semiconductors
68.35.Md Surface thermodynamics, surface energies
61.72.Mm Grain and twin boundaries

Synthesis and characterization of N-rich single crystalline SiOxNy nanowires with three-dimensional branches

Lin Gu, Yan Yu, Varun Penmatsa, Chunlei Wang, Joachim Maier, and Peter A. van Aken

Appl. Phys. Lett. 94, 231903 (2009); http://dx.doi.org/10.1063/1.3151954 (3 pages) | Cited 2 times

Online Publication Date: 8 June 2009

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N-rich single crystalline SiOxNy nanowires with three-dimensional (3D) branches have been synthesized and characterized. In contrast to the reported SiOxNy nanowires, our products exhibit a predominant N concentration and a single crystalline phase throughout the 3D branched structure. These properties are highly favorable for applications on which high dielectric constant and high refractive index are required. Valence electron energy-loss spectroscopy utilizing monochromated electrons reveals that the band gap of the materials is 4.4±0.2 eV. Energy-loss near edge structures of Si L2,3, N K, and O K edges display a strong orbital hybridization.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
71.20.Ps Other inorganic compounds
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
81.16.-c Methods of micro- and nanofabrication and processing
77.22.Ch Permittivity (dielectric function)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Atomic-scale structural evolution in amorphous Nd9Fe85B6 subjected to severe plastic deformation at room temperature

Wei Li, Xiaohong Li, Defeng Guo, Kiminori Sato, Dmitry V. Gunderov, Vladimir V. Stolyarov, and Xiangyi Zhang

Appl. Phys. Lett. 94, 231904 (2009); http://dx.doi.org/10.1063/1.3152013 (3 pages) | Cited 6 times

Online Publication Date: 8 June 2009

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Understanding the deformation-induced nanocrystallization in amorphous alloys at room temperature is proved to be a great challenge. In the present study, the formation of vacancy-type defects richly surrounded with Fe atoms in amorphous Nd9Fe85B6 subjected to room-temperature high-pressure torsion deformation is directly evidenced by positron lifetime measurements combined with a coincident Doppler broadening measurement of the positron-electron annihilation photons. This demonstrates a direct experimental evidence for shear inducing the enrichment of Fe atoms in the deformed amorphous alloy. These results presented here are of importance for understanding the deformation-induced nanocrystallization and for the technique development of nanocrystalline materials.
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61.72.jd Vacancies
62.50.-p High-pressure effects in solids and liquids
81.40.Lm Deformation, plasticity, and creep
78.70.Bj Positron annihilation
64.70.kd Metals and alloys
62.20.fq Plasticity and superplasticity
62.25.-g Mechanical properties of nanoscale systems

Very simple metallic subwavelength cell for constructing left-handed metamaterial

Zhiyu Wang, Dongxing Wang, Tao Jiang, Liang Peng, Jiangtao Huangfu, and Lixin Ran

Appl. Phys. Lett. 94, 231905 (2009); http://dx.doi.org/10.1063/1.3152283 (3 pages) | Cited 2 times

Online Publication Date: 8 June 2009

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In this letter, a very simple metallic subwavelength cell is designed for constructing left-handed metamaterial. The conductive current mode inside the metallic resonator of this cell imitates one reported displacement current mode inside a dielectric subwavelength resonator. We show by simulation and experiments that an artificial metamaterial composed of cells with such kind of current mode can behave simultaneously negative permittivity and permeability. The metallic cell with double negative property obtained in this letter is suitable for the applications in the high frequency band, such as in millimeter or even terahertz bands.
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84.40.-x Radiowave and microwave (including millimeter wave) technology
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
42.70.-a Optical materials

Nanograin crystalline transformation enhanced UV transparency of annealing refined indium tin oxide film

Wei-Lun Hsu, Yi-Hao Pai, Fan-Shuen Meng, Chee-Wee Liu, and Gong-Ru Lin

Appl. Phys. Lett. 94, 231906 (2009); http://dx.doi.org/10.1063/1.3147868 (3 pages) | Cited 3 times

Online Publication Date: 9 June 2009

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This work investigates enhancing UV transmittance and resistivity of indium tin oxide (ITO) film via nanograin crystalline transformation. After annealing, the ITO transforms its crystallinity from amorphous to columnar nanograins, and enriches the Sn–O bonds with absorption at 572 cm−1 to greatly reduce its resistivity to 1.2×10−4 Ω cm. Long-term annealing beyond 475 °C transforms ITO crystallinity to equiaxed nanograins, promoting high UV transmittance of 50%–76% at 325–405 nm but increasing resistivity up to 1.6×10−3 Ω cm. A compromised UV transmittance of >50% and resistivity of <2×10−4 Ω cm can be simultaneously achieved in annealed ITO with hybrid crystallinity of columnar and equiaxed grains.
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78.66.Li Other semiconductors
81.05.Hd Other semiconductors
73.61.Le Other inorganic semiconductors
68.55.ag Semiconductors
81.40.Gh Other heat and thermomechanical treatments
61.72.Cc Kinetics of defect formation and annealing
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
64.70.kg Semiconductors
78.30.Hv Other nonmetallic inorganics

Raman spectroscopy of rare earth doped silver halide crystals

I. Shafir, L. Nagli, and A Katzir

Appl. Phys. Lett. 94, 231907 (2009); http://dx.doi.org/10.1063/1.3148707 (3 pages) | Cited 4 times

Online Publication Date: 9 June 2009

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The phonon energy of rare earth doped silver halide crystals was investigated using Raman spectroscopy. An additional phonon vibrational mode was observed and attributed to localized defect vibrational modes. Good agreement was found between the measured and the predicted frequencies of the local modes. These additional low energy (65–80 cm−1) vibrational modes do not increase the thermal quenching of mid-IR luminescence of the rare earth ions in silver halide crystals. The rare earth doped silver halide crystals are suitable for the fabrication of mid-IR solid state lasers and fiber lasers due to their extremely low phonon energies.
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78.30.Hv Other nonmetallic inorganics
63.20.Pw Localized modes
78.55.Hx Other solid inorganic materials
81.40.Gh Other heat and thermomechanical treatments
42.55.Wd Fiber lasers
42.60.By Design of specific laser systems

Surface stress-induced change in overall elastic behavior and self-bending of ultrathin cantilever plates

H. Sadeghian, J. F. L. Goosen, A. Bossche, and F. van Keulen

Appl. Phys. Lett. 94, 231908 (2009); http://dx.doi.org/10.1063/1.3153158 (3 pages) | Cited 6 times

Online Publication Date: 9 June 2009

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In this letter, the dominant role of surface stress and surface elasticity on the overall elastic behavior of ultrathin cantilever plates is studied. A general framework based on two-dimensional plane-stress analysis is presented. Because of either surface reconstruction or molecular adsorption, there exists a surface stress and a surface elasticity imbalance between top and bottom surface of the cantilever. The surface elasticity imbalance creates an extra bending-extensional coupling which has not been taken into account previously. This leads to a modified extensional stiffness, bending stiffness and bending-extensional coupling stiffness. Due to the surface stress imbalance, an extended Stoney’s formula for self-bending of ultrathin cantilevers is derived.
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68.35.Gy Mechanical properties; surface strains
62.20.D- Elasticity
62.20.F- Deformation and plasticity
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.43.Mn Adsorption kinetics

10-nm-thick quinary (AlCrTaTiZr)N film as effective diffusion barrier for Cu interconnects at 900 °C

Shou-Yi Chang and Dao-Sheng Chen

Appl. Phys. Lett. 94, 231909 (2009); http://dx.doi.org/10.1063/1.3155196 (3 pages) | Cited 13 times

Online Publication Date: 10 June 2009

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In this study, an ultrathin quinary nitride film (AlCrTaTiZr)N of only 10 nm thick has been developed as a diffusion barrier layer for Cu interconnects. The (AlCrTaTiZr)N nanocomposite film was constructed of nanocrystallites embedded in an amorphous matrix. At an extremely high temperature of 900 °C, the Si/(AlCrTaTiZr)N/Cu film stack remained thermally stable. Neither interdiffusion between Si and Cu through the (AlCrTaTiZr)N layer nor formation of any silicides occurred. The nanocomposite structure and severe lattice distortions attributed to the addition of multiple elements were expected as the dominant factors for the superior diffusion resistance of the (AlCrTaTiZr)N film.
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66.30.Pa Diffusion in nanoscale solids
66.30.Ny Chemical interdiffusion; diffusion barriers
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.35.Fx Diffusion; interface formation

Transport properties in heterogeneous compacted granular media made of carbon nanotubes and potassium bromide

Michael Depriester, Abdelhak Hadj Sahraoui, Philippe Hus, and Frédérick Roussel

Appl. Phys. Lett. 94, 231910 (2009); http://dx.doi.org/10.1063/1.3154521 (3 pages) | Cited 4 times

Online Publication Date: 11 June 2009

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Thermal properties of pellets composed of carbon nanotubes (CNTs), single-walled or multiple-walled, and potassium bromide have been investigated via photothermal radiometry. Pellets containing 2 wt % CNT show a significant enhancement in thermal conductivity (k) by at least four times. However, when the concentration of a CNT is raised to 3 wt % or higher, a sudden drop in k is observed whereas the electrical conductivity keeps increasing and follows the percolation law. The thermal conductivity data have been modeled and interpreted in terms of a morphological transition between a compacted and an unconsolidated granular media.
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73.63.Fg Nanotubes
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.

Alteration of the mechanical properties of azopolymer film in the process of surface relief grating formation

Padmanabh U. Veer, Ullrich Pietsch, and Anne D. Mueller

Appl. Phys. Lett. 94, 231911 (2009); http://dx.doi.org/10.1063/1.3153847 (3 pages) | Cited 4 times

Online Publication Date: 12 June 2009

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Alterations of local hardness in azopolymer films have been investigated using atomic force microscope after light-induced surface relief gratings inscribed at temperatures between 25 °C and the glass transition. Compared to nonpatterned regions of same material, local hardness is increased at positions of crests but reduced in troughs. Surface relief gratings on films at room temperature show relative hardness variation up to 50% and decreases linearly with grating height and temperature. The findings can be explained by increased/decreased density of parallel-aligned polymer chains in crests/troughs as result of cooperative motion due to trans-cis-trans isomerisation during grating formation in competition with thermal disorder.
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68.60.Bs Mechanical and acoustical properties
61.41.+e Polymers, elastomers, and plastics
64.70.pj Polymers
62.20.Qp Friction, tribology, and hardness
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
68.37.Ps Atomic force microscopy (AFM)

Temperature-dependent bending rigidity of graphene

P. Liu and Y. W. Zhang

Appl. Phys. Lett. 94, 231912 (2009); http://dx.doi.org/10.1063/1.3155197 (3 pages) | Cited 13 times

Online Publication Date: 12 June 2009

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Both previous theoretical and experimental work showed that the bending rigidity of a liquid membrane decreases with increasing temperature. We demonstrate that the elastic energy forms for a solid membrane and a liquid membrane are identical under equal-biaxial stretching, implying the bending rigidity of a solid membrane should decrease with increasing temperature. We perform molecular dynamics simulations to study how thermal fluctuation affects the bending rigidity of graphene, and find that the bending rigidity decreases exponentially with increasing temperature. This is in contrast with recent atomistic Monte Carlo simulation result that the bending rigidity of graphene increases with increasing temperature.
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81.05.ub Fullerenes and related materials
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Dielectric response of AlSb from 0.7 to 5.0 eV determined by in situ ellipsometry

Y. W. Jung, T. H. Ghong, J. S. Byun, Y. D. Kim, H. J. Kim, Y. C. Chang, S. H. Shin, and J. D. Song

Appl. Phys. Lett. 94, 231913 (2009); http://dx.doi.org/10.1063/1.3153127 (3 pages) | Cited 3 times

Online Publication Date: 12 June 2009

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We present pseudodielectric function data 〈ε〉 = 〈ε1〉+i〈ε2〉 from 0.7 to 5.0 eV of oxide-free AlSb that are the closest representation to date of the intrinsic bulk dielectric response ε of the material. Measurements were done on a 1.5 μm thick film grown on (001) GaAs by molecular beam epitaxy. Data were obtained with the film in situ to avoid oxidation artifacts. Overlapping critical-point (CP) structures in the E2 energy region were identified by means of band-structure calculations done with the linear augmented Slater-type orbital method. Calculated CP energies agree well with those obtained from data, confirming the validity of the calculations.
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77.22.Ch Permittivity (dielectric function)
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
68.55.ag Semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
64.60.F- Equilibrium properties near critical points, critical exponents
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Carrier compensation by deep levels in Zn1−xMgxO/sapphire

A. Hierro, G. Tabares, J. M. Ulloa, E. Muñoz, A. Nakamura, T. Hayashi, and J. Temmyo

Appl. Phys. Lett. 94, 232101 (2009); http://dx.doi.org/10.1063/1.3149699 (3 pages) | Cited 11 times

Online Publication Date: 8 June 2009

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A systematic analysis of the deep level spectrum in the lower half of the bandgap of Au–Zn1−xMgxO (0.056<x<0.18) Schottky diodes is presented. Two deep levels are observed at Ev+580 and Ev+280 meV regardless of the bandgap energy with trap concentrations linearly increasing with the Mg content. The Ev+280 meV trap concentration becomes as high as 1.01×1018 cm−3 at 18% Mg, partially compensating the films and causing a decrease from 8.02×1016 to 1.27×1016 cm−3 in the net electron concentration and an increase by three orders of magnitude in the diode series resistance due to electron trapping.
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71.55.Gs II-VI semiconductors
85.30.Kk Junction diodes
72.80.Jc Other crystalline inorganic semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Nonadiabatic small polaron tunneling conduction in reduced Cr-doped SrTiO3−δ thin films

Bach Thang Phan and Jaichan Lee

Appl. Phys. Lett. 94, 232102 (2009); http://dx.doi.org/10.1063/1.3151957 (3 pages) | Cited 6 times

Online Publication Date: 9 June 2009

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We investigated the electrical conduction and dielectric relaxation of reduced Cr-doped SrTiO3−δ thin films. The electrical conduction behavior indicates the formation of small polarons in oxygen deficient Cr-doped SrTiO3−δ thin films. The associated dielectric relaxation further indicates nonadiabatic small polaron tunneling conduction. A strong electron-phonon interaction is identified based on the large polaron coupling constant, α ≈ 28(α⪢4).
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77.22.Gm Dielectric loss and relaxation
73.61.Ng Insulators
71.38.-k Polarons and electron-phonon interactions
77.55.-g Dielectric thin films
63.20.kd Phonon-electron interactions
73.40.Gk Tunneling

Frequency-dependent complex conductivity of an organic thin-film transistor

Daniel R. Lenski, Adrian Southard, and Michael S. Fuhrer

Appl. Phys. Lett. 94, 232103 (2009); http://dx.doi.org/10.1063/1.3153159 (3 pages) | Cited 3 times

Online Publication Date: 10 June 2009

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We measure the complex impedance between source/drain electrodes and the gate electrode of a pentacene thin-film transistor (TFT) at frequencies 50 Hz<ω/2π<20 kHz. Modeling the TFT as a distributed resistor and capacitor (RC) network (RC transmission line), we find that the data cannot be explained by a model including only a real, frequency-independent sheet conductivity. Instead, we use the RC transmission line model to extract the frequency-dependent complex sheet conductivity σ(ω) = σ′(ω)+jσ″(ω) of the pentacene film. At high frequencies, σ(ω) increases with frequency, σ′(ω) and σ″(ω) become similar in magnitude, and the on/off ratio is significantly reduced.
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85.30.Tv Field effect devices

Strong enhancement of terahertz emission from GaAs in InAs/GaAs quantum dot structures

Elmer Estacio, Minh Hong Pham, Satoru Takatori, Marilou Cadatal-Raduban, Tomoharu Nakazato, Toshihiko Shimizu, Nobuhiko Sarukura, Armando Somintac, Michael Defensor, Fritz Christian B. Awitan, Rafael B. Jaculbia, Arnel Salvador, and Alipio Garcia

Appl. Phys. Lett. 94, 232104 (2009); http://dx.doi.org/10.1063/1.3148670 (3 pages) | Cited 7 times

Online Publication Date: 11 June 2009

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We report on the intense terahertz emission from InAs/GaAs quantum dot (QD) structures grown by molecular beam epitaxy. Results reveal that the QD sample emission was as high as 70% of that of a p-type InAs wafer, the most intense semiconductor emitter to date. Excitation wavelength studies showed that the emission was due to absorption in strained undoped GaAs, and corresponds to a two order-of-magnitude enhancement. Moreover, it was found that multilayer QDs emit more strongly compared with a single layer QD sample. At present, we ascribe the intense radiation to huge strain fields at the InAs/GaAs interface.
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78.67.Hc Quantum dots
81.07.Ta Quantum dots
78.70.Gq Microwave and radio-frequency interactions
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.47.D- Time resolved spectroscopy (>1 psec)

Electron transport in carbon nanotube-silicon heterodimensional heterojunction array: An experimental investigation

Teng-Fang Kuo, Marian B. Tzolov, Daniel A. Straus, and Jimmy Xu

Appl. Phys. Lett. 94, 232105 (2009); http://dx.doi.org/10.1063/1.3151858 (3 pages) | Cited 4 times

Online Publication Date: 11 June 2009

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Current-voltage experiments on a highly ordered array of carbon nanotubes interfaced with silicon reveal interesting features arising from the regular array of heterojunctions between one-dimensional (1D) and three-dimensional materials. At high temperature, the vertically aligned and ordered nanotubes behave as an array of point junction contacts to the silicon below, which merge into a planar junction as temperature decreases. This model is further supported by the observation of signature space charge limited conduction, whose origin is attributed to deep levels in the silicon substrate and to the strong field enhancement due to the quasi-1D nanotubes.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Ht High-field and nonlinear effects
68.47.Fg Semiconductor surfaces
73.63.Fg Nanotubes
61.46.Fg Nanotubes

Control and elimination of nucleation-related defects in GaP/Si(001) heteroepitaxy

T. J. Grassman, M. R. Brenner, S. Rajagopalan, R. Unocic, R. Dehoff, M. Mills, H. Fraser, and S. A. Ringel

Appl. Phys. Lett. 94, 232106 (2009); http://dx.doi.org/10.1063/1.3154548 (3 pages) | Cited 22 times

Online Publication Date: 11 June 2009

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GaP films were grown on offcut Si(001) substrates using migration enhanced epitaxy nucleation followed by molecular beam epitaxy, with the intent of controlling and eliminating the formation of heterovalent (III-V/IV) nucleation-related defects—antiphase domains, stacking faults, and microtwins. Analysis of these films via reflection high-energy electron diffraction, atomic force microscopy, and both cross-sectional and plan-view transmission electron microscopies indicate high-quality GaP layers on Si that portend a virtual GaP substrate technology, in which the aforementioned extended defects are simultaneously eliminated. The only prevalent remaining defects are the expected misfit dislocations due to the GaP–Si lattice mismatch.
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68.55.ag Semiconductors
61.72.Nn Stacking faults and other planar or extended defects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Ps Atomic force microscopy (AFM)

Temperature dependence of microwave-induced magnetoresistance oscillation in two-dimensional electron systems

X. L. Lei and S. Y. Liu

Appl. Phys. Lett. 94, 232107 (2009); http://dx.doi.org/10.1063/1.3136757 (3 pages) | Cited 3 times

Online Publication Date: 12 June 2009

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Microwave-induced magnetoresistance oscillations in two-dimensional electron systems are examined from a photon-assisted transport scheme with short-range impurity scatterings. Analytical results at high filling factors strongly support early considerations and the recent experimental observation that the temperature dependence of the oscillation amplitude is exponential and originates primarily from the single-particle lifetime.
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72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)

Study of hole accumulation in individual germanium quantum dots in p-type silicon by off-axis electron holography

Luying Li, Sutharsan Ketharanathan, Jeff Drucker, and Martha R. McCartney

Appl. Phys. Lett. 94, 232108 (2009); http://dx.doi.org/10.1063/1.3154524 (3 pages) | Cited 3 times

Online Publication Date: 12 June 2009

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Epitaxial germanium quantum dots (QDs) embedded in boron-doped silicon have been studied using off-axis electron holography to estimate the number of holes associated with a single QD. Holes were confined near the base of the pyramidal, 25-nm-wide Ge QDs. The resulting estimate of charge density was 0.03 holes/nm3 which corresponded to about 30 holes localized to the investigated dot. For comparison, the average number of holes confined to each Ge dot was found to be about 40, using a capacitance-voltage measurement. The difference emphasizes the value of measuring charges confined to individual nm-scale regions of a heterogeneous sample.
Show PACS
73.63.Kv Quantum dots
73.61.Cw Elemental semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
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