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30 Jul 2007

Volume 91, Issue 5, Articles (05xxxx)

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Appl. Phys. Lett. 91, 052901 (2007); http://dx.doi.org/10.1063/1.2767146 (3 pages)

Wei-Feng Rao and Yu U. Wang
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Cavity-enhanced blue single-photon emission from a single InGaN/GaN quantum dot

Anas F. Jarjour, Robert A. Taylor, Rachel A. Oliver, Menno J. Kappers, Colin J. Humphreys, and Abbes Tahraoui

Appl. Phys. Lett. 91, 052101 (2007); http://dx.doi.org/10.1063/1.2767217 (3 pages) | Cited 20 times

Online Publication Date: 30 July 2007

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The authors report on the generation of single photons in the blue spectral region from a single InGaN/GaN quantum dot. The collection efficiency was enhanced by embedding the quantum dot layer in the middle of a low-Q microcavity. The microphotoluminescence is observed to be approximately ten times stronger than typical InGaN quantum dot emission without a cavity. The measurements were performed using nonlinear excitation spectroscopy in order to suppress the background emission from the underlying wetting layer.
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78.67.Hc Quantum dots
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
68.65.La Quantum wires (patterned in quantum wells)
68.08.Bc Wetting

Interfacial electronic structure of N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine/copper phthalocyanine:C60 composite/Au studied by ultraviolet photoemission spectroscopy

Sang Wan Cho, Kyung-Hwa Yoo, Kwangho Jeong, Chung-Nam Whang, Yeonjin Yi, and Myungkeun Noh

Appl. Phys. Lett. 91, 052102 (2007); http://dx.doi.org/10.1063/1.2761211 (3 pages) | Cited 12 times

Online Publication Date: 30 July 2007

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The interfacial electronic structures of N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB)/copper phthalocyanine (CuPc)/Au, NPB/C60/Au, and NPB/CuPc:C60 composite/Au were investigated by in situ ultraviolet photoelectron spectroscopy to understand the highly efficient hole injection in organic light-emitting diode. The hole-injection barrier of CuPc:C60/Au was 0.52 eV, while those of CuPc/Au and C60/Au were 0.96 and 1.62 eV, respectively. The lowered injection barrier is attributed to the smaller interface dipole of CuPc:C60 compared to that of pristine CuPc. This small interface dipole pulled up the highest occupied molecular orbital of CuPc in composite, which results in the decreased hole-injection barrier.
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73.20.-r Electron states at surfaces and interfaces
79.60.-i Photoemission and photoelectron spectra

Electronic conductance of ion implanted and plasma modified polymers

Z. J. Han, B. K. Tay, P. C. T. Ha, M. Shakerzadeh, A. A. Cimmino, S. Prawer, and D. McKenzie

Appl. Phys. Lett. 91, 052103 (2007); http://dx.doi.org/10.1063/1.2761233 (3 pages) | Cited 8 times

Online Publication Date: 30 July 2007

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The authors used the plasma immersion ion implantation and deposition technique to modify polyethylene terephthalate (PET) and by using conductive atomic force microscope, the spatial distribution of ∼ 10 nm size titanium nanoclusters embedded in PET matrices were observed. The I-V plots showed typical metal-semiconductor junction conductivity between the conductive tip and the surface. In addition, the authors also measured the temperature dependent conductivity and fitted it well to the Mott law, which implied that the conductance arose from electron hopping process. Such technique to create the surface structure of metal/polymer nanocomposites may open an alternative way for plastic nanoelectronics.
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73.40.Ns Metal-nonmetal contacts
71.20.Rv Polymers and organic compounds
72.20.Ee Mobility edges; hopping transport
61.72.up Other materials
52.77.Dq Plasma-based ion implantation and deposition
68.37.Ps Atomic force microscopy (AFM)

Spin Hall effect of excitons with spin-orbit coupling

Jian-Wei Wang and Shu-Shen Li

Appl. Phys. Lett. 91, 052104 (2007); http://dx.doi.org/10.1063/1.2757604 (3 pages) | Cited 5 times

Online Publication Date: 31 July 2007

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The center-of-mass motion of a quasi-two-dimensional exciton with spin-orbit coupling (SOC) in the presence of a perpendicular electric field is calculated by perturbation theory. The results indicate that a quasi-two-dimensional exciton with SOC can exhibit the spin Hall effect (SHE), which is similar to two-dimensional electrons and holes. A likely way to establish exciton SHE in experiments and a possible phase transition from dark to bright state driven by SOC are suggested.
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72.25.-b Spin polarized transport
72.20.My Galvanomagnetic and other magnetotransport effects
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.35.-y Excitons and related phenomena

Confinement of fractional quantum Hall states in narrow conducting channels

R. L. Willett, M. J. Manfra, L. N. Pfeiffer, and K. W. West

Appl. Phys. Lett. 91, 052105 (2007); http://dx.doi.org/10.1063/1.2762299 (3 pages) | Cited 2 times

Online Publication Date: 31 July 2007

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Confinement of small gapped fractional quantum Hall states facilitates quasiparticle manipulation and is an important step toward quasiparticle interference measurements. Demonstrated here is conduction through top gate defined, narrow channels in high density, ultrahigh mobility heterostructures. Transport evidence for the persistence of a correlated state at a filling fraction of 5/3 is shown in channels of 2 μm length but is gated to near 0.3 μm in width. The methods employed to achieve this confinement hold promise for interference devices proposed for studying potential non-Abelian statistics at a filling fraction of 5/2.
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73.43.-f Quantum Hall effects
73.63.Hs Quantum wells
73.21.Fg Quantum wells
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
71.70.Di Landau levels

Electric-pulse-induced resistive switching effect enhanced by a ferroelectric buffer on the Pr0.7Ca0.3MnO3 thin film

Z. W. Xing, N. J. Wu, and A. Ignatiev

Appl. Phys. Lett. 91, 052106 (2007); http://dx.doi.org/10.1063/1.2759476 (3 pages) | Cited 11 times

Online Publication Date: 31 July 2007

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An enhanced electric-pulse-induced resistance (EPIR) switching effect is observed in the Ag/Pb0.7Zr0.3TiO3/Pr0.7Ca0.3MnO3/YBa2Cu3O7 (Ag/PZT/PCMO/YBCO) structures. Compared with the Ag/PCMO/YBCO devices, the insertion of the PZT buffer into the Ag/PCMO interface is found to greatly increase the EPIR ratio and significantly decrease the threshold pulse voltage necessary to switching the resistive device decrease. They are attributed to the resistive change of the depletion region at the Ag/PCMO interface including the PZT buffer, in which ferroelectric polarizations play a crucial role in the enhanced EPIR switching effect.
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77.80.Fm Switching phenomena
77.22.Ej Polarization and depolarization
77.55.-g Dielectric thin films

Inherent linearity in carbon nanotube field-effect transistors

James E. Baumgardner, Aaron A. Pesetski, James M. Murduck, John X. Przybysz, John D. Adam, and Hong Zhang

Appl. Phys. Lett. 91, 052107 (2007); http://dx.doi.org/10.1063/1.2760159 (3 pages) | Cited 11 times

Online Publication Date: 1 August 2007

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The authors consider the suitability of carbon nanotubes for use in analog rf amplifiers, where the linearity of the device is critical. They show that in the limit of large electrostatic gate-channel capacitance, their theory predicts that an Ohmically contacted, ballistic carbon-nanotube-based field-effect transistor is inherently linear. While they have not achieved this limit in their experimental work, they compare the theory to experiment in the limit of small electrostatic gate-channel capacitance and find excellent agreement at virtually all bias conditions.
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85.35.Kt Nanotube devices
85.30.Tv Field effect devices

Nanostructural origin of the ac conductance in dielectric granular metals: The case study of Co20(ZrO2)80

Z. Konstantinović, M. García del Muro, X. Batlle, A. Labarta, and M. Varela

Appl. Phys. Lett. 91, 052108 (2007); http://dx.doi.org/10.1063/1.2766858 (3 pages) | Cited 3 times

Online Publication Date: 1 August 2007

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The authors show which is the nanostructure required in granular Co20(ZrO2)80 thin films to produce an ac response such as the one that is universally observed in a very wide variety of dielectric materials. A bimodal size distribution of Co particles yields randomly competing conductance channels which allow both the thermally assisted tunneling through small particles and capacitive conductance among larger particles that are further apart. A model consisting on a simple cubic random resistance-capacitor network describes quantitatively the experimental results as functions of temperature and frequency, and enables the determination of the microscopic parameters controlling the ac response of the samples.
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73.63.Bd Nanocrystalline materials
73.40.Gk Tunneling

Single electron pumping in InAs nanowire double quantum dots

A. Fuhrer, C. Fasth, and L. Samuelson

Appl. Phys. Lett. 91, 052109 (2007); http://dx.doi.org/10.1063/1.2767197 (3 pages) | Cited 16 times

Online Publication Date: 1 August 2007

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Closely spaced local gate electrodes are used to electrically define a double quantum dot along an InAs nanowire crystal. By applying a periodic pulse sequence to two plunger gate electrodes controlling the double quantum dot charge configuration, the device is operated as a single electron pump. The authors find that within measurement accuracy, the pumping current equals one electron per cycle for frequencies up to 2 MHz, demonstrating the suitability of nanowire based quantum dots for pumping applications.
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73.63.Nm Quantum wires
73.63.Kv Quantum dots
85.35.Gv Single electron devices

Influence of anthracene-2-thiol treatment on the device parameters of pentacene bottom-contact transistors

C. Bock, D. V. Pham, U. Kunze, D. Käfer, G. Witte, and A. Terfort

Appl. Phys. Lett. 91, 052110 (2007); http://dx.doi.org/10.1063/1.2767235 (3 pages) | Cited 16 times

Online Publication Date: 1 August 2007

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In pentacene-based bottom-contact field-effect transistors, the authors study the influence of anthracene-2-thiol-modified gold electrodes on the morphology, the contact and sheet resistance, the trap density, and the charge-carrier activation energy. The data are compared to reference samples with untreated gold electrodes. Anthracene-2-thiol treatment leads to a reduced sheet resistance, a reduced activation energy, and an improved film morphology.
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85.30.Tv Field effect devices

Ultrafast interface magnetization dynamics in Fe/AlGaAs (001) heterostructure

H. B. Zhao, D. Talbayev, G. Lüpke, A. T. Hanbicki, C. H. Li, and B. T. Jonker

Appl. Phys. Lett. 91, 052111 (2007); http://dx.doi.org/10.1063/1.2767773 (3 pages) | Cited 3 times

Online Publication Date: 2 August 2007

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Time-resolved magnetization-induced second-harmonic generation is used to initiate and monitor coherent electronic spin precession in the Fe interface layer of a Fe/AlGaAs (001) heterostructure. The frequency, phase, and hysteretic behavior of the interface magnetization precession are found to be different from the bulk Fe film. The results indicate that faster magnetization switching can be achieved in nanostructures where interface properties dominate.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys

Dingle temperatures for a two-band model: Application to the two-dimensional electron gas on silicon (111)

A. Gold, L. Fabie, and V. T. Dolgopolov

Appl. Phys. Lett. 91, 052112 (2007); http://dx.doi.org/10.1063/1.2767982 (3 pages) | Cited 1 time

Online Publication Date: 2 August 2007

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For zero temperature, we present theoretical results for the Dingle temperatures of a two-dimensional electron gas with two occupied bands. For impurity scattering, we apply their calculation to a two-band model for valley degeneracy gv = 2 and gv = 4 proposed recently for silicon (111). Taking into account the density of states and screening effects of the two electron gases, we predict huge differences for the Dingle temperature of the two bands and a strong density dependence for the Dingle temperature of the first band due to screening by the second band. The mobility of the two-band model shows a strong density dependence.
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71.20.Mq Elemental semiconductors
73.20.At Surface states, band structure, electron density of states
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)

Spin-polarized transport of electrons from polycrystalline Fe3O4 to amorphous Si

L. B. Zhao, W. B. Mi, E. Y. Jiang, and H. L. Bai

Appl. Phys. Lett. 91, 052113 (2007); http://dx.doi.org/10.1063/1.2766845 (3 pages) | Cited 9 times

Online Publication Date: 3 August 2007

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Polycrystalline Fe3O4∕amorphous Si heterostructure was prepared by facing-target sputtering and its microstructure and electrical transport properties were studied. The polycrystalline Fe3O4 layer was grown in column structure. The electrical transport mechanism across the disordered interface between polycrystalline Fe3O4 and amorphous Si layers is tunneling above the Verwey temperature [Nature (London) 144, 327 (1939) ] of 120 K. Nonlinear I‐V characteristics of the Schottky diode reveal thermionic emission∕diffusion mechanism below the Verwey temperature, and Schottky barrier height is 0.27 eV, calculated by a standard theory of thermionic emission∕diffusion. Based on a simplified band structure, the spin polarization of the polycrystalline Fe3O4 layer was determined to be ∼ 45%.
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73.40.-c Electronic transport in interface structures
72.25.-b Spin polarized transport
82.45.-h Electrochemistry and electrophoresis
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