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29 Oct 2007

Volume 91, Issue 18, Articles (18xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 91, 183501 (2007); http://dx.doi.org/10.1063/1.2801554 (3 pages)

Aurelien Du Pasquier, Daniel D. T. Mastrogiovanni, Lauren A. Klein, Tong Wang, and Eric Garfunkel
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Particle formation in acetylene very low-pressure high density magnetized plasmas

Maria Calafat, David Escaich, Richard Clergereaux, Patrice Raynaud, and Yvan Segui

Appl. Phys. Lett. 91, 181502 (2007); http://dx.doi.org/10.1063/1.2804007 (3 pages) | Cited 4 times

Online Publication Date: 1 November 2007

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Particle formation in cold plasmas is a matter of a large number of studies in capacitive, high-pressure, and low-density discharges. Conversely, under very-low working pressure and high plasma density conditions, as in microwave multipolar plasma excited at distributed electron cyclotron resonance (MMP-DECR), particle formation is generally not favored: the gas phase interaction probability is low due to the very-low working pressure. However, in this work, we report observations and analyses of particles formed in acetylene MMP-DECR discharges. It is proposed that the presence of the magnetic field compensates for the very-low working pressure inducing an increase in the gas phase interaction probability: negative ions are repelled by the sheath and confined within the magnetic field. Thus, particles can be formed similarly to in rf plasma.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.40.Kh Plasma sheaths
52.80.-s Electric discharges
52.55.-s Magnetic confinement and equilibrium
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Infrared thermal emission in macroporous silicon three-dimensional photonic crystals

M. Garín, T. Trifonov, A. Rodríguez, and R. Alcubilla

Appl. Phys. Lett. 91, 181901 (2007); http://dx.doi.org/10.1063/1.2804002 (3 pages) | Cited 6 times

Online Publication Date: 29 October 2007

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In this paper we investigate the infrared thermal emission properties of macroporous silicon with modulated pore diameter. Samples with different pore modulation periodicities but fixed in-plane lattice constant are fabricated. Normal emission of these samples is measured between 373 and 673 K. Room-temperature normal-incidence reflectance and transmission spectra are also measured and compared with the photonic band structure simulation. It is shown that thermal emission is suppressed due to photonic band gap effect along the pore axis in excellent agreement with the numerical calculations.
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61.43.Gt Powders, porous materials
42.70.Qs Photonic bandgap materials
78.60.Kn Thermoluminescence
61.66.Bi Elemental solids
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Growing extremely thin bulklike metal film on a semiconductor surface: Monolayer Al(111) on Si(111)

Ying Jiang, Yong-Hyun Kim, S. B. Zhang, Philipp Ebert, Shenyuan Yang, Zhe Tang, Kehui Wu, and E. G. Wang

Appl. Phys. Lett. 91, 181902 (2007); http://dx.doi.org/10.1063/1.2804010 (3 pages) | Cited 4 times

Online Publication Date: 29 October 2007

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We report combined scanning tunneling microscopy, x-ray photoelectron emission spectroscopy, electron energy loss spectroscopy, and theoretical study of the growth of ultrathin Al film on the Si(111) substrate. We show that by (i) a modification of the substrate reconstruction with a math×math surface and (ii) a choice of materials with commensurate lattices, atomically flat film can be obtained even at the ultimate one monolayer limit, while maintaining a bulklike atomic structure. Detailed analysis shows that this monolayer Al(111)-1×1 film is electronically decoupled from the Si substrate, and it shows metallic characteristics.
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68.55.-a Thin film structure and morphology
61.46.-w Structure of nanoscale materials
73.22.-f Electronic structure of nanoscale materials and related systems

Quantum-confined Stark effects in the m-plane In0.15Ga0.85N/GaN multiple quantum well blue light-emitting diode fabricated on low defect density freestanding GaN substrate

T. Onuma, H. Amaike, M. Kubota, K. Okamoto, H. Ohta, J. Ichihara, H. Takasu, and S. F. Chichibu

Appl. Phys. Lett. 91, 181903 (2007); http://dx.doi.org/10.1063/1.2802042 (3 pages) | Cited 18 times

Online Publication Date: 29 October 2007

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Quantum-confined Stark effects (QCSEs) in a polarization-free m-plane In0.15Ga0.85N/GaN multiple quantum well (MQW) blue light-emitting diode fabricated on the low defect density (DD) freestanding GaN substrate were investigated. The electroluminescence (EL) peak at 2.74 eV little shifted to the higher energy with the increase in current because of the absence of the polarization fields. The effective radiative lifetime increased and the nonradiative lifetime decreased with the increase in the junction field, and the results were quantitatively explained in terms of field-induced QCSE including tunneling escape of holes from the MQW. As a result of the use of the low DD substrate, the equivalent internal quantum efficiency, which was approximated as the spectrally integrated EL intensity at 300 K divided by that at 150 K, of 43% was achieved.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.07.St Quantum wells

Partitioning of salt ions in FT30 reverse osmosis membranes

Xijing Zhang, David G. Cahill, Orlando Coronell, and Benito J. Mariñas

Appl. Phys. Lett. 91, 181904 (2007); http://dx.doi.org/10.1063/1.2802562 (3 pages) | Cited 4 times

Online Publication Date: 29 October 2007

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FT30 membranes consist of a polyamide active layer interfacially polymerized on a porous polysulfone support. The ion partition coefficient κ in the active layer is a key thermodynamic parameter that partially controls the ability of the membrane to desalinate water. Membranes are soaked in aqueous solutions of CsCl, KBr, or Na2WO4 with salt concentrations of 0.002M<Cs<2M, freeze dried to remove water without disturbing ion distribution, and analyzed by Rutherford backscattering spectrometry. For Cs<0.01M, κ is surprisingly large and independent of Cs, κ = 6±2. The porosity ϕ of the top 500 nm of the support layer is also extracted from the RBS data: ϕ = 0.45±0.05.
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82.45.Mp Thin layers, films, monolayers, membranes
82.35.-x Polymers: properties; reactions; polymerization
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)

Wetting behavior of molten In–Sn alloy on bulk amorphous and crystalline Cu40Zr44Al8Ag8

G. F. Ma, H. F. Zhang, H. Li, and Z. Q. Hu

Appl. Phys. Lett. 91, 181905 (2007); http://dx.doi.org/10.1063/1.2804559 (3 pages) | Cited 3 times

Online Publication Date: 30 October 2007

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Using the sessile-drop method, the wettability of the molten In–Sn alloy on bulk amorphous and crystalline Cu40Zr44Al8Ag8 alloy was studied at different temperatures. It was found that the equilibrium contact angle of In–Sn alloy melt on bulk amorphous substrate was smaller than that of the crystalline one. An intermetallic compound existed at the interface of In–Sn alloy on amorphous Cu40Zr44Al8Ag8, while no intermediate reaction layer was formed at the interface of In–Sn alloy on crystalline Cu40Zr44Al8Ag8 in the temperature range studied.
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68.08.Bc Wetting
81.05.Bx Metals, semimetals, and alloys
61.43.Dq Amorphous semiconductors, metals, and alloys
61.25.Mv Liquid metals and alloys

Enhanced visibility of graphene: Effect of one-dimensional photonic crystal

Kai Chang, J. T. Liu, J. B. Xia, and N. Dai

Appl. Phys. Lett. 91, 181906 (2007); http://dx.doi.org/10.1063/1.2804569 (3 pages) | Cited 10 times

Online Publication Date: 30 October 2007

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We investigate theoretically the light reflectance of a graphene layer prepared on the top of one-dimensional Si/SiO2 photonic crystal (1DPC). It is shown that the visibility of the graphene layers is enhanced greatly when 1DPC is added, and the visibility can be tuned by changing the incident angle and light wavelengths. This phenomenon is caused by the absorption of the graphene layer and the enhanced reflectance of the 1DPC.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
42.70.Qs Photonic bandgap materials

Single-crystal elastic constants of Co3(Al,W) with the L12 structure

Katsushi Tanaka, Takashi Ohashi, Kyosuke Kishida, and Haruyuki Inui

Appl. Phys. Lett. 91, 181907 (2007); http://dx.doi.org/10.1063/1.2805020 (3 pages) | Cited 17 times

Online Publication Date: 30 October 2007

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Single-crystal elastic constants of Co3(Al,W) with cubic L12 structure have been experimentally measured by resonance ultrasound spectroscopy at liquid helium temperature. The values of all three independent single-crystal elastic constants and polycrystalline elastic constants of Co3(Al,W) experimentally determined are 15%–25% larger than those of Ni3(Al,Ta) but are considerably smaller than previously calculated values of the constants. When judged from the values of Poisson’s ratio, Cauchy pressure, and Gh/Bh, the ductility of Co3(Al,W) is expected to be sufficiently high so that Co3(Al,W) can be practically used as the constituent phase of “Co-base superalloys.”
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62.20.D- Elasticity
81.40.Gh Other heat and thermomechanical treatments
61.66.Fn Inorganic compounds
61.05.-a Techniques for structure determination

Resonant condition of unitary dendritic structure with overlapping negative permittivity and permeability

X. Zhou and X. P. Zhao

Appl. Phys. Lett. 91, 181908 (2007); http://dx.doi.org/10.1063/1.2798063 (3 pages) | Cited 26 times

Online Publication Date: 30 October 2007

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We demonstrate that a two-dimensional isotropic left-handed materials (LHMs) can be built based on unitary dendritic structure units. Utilizing parameter design, we theoretically deduce a resonant condition in unitary dendritic structure unit, which provided an overlapping negative permittivity and negative permeability response over a frequency band. Employing microwave transmission and prism refractive index experiments, the medium with dendritic structure exhibits a distinct left-handed effect. The proposed implementation of the dendritic structure opens the possibility of realizing integrative isotropic LHMs, especially for simple chemical prepared infrared or visible frequency LHMs.
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77.22.Ch Permittivity (dielectric function)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.-a Optical materials

RbCdF3:Mn2+: A potential ultraviolet dosimeter material

C. Dotzler, G. V. M. Williams, and A. Edgar

Appl. Phys. Lett. 91, 181909 (2007); http://dx.doi.org/10.1063/1.2805072 (3 pages) | Cited 1 time

Online Publication Date: 30 October 2007

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Optical absorption and optically stimulated luminescence measurements have been made on RbCdF3:Mn2+. We show that there is an ultraviolet (UV) response that covers the UV spectrum and hence this compound is applicable for passive UV detection and dosimetry. There is a fast UV-A and UV-B stimulated luminescence decay when compared with the bleaching of the deep UV induced optical absorption that can be explained in terms of a distribution of carrier traps with different detrapping rates.
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42.70.-a Optical materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.55.Hx Other solid inorganic materials
87.50.wj Dosimetry/exposure assessment
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Sk Insulators

A hydrogen sensor based on tunneling between palladium clusters

J. van Lith, A. Lassesson, S. A. Brown, M. Schulze, J. G. Partridge, and A. Ayesh

Appl. Phys. Lett. 91, 181910 (2007); http://dx.doi.org/10.1063/1.2802730 (3 pages) | Cited 24 times

Online Publication Date: 30 October 2007

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We describe nanocluster based tunneling sensors for detecting hydrogen. Pd clusters with diameters ranging from 3.5 to 6 nm are deposited between a pair of contacts until a predetermined resistance between the contacts is obtained. We demonstrate that the conduction through the cluster film is dominated by tunneling gaps. Upon exposure to hydrogen, the clusters expand, reducing the average size of the gaps and reducing the measured resistance. The sensor response as a function of external hydrogen pressure is described, for different cluster sizes and different operating temperatures, by a simple model with a single physically meaningful fitting parameter.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Molecular beam epitaxial growth and photoluminescence characterization of self-organized Pb1−xSnxTe quantum dots embedded in a single-crystalline CdTe host matrix

Kazuto Koike, Tomoyuki Itakura, Takanori Hotei, and Mitsuaki Yano

Appl. Phys. Lett. 91, 181911 (2007); http://dx.doi.org/10.1063/1.2804574 (3 pages) | Cited 5 times

Online Publication Date: 31 October 2007

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This report describes molecular beam epitaxial growth and photoluminescence properties of coherently embedded centrosymmetric Pb1−xSnxTe quantum dots (QDs) in a wide bandgap CdTe host matrix. These QDs were self-organized by a Pb1−xSnxTe growth on CdTe buffer layer at a high temperature of 280 °C. A highly efficient midinfrared emission from the QDs was obtained even at 300 K with a proportional redshift to the Sn content in QDs. By considering both effects of strain-induced band deformation and quantum confinement in QD potentials, the transition energy observed was found to agree well with a theoretical calculation.
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78.67.Hc Quantum dots
78.55.Hx Other solid inorganic materials
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Hd Other semiconductors

Photoluminescence spectroscopy of nearly defect-free InN microcrystals exhibiting nondegenerate semiconductor behaviors

Ching-Lien Hsiao, Hsu-Cheng Hsu, Li-Chyong Chen, Chien-Ting Wu, Chun-Wei Chen, Min Chen, Li-Wei Tu, and Kuei-Hsien Chen

Appl. Phys. Lett. 91, 181912 (2007); http://dx.doi.org/10.1063/1.2804568 (3 pages) | Cited 12 times

Online Publication Date: 1 November 2007

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Nearly defect-free InN microcrystals grown on Si(111) substrates have been realized by plasma-assisted molecular beam epitaxy. High-resolution transmission electron microscope images reveal that these microcrystals exhibit single-crystalline wurtzite structure. Low temperature photoluminescence (PL) shows a strong emission peak at 0.679 eV with a very narrow linewidth of 17 meV at excitation power density of 3.4 W/cm2. Temperature-dependent PL spectra follow the Varshni equation well, and peak energy blueshifts by ∼ 45 meV from 300 to 15 K. Power-density-dependent PL spectroscopy manifests direct near-band-edge transition. A low carrier density of 3×1017 cm−3 has been estimated from PL empirical relation, which is close to the critical carrier density of the Mott transition of 2×1017 cm−3.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
52.77.Dq Plasma-based ion implantation and deposition

Reducing exciton-longitudinal-optical phonon interaction with shrinking ZnO quantum dots

Wei-Tse Hsu, Kuo-Feng Lin, and Wen-Feng Hsieh

Appl. Phys. Lett. 91, 181913 (2007); http://dx.doi.org/10.1063/1.2805192 (3 pages) | Cited 9 times

Online Publication Date: 1 November 2007

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The exciton-longitudinal-optical-phonon (LO-phonon) interaction was observed to decrease with reducing ZnO particle size to its exciton Bohr radius (aB). The unapparent LO-phonon replicas of free exciton (FX) emission and the smaller FX energy difference between 13 and 300 K reveal decreasing weighting of exciton-LO phonon coupling strength. The diminished Fröhlich interaction mainly results from the reducing aB with size due to the quantum confinement effect that makes the exciton less polar.
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71.55.Gs II-VI semiconductors
71.35.-y Excitons and related phenomena
81.07.Wx Nanopowders
81.07.Ta Quantum dots

Measurement of thermal diffusivity at high pressure using a transient heating technique

Pierre Beck, Alexander F. Goncharov, Viktor V. Struzhkin, Burkhard Militzer, Ho-kwang Mao, and Russell J. Hemley

Appl. Phys. Lett. 91, 181914 (2007); http://dx.doi.org/10.1063/1.2799243 (3 pages) | Cited 14 times

Online Publication Date: 2 November 2007

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We describe a flash-heating procedure designed to measure thermal diffusivity of materials at high pressure and temperature in diamond anvil cells. This technique involves time-resolved radiometry combined with a pulsed IR laser source. Results for MgO, NaCl, and KCl are presented (to P = 32 GPa and T = 2600 K). These measurements agree with previous studies at low pressure and high temperature and enable to test models for the combined P-T dependence of thermal conductivity. This technique can be extended to a broader range of pressures and can be used to address a variety of problems in geoscience, planetary sciences, and materials science.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
62.50.-p High-pressure effects in solids and liquids
81.40.Vw Pressure treatment
81.40.Gh Other heat and thermomechanical treatments
78.47.-p Spectroscopy of solid state dynamics
78.30.-j Infrared and Raman spectra

Microlens array for focusing airborne ultrasound using heated wire grid

Liang-Wu Cai and José Sánchez-Dehesa

Appl. Phys. Lett. 91, 181915 (2007); http://dx.doi.org/10.1063/1.2804564 (3 pages) | Cited 2 times

Online Publication Date: 2 November 2007

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This letter reports on the focusing of airborne ultrasound by a simple grid of heated wires. The focusing is analogous to that of an array of optical microlenses. The focusing pattern is determined by the spacing between wires, and the focusing areas are tightly confined with a great “depth of field.” Such acoustical microlens arrays have great potentials for shaping beams produced by ultrasonic transducers, in applications such as ultrasonic cleaning and nondestructive testing.
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43.38.-p Transduction; acoustical devices for the generation and reproduction of sound
43.58.-e Acoustical measurements and instrumentation
43.60.Lq Acoustic imaging, displays, pattern recognition, feature extraction

Energy pathways and directionality in deformation twinning

S. Kibey, J. B. Liu, D. D. Johnson, and H. Sehitoglu

Appl. Phys. Lett. 91, 181916 (2007); http://dx.doi.org/10.1063/1.2800806 (3 pages) | Cited 8 times

Online Publication Date: 2 November 2007

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We present ab initio density functional theory calculations of twinning energy pathways for two opposite twinning modes, (111)[11math] and (111)[mathmath2], in fcc materials to examine the directional nature of twinning which cannot be explained by classical twin nucleation models or the “twinnability” criterion. By accounting for these energy pathways in a multiscale model, we quantitatively predict the critical twinning stress for the (111)[mathmath2] mode to be substantially higher compared to the favorable (111)[11math] mode (whose predicted stresses are in agreement with experiment), thus, ruling out twinning in the (111)[mathmath2] mode.
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61.72.Mm Grain and twin boundaries
61.72.Bb Theories and models of crystal defects
62.20.F- Deformation and plasticity

Large and opposite changes of the third-order optical nonlinearities of chalcogenide glasses by femtosecond and continuous-wave laser irradiation

Qiming Zhang, Wei Liu, Liying Liu, Lei Xu, Yinsheng Xu, and Guorong Chen

Appl. Phys. Lett. 91, 181917 (2007); http://dx.doi.org/10.1063/1.2805636 (3 pages) | Cited 5 times

Online Publication Date: 2 November 2007

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We report that the nonlinear refractive index (n2) of As2S3 glass can be enhanced after irradiation by a femtosecond laser but suppressed after irradiation by a continuous-wave (cw) laser, although both the femtosecond laser and cw laser induce photodarkening in the glass. Photodarkening by the femtosecond laser increases n2 by as much as 50%, while irradiation by a subbandgap cw laser decreases n2 by as much as 60% of its original value. The results provide a way to manipulate the third-order optical nonlinearity of this photonic glass. Mechanisms of the optical nonlinearity changes are discussed.
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42.70.Ce Glasses, quartz
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.66.Jg Amorphous semiconductors; glasses
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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ZnO-based thin film transistors having high refractive index silicon nitride gate

K. Remashan, J. H. Jang, D. K. Hwang, and S. J. Park

Appl. Phys. Lett. 91, 182101 (2007); http://dx.doi.org/10.1063/1.2804566 (3 pages) | Cited 17 times

Online Publication Date: 29 October 2007

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The effect of properties of silicon nitride films on the electrical performance of zinc oxide (ZnO) thin film transistors (TFTs) has been investigated by utilizing silicon nitride films having refractive indices of 2.45 and 1.85. The ZnO TFTs having a silicon nitride with a high refractive index of 2.45 exhibited a field effect mobility of 8 cm2/V s, on/off current ratio of 106, and subthreshold slope of 0.9 V/decade. On the other hand, TFTs having a silicon nitride with a low refractive index of 1.85 showed a field effect mobility of 0.5 cm2/V s, on/off current ratio of less than 102, and subthreshold slope of 19 V/decade. The improved device performance was ascribed to a better interface between ZnO and high refractive index silicon nitride, and hydrogenation of the ZnO channel with the hydrogen originated from the high refractive index silicon nitride.
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85.30.Tv Field effect devices
85.75.Hh Spin polarized field effect transistors

The mechanism study on transport properties in perovskite oxide p-n junctions

Peng Han, Kui-juan Jin, Hui-bin Lu, Qing-Li Zhou, Yue-Liang Zhou, and Guo-Zhen Yang

Appl. Phys. Lett. 91, 182102 (2007); http://dx.doi.org/10.1063/1.2804608 (3 pages) | Cited 22 times

Online Publication Date: 30 October 2007

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The drift-diffusion mechanism, the interband Zener tunneling theory, and the trap assisted tunneling model are combined to reveal the transport properties in a multicorrelated system of the p-La0.9Sr0.1MnO3/n-SrNb0.01Ti0.99O3 junction with various temperatures. The good agreement between the calculated and measured I-V curves reveal that the drift-diffusion mechanism dominates the transport process with forward bias, and the interband Zener tunneling plays an important role for the carrier transport with high reverse bias. In the low reverse bias, the I-V characteristic of oxide device is mainly attributed to the trap assisted tunneling process caused by the oxygen vacancy induced states.
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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
73.40.Gk Tunneling
66.30.-h Diffusion in solids

Electron irradiation-induced increase of minority carrier diffusion length, mobility, and lifetime in Mg-doped AlN/AlGaN short period superlattice

O. Lopatiuk-Tirpak, L. Chernyak, B. A. Borisov, V. V. Kuryatkov, S. A. Nikishin, and K. Gartsman

Appl. Phys. Lett. 91, 182103 (2007); http://dx.doi.org/10.1063/1.2805190 (3 pages)

Online Publication Date: 30 October 2007

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Minority carrier diffusion length in a p-type Mg-doped AlN/Al0.08Ga0.92N short period superlattice was shown to undergo a multifold and persistent (for at least 1 week) increase under continuous irradiation by low-energy beam of a scanning electron microscope. Since neither the diffusion length itself nor the rate of its increase exhibited any measurable temperature dependence, it is concluded that this phenomenon is attributable to the increase in mobility of minority electrons in the two-dimensional electron gas, which in turn is limited by defect scattering. Cathodoluminescence spectroscopy revealed ∼ 40% growth of carrier lifetime under irradiation with an activation energy of 240 meV.
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73.63.-b Electronic transport in nanoscale materials and structures
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.82.Fk Semiconductors
61.80.Fe Electron and positron radiation effects
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.60.Hk Cathodoluminescence, ionoluminescence

Series resistance imaging of solar cells by voltage dependent electroluminescence

David Hinken, Klaus Ramspeck, Karsten Bothe, Bernhard Fischer, and Rolf Brendel

Appl. Phys. Lett. 91, 182104 (2007); http://dx.doi.org/10.1063/1.2804562 (3 pages) | Cited 18 times

Online Publication Date: 31 October 2007

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This letter introduces a method based on electroluminescence imaging to determine mappings of the local series resistance of large area semiconductor devices such as solar cells. The method combines the local electroluminescence emission Φi(U) and its derivative Φi′(U) with respect to the applied voltage U. The combined analysis of these two quantities yields the local series resistance Rise and proves the physical validity of the used current transport model and thus the physical relevance of the determined Rise value. The method is verified on a monocrystalline silicon solar cell with local shunts and local series resistance problems.
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78.60.Fi Electroluminescence
81.05.Cy Elemental semiconductors
84.60.Jt Photoelectric conversion

Route to a correct description of the fundamental properties of cubic InN

M. Briki, A. Zaoui, F. Boutaiba, and M. Ferhat

Appl. Phys. Lett. 91, 182105 (2007); http://dx.doi.org/10.1063/1.2805223 (3 pages) | Cited 6 times

Online Publication Date: 31 October 2007

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The main fundamental properties of the cubic InN are studied within the density functional theory. We used the full-potential augmented plane wave method with two different exchange-correlation potentials, the Perdew-Wang (PW) and the Engel-Vosko (EV) approximations, in both cases nonrelativistic and relativistic. We found that the PW and relativistic approximations give a metallic ground state. The use of the EV and nonrelativistic approximations gives, however, a semiconductor phase with a band-gap value of 0.57 eV, which is in fairly good agreement with the recent measurement of 0.61 eV.
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71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Nr Semiconductor compounds
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons

Nonalloyed Cr/Au-based Ohmic contacts to n-GaN

Ming-Lun Lee, Jinn-Kong Sheu, and C. C. Hu

Appl. Phys. Lett. 91, 182106 (2007); http://dx.doi.org/10.1063/1.2803067 (3 pages) | Cited 24 times

Online Publication Date: 31 October 2007

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Nonalloyed Cr/Au-based metal contacts to n-GaN have been demonstrated. The deposited Au/Cr/n-GaN contacts exhibited a specific contact resistance (ρc) of approximately 5.6×10−5 Ω cm2. Although the nonalloyed Ti/Al-based contacts to n-GaN can also exhibit a comparable ρc value, their thermal stability is inferior to the Cr/Au-based contacts. This could be attributed to the fact that Al tends to ball up during thermal annealing. Thus, the surface morphology of most of the annealed Ti/Al-based contacts was quite rough, and the contacts became rectified when they were annealed at a temperature below 700 °C. However, the annealed Cr/Au-based contacts exhibited an Ohmic characteristic and had a smooth surface when annealing temperatures did not exceed 700 °C. In addition, the thermal stability could be further improved by inserting a Pt layer between the Cr and Au layers. This scheme could prevent the diffusion of Au into the Cr layer, thus preventing Au from reaching the Cr/GaN interface where it could form a possible Ga–Au phase, which would degrade the Ohmic contacts.
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73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
81.05.Ea III-V semiconductors
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Carrier transport mechanisms of the writing and the erasing processes for Al/ZnO nanoparticles embedded in a polyimide layer/p-Si diodes

J. H. Jung, H. J. Kim, B. J. Kim, T. W. Kim, and Y.-H. Kim

Appl. Phys. Lett. 91, 182107 (2007); http://dx.doi.org/10.1063/1.2803754 (3 pages) | Cited 6 times

Online Publication Date: 1 November 2007

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Show Abstract
Capacitance-voltage measurements on Al/ZnO nanocrystals embedded in polyimide (PI) layer/p-Si diodes at 300 K showed a metal-insulator-semiconductor behavior with a flatband voltage shift. Current-voltage (I-V) measurements on the diodes showed that carrier transport processes were attributed to the Poole-Frenkel effect and to thermionic emission. Possible carrier transport mechanisms of the writing and the erasing processes for the Al/ZnO nanocrystals embedded in PI layer/p-Si diodes are described on the basis of the I-V results.
Show PACS
84.30.Sk Pulse and digital circuits
73.63.Bd Nanocrystalline materials
73.61.Ga II-VI semiconductors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
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