APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

7 Feb 2005

Volume 86, Issue 6, Articles (06xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 86, 063101 (2005); http://dx.doi.org/10.1063/1.1861133 (3 pages)

Choongho Yu, Qing Hao, Sanjoy Saha, Li Shi, Xiangyang Kong, and Z. L. Wang
Enlarge Image | Read More
Page 2 of 4 Pages Previous Page Next Page | Jump to Page
back to top
RSS Feeds

Quantitative high-pressure pair distribution function analysis of nanocrystalline gold

C. David Martin, Sytle M. Antao, Peter J. Chupas, Peter L. Lee, Sarvjit D. Shastri, and John B. Parise

Appl. Phys. Lett. 86, 061910 (2005); http://dx.doi.org/10.1063/1.1856691 (3 pages) | Cited 10 times

Online Publication Date: 3 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using a diamond anvil cell with high-energy monochromatic x rays, we have studied the total scattering of nanocrystalline gold to 20 Å−1 at pressures up to 10 GPa in a hydrostatic alcohol pressure-medium. Through direct Fourier transformation of the structure function [S(Q)], pair distribution functions (PDFs) [G(r)] are calculated without Kaplow-type iterative corrections. Quantitative high-pressure PDF (QHP-PDF) analysis is performed via full-profile least-squares modeling and confirmed through comparison of Rietveld analysis of Bragg diffraction. The quality of the high pressure PDFs obtained demonstrates the integrity of our technique and suggests the feasibility of future QHP-PDF studies of liquids, disordered solids, and materials at phase transition under pressure.
Show PACS
61.46.-w Structure of nanoscale materials
78.70.Ck X-ray scattering
62.50.-p High-pressure effects in solids and liquids
61.43.Bn Structural modeling: serial-addition models, computer simulation

Why is the band model not contradictory to molecular theory in organic electroluminescence?

Zheng Xu, Chong Qu, Feng Teng, Fujun Zhang, Lijian Meng, and Xurong Xu

Appl. Phys. Lett. 86, 061911 (2005); http://dx.doi.org/10.1063/1.1861134 (3 pages) | Cited 10 times

Online Publication Date: 4 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In organic electroluminescence there is a sharp contradiction between the applicability of band model and molecular theory. This contradiction arose from the very beginning of extended study. In this report we studied the blue spectral shift in the newly discovered solid state cathodoluminescence when the applied voltage is increased. There are three different kinds of spectra in three intervals of applied voltage. The reason of this spectral shift is found to be the field ionization of exciton. The switching on of recombination starts only after the beginning of this field ionization. The exciton emission obeys molecular theory and the recombination obeys band model. Thus the demarcation is the appearance of field ionization of excitons. Since the ionization changes with electric field continuously, there is a region of coexistence of these two processes.
Show PACS
78.60.Fi Electroluminescence
78.60.Hk Cathodoluminescence, ionoluminescence
78.55.Kz Solid organic materials
79.70.+q Field emission, ionization, evaporation, and desorption
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Reorientation of the H2O cage studied by terahertz time-domain spectroscopy

B. L. Yu, Y. Yang, F. Zeng, X. Xin, and R. R. Alfano

Appl. Phys. Lett. 86, 061912 (2005); http://dx.doi.org/10.1063/1.1862788 (3 pages) | Cited 6 times

Online Publication Date: 4 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The terahertz absorption spectrum of a thin film of liquid H2O of ∼ 14 μm thickness showed a clear absorption mode at 1.56 THz ( ∼ 53 cm−1). This mode is attributed to the bending motion of the intermolecular hydrogen-bond coordinate in a water cage. The dielectric relaxation times of a slow τ1 ∼ 9 ps and a fast τ2 ∼ 0.2 ps component (0.4–2.0 THz) were determined using a double Debye dielectric model.
Show PACS
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
77.55.-g Dielectric thin films
68.15.+e Liquid thin films
78.70.Gq Microwave and radio-frequency interactions
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Atomic dynamics in molecular dynamics simulations of glassy CuTi thin films

Sebastian Vauth and S. G. Mayr

Appl. Phys. Lett. 86, 061913 (2005); http://dx.doi.org/10.1063/1.1861982 (3 pages) | Cited 4 times

Online Publication Date: 4 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present results on atomic dynamics in metallic glass thin films below the glass transition temperature using molecular dynamics simulations. Thin CuTi films of different compositions are prepared by quenching the liquid to an amorphous state. The atomic dynamics on the amorphous surface and inside the bulk of the samples are quantitatively compared by calculating diffusion constants and jump length distributions. Here, we focus on the collective or single particle character of the diffusion mechanism in dependence of the atom type. In addition, single atom exemplifications are analyzed for the different kinds of atomic dynamics. We find that Cu surface atoms diffuse with a single atom jump dynamics, whereas inside the bulk collective behavior dominates for both species.
Show PACS
61.43.Fs Glasses
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
61.43.Bn Structural modeling: serial-addition models, computer simulation
68.35.Fx Diffusion; interface formation
81.05.Kf Glasses (including metallic glasses)
66.30.Dn Theory of diffusion and ionic conduction in solids
81.40.Gh Other heat and thermomechanical treatments

Nondestructive characterization of dislocations and micropipes in high-resistivity 6H–SiC wafers by deep-level photoluminescence mapping

M. Tajima, E. Higashi, T. Hayashi, H. Kinoshita, and H. Shiomi

Appl. Phys. Lett. 86, 061914 (2005); http://dx.doi.org/10.1063/1.1862330 (3 pages) | Cited 11 times

Online Publication Date: 4 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We demonstrated the effectiveness of deep-level photoluminescence (PL) mapping for nondestructive detection of dislocations and micropipes in high-resistivity 6H–SiC wafers. PL spectra of the wafers at room temperature were dominated by a broad band with a peak at 1.3 eV, which was traceable to the Si vacancy-related V1, V2, and V3 lines at 4.2 K. The intensity-mapping pattern agreed closely with the etch-pit pattern both on a wafer scale and on a microscopic scale. Large dark spots with one or two bright cores, small dark spots, and dark lines corresponded to micropipes, threading screw dislocations, and edge dislocations forming small angle grain boundaries, respectively. The intensity reduction around dislocations and micropipes was attributed to a decrease of the radiative centers for the 1.3 eV band, which occurred as a result either of the interaction between vacancies and dislocations or of the gettering effect of vacancy-related defects.
Show PACS
81.70.Fy Nondestructive testing: optical methods
61.72.Yx Interaction between different crystal defects; gettering effect
81.05.Hd Other semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
78.55.Hx Other solid inorganic materials
61.72.J- Point defects and defect clusters
61.72.Mm Grain and twin boundaries

Perylene monolayer on the Ru(0001) surface

B. Lu, H. J. Zhang, Y. S. Tao, H. Huang, H. Y. Li, S. N. Bao, P. He, and Q. Chen

Appl. Phys. Lett. 86, 061915 (2005); http://dx.doi.org/10.1063/1.1862341 (3 pages) | Cited 6 times

Online Publication Date: 4 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The growth of epitaxial monolayer of perylene on Ru(0001) was investigated by means of scanning tunneling microscopy (STM). The STM images showed a coexistence of the ordered phase with a 12×12 superstructure and the disordered phase in a monolayer of perylene on Ru(0001). In the disordered region, the perylene molecules are randomly distributed, and orientated uniformly with their long axis in the [1000] direction. For the ordered phase, a model of the Ru(0001)-(12×12)-8 perylene superstructure was proposed. The results indicate that the growth behavior of perylene on Ru(0001) is mainly controlled by laterally repulsive molecule-molecule interaction.
Show PACS
81.05.Hd Other semiconductors
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
61.43.Dq Amorphous semiconductors, metals, and alloys
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
back to top
RSS Feeds

Preparation of As-doped p-type ZnO films using a Zn3As2/ZnO target with pulsed laser deposition

Veeramuthu Vaithianathan, Byung-Teak Lee, and Sang Sub Kim

Appl. Phys. Lett. 86, 062101 (2005); http://dx.doi.org/10.1063/1.1854748 (3 pages) | Cited 80 times

Online Publication Date: 31 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report the preparation of arsenic doped p-type ZnO films using a Zn3As2/ZnO target by pulsed laser deposition. Zn3As2 was used as a p-type dopant source material for arsenic doping in ZnO. The existence of As in the As-doped ZnO films was confirmed by the x-ray photoelectron spectroscopy study. The p-type behavior of the As-doped ZnO films was determined by the Hall and photoluminescence measurements. Room temperature Hall measurements revealed that the As-doped ZnO films exhibited p-type conductivity after being annealed at 200 °C in N2 ambient for 2 min with the hole concentrations varied between 2.48×1017 and 1.18×1018 cm−3. The resistivity and carrier mobility of the As-doped p-type ZnO films were in the range of 2.2–6.7 Ω cm and 0.83–11.4 cm2/V s, respectively. The low temperature photoluminescence measurements confirmed the peak associated with the neutral-acceptor bound exciton (A0X) emission in the As-doped p-type ZnO films.
Show PACS
81.05.Dz II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Fg Pulsed laser ablation deposition
78.66.Hf II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
71.55.Gs II-VI semiconductors
61.72.S- Impurities in crystals
78.55.Et II-VI semiconductors
73.61.Ga II-VI semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.60.Dp Adsorbed layers and thin films
68.37.Xy Scanning Auger microscopy, photoelectron microscopy

Effective diffusion coefficient for two-band systems

P. Kleinert and V. V. Bryksin

Appl. Phys. Lett. 86, 062102 (2005); http://dx.doi.org/10.1063/1.1863435 (3 pages) | Cited 1 time

Online Publication Date: 1 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effective longitudinal diffusion coefficient for two-band systems is determined. Emphasis is put on the nonlinear transport regime realized at high electric fields. Particular results are obtained for bipolar transport in two-band semiconductors and vertical transport in semiconductor superlattices. An additional contribution to the effective diffusion coefficient is identified, which results from different drift velocities in the respective bands (minibands).
Show PACS
72.10.Bg General formulation of transport theory
72.90.+y Other topics in electronic transport in condensed matter (restricted to new topics in section 72)
73.50.Td Noise processes and phenomena

Cu-doped indium oxide/Ag ohmic contacts for high-power flip-chip light-emitting diodes

June-O Song, Joon Seop Kwak, and Tae-Yeon Seong

Appl. Phys. Lett. 86, 062103 (2005); http://dx.doi.org/10.1063/1.1861494 (3 pages) | Cited 33 times

Online Publication Date: 1 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated Cu-doped In2O3(CIO)(3 nm)/Ag(250 nm) schemes for forming high-quality ohmic contacts to p-type GaN for high-power flip-chip light-emitting diodes (FCLEDs). It is shown that the CIO/Ag contacts produce specific contact resistance of 1.28×10−5 Ω cm2 and reflectance of about 90% at a wavelength of 460 nm when annealed at 530 °C for 1 min in air ambient. It is also shown that unlike single Ag contacts, the CIO/Ag contacts are fairly stable without surface and interface degradation although annealed at 530 °C for 1 min in air ambient. In addition, blue multiquantum-well InGaN/GaN LEDs fabricated with the annealed CIO/Ag contact layers give forward-bias voltages of around 3.0 V at an injection current of 20 mA. The results strongly indicate that the CIO/Ag scheme can be a highly promising p-type contact for high-power GaN-based FCLEDs for solid-state lighting application.
Show PACS
85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
61.72.Cc Kinetics of defect formation and annealing

Ohmic and degradation mechanisms of Ag contacts on p-type GaN

June-O Song, Joon Seop Kwak, Yongjo Park, and Tae-Yeon Seong

Appl. Phys. Lett. 86, 062104 (2005); http://dx.doi.org/10.1063/1.1863441 (3 pages) | Cited 51 times

Online Publication Date: 1 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The electrical and optical properties of the Ag contacts have been investigated as a function of the annealing temperature. The as-deposited contact becomes good Ohmic with contact resistivity of 2.47×10−4 Ω cm2 and produces reflectance of ∼ 84% when annealed at 330 °C for 1 mm in air ambient. However, annealing at 530 °C results in nonlinear current–voltage behavior and degraded reflectance. The light output of InGaN/GaN blue light emitting diodes (LEDs) fabricated with the as-deposited Ag contact shows somewhat better output performance than those of LEDs with the annealed Ag contacts. Based on the transmission electron microscopy-energy dispersive x-ray analysis, synchrotron x-ray diffraction, and x-ray photoemission spectroscopy results, possible mechanisms for the ohmic formation and degradation of the Ag contacts are described.
Show PACS
85.60.Jb Light-emitting devices
73.40.Ns Metal-nonmetal contacts
61.72.Cc Kinetics of defect formation and annealing
68.37.Lp Transmission electron microscopy (TEM)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Electrical properties of InAlP native oxides for metal–oxide–semiconductor device applications

Y. Cao, J. Zhang, X. Li, T. H. Kosel, P. Fay, D. C. Hall, X. B. Zhang, R. D. Dupuis, J. B. Jasinski, and Z. Liliental-Weber

Appl. Phys. Lett. 86, 062105 (2005); http://dx.doi.org/10.1063/1.1861981 (3 pages) | Cited 10 times

Online Publication Date: 1 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Data are presented on the insulating properties and capacitance–voltage characteristics of metal–oxide–semiconductor (MOS) device-thickness (below ∼ 100 nm) native oxides formed by wet thermal oxidation of thin InAlP epilayers lattice matched to GaAs. Low leakage current densities of J = 1.4×10−9 A/cm2 and J = 8.7×10−11 A/cm2 are observed at an applied field of 1 MV/cm for MOS capacitors fabricated with 17 and 48 nm oxides, respectively. Transmission electron microscopy images show that the In-rich interfacial particles which exist in 110 nm oxides are absent in 17 nm oxide films. Quasistatic capacitance–voltage measurements of MOS capacitors fabricated on both n-type and p-type GaAs show that the InAlP oxide–GaAs interface is sufficiently free of traps to support inversion, indicating an unpinned Fermi level. These data suggest that InAlP native oxides may be a viable insulator for GaAs MOS device applications.
Show PACS
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.Mq Oxidation
73.20.At Surface states, band structure, electron density of states
84.32.Tt Capacitors
68.37.Lp Transmission electron microscopy (TEM)

Manipulating the transmission of a two-dimensional electron gas via spatially varying magnetic fields

J.-F. Song, J. P. Bird, and Y. Ochiai

Appl. Phys. Lett. 86, 062106 (2005); http://dx.doi.org/10.1063/1.1861957 (3 pages) | Cited 8 times

Online Publication Date: 1 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We explore how the transmission properties of a two-dimensional electron gas can be modified by manipulating the fringing magnetic fields that emanate from a set of patterned gates, deposited on the top surface of its heterojunction. We propose a multigate device whose conductance is shown to depend sensitively upon the relative magnetization of its gates, and which may therefore be of use as a planar magnetoresistance device, or as a memory structure.
Show PACS
72.20.My Galvanomagnetic and other magnetotransport effects
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.75.Bb Magnetic memory using giant magnetoresistance

Enhanced optical and structural properties of 1.3 μm GaInNAs/GaAs multiple quantum-well heterostructures with stepped strain-mediating layers

H. Y. Liu, W. M. Soong, P. Navaretti, M. Hopkinson, and J. P. R. David

Appl. Phys. Lett. 86, 062107 (2005); http://dx.doi.org/10.1063/1.1862784 (3 pages)

Online Publication Date: 2 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effects of inserting GaInNAs single or stepped strain-mediating layers between GaInNAs quantum wells and the surrounding matrix on the structural and optical properties of 1.3 μm GaInNAs/GaAs multiple quantum-well (QW) structures have been investigated. Compared to control samples with simple GaInNAs multiple quantum wells, samples with strain-mediating layers exhibit improved optical and structural properties. A further strong enhancement of photoluminescence efficiency at room temperature and a remarkable reduction of emission linewidth of GaInNAs multiple QWs have been observed using a compositionally stepped strain-mediating layer. These results imply that the strain profile between the quantum well and the surrounding matrix has a major effect on the optical and structural qualities of GaInNAs quantum wells.
Show PACS
78.67.De Quantum wells
68.65.Fg Quantum wells
78.55.Cr III-V semiconductors
62.25.-g Mechanical properties of nanoscale systems
68.35.Gy Mechanical properties; surface strains

Tuning of NiSi/Si Schottky barrier heights by sulfur segregation during Ni silicidation

Q. T. Zhao, U. Breuer, E. Rije, St. Lenk, and S. Mantl

Appl. Phys. Lett. 86, 062108 (2005); http://dx.doi.org/10.1063/1.1863442 (3 pages) | Cited 46 times

Online Publication Date: 2 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The Schottky barrier height (SBH) of NiSi on Si(100) was tuned in a controlled manner by the segregation of sulfur (S) to the silicide∕silicon interface. S was implanted into silicon prior to silicidation. During subsequent Ni silicidation, the segregation of S at the NiSi/Si interface leads to the change of the SBH. The SBH of NiSi decreased gradually on n-Si(100) from 0.65 eV to 0.07 eV and increased correspondingly on p-Si(100).
Show PACS
61.72.uf Ge and Si
73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions
68.35.Dv Composition, segregation; defects and impurities

Band alignment at the CdS∕Cu(In,Ga)S2 interface in thin-film solar cells

L. Weinhardt, O. Fuchs, D. Groß, G. Storch, E. Umbach, N. G. Dhere, A. A. Kadam, S. S. Kulkarni, and C. Heske

Appl. Phys. Lett. 86, 062109 (2005); http://dx.doi.org/10.1063/1.1861958 (3 pages) | Cited 16 times

Online Publication Date: 2 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The band alignment at the CdS∕Cu(In,Ga)S2 interface in thin-film solar cells on a stainless steel substrate was investigated using photoelectron spectroscopy and inverse photoemission. By combining both techniques, the conduction and valence band offsets were independently determined. We find an unfavorable conduction band offset of −0.45 (±0.15) eV, accounting for the generally observed low open-circuit voltage and indicating the great importance of the buffer∕absorber conduction band offset for such devices. The surface band gap of the Cu(In,Ga)S2 absorber is 1.76 (±0.15) eV, being increased with respect to the expected bulk value by a copper depletion near the surface.
Show PACS
84.60.Jt Photoelectric conversion

Capacitance-voltage spectroscopy of silicon nanodots

Alex Yu-Kwen Su, H. L. Hwang, M. H. Pilkuhn, and Z. Pei

Appl. Phys. Lett. 86, 062110 (2005); http://dx.doi.org/10.1063/1.1862773 (3 pages) | Cited 3 times

Online Publication Date: 3 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Frequency-dependent capacitance-voltage spectroscopy was applied to investigate the carrier transport dynamics in a silicon nanodots resonant tunneling device structure. Two negative differential resistance (NDR) regions in the current-voltage characteristics were found in this investigated structure. Two anomalous regions were also found in the capacitance-voltage spectroscopy, which coincide with the NDR regions in the current-voltage characteristics. The origin of the anomalous phenomenon was attributed to the mesoscopic quantum capacitance due to the holes transport through the energy states associated with the Si nanodots. An equivalent circuit model was proposed to quantitatively evaluate the frequency dependence of the capacitance-voltage spectroscopy.
Show PACS
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.23.-b Electronic transport in mesoscopic systems
73.61.Cw Elemental semiconductors

Bismuth telluride nanotubes and the effects on the thermoelectric properties of nanotube-containing nanocomposites

X. B. Zhao, X. H. Ji, Y. H. Zhang, T. J. Zhu, J. P. Tu, and X. B. Zhang

Appl. Phys. Lett. 86, 062111 (2005); http://dx.doi.org/10.1063/1.1863440 (3 pages) | Cited 149 times

Online Publication Date: 3 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Nanotubes of quasilayered bismuth telluride compound were prepared by hydrothermal synthesis. Nanotubes have diameters smaller than 100 nm and spiral tube-walls. The low-dimensional morphology and hollow structure enable bismuth telluride nanotubes to be a potential thermoelectric material with a high figure of merit due to the efficient phonon blocking effect. The experimental results show that the addition of nanotubes leads to a remarkable decrease in the thermal conductivity with the electrical conductivity much less affected and thus to an increase in the figure of merit of the Bi2Te3-based material.
Show PACS
81.07.De Nanotubes
81.05.Hd Other semiconductors
73.63.Fg Nanotubes
73.50.Lw Thermoelectric effects
61.46.-w Structure of nanoscale materials
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.16.Be Chemical synthesis methods
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Positive temperature coefficient effect in multiwalled carbon nanotube/high-density polyethylene composites

X. J. He, J. H. Du, Z. Ying, H. M. Cheng, and X. J. He

Appl. Phys. Lett. 86, 062112 (2005); http://dx.doi.org/10.1063/1.1863452 (3 pages) | Cited 38 times

Online Publication Date: 3 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Multiwalled carbon nanotube (MWNT)-filled high-density polyethylene (HDPE) composites were prepared by a solution-precipitation process, and the temperature dependence of electrical conductivity of the MWNT/HDPE composites was studied. An obvious positive temperature coefficient (PTC) effect was found in the MWNT/HDPE composites with a relatively low MWNT concentration. Compared with that of carbon black (CB)/HDPE composite, the negative temperature coefficient (NTC) effect of the MWNT/HDPE composite at temperature above the melting temperature of HDPE was much less obvious and could be further eliminated after 80 kGy γ-ray irradiation. The mechanism of the PTC and NTC effects in MWNT/HDPE composites was discussed.
Show PACS
81.05.Qk Reinforced polymers and polymer-based composites
72.80.Tm Composite materials
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.30.Mh Solid-phase precipitation
64.75.-g Phase equilibria
61.46.-w Structure of nanoscale materials
61.41.+e Polymers, elastomers, and plastics
64.70.D- Solid-liquid transitions

Interface-roughness-induced broadening of intersubband electroluminescence in p-SiGe and n-GaInAs∕AlInAs quantum-cascade structures

S. Tsujino, A. Borak, E. Müller, M. Scheinert, C. V. Falub, H. Sigg, D. Grützmacher, M. Giovannini, and J. Faist

Appl. Phys. Lett. 86, 062113 (2005); http://dx.doi.org/10.1063/1.1862344 (3 pages) | Cited 31 times

Online Publication Date: 3 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effect of intrasubband interface roughness scattering on intersubband transition linewidths in double-quantum-well and quantum-cascade (QC) structures is studied. In n-GaInAs∕AlInAs structures, the calculated ratios between the linewidths of the spatially vertical and diagonal transitions agree with the experimental values. In p-Si∕Si0.2Ge0.8 QC structures, the experimentally observed linewidth is a factor of 4–7 smaller than the predicted value. However, by assuming a vertical interface correlation between adjacent interfaces separated by less than ∼ 1.5 nm, the theory reproduces the experiment. Transmission electron microscopy of the SiGe QC sample reveals this vertical correlation, supporting the model.
Show PACS
78.67.De Quantum wells
73.21.Fg Quantum wells
68.65.Fg Quantum wells
73.20.At Surface states, band structure, electron density of states
78.60.Fi Electroluminescence
68.37.Lp Transmission electron microscopy (TEM)
78.20.Bh Theory, models, and numerical simulation
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)

Crystallite size effect on the hole mobility of uniaxially aligned copper phthalocyanine thin-film field-effect transistors

Masato Ofuji, Ken Ishikawa, Hideo Takezoe, Katsuhiko Inaba, and Kazuhiko Omote

Appl. Phys. Lett. 86, 062114 (2005); http://dx.doi.org/10.1063/1.1861499 (3 pages) | Cited 25 times

Online Publication Date: 4 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We fabricated copper phthalocyanine (CuPc) thin-film field-effect transistors (FETs) with three different orientations of CuPc with respect to channels. The substrate rubbing treatment induced uniaxial orientation in CuPc layers, yielding higher hole mobility ( ∼ 0.02 cm2/V s) than that of untreated FETs. Although the rubbing treatment bore high-aspect-ratio (>10) CuPc domains oriented to rubbing direction, the mobility anisotropy of the film was only 1.4. This discrepancy was explained by analyzing grazing-incidence x-ray diffraction profiles, i.e.: (1) In-plane mean size of crystals was smaller than their appearance in atomic force microscopy, and (2) the crystallites were much shorter in the apparent long-hand direction (11 nm) than the direction perpendicular to it (44 nm).
Show PACS
85.30.Tv Field effect devices
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.65.Ps Polishing, grinding, surface finishing
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Ph Polymers; organic compounds
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.37.Ps Atomic force microscopy (AFM)

Optical and electrical properties of polycrystalline silicon–germanium thin films prepared by aluminum-induced layer exchange

M. Gjukic, R. Lechner, M. Buschbeck, and M. Stutzmann

Appl. Phys. Lett. 86, 062115 (2005); http://dx.doi.org/10.1063/1.1863443 (3 pages) | Cited 1 time

Online Publication Date: 4 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Large-grained polycrystalline silicon–germanium (poly-Si1−xGex) thin films have been obtained by the aluminum-induced layer exchange (ALILE) process. The optical and electrical properties of these layers have been investigated as a function of the alloy composition. Optical reflection spectra and Hall effect mobility measurements indicate a high structural quality of the recrystallized thin films, which is comparable to bulk crystalline silicon–germanium (c-Si1−xGex) samples prepared by more sophisticated methods. Due to the increasing solubility of aluminum as a substitutional shallow acceptor with increasing germanium content, the room temperature carrier density of holes is found to increase from 1.5×1018 cm−3 in poly-Si to 5×1020 cm−3 in poly-Ge produced by ALILE.
Show PACS
78.66.Li Other semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Ht Other nonmetals
78.40.Fy Semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
64.75.-g Phase equilibria
68.55.Nq Composition and phase identification
61.72.S- Impurities in crystals
back to top
RSS Feeds

X-ray absorption spectroscopy in MnxGe1−x diluted magnetic semiconductor: Experiment and theory

S. Picozzi, L. Ottaviano, M. Passacantando, G. Profeta, A. Continenza, F. Priolo, M. Kim, and A. J. Freeman

Appl. Phys. Lett. 86, 062501 (2005); http://dx.doi.org/10.1063/1.1861127 (3 pages) | Cited 18 times

Online Publication Date: 31 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Accurate first-principles calculations of soft x-ray absorption spectra are compared with experimental data obtained for the ion-implanted MnxGe1−x ferromagnetic semiconductor. The well-defined features in the spectra are recognized as a signature of homogeneous Mn dilution within the Ge host, as demonstrated by comparing the Mn spectra in diluted MnGe alloys with other competing Mn–Ge crystalline phases. Moreover, provided that an efficient Mn dilution is achieved, the nature of the semiconducting host is shown to affect only slightly the Mn absorption spectrum, as shown by the similarity of the present results with those for other magnetic semiconductors. Both these findings establish the relevance of ion-implantation in the dilute magnetic semiconductor framework, emphasizing its potential impact in device technology.
Show PACS
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
78.70.Dm X-ray absorption spectra
78.40.Fy Semiconductors
61.72.S- Impurities in crystals

Enhanced magnetoresistance in strain-free manganite network

T. Wu and J. F. Mitchell

Appl. Phys. Lett. 86, 062502 (2005); http://dx.doi.org/10.1063/1.1861493 (3 pages) | Cited 12 times

Online Publication Date: 31 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A network structure of a ferromagnetic metallic (FMM)∕charge-ordered insulator (COI) mixed phase manganite has been obtained by annealing a 150 Å Pr0.65(Ca0.75Sr0.25)0.35MnO3 film under tensile strain on a SrTiO3 substrate. Under the same deposition and annealing conditions, a film deposited on a LaAlO3 substrate, which provides compressive strain, remains continuous. The network structure also manifests a larger magnetoresistance than the continuous film. It is suggested that the lateral confinement in this filamentary structure may affect the percolative transport in this mixed FMM∕COI system.
Show PACS
75.50.Dd Nonmetallic ferromagnetic materials
75.47.Lx Magnetic oxides
75.70.Ak Magnetic properties of monolayers and thin films
81.40.Rs Electrical and magnetic properties related to treatment conditions
68.55.-a Thin film structure and morphology
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.40.Gh Other heat and thermomechanical treatments
68.35.B- Structure of clean surfaces (and surface reconstruction)

Easy axis alignment of chemically partially ordered FePt nanoparticles

Shishou Kang, Zhiyong Jia, Shifan Shi, David E. Nikles, and J. W. Harrell

Appl. Phys. Lett. 86, 062503 (2005); http://dx.doi.org/10.1063/1.1856698 (3 pages) | Cited 48 times

Online Publication Date: 31 January 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Partially ordered Fe53Pt47 nanoparticles with size around 8 nm were prepared by the simultaneous decomposition of iron pentacarbonyl and platinum acetylacetonate. The high boiling point chemical, hexadecylamine, was used as a solvent, and 1-adamantanecarboxylic acid was used as a stabilizer. X-ray diffraction measurements reveal that as-made FePt particles were partially transformed into the ordered L10 phase with some weak superlattice peaks. The room-temperature hysteresis loop and remanence curve suggest a broad distribution of anisotropies in the partially ordered particles. By coating the partially ordered FePt nanoparticles with a polyvinylchloride polymer binder, the particles could be re-dispersed in cyclohexanone. Furthermore, the easy axis of the particles coated with the polyvinylchloride polymer binder could be aligned under an external field. Easy axis alignment was confirmed from both alternating gradient magnetometer and x-ray diffraction measurements.
Show PACS
75.50.Bb Fe and its alloys
75.50.Tt Fine-particle systems; nanocrystalline materials
81.07.Bc Nanocrystalline materials
75.75.-c Magnetic properties of nanostructures
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ww Permanent magnets
81.16.Be Chemical synthesis methods
81.05.Bx Metals, semimetals, and alloys
75.30.Gw Magnetic anisotropy
64.70.K- Solid-solid transitions
61.46.-w Structure of nanoscale materials

Electronic structure and magnetic properties of Al-doped Fe3O4 films studied by x-ray absorption and magnetic circular dichroism

C. K. Yang, J. W. Chiou, H. M. Tsai, C. W. Pao, J. C. Jan, S. C. Ray, C. L. Yeh, K. C. Huang, H. C. Hsueh, W. F. Pong, M.-H. Tsai, H. H. Hsieh, H. J. Lin, T. Y. Hou, and J. H. Hsu

Appl. Phys. Lett. 86, 062504 (2005); http://dx.doi.org/10.1063/1.1863450 (3 pages) | Cited 4 times

Online Publication Date: 1 February 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The electronic structure and magnetic properties of Al-doped Fe3O4 films at various Al concentrations were investigated by Al and O K-edge x-ray absorption near-edge structure (XANES) and Fe L3,2-edge magnetic circular dichroism (MCD) measurements. The O K-edge XANES spectra reveal that the intensity of O 2p–Fe 3d hybridized states decreases linearly as the Al concentration increases, suggesting that nonmagnetic Al substitution reduces couplings of the O 2p with Fe 3d orbitals. The Fe L3-edge MCD spectra show that the intensities of MCD features decrease as the Al concentration increases, which suggests that Al substitution reduces the magnetic moments of Fe ions. The Fe L3,2 XANES spectra suggest the absence of mixed valence states in agreement with previous x-ray resonance scattering measurements.
Show PACS
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
73.20.At Surface states, band structure, electron density of states
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Ht Other nonmetals
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Et Exchange and superexchange interactions
78.20.Ls Magneto-optical effects
78.70.Dm X-ray absorption spectra
61.72.S- Impurities in crystals
Page 2 of 4 Pages Previous Page Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close