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

15 Oct 2007

Volume 91, Issue 16, Articles (16xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 91, 162101 (2007); http://dx.doi.org/10.1063/1.2794995 (3 pages)

D. J. Reilly, C. M. Marcus, M. P. Hanson, and A. C. Gossard
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds

Surface elastic properties of porous nanosilica coatings by scanning force microscopy

A. Vincent, S. Babu, and S. Seal

Appl. Phys. Lett. 91, 161901 (2007); http://dx.doi.org/10.1063/1.2799249 (3 pages) | Cited 3 times

Online Publication Date: 15 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Surface elastic properties of sol-gel derived porous nanosilica optical coatings were determined using scanning force microscopy. Silica nanocoatings prepared under acid and base catalyzed sol-gel process exhibited varying surface morphology, particle size and porosity. Force-distance spectroscopy measurements were conducted on these coatings using scanning force microscopy, and their elastic moduli were obtained by applying Hertz model. The elastic modulus of the coatings varied from 2.4 to 13.4 GPa depending on the nature and concentration of the catalyst used.
Show PACS
68.60.Bs Mechanical and acoustical properties
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Gy Mechanical properties; surface strains
61.46.-w Structure of nanoscale materials

Probing the phase composition of silicon films in situ by etch product detection

G. Dingemans, M. N. van den Donker, A. Gordijn, W. M. M. Kessels, and M. C. M. van de Sanden

Appl. Phys. Lett. 91, 161902 (2007); http://dx.doi.org/10.1063/1.2799738 (3 pages) | Cited 8 times

Online Publication Date: 15 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Exploiting the higher etch probability for amorphous silicon relative to crystalline silicon, the transiently evolving phase composition of silicon films in the microcrystalline growth regime was probed in situ by monitoring the etch product (SiH4) gas density during a short H2 plasma treatment step. Etch product detection took place by the easy-to-implement techniques of optical emission spectroscopy and infrared absorption spectroscopy. The phase composition of the films was probed as a function of the SiH4 concentration during deposition and as a function of the film thickness. The in situ results were corroborated by Raman spectroscopy and solar cell analysis.
Show PACS
68.55.Nq Composition and phase identification
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
64.70.K- Solid-solid transitions
81.65.Cf Surface cleaning, etching, patterning
81.15.Jj Ion and electron beam-assisted deposition; ion plating

High porosity metallic glass foam: A powder metallurgy route

Marios D. Demetriou, Joseph P. Schramm, Chris Veazey, William L. Johnson, Jay C. Hanan, and Nicholas B. Phelps

Appl. Phys. Lett. 91, 161903 (2007); http://dx.doi.org/10.1063/1.2799248 (3 pages) | Cited 9 times

Online Publication Date: 15 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A powder metallurgy route to the fabrication of metallic glass foam is introduced. The method involves consolidating metallic glass powder blended with blowing agent particulates to produce expandable precursors, capable of yielding foams with porosities as high as 86%. The foams are found to inherit the strength of the parent metallic glass and to be able to deform heavily toward full densification absorbing high amounts of energy.
Show PACS
82.70.Rr Aerosols and foams
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

In situ investigation of growth modes during plasma-assisted molecular beam epitaxy of (0001) GaN

G. Koblmüller, S. Fernández-Garrido, E. Calleja, and J. S. Speck

Appl. Phys. Lett. 91, 161904 (2007); http://dx.doi.org/10.1063/1.2789691 (3 pages) | Cited 26 times

Online Publication Date: 15 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Real-time analysis of the growth modes during homoepitaxial (0001) GaN growth by plasma-assisted molecular beam epitaxy was performed using reflection high energy electron diffraction. A growth mode map was established as a function of Ga/N flux ratio and growth temperature, exhibiting distinct transitions between three-dimensional (3D), layer-by-layer, and step-flow growth modes. The layer-by-layer to step-flow growth transition under Ga-rich growth was surfactant mediated and related to a Ga adlayer coverage of one monolayer. Under N-rich conditions the transition from 3D to layer-by-layer growth was predominantly thermally activated, facilitating two-dimensional growth at temperatures of thermal decomposition.
Show PACS
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
68.35.B- Structure of clean surfaces (and surface reconstruction)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Effect of backing layer thickness on adhesion of single-level elastomer fiber arrays

Seok Kim, Metin Sitti, Chung-Yuen Hui, Rong Long, and Anand Jagota

Appl. Phys. Lett. 91, 161905 (2007); http://dx.doi.org/10.1063/1.2801371 (3 pages) | Cited 16 times

Online Publication Date: 15 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effect of the backing layer thickness on adhesion was investigated for single-level elastomer fibrillar adhesives. Polyurethane microfiber arrays with spatulated tips on a 160 μm thick backing layer show nine times greater adhesion strength (around 22 N/cm2) than those with a 1120 μm thick backing. A theoretical model is proposed to explain this difference in which very thin backing layers promote equal load sharing, maximizing adhesion, while very thick backings can lead to reduced adhesion due to edge stress concentration. Therefore, backing layer thickness should be considered as a significant parameter for design of high performance fibrillar adhesives.
Show PACS
82.35.Gh Polymers on surfaces; adhesion
62.20.-x Mechanical properties of solids
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties

Initial interactions between water molecules and Ti-adsorbed carbon nanotubes

Yang Lei, Zheng Xiao Guo, Wenguang Zhu, Sheng Meng, and Zhenyu Zhang

Appl. Phys. Lett. 91, 161906 (2007); http://dx.doi.org/10.1063/1.2793182 (3 pages) | Cited 5 times

Online Publication Date: 16 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Spin-polarized first-principles calculations were employed to study the initial stages of water interactions with Ti-doped carbon nanotubes (CNTs), aiming to explore their potentials for water splitting to generate hydrogen or as practical hydrogen storage systems involving moisture. The rate-limiting barrier for splitting the first H2O is 0.48 eV on a semiconducting (8,0) CNT, and 0.41 eV on a metallic (5,5) CNT. The barrier for splitting the second H2O is only 0.12 eV, accompanied by the formation and release of a H2 molecule.
Show PACS
68.43.Mn Adsorption kinetics
84.60.-h Direct energy conversion and storage

Cross-sectional scanning tunneling microscopy study on II–VI multilayer structures

A. Wierts, J. M. Ulloa, C. Çelebi, P. M. Koenraad, H. Boukari, L. Maingault, R. André, and H. Mariette

Appl. Phys. Lett. 91, 161907 (2007); http://dx.doi.org/10.1063/1.2799254 (3 pages)

Online Publication Date: 17 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Cross-sectional scanning tunneling microscopy is used to study in the atomic scale the structural properties of ZnSeTe/ZnTe multiple quantum wells and N:ZnTe delta-doped structures. Some peculiar effects are found on the cleaved (110) ZnTe surface plane, which have not been observed in III–V semiconductors. In particular, cleavage induced monatomic wide vacancy chains are always present on the Te sublattice. Furthermore, the semiconductor surface is manipulated when certain positive voltages are applied to the sample. Regarding the heterostructures, the ZnSeTe/ZnTe quantum wells are found to have abrupt interfaces and the Se concentration is determined to be significantly larger than the nominal value.
Show PACS
68.65.Fg Quantum wells
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Low-temperature formation of SiO2 layers using a two-step atmospheric pressure plasma-enhanced deposition-oxidation process

Hiroaki Kakiuchi, Hiromasa Ohmi, Makoto Harada, Heiji Watanabe, and Kiyoshi Yasutake

Appl. Phys. Lett. 91, 161908 (2007); http://dx.doi.org/10.1063/1.2801516 (3 pages) | Cited 1 time

Online Publication Date: 17 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Silicon oxide (SiO2) layers were fabricated at low temperatures ( ⩽ 400 °C) by combining the deposition of hydrogenated amorphous Si (a-Si:H) with its oxidation using atmospheric pressure plasmas excited by a 150 MHz very high-frequency (VHF) power. The surface excitation by the atmospheric pressure VHF plasma was capable of reducing the temperature for the hydrogen effusion from a-Si:H. As a result, a porous a-Si:H film containing a large amount of hydrogen could be transformed into a stoichiometric SiO2 with an approximately 24% increase in oxidation rate compared with the oxidation of Si(001) at a temperature of 400 °C.
Show PACS
61.66.Bi Elemental solids
61.66.Dk Alloys
81.65.Mq Oxidation
81.15.Jj Ion and electron beam-assisted deposition; ion plating
61.43.Gt Powders, porous materials
61.43.Dq Amorphous semiconductors, metals, and alloys
52.77.Dq Plasma-based ion implantation and deposition

Nonlinear behavior of the energy gap in Ge1−xSnx alloys at 4 K

H. Pérez Ladrón de Guevara, A. G. Rodríguez, H. Navarro-Contreras, and M. A. Vidal

Appl. Phys. Lett. 91, 161909 (2007); http://dx.doi.org/10.1063/1.2800296 (3 pages) | Cited 6 times

Online Publication Date: 17 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The optical energy gap of Ge1−xSnx alloys (x ⩽ 0.14) grown on Ge substrates has been determined by performing transmittance measurements at 4 K using a fast fourier transform infrared interferometer. The direct energy gap transitions in Ge1−xSnx alloys behave following a nonlinear dependence on the Sn concentration, expressed by a quadratic equation, with a so called bowing parameter b0 that describes the deviation from a simple linear dependence. Our observations resulted in b0RT = 2.30±0.10 eV and b04 K = 2.84±0.15 eV, at room temperature and 4 K, respectively. The validity of our fit is limited for Sn concentrations lower than 15%.
Show PACS
71.20.Nr Semiconductor compounds
78.30.Hv Other nonmetallic inorganics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Decoherence of exciton complexes in single InAlAs quantum dots measured by Fourier spectroscopy

S. Adachi, N. Yatsu, R. Kaji, S. Muto, and H. Sasakura

Appl. Phys. Lett. 91, 161910 (2007); http://dx.doi.org/10.1063/1.2800373 (3 pages) | Cited 13 times

Online Publication Date: 17 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report the single-photon Fourier spectroscopy of exciton and exciton complexes in single self-assembled InAlAs/AlGaAs quantum dots. A Michelson interferometer was inserted in the photoluminescence path for measuring the coherence length of the time-averaged emission of neutral excitons and their complexes. The effects of exchange interactions and fluctuations in the surrounding excess charges were estimated by comparing the coherence times and the excitation energies of the excitons and their complexes.
Show PACS
78.67.Hc Quantum dots
73.21.La Quantum dots
78.55.Cr III-V semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Free exciton emission and dephasing in individual ZnO nanowires

Yang Zhang, Dai-Jang Chen, and Ching-Ting Lee

Appl. Phys. Lett. 91, 161911 (2007); http://dx.doi.org/10.1063/1.2793178 (3 pages) | Cited 7 times

Online Publication Date: 17 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on systematic measurements of the dephasing of the free excitonic transition in individual ZnO nanowires with a diameter of about 70 nm. The temperature-dependent intensity of the free exciton (FX) emission is well reproduced by a thermally activated behavior having two constant activation energies of 5.98 and 30.63 meV. The FX linewidth broadening with temperature reveals the dephasing of FX scattered by acoustic phonons rather than longitudinal optical phonons. These findings indicate that the dephasing mechanism scattering from acoustic phonons in individual ZnO nanowires result from the compensation of acoustic phonons to the nonconservation of crystal momentum.
Show PACS
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

White light-emitting diodes based on a single InGaN emission layer

X. H. Wang, H. Q. Jia, L. W. Guo, Z. G. Xing, Y. Wang, X. J. Pei, J. M. Zhou, and H. Chen

Appl. Phys. Lett. 91, 161912 (2007); http://dx.doi.org/10.1063/1.2800797 (3 pages) | Cited 9 times

Online Publication Date: 18 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
White light-emitting InGaN/GaN diode with an InGaN underlying layer grown on the (0001) sapphire substrate was fabricated by low pressure metal-organic vapor phase epitaxy. The electroluminescence measurements show that the emitted white light is composed of blue and yellow lights, centered at around 440 and 570 nm, respectively, for an injection current of 20 mA. Cross-sectional transmission electron microscopy reveals that In-rich quantum dots were formed in InGaN wells due to phase separation of indium. It is suggested that the yellow and blue lights come from In-rich quantum dots and the low-indium regions, respectively, in InGaN quantum wells.
Show PACS
85.60.Jb Light-emitting devices
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.60.Fi Electroluminescence
78.67.Hc Quantum dots
78.66.Fd III-V semiconductors

Sample size effect and microcompression of Mg65Cu25Gd10 metallic glass

C. J. Lee, J. C. Huang, and T. G. Nieh

Appl. Phys. Lett. 91, 161913 (2007); http://dx.doi.org/10.1063/1.2800313 (3 pages) | Cited 58 times

Online Publication Date: 19 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Micropillars with diameters of 1 and 3.8 μm were fabricated from Mg-based metallic glasses using focus ion beam, and then tested in compression at strain rates ranging from 6×10−5 to 6×10−1 s−1. The apparent yield strength of the micropillars is 1342–1580 MPa, or 60%–100% increment over the bulk specimens. This strength increase can be rationalized using the Weibull statistics for brittle materials, and the Weibull modulus of the Mg-based metallic glasses is estimated to be about 35. Preliminary results indicated that the number of shear bands increased with the sample size and strain rates.
Show PACS
81.40.Lm Deformation, plasticity, and creep
61.43.Fs Glasses
62.20.F- Deformation and plasticity
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close