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7 Aug 2006

Volume 89, Issue 6, Articles (06xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 89, 062501 (2006); http://dx.doi.org/10.1063/1.2259813 (3 pages)

Sangkook Choi, Ki-Suk Lee, and Sang-Koog Kim
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Observation of whispering gallery modes in cathode luminescence in TiO2:Eu3+ microspheres

Makoto Tomita, Kouki Totsuka, Hiroshi Ikari, Kenji Ohara, Hidenori Mimura, Hideyuki Watanabe, Hiroshi Kume, and Takahiro Matsumoto

Appl. Phys. Lett. 89, 061126 (2006); http://dx.doi.org/10.1063/1.2335578 (3 pages) | Cited 7 times

Online Publication Date: 11 August 2006

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We report cavity enhanced periodic structures in cathode luminescence spectra in TiO2:Eu3+ microspheres ranging from 6.2 to 12.2 μm in diameter. The spectral structures observed at the accelerating voltage below 10 kV are attributed to the lower order whispering galley modes, while the additional components appearing at 20 kV are to the higher order modes within the microsphere. These observations illustrate that the basic properties of phosphors can be advanced from the point of view of cavity quantum electrodynamics by fabricating a microcavity structure onto a single phosphor crystal.
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78.60.Hk Cathodoluminescence, ionoluminescence
12.20.Fv Experimental tests

Transient spectrometer for near-IR fluorescence based on parametric frequency upconversion

Xing-Hai Chen, Xiao-Feng Han, Yu-Xiang Weng, and Jing-Yuan Zhang

Appl. Phys. Lett. 89, 061127 (2006); http://dx.doi.org/10.1063/1.2335607 (3 pages) | Cited 13 times

Online Publication Date: 11 August 2006

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The authors report a unique technique for recording femtosecond time-resolved fluorescence spectra in the near IR by using idler-to-signal frequency upconversion in a 400 nm pumped femtosecond noncollinear optical parametric amplifier, in which the IR fluorescence was seeded as the idler and the corresponding amplified signal branch is recorded. The spectra of the upconverted signal carry the information of the IR fluorescence and it were used in constructing the spectra of the IR dye. The transient fluorescence spectra from the upconverted signal reconstruct the spectra of the IR dye very well after deconvolution from the pump beam.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.55.Kz Solid organic materials
78.47.-p Spectroscopy of solid state dynamics
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Low-power magnetized microdischarge ion source

Tsuyohito Ito and Mark A. Cappelli

Appl. Phys. Lett. 89, 061501 (2006); http://dx.doi.org/10.1063/1.2335612 (3 pages) | Cited 8 times

Online Publication Date: 8 August 2006

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The authors report on the design and operation of a magnetized microdischarge ion source. The discharge is a coaxial (E×B) configuration with a closed-electron drift. Conditions are selected such that the ions are nonmagnetized and the electrons strongly magnetized. The operating characteristics of this ion source are studied in the 10–40 W power range, generating a total ion current as high as 0.15 A and a peak ion energy of ∼ 150 eV at an operating voltage of 200 V. The ionization efficiency approaches 100%, although the present design has a fairly large ion beam divergence ( ∼ 80° half-angle). The compact nature of this ion source is suitable for localized processing or can be easily clustered for multi-ion processing.
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52.50.Dg Plasma sources
52.80.-s Electric discharges
52.25.Fi Transport properties
52.25.Xz Magnetized plasmas
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions

Study of geometrical and operational parameters controlling the low frequency microjet atmospheric pressure plasma characteristics

Dan Bee Kim, J. K. Rhee, S. Y. Moon, and W. Choe

Appl. Phys. Lett. 89, 061502 (2006); http://dx.doi.org/10.1063/1.2335956 (3 pages) | Cited 15 times

Online Publication Date: 10 August 2006

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Controllability of small size atmospheric pressure plasma generated at low frequency in a pin to dielectric plane electrode configuration was studied. It was shown that the plasma characteristics could be controlled by geometrical and operational parameters of the experiment. Under most circumstances, continuous glow discharges were observed, but both the corona and/or the dielectric barrier discharge characteristics were observed depending on the position of the pin electrode. The plasma size and the rotational temperature were also varied by the parameters. The rotational temperature was between 300 and 490 K, being low enough to treat thermally sensitive materials.
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52.50.Dg Plasma sources
52.80.Hc Glow; corona
52.25.-b Plasma properties
52.70.Ds Electric and magnetic measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.77.Fv High-pressure, high-current plasmas (plasma spray, arc welding, etc.)

Depleted uranium (math) induced preionization for enhanced and reproducible x-ray emission from plasma focus

S. Ahmad, M. Shafiq, M. Zakaullah, and A. Waheed

Appl. Phys. Lett. 89, 061503 (2006); http://dx.doi.org/10.1063/1.2244055 (3 pages) | Cited 5 times

Online Publication Date: 10 August 2006

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The effect of preionization induced by depleted uranium (math) around the insulator sleeve on the x-ray emission of (2.3–3.9 kJ) plasma focus device is investigated by employing Quantrad Si p-i-n diodes and a multipinhole camera. X-ray emission in 4π geometry is measured as a function of charging voltage with and without preionization. It is found that the preionization enhances Cu Kα and total x-ray yield about 100%, broadens the x-ray emission pressure range and x-ray pulse width, and improves shot to shot reproducibility of plasma focus operation. The pinhole images of x-ray emitting zones indicate that dominant x-ray emission is from the anode tip.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Jm Ionization of plasmas
52.58.Lq Z-pinches, plasma focus, and other pinch devices
52.75.-d Plasma devices
52.70.La X-ray and γ-ray measurements

Generation of highly collimated high-current ion beams by skin-layer laser-plasma interaction at relativistic laser intensities

J. Badziak, S. Jabłoński, and S. Głowacz

Appl. Phys. Lett. 89, 061504 (2006); http://dx.doi.org/10.1063/1.2266232 (3 pages) | Cited 15 times

Online Publication Date: 11 August 2006

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Generation of fast ion beams by laser-induced skin-layer ponderomotive acceleration has been studied using a two-dimensional (2D) two-fluid relativistic computer code. It is shown that the key parameter determining the spatial structure and angular divergence of the ion beam is the ratio dL/Ln, where dL is the laser beam diameter and Ln is the plasma density gradient scale length. When dL⪢Ln, a dense highly collimated megaampere ion (proton) beam of the ion current density approaching TA/cm2 can be generated by skin-layer ponderomotive acceleration, even with a tabletop subpicosecond laser.
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52.38.Ph X-ray, γ-ray, and particle generation
52.27.Ny Relativistic plasmas
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.38.Kd Laser-plasma acceleration of electrons and ions
52.65.Kj Magnetohydrodynamic and fluid equation
52.25.Fi Transport properties
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Heat capacity and phonon mean free path of wurtzite GaN

B. A. Danilchenko, T. Paszkiewicz, S. Wolski, A. Jeżowski, and T. Plackowski

Appl. Phys. Lett. 89, 061901 (2006); http://dx.doi.org/10.1063/1.2335373 (3 pages) | Cited 15 times

Online Publication Date: 7 August 2006

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The authors report lattice specific heat of bulk hexagonal GaN measured by the heat flow method in the temperature range of 20–300 K and by the adiabatic method in the range of 5–70 K. The best fit with the accuracy of 3% was obtained for the temperature-independent Debye temperature ΘD = 365 K and Einstein temperature ΘE = 880 K. The authors relate these temperatures to the function of density of states. Using their results for heat conduction coefficient, they established in the temperature range of 10–100 K the explicit dependence of the phonon mean free path on temperature ℓph∝T−2. Above 100 K, there is an evidence of contribution of the Umklapp processes, which limits phonon free path at high temperatures.
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65.40.Ba Heat capacity
63.20.K- Phonon interactions
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

On the tunnel injection of excitons and free carriers from In0.53Ga0.47As/In0.53Ga0.23Al0.24As quantum well to InAs/In0.53Ga0.23Al0.24As quantum dashes

P. Podemski, R. Kudrawiec, J. Misiewicz, A. Somers, J. P. Reithmaier, and A. Forchel

Appl. Phys. Lett. 89, 061902 (2006); http://dx.doi.org/10.1063/1.2243889 (3 pages) | Cited 9 times

Online Publication Date: 7 August 2006

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The authors investigate the efficiency of exciton and free carrier injections from quantum well (QW) to quantum dashes (QDashes) in tunnel-injection structures composed of In0.53Ga0.47As/In0.53Ga0.23Al0.24As QW and InAs/In0.53Ga0.23Al0.24As QDashes with ground state transitions separated by the energy close to the energy of LO phonon. As far as the thermal energy is smaller than the binding energy of QW excitons, almost all of the carriers created in QW tunnel to QDash. The injection process is much less efficient for free carriers because the energy difference between energy levels in QW and QDashes is not favorable for tunneling of electrons and holes separately.
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73.21.Fg Quantum wells
73.63.Hs Quantum wells
71.35.-y Excitons and related phenomena
73.40.Gk Tunneling
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

Nitrogen related vacancies in GaAs based quantum well superlattices

J. Slotte, K. Saarinen, E.-M. Pavelescu, T. Hakkarainen, and M. Pessa

Appl. Phys. Lett. 89, 061903 (2006); http://dx.doi.org/10.1063/1.2335402 (3 pages) | Cited 1 time

Online Publication Date: 7 August 2006

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The authors report on the influence of nitrogen incorporation on vacancies in GaAs based superlattices. The samples were molecular beam epitaxy grown on p-type GaAs substrates with the superlattice structure consisting of ten periods of quantum well material separated by GaAs buffers. Three different quantum well compositions were used, Ga0.63In0.37As, Ga0.63In0.37N0.01As0.99, and GaN0.01As0.99. Rapid thermal anneals were performed on each sample set. Positron spectroscopy was used for vacancy detection in the superlattice structure. Annealed GaNAs and GaInNAs superlattice samples were found to contain vacancy-type defects. A comparison with photoluminescence measurements shows that the detected vacancy-type defects are not optically active.
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61.72.J- Point defects and defect clusters
61.72.Cc Kinetics of defect formation and annealing
68.65.Cd Superlattices
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.70.Bj Positron annihilation

Hydrogen-nitrogen complexes in dilute nitride alloys: Origin of the compressive lattice strain

G. Bisognin, D. De Salvador, A. V. Drigo, E. Napolitani, A. Sambo, M. Berti, A. Polimeni, M. Felici, M. Capizzi, M. Güngerich, P. J. Klar, G. Bais, F. Jabeen, M. Piccin, S. Rubini, et al.

Appl. Phys. Lett. 89, 061904 (2006); http://dx.doi.org/10.1063/1.2335508 (3 pages) | Cited 16 times

Online Publication Date: 7 August 2006

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Hydrogenation of GaAs1−xNx and GaP1−xNx epilayers grown on GaAs(001) and GaP(001) surfaces, respectively, is known to passivate the electronic activity of nitrogen through the formation of specific nitrogen-hydrogen complexes. The same epilayers also undergo a strain reversal from tensile (as grown) to compressive (fully hydrogenated). The authors show that the extent of strain reversal is determined exclusively by the nitrogen concentration. By performing in situ high resolution x-ray diffraction measurements during annealing and photoluminescence studies, the authors demonstrate that the lattice properties of fully hydrogenated GaAs1−xNx are ruled by a H complex, which is different and less stable than that responsible for electronic passivation of nitrogen in GaAs1−xNx.
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68.60.Bs Mechanical and acoustical properties
81.65.Rv Passivation
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing

Raman spectroscopy of sputtered AlN films: E2(high) biaxial strain dependence

H. J. Trodahl, F. Martin, P. Muralt, and N. Setter

Appl. Phys. Lett. 89, 061905 (2006); http://dx.doi.org/10.1063/1.2335582 (3 pages) | Cited 4 times

Online Publication Date: 7 August 2006

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Sputtered [0001] AlN films with directly measured biaxial strain have been investigated by Raman spectroscopy to determine the strain dependence of the zone-center mode frequencies. The E2(high) feature near 655 cm−1 is found to vary linearly with stress, and we determine the strain derivative of the line as −2.9±0.3 cm−1/GPa, confirming the lowest previously reported derivative and a factor of 2 smaller than the largest. The result is 13% larger than has been predicted by ab initio calculations. The other zone-center lines accessible under normally incident geometry from a c-axis film are shown to be unsuitable as strain gauges.
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81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
81.15.Cd Deposition by sputtering
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
68.60.Bs Mechanical and acoustical properties

X-ray absorption of Zn1−xCoxO thin films: A local structure study

G. Martínez-Criado, A. Segura, J. A. Sans, A. Homs, J. Pellicer-Porres, and J. Susini

Appl. Phys. Lett. 89, 061906 (2006); http://dx.doi.org/10.1063/1.2335597 (3 pages) | Cited 20 times

Online Publication Date: 7 August 2006

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In this study, the application of synchrotron radiation microprobe to the analysis of Co incorporation in Zn1−xCoxO is reported. From the Co and Zn fluorescence line intensity ratio, the Co concentrations were deduced. A combination of fluorescence mapping with x-ray absorption spectroscopic techniques made possible to examine not only the uniform elemental distribution but also the short range structural order with the Co content. In Zn1−xCoxO films grown by pulsed laser depositions the Co atoms are in tetrahedral site configuration, corresponding to a substitutional site in wurtzite structure. Within the experimental accuracy, no significant bond length deviation from the pure ZnO structure was observed in the considered compositional range.
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81.05.Dz II-VI semiconductors
78.70.Dm X-ray absorption spectra
78.66.Hf II-VI semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Pp Magnetic semiconductors
81.15.Fg Pulsed laser ablation deposition

Molecular modeling of low-k films of carbon-doped silicon oxides for theoretical investigations of the mechanical and dielectric properties

N. Tajima, T. Ohno, T. Hamada, K. Yoneda, N. Kobayashi, S. Hasaka, and M. Inoue

Appl. Phys. Lett. 89, 061907 (2006); http://dx.doi.org/10.1063/1.2336273 (3 pages) | Cited 8 times

Online Publication Date: 8 August 2006

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For theoretical studies on the mechanical and dielectric properties of low dielectric constant (low-k) films of carbon doped SiO2 (SiOCH), the authors developed a method to create molecular models of amorphous polymers with cross-links. This method generates chemically possible molecular structures from a given atom-group composition. They have applied this method to the molecular modeling of a typical SiOCH low-k film which is made by plasma enhanced chemical vapor deposition. They have confirmed that this method creates reasonable SiOCH film structures that explain the experimental results of infrared spectrum, dielectric constant, and Young’s modulus.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
68.60.Bs Mechanical and acoustical properties
77.22.Ch Permittivity (dielectric function)
61.43.Bn Structural modeling: serial-addition models, computer simulation
61.43.Er Other amorphous solids

Annealing of indium tin oxide films by electric current: Properties and structure evolution

A. Rogozin, N. Shevchenko, M. Vinnichenko, M. Seidel, A. Kolitsch, and W. Möller

Appl. Phys. Lett. 89, 061908 (2006); http://dx.doi.org/10.1063/1.2335808 (3 pages) | Cited 5 times

Online Publication Date: 8 August 2006

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A method of annealing thin films of indium tin oxide in vacuum is proposed using a direct electric current flow through the film. During annealing at a constant electric power, the film resistance, free electron density, and structure evolution were monitored in situ. In comparison with the conventional isothermal annealing, the current annealing is more efficient providing a noticeable reduction in the thermal budget and a decrease in the kinetic exponent of crystallization. Electrical inhomogeneities in the film, which produce locally overheated regions, are discussed as a possible reason for the acceleration of the crystallization process.
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73.61.Ng Insulators
68.55.-a Thin film structure and morphology
81.40.Gh Other heat and thermomechanical treatments

Low writing field with large writing margin in toggle magnetic random access memories using synthetic antiferromagnet ferromagnetically coupled with soft magnetic layers

Yoshiyuki Fukumoto, Tetsuhiro Suzuki, and Shuichi Tahara

Appl. Phys. Lett. 89, 061909 (2006); http://dx.doi.org/10.1063/1.2335810 (3 pages) | Cited 12 times

Online Publication Date: 8 August 2006

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The authors propose free layer structures that can simultaneously reduce the writing field and enlarge the writing margin in toggle magnetic random access memories. In the free layers, two soft magnetic layers of NiFe and a synthetic antiferromagnet trilayer of NiFe/Ru/NiFe were ferromagnetically coupled through two ferromagnetic coupling layers (FCLs). The FCLs were composed of ultrathin Ta-based layers. As the coupling strength through the FCLs decreased, the spin-flop field (Hflop) decreased and the saturation field increased in these free layers, by which the Hflop could be freely decreased within the allowable range of its variation even for the 0.24-μm-wide bits.
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85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
84.30.Sk Pulse and digital circuits

Segregation of lead in Cu–Zn alloy under electric current pulses

X. L. Wang, J. D. Guo, Y. M. Wang, X. Y. Wu, and B. Q. Wang

Appl. Phys. Lett. 89, 061910 (2006); http://dx.doi.org/10.1063/1.2266034 (3 pages) | Cited 10 times

Online Publication Date: 9 August 2006

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In this letter, it is found that when the critical electric current pulse (ECP) passes through a Cu–Zn alloy with lead inclusions, those inclusions will disappear and transfer into grain boundaries or defects, forming many dispersed small particles of lead. Such kind of lead transfer can be produced by no other heat treatments than ECP. The theoretical analysis points out that this phenomenon is attributed to its specific effect on reducing considerably the diffusion activation energy of lead in the alloy. Therefore, the ECP treatment would provide a promising method to refine materials and to improve their physical properties.
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64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
81.40.Gh Other heat and thermomechanical treatments
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.72.Mm Grain and twin boundaries
66.30.J- Diffusion of impurities

Elastic behavior of polycrystalline thin films inferred from in situ micromechanical testing and modeling

D. Faurie, P.-O. Renault, E. Le Bourhis, Ph. Goudeau, O. Castelnau, R. Brenner, and G. Patriarche

Appl. Phys. Lett. 89, 061911 (2006); http://dx.doi.org/10.1063/1.2335779 (3 pages) | Cited 8 times

Online Publication Date: 9 August 2006

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Synchrotron x-ray diffraction combined with in situ tensile testing is used to investigate the anisotropic elastic behavior of gold thin films exhibiting a fiber texture and columnar grains. Micromechanical modeling based on the self-consistent model and accounting for both crystallographic and morphological textures is applied. Flat-disk shaped inclusions must be used in the model to reproduce accurately experimental data, owing to the surface effects.
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68.60.Bs Mechanical and acoustical properties
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
62.20.D- Elasticity
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology

High intensity fluorescence of photoactivated silver oxide from composite thin film with periodic array structure

Chih-Min Chuang, Ming-Chung Wu, Wei-Fang Su, Kuo-Chung Cheng, and Yang-Fang Chen

Appl. Phys. Lett. 89, 061912 (2006); http://dx.doi.org/10.1063/1.2222252 (3 pages) | Cited 9 times

Online Publication Date: 9 August 2006

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We have fabricated a composite thin film that exhibits intense photoactivated fluorescence of silver oxide at 522 and 529 nm under the irradiation of a 488 nm laser. This film consists of a silver coated polymeric periodic array on indium tin oxide glass substrate. By adjusting the column diameters and lattice constants of the array to coincide with the excitation wavelength, an order increase in fluorescence intensity was obtained due to the surface plasmon polariton resonance of silver. This composite film has many potential applications in highly efficient optoelectronic devices.
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78.66.Sq Composite materials
78.55.Hx Other solid inorganic materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Tuning the structural, electronic, and optical properties of BexZn1−xTe alloys

J. S. de Almeida and R. Ahuja

Appl. Phys. Lett. 89, 061913 (2006); http://dx.doi.org/10.1063/1.2219341 (3 pages) | Cited 10 times

Online Publication Date: 9 August 2006

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A series of first principles calculations have been carried out to investigate structural, electronic, and optical properties of BexZn1−xTe alloys for five beryllium compositions. Our results show that the lattice constant scales linearly with beryllium composition and there is a direct-to-indirect band gap crossover nearly at the composition of 20%. It is also found that no bowing effect in the absorption edge is observed unlike other II-VI semiconductor alloys. Our results are in good qualitative agreements with experimental observations.
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61.66.Fn Inorganic compounds
71.20.Nr Semiconductor compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Intense blue emission from tantalum-doped silicate glass

Xiangeng Meng, Shunsuke Murai, Koji Fujita, and Katsuhisa Tanaka

Appl. Phys. Lett. 89, 061914 (2006); http://dx.doi.org/10.1063/1.2335394 (3 pages) | Cited 2 times

Online Publication Date: 9 August 2006

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The authors report on an intense blue emission centered at 420 nm under ultraviolet excitation from pentavalent tantalum ion-doped silicate glasses. The blue emission is distinctly different from emission due to defects in silica glass, which is also reflected in both absorption spectrum and remarkably enhanced emission. The authors suggest that localized Ta 5d0 energy level is responsible for the blue emission.
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42.70.Ce Glasses, quartz
78.55.Hx Other solid inorganic materials

Quantitative analysis of compositional changes in InGaAs/InGaAsP quantum wells on GaAs induced by intermixing with a low temperature grown InGaP cap layer

O. Hulko, D. A. Thompson, J. A. Czaban, and J. G. Simmons

Appl. Phys. Lett. 89, 061915 (2006); http://dx.doi.org/10.1063/1.2236202 (3 pages) | Cited 5 times

Online Publication Date: 9 August 2006

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Energy-dispersive x-ray spectroscopy was used to analyze quantum well intermixing between an InGaAs quantum well (QW) and InGaAsP barriers grown on GaAs induced by a low temperature, molecular beam epitaxy grown, InGaP cap. This cap layer produces an enhanced blueshift of the photoluminescence (PL) wavelength following postgrowth annealing, and degradation of the PL signal. Cross-sectional transmission electron microscopy reveals modification of the whole structure, with formation of arsenic precipitates, broadening, and subsequent disappearance of the QWs in the capped structure. Uncapped samples are relatively unchanged. Increased phosphorus observed in the QW for capped structures confirms the diffusion of phosphorus from the P-rich cap.
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68.65.Fg Quantum wells
78.67.De Quantum wells
78.55.Cr III-V semiconductors
64.75.-g Phase equilibria
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.Cc Kinetics of defect formation and annealing

Time- and space-resolved fluorescence study on interfacial mobility of polymers

Keiji Tanaka, Yu Tsuchimura, Kei-ichi Akabori, Fuyuki Ito, and Toshihiko Nagamura

Appl. Phys. Lett. 89, 061916 (2006); http://dx.doi.org/10.1063/1.2335593 (2 pages) | Cited 8 times

Online Publication Date: 9 August 2006

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Segmental mobility of a typical amorphous polymer, polystyrene, at the interface with a solid substrate was examined noninvasively by fluorescence lifetime measurement using evanescent wave excitation. Glass transition temperature (Tg) was discernibly higher at the interface than in the bulk. Measurements at different incident angles of excitation pulses revealed that Tg became higher the closer to the interface. This is the observation for a Tg gradient of polymers at the interface.
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78.66.Qn Polymers; organic compounds
78.55.Kz Solid organic materials
78.47.-p Spectroscopy of solid state dynamics
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Mechanomagnetic spectroscopy of phase transitions in ferromagnetic shape memory alloys

Sergey Kustov, Francesc Masdeu, and Eduard Cesari

Appl. Phys. Lett. 89, 061917 (2006); http://dx.doi.org/10.1063/1.2335813 (3 pages) | Cited 5 times

Online Publication Date: 10 August 2006

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A technique for direct experimental investigations of coupling between applied elastic stress and magnetic response in ferromagnetic shape memory alloys over the temperature ranges of paramagnetic to ferromagnetic and martensitic transformations has been developed, based on the inverse magnetostriction (Villary) effect. Primary characteristics available from the experiment are elastic and anelastic properties and, the most important, signal related to stress-induced magnetization.
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75.50.Bb Fe and its alloys
75.20.En Metals and alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.80.+q Magnetomechanical effects, magnetostriction

Experimental verification of the temperature effects on Sader’s model for multilayered cantilevers immersed in an aqueous medium

S. Kim and K. D. Kihm

Appl. Phys. Lett. 89, 061918 (2006); http://dx.doi.org/10.1063/1.2240737 (3 pages) | Cited 7 times

Online Publication Date: 10 August 2006

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Recently, Sader [J. Appl. Phys. 84, 64 (1998) ] and Green and Sader [J. Appl. Phys. 92, 6262 (2002) ] developed a theory predicting thermally driven frequency responses of a microcantilever immersed in a fluid. This letter presents an experimental investigation of the temperature effects on Sader’s model using three cantilevers, with aspect ratios (AR = cantilever length/cantilever width) <4, for temperatures ranging from 10 to 70 °C. It is shown that liquid viscosity is primarily responsible for variations in the frequency response to liquid temperature. Two cantilevers, with AR ∼ 3.0, verify Sader’s predictions for the tested temperature range, while the third cantilever with AR ∼ 2.0 shows gradual deviations with increasing temperature.
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07.10.Cm Micromechanical devices and systems
66.20.-d Viscosity of liquids; diffusive momentum transport

Embrittlement in a bulk nanocrystalline alloy induced by room-temperature aging

G. J. Fan, H. Choo, and P. K. Liaw

Appl. Phys. Lett. 89, 061919 (2006); http://dx.doi.org/10.1063/1.2336595 (3 pages) | Cited 2 times

Online Publication Date: 10 August 2006

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Show Abstract
The effect of room-temperature aging on the mechanical behaviors of an electrodeposited bulk nanocrystalline (nc) Ni–Fe alloy has been investigated. The tensile elongation to failure, εf, of the bulk nc Ni–Fe alloy decreased from approximately 7.2% in the as-deposited state to 5.0%, after aging at room temperature for one year. Moreover, the fatigue-endurance limit decreased from about 260 to 190 MPa. This aging-induced embrittlement may be mainly due to the enhanced atomic diffusivity in the nc materials, leading to the segregation of the impurity atoms at the grain boundaries.
Show PACS
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Lm Deformation, plasticity, and creep
62.20.M- Structural failure of materials
62.20.F- Deformation and plasticity
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
61.72.Mm Grain and twin boundaries
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