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31 Jul 2006

Volume 89, Issue 5, Articles (05xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 89, 053101 (2006); http://dx.doi.org/10.1063/1.2236382 (3 pages)

Y. Xin, Z. H. Huang, E. Y. Yan, W. Zhang, and Q. Zhao
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Group velocity measurement using spectral interference in near-field scanning optical microscopy

John D. Mills, Tipsuda Chaipiboonwong, William S. Brocklesby, Martin D. B. Charlton, Caterina Netti, Majd E. Zoorob, and Jeremy J. Baumberg

Appl. Phys. Lett. 89, 051101 (2006); http://dx.doi.org/10.1063/1.2243632 (3 pages) | Cited 4 times

Online Publication Date: 31 July 2006

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Near-field scanning optical microscopy provides a tool for studying the behavior of optical fields inside waveguides. In this experiment the authors measure directly the variation of group velocity between different modes of a planar slab waveguide as the modes propagate along the guide. The measurement is made using the spectral interference between pulses propagating inside the waveguide with different group velocities, collected using a near-field scanning optical microscope at different points down the guide and spectrally resolved. The results are compared to models of group velocities in simple guides.
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07.79.Fc Near-field scanning optical microscopes
07.60.Pb Conventional optical microscopes
06.30.Gv Velocity, acceleration, and rotation
42.79.Gn Optical waveguides and couplers

Optical properties of neodymium-containing polymethylmethacrylate films for the organic light emitting diode color filter

Y. Cho, Y. K. Choi, and S. H. Sohn

Appl. Phys. Lett. 89, 051102 (2006); http://dx.doi.org/10.1063/1.2244042 (3 pages) | Cited 8 times

Online Publication Date: 31 July 2006

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In order to improve the primary color purity of the organic light emitting diode (OLED), neodymium(Nd)-containing polymethylmethacrylate (PMMA) films have been fabricated by a solvent casting method, and their optical properties have been investigated as functions of Nd content in films. The study has revealed that absorption in Nd-containing PMMA films is due to intratransition within the 4f shell of the Nd3+ ion, and that it becomes larger with an increase in the Nd concentration in films. In OLED devices with color filters, luminance from unnecessary emissive light is sufficiently reduced, resulting in a wider color gamut and higher color purity.
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42.79.Wc Optical coatings
85.60.Jb Light-emitting devices

High-brightness top-emissive polymer light-emitting diodes utilizing organic oxide/Al/Ag composite cathode

Tzung-Fang Guo, Fuh-Shun Yang, Zen-Jay Tsai, Guan-Weng Feng, Ten-Chin Wen, Sung-Nien Hsieh, Chia-Tin Chung, and Ching-In Wu

Appl. Phys. Lett. 89, 051103 (2006); http://dx.doi.org/10.1063/1.2234317 (3 pages) | Cited 10 times

Online Publication Date: 1 August 2006

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This work presents the fabrication of high-brightness (over 30 000 cd/m2) top-emissive polymer light-emitting diodes (PLEDs) using a hybrid semitransparent cathode capable of efficient injection of electrons. The composite cathode is comprised of the organic oxide/Al complex as the injection buffer layer covered by a thin Ag overlayer. The anode is made of Ag:Ag2O coated on the glass substrate. The electroluminescence (EL) efficiency of 8.9 cd/A for phenyl-substituted poly(para-phenylene vinylene) copolymer based top-emissive PLED markedly exceeds that of 4.3 cd/A for the control device with the bottom-emissive configuration. The high performance is attributed to the balanced injection of charge carriers and the effective extraction of EL emission from the top cathode. The optical microcavity effect significantly promotes the EL emission in the direction along the surface normal.
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85.60.Jb Light-emitting devices

Recombination processes in midinfrared InGaAsSb diode lasers emitting at 2.37 μm

K. O’Brien, S. J. Sweeney, A. R. Adams, B. N. Murdin, A. Salhi, Y. Rouillard, and A. Joullié

Appl. Phys. Lett. 89, 051104 (2006); http://dx.doi.org/10.1063/1.2243973 (3 pages) | Cited 14 times

Online Publication Date: 1 August 2006

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The temperature dependence of the threshold current of InGaAsSb/AlGaAsSb compressively strained lasers is investigated by analyzing the spontaneous emission from working laser devices through a window formed in the substrate metallization and by applying high pressures. It is found that nonradiative recombination accounts for 80% of the threshold current at room temperature and is responsible for the high temperature sensitivity. The authors suggest that Auger recombination involving hot holes is suppressed in these devices because the spin-orbit splitting energy is larger than the band gap, but other Auger processes persist and are responsible for the low T0 values.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Isotropic photonic pseudogap in electrodeposited ZnO inverse opal

L. K. Teh, K. H. Yeo, and C. C. Wong

Appl. Phys. Lett. 89, 051105 (2006); http://dx.doi.org/10.1063/1.2244044 (3 pages) | Cited 8 times

Online Publication Date: 1 August 2006

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The authors achieved an isotropic photonic stop band in the blue region near the L point in the Brillouin zone of ZnO inverse opal. This was fabricated by electrochemical infiltration in a polystyrene opal template self-assembled with the meniscus method. In the ZnO inverse opal, the stop band is “blueshifted,” widened (compared to its parent opal), and remained fixed at its central frequency along different directions. The extensive spectral overlap of the stop bands indicates a smooth angular dispersion approaching omnidirectionality within a specific range of directions. The isotropic pseudogap could interact with the emission of ZnO material, resulting in useful luminescent behavior.
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42.70.Qs Photonic bandgap materials

Luminescence from two different crystallographic sites in Sr6BP5O20:Eu2+

Kee-Sun Sohn, Sang Ho Cho, Sung Soo Park, and Namsoo Shin

Appl. Phys. Lett. 89, 051106 (2006); http://dx.doi.org/10.1063/1.2245218 (3 pages) | Cited 8 times

Online Publication Date: 1 August 2006

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The time resolved luminescence and concentration quenching behavior were examined for Sr6BP5O20:Eu2+ phosphors. The emission spectrum of the Sr6BP5O20:Eu2+ phosphor could be deconvoluted into two well defined Gaussian peaks. This implies that the Eu2+ emission emanates from two different crystallographic sites for Sr2+ ions. Each deconvoluted Gaussian peak was assigned to its corresponding Sr2+ crystallographic site with the assistance of density functional theory (DFT) calculations. The accurate assignment achieved by the DFT calculation will provide some basic guidelines for improving the color purity of Sr6BP5O20:Eu2+ phosphors, when they are to be applied to blue components in plasma display panels.
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78.55.Hx Other solid inorganic materials
78.47.-p Spectroscopy of solid state dynamics
42.70.-a Optical materials

Lasing in high-Q quantum-dot micropillar cavities

S. Reitzenstein, A. Bazhenov, A. Gorbunov, C. Hofmann, S. Münch, A. Löffler, M. Kamp, J. P. Reithmaier, V. D. Kulakovskii, and A. Forchel

Appl. Phys. Lett. 89, 051107 (2006); http://dx.doi.org/10.1063/1.2266231 (3 pages) | Cited 13 times

Online Publication Date: 2 August 2006

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We present lasing in optically pumped high-Q micropillar cavity lasers with low thresholds and high β factors. The micropillar cavities with diameters between 1.0 and 4.0 μm contain a single layer of low density In0.3Ga0.7As quantum dots as active region. Cavity Q factors of up to 23.000 for 4.0 μm micropillar cavities and lasing based on less than 70 quantum dots is demonstrated.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Sa Microcavity and microdisk lasers
42.60.By Design of specific laser systems

Optical gain and lasing of ZnO/ZnMgO multiple quantum wells: From low to room temperature

Jian Cui, S. Sadofev, S. Blumstengel, J. Puls, and F. Henneberger

Appl. Phys. Lett. 89, 051108 (2006); http://dx.doi.org/10.1063/1.2266371 (3 pages) | Cited 17 times

Online Publication Date: 2 August 2006

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Optical gain and lasing properties of ZnO/ZnMgO multiple quantum wells with and without separate optical confinement are investigated in the temperature range from 5 to 290 K. The data signify that localized states are crucially involved in the laser action up to room temperature. The lasing threshold increases by about one order of magnitude and reaches 140 kW/cm2 at 290 K. The room temperature material gain is in the 103 cm−1 range.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Solution-processed pentacene quantum-dot polymeric nanocomposite for infrared photodetection

Kaushik Roy Choudhury, Won Jin Kim, Yudhisthira Sahoo, Kwang-Sup Lee, and Paras N. Prasad

Appl. Phys. Lett. 89, 051109 (2006); http://dx.doi.org/10.1063/1.2266791 (3 pages) | Cited 6 times

Online Publication Date: 2 August 2006

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An organic/inorganic polymeric nanocomposite thin film device, consisting of poly-N-vinyl carbazole as host matrix, lead selenide quantum dots as photosensitizer, and the organic semiconductor pentacene as a conductivity booster, is fabricated. Because of the inherent insolubility of pentacene, it is incorporated in the form of a soluble precursor which is made to undergo thermal conversion into pentacene. The device exhibits dramatic enhancement of infrared photocurrent due to pentacene. Efficient photogeneration of carriers coupled with enhanced conductance results in high photoconductive quantum efficiency.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Highly efficient epitaxial Bragg mirrors with broad omnidirectional reflectance bands in the midinfrared

E. W. Baumgartner, T. Schwarzl, G. Springholz, and W. Heiss

Appl. Phys. Lett. 89, 051110 (2006); http://dx.doi.org/10.1063/1.2335410 (3 pages) | Cited 7 times

Online Publication Date: 2 August 2006

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Laser-quality low-loss epitaxial Bragg mirrors exhibiting a broad omnidirectional stop band in the midinfrared at wavelengths around 7 μm are presented. The mirror layers, composed of PbTe and EuTe, exhibit a high refractive index contrast of 80%. Thus, with only three layer pairs, reflectances higher than 99% are achieved for angles of incidence up to 40° and higher than 98% for angles of incidence up to 60°. The angle dependence of the reflectance is accurately determined by analyzing the width of the cavity resonance in a half-wavelength microcavity, formed by two such Bragg mirrors. The experimentally determined omnidirectional stop bandwidth is as high as 50% of the target wavelength. The results are in good agreement to analytical calculations based on the transfer matrix method.
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42.79.Bh Lenses, prisms and mirrors
42.79.Wc Optical coatings
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Efficient stimulated emission due to bimolecular annihilation reduction in oligothiophene dioxide thin films

S. Lattante, G. Barbarella, L. Favaretto, G. Gigli, R. Cingolani, and M. Anni

Appl. Phys. Lett. 89, 051111 (2006); http://dx.doi.org/10.1063/1.2266033 (3 pages) | Cited 3 times

Online Publication Date: 3 August 2006

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We have studied the optical properties of a thienyl-S, S-dioxide oligothiophene under strong excitation. No stimulated emission is observed in neat films due to singlet-singlet bimolecular annihilation, with a bimolecular constant of A = (4.5±0.5)×10−11 cm3 s−1. On the contrary we show that strong stimulated emission is observed if the active molecule is blended to an inert polymer [poly(bisphenol A carbonate] (PC) even for a PC content as low as one PC molecule every 500 active molecules. We suggest that small PC quantities modify the film superamolecular packing, thus reducing the bimolecular recombination efficiency. These results are expected to be quite general and could allow a considerable extension of the number of molecules showing stimulated emission for organic laser applications.
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78.45.+h Stimulated emission
78.66.Qn Polymers; organic compounds
42.55.Rz Doped-insulator lasers and other solid state lasers

Field effect luminescence from Si nanocrystals obtained by plasma-enhanced chemical vapor deposition

M. Perálvarez, C. García, M. López, B. Garrido, J. Barreto, C. Domínguez, and J. A. Rodríguez

Appl. Phys. Lett. 89, 051112 (2006); http://dx.doi.org/10.1063/1.2268706 (3 pages) | Cited 30 times

Online Publication Date: 3 August 2006

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Field effect induced luminescence has been achieved by alternate tunnel injection of electrons and holes into Si nanocrystals. The emitting device is a metal-oxide-semiconductor structure with a semitransparent polycrystalline Si contact ∼ 250 nm thick and a silicon-rich silicon oxide layer of about 40 nm deposited on a p-type Si substrate by plasma-enhanced chemical vapor deposition. The electroluminescence is optimized for a Si excess of 17% and annealing at 1250 °C for 1 h in nitrogen-rich atmosphere. The pulsed emission presents typical decay times of ∼ 5 μs and external quantum efficiencies of ∼ 0.03%.
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85.60.Jb Light-emitting devices
84.32.Tt Capacitors
85.30.Tv Field effect devices

Tunable quantum cascade lasers with phase-matched third harmonic generation

S. Banerjee, P. S. Spencer, and K. A. Shore

Appl. Phys. Lett. 89, 051113 (2006); http://dx.doi.org/10.1063/1.2236106 (3 pages) | Cited 1 time

Online Publication Date: 3 August 2006

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The design of two tunable quantum cascade laser structures using intracavity phase-matched third harmonic generation is reported. The transverse mode at the lasing wavelength was phase matched with third order transverse mode of the third harmonic signal in one structure and to the fifth order transverse mode in the second structure. The effects of small perturbations in the widths and refractive indices of the waveguide layers are also studied. This analysis yielded optical-waveguide structures capable of generating third harmonic power with a conversion efficiency of about 1 mW/W.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Linear to axial or radial polarization conversion using a liquid crystal gel

Hongwen Ren, Yi-Hsin Lin, and Shin-Tson Wu

Appl. Phys. Lett. 89, 051114 (2006); http://dx.doi.org/10.1063/1.2335589 (3 pages) | Cited 22 times

Online Publication Date: 3 August 2006

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Two types of liquid crystal (LC) gels with radial or twisted-radial molecular orientation are fabricated using a radial electric field generated by an indium-tin-oxide hole electrode in the bottom substrate. If the top substrate is not buffed, the radial-type LC gel is formed which can convert linearly polarized light into axially polarized light. On the other hand, if the top substrate is homogeneously buffed, then a twisted-radial LC gel is produced which can convert linearly polarized light into radially polarized light. These polarization converters are useful for diffractive optics and optical imaging systems.
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42.70.Df Liquid crystals
61.30.-v Liquid crystals

Chemical oxygen-iodine laser with CO2 buffer gas

I. O. Antonov, V. N. Azyazov, A. V. Mezhenin, G. N. Popkov, and N. I. Ufimtsev

Appl. Phys. Lett. 89, 051115 (2006); http://dx.doi.org/10.1063/1.2222405 (3 pages) | Cited 3 times

Online Publication Date: 4 August 2006

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The efficient power operation in a chemical oxygen-iodine laser for subsonic and supersonic modes has been demonstrated. It is shown that the substitution of the buffer gas N2 by CO2 does not cause any significant variation in the dependence of the output power on the degree of dilution of the active medium. The maximum power was 581 W for the flow rate of molecular chlorine 22 mMol/s that corresponds to a chemical efficiency of ηchem = 29%.
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42.55.Ks Chemical lasers
42.60.By Design of specific laser systems

Highly transparent and conductive double-layer oxide thin films as anodes for organic light-emitting diodes

Yu Yang, Lian Wang, He Yan, Shu Jin, Tobin J. Marks, and Shuyou Li

Appl. Phys. Lett. 89, 051116 (2006); http://dx.doi.org/10.1063/1.2240110 (3 pages) | Cited 19 times

Online Publication Date: 4 August 2006

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Double-layer transparent conducting oxide thin film structures containing In-doped CdO (CIO) and Sn-doped In2O3 (ITO) layers were grown on glass by metal-organic chemical vapor deposition and ion-assisted deposition (IAD), respectively, and used as anodes for polymer light-emitting diodes (PLEDs). These films have a very low overall In content of 16 at. %. For 180-nm-thick CIO/ITO films, the sheet resistance is 5.6 Ω/◻, and the average optical transmittance is 87.1% in the 400–700 nm region. The overall figure of merit (Φ = T10/Rsheet) of the double-layer CIO/ITO films is significantly greater than that of single-layer CIO, IAD-ITO, and commercial ITO films. CIO/ITO-based PLEDs exhibit comparable or superior device performance versus ITO-based control devices. CIO/ITO materials have a much lower sheet resistance than ITO, rendering them promising low In content electrode materials for large-area optoelectronic devices.
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73.61.-r Electrical properties of specific thin films
78.66.-w Optical properties of specific thin films
68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Jj Ion and electron beam-assisted deposition; ion plating
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Focusing a multimillijoule soft x-ray laser at 21 nm

T. Mocek, B. Rus, M. Stupka, M. Kozlová, A. R. Präg, J. Polan, M. Bittner, R. Sobierajski, and L. Juha

Appl. Phys. Lett. 89, 051501 (2006); http://dx.doi.org/10.1063/1.2260822 (3 pages) | Cited 17 times

Online Publication Date: 1 August 2006

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The authors focused the beam of currently the most powerful soft x-ray laser at 21 nm using a spherical Mo:Si multilayer mirror. Focal spots were directly observed by imaging the fluorescence induced by the soft x-ray beam on a Tb doped phosphor screen. The energy density within the 40×60 μm2 focal spot was 48 J/cm2, which corresponds to radiation peak intensity of 5×1011 W/cm2. The first observation of material ablation with a laser at 21 nm is reported.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
42.55.Vc X- and γ-ray lasers
52.38.Mf Laser ablation
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.38.Ph X-ray, γ-ray, and particle generation

Energy distribution of O− ions during reactive magnetron sputtering

Stanislav Mráz and Jochen M. Schneider

Appl. Phys. Lett. 89, 051502 (2006); http://dx.doi.org/10.1063/1.2266888 (3 pages) | Cited 11 times

Online Publication Date: 1 August 2006

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Low, medium, and high energy O− ion populations were experimentally detected during magnetron sputtering of Al in an Ar/O2 atmosphere. Based on calculations, the authors propose that nonsputtered O− ions originating from the target surface are accelerated in the cathode fall, while sputtered O− ions may be excluded as a significant contribution to the high energy ion population. Furthermore, the formation of medium energy O− ions is consistent with the notion of sputtered, in the cathode fall accelerated, and subsequently dissociated AlO− and AlO2− clusters. These findings may be of importance for understanding plasma energetics and growth involving electronegative species.
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52.70.Nc Particle measurements
52.40.Hf Plasma-material interactions; boundary layer effects
52.25.Fi Transport properties
52.77.Dq Plasma-based ion implantation and deposition
81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth

Conditions for formation of a kinetic anode layer in crossed E×B fields

A. Yu. Kovalenko, Yu. A. Kovalenko, and M. Keidar

Appl. Phys. Lett. 89, 051503 (2006); http://dx.doi.org/10.1063/1.2240479 (3 pages) | Cited 1 time

Online Publication Date: 4 August 2006

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A discharge in crossed electric and magnetic fields (E×B) is considered. E×B discharge serves as a basis for Hall-effect plasma accelerators. In this letter the authors present conditions for formation of a kinetic anode layer by considering an interface between kinetic and hydrodynamic regions. It is found that the kinetic anode layer, which has a thickness of about the electron Larmor radius, is formed in the case of a high magnetic field.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.25.Dg Plasma kinetic equations
52.80.-s Electric discharges
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.25.Fi Transport properties
52.75.Di Ion and plasma propulsion
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Propagation and dual-localization of surface plasmon polaritons in a quasiperiodic metal heterowaveguide

Lin Zhou, Xiao-qiang Yu, and Yong-yuan Zhu

Appl. Phys. Lett. 89, 051901 (2006); http://dx.doi.org/10.1063/1.2236297 (3 pages) | Cited 5 times

Online Publication Date: 31 July 2006

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Based on the transfer matrix method and the finite-difference time-domain analysis, we investigate the propagation and scattering of surface plasmon polaritons (SPPs) in a quasiperiodic metal heterowaveguide. By selecting appropriate thickness of the defect layer, the two SPP modes can be adjusted to localize at around 1310 and 1550 nm simultaneously. The numerical results reveal that the realization of miniaturized photonic devices is feasible at the two important telecommunicate wavelengths. The structure can be applied to the double-band plasmon Bragg reflector, double-channel light emitters and filters.
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42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
78.68.+m Optical properties of surfaces
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Strong electric field and nonuniformity effects in GaN/AlN quantum dots revealed by high pressure studies

H. Teisseyre, T. Suski, S. P. Łepkowski, P. Perlin, G. Jurczak, P. Dłużewski, B. Daudin, and N. Grandjean

Appl. Phys. Lett. 89, 051902 (2006); http://dx.doi.org/10.1063/1.2219381 (3 pages) | Cited 3 times

Online Publication Date: 31 July 2006

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The photoluminescence (PL) from GaN quantum dots (QDs) embedded in AlN has been investigated under hydrostatic pressure. The measured pressure coefficient of emitted light energy [dEE/dP] shows a negative value, in contrast with the positive pressure coefficient of the GaN band gap. We also observed that increasing pressure leads to a significant decrease of the light emission intensity and an asymmetric broadening of the PL band. All these effects are related to the pressure-induced increase of the built-in electric field. A comparison is made between experimental results and the proposed theoretical model which describes the pressure behavior of nitride QDs.
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73.63.Kv Quantum dots
73.21.La Quantum dots
78.67.Hc Quantum dots
62.50.-p High-pressure effects in solids and liquids
78.55.Cr III-V semiconductors
71.20.Nr Semiconductor compounds

Large g factors of higher-lying excitons detected with reflectance difference spectroscopy in GaAs-based quantum wells

Y. H. Chen, X. L. Ye, B. Xu, Z. G. Wang, and Z. Yang

Appl. Phys. Lett. 89, 051903 (2006); http://dx.doi.org/10.1063/1.2245213 (3 pages) | Cited 1 time

Online Publication Date: 31 July 2006

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Exciton g factors in GaAs-based quantum wells (QWs) were evaluated by reflectance difference spectroscopy (RDS) under a weak magnetic field. The well-width dependence of the n = 1 heavy-hole exciton (1H1E) g factor agrees well with the reported results, demonstrating RDS as a sensitive tool for detection of g factor. By comparison, the n = 1 light-hole exciton g factor increases with the well width, and shows a larger value than that of 1H1E. In a 20-nm-wide Al0.02Ga0.98As/AlAs multiple QW sample, the g factors of up to ten excitons are obtained, and the higher-lying exciton g factors are found to be one order larger than that of the 1H1E exciton.
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71.35.-y Excitons and related phenomena
78.67.De Quantum wells
73.21.Fg Quantum wells
78.20.Ls Magneto-optical effects
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Biomolecular origin of the rate-dependent deformation of prismatic enamel

Jikou Zhou and Luke L. Hsiung

Appl. Phys. Lett. 89, 051904 (2006); http://dx.doi.org/10.1063/1.2245439 (3 pages) | Cited 15 times

Online Publication Date: 31 July 2006

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Penetration deformation of columnar prismatic enamel was investigated using instrumented nanoindentation testing that was carried out at three constant strain rates (0.05, 0.005, and 0.0005 s−1). Enamel demonstrated better resistance to penetration deformation and greater elastic modulus values were measured at higher strain rates. The origin of rate-dependent deformation was rationalized to be the shear deformation of nanoscale protein matrix surrounding each hydroxyapatite crystal rod. The shear modulus of protein matrix was determined. It depends on strain rate in a format Gp = 0.213+0.021 ln math.
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87.15.La Mechanical properties
87.14.E- Proteins

Temperature dependence of very deep emission from an exciton bound to an isoelectronic defect in polycrystalline CuInS2

J. Krustok, J. Raudoja, and R. Jaaniso

Appl. Phys. Lett. 89, 051905 (2006); http://dx.doi.org/10.1063/1.2266597 (3 pages) | Cited 6 times

Online Publication Date: 1 August 2006

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Zero-phonon lines (ZPLs) of deep exciton bound to isoelectronic deep-donor–deep-acceptor pair in CuInS2 are studied by photoluminescence. These ZPLs have peak positions at 0.6241 eV (A line) and 0.6220 eV (B line), followed by two series of phonon replicas with phonon energies of 8 and 40.5 meV. Temperature dependence of the intensity of these ZPLs is explained by electron-phonon coupling to a single phonon mode with energy of 8 meV and shows that the lines are originated from two excited state levels of the same exciton. The (anomalously strong) temperature broadening of ZPLs follows ∼ T2.6 law and can be explained by assuming a strong vibronic coupling between two excited states.
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78.55.Hx Other solid inorganic materials
63.20.kk Phonon interactions with other quasiparticles
71.35.Gg Exciton-mediated interactions
71.55.Ht Other nonmetals
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions

Optical and mechanical anisotropies of oriented poly(ethylene terephthalate) films

K. Schmidegg, L. D. Sun, and P. Zeppenfeld

Appl. Phys. Lett. 89, 051906 (2006); http://dx.doi.org/10.1063/1.2234297 (3 pages) | Cited 4 times

Online Publication Date: 1 August 2006

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Reflectance difference spectroscopy (RDS) is used to characterize the optical anisotropy of thin, biaxially oriented poly(ethylene terephthalate) films. Molecular orientation in these films results in birefringence and thus gives rise to a RDS signal, which changes characteristically with external strain. A clear link between the optical and mechanical anisotropies can be established by comparing the azimuthal dependence of the elastic modulus with the RDS signal. Online measurements during tensile tests provide information on the evolution of the optical properties as a function of external strain, thus making RDS a highly sensitive probe for strain in oriented polymers.
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78.66.Qn Polymers; organic compounds
68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
78.20.Fm Birefringence
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