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27 Aug 2012

Volume 101, Issue 9, Articles (09xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 091102 (2012); http://dx.doi.org/10.1063/1.4747168 (3 pages)

Hagay Shpaisman, Bhaskar Jyoti Krishnatreya, and David G. Grier
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Lasing in localized mode at optimized photonic amorphous structure

Kwang-Yong Jeong, Yong-Hee Lee, Hui Cao, and Jin-Kyu Yang

Appl. Phys. Lett. 101, 091101 (2012); http://dx.doi.org/10.1063/1.4748109 (4 pages) | Cited 1 time

Online Publication Date: 27 August 2012

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We demonstrated lasing in localized modes of an optimized photonic amorphous structure with short-range order. The InGaAsP multiple quantum wells embedded in a free-standing InGaAsP slab were employed as an active medium by optical pumping at room temperature. The high index contrast between air and InGaAsP, combined with uniformity of local topology and short-range order, enables strong confinement of light via multiple scattering. We confirmed the characteristic of lasing modes in the complex geometry with numerical simulations based on the real images of fabricated samples.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.70.Qs Photonic bandgap materials

Holographic microrefractometer

Hagay Shpaisman, Bhaskar Jyoti Krishnatreya, and David G. Grier

Appl. Phys. Lett. 101, 091102 (2012); http://dx.doi.org/10.1063/1.4747168 (3 pages) | Cited 1 time

Online Publication Date: 27 August 2012

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In-line holographic microscopy of micrometer-scale colloidal spheres yields heterodyne scattering patterns that may be interpreted with Lorenz-Mie theory to obtain precise time-resolved information on the refractive index of the suspending medium. We demonstrate this approach to spatially resolved refractometry with measurements on calibrated refractive index standards and use it to monitor chemical concentration in a microfluidic channel. Using commercially available colloidal spheres as probe particles and a standard video camera for detection yields values for the fluid’s refractive index at the position of each probe particle in each holographic snapshot with a demonstrated resolution of 2×10−3 refractive index units (RIU) and a potential resolution surpassing 10−4 RIU. The combination of spatial resolution, temporal resolution, multi-point in situ access, and technical simplicity recommends this technique for cost-effective lab-on-a-chip applications.
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07.60.Hv Refractometers and reflectometers
07.60.Pb Conventional optical microscopes
42.40.Kw Holographic interferometry; other holographic techniques
82.80.-d Chemical analysis and related physical methods of analysis
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems

Dual-band terahertz metamaterials based on nested split ring resonators

Sajid Hussain, Jeong Min Woo, and Jae-Hyung Jang

Appl. Phys. Lett. 101, 091103 (2012); http://dx.doi.org/10.1063/1.4748163 (4 pages)

Online Publication Date: 27 August 2012

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Two dual-band terahertz metamaterials based on nested split ring resonators (SRRs) were designed and fabricated on a flexible plastic substrate. Each nested SRR structure composed of two electric field coupled resonators exhibited two transmission minimums, which inherently come from the LC resonances of the respective SRRs. The primary and secondary resonance frequencies can be individually fine-tuned by adjusting the geometry of the respective resonator. The fabricated devices exhibited very low insertion loss of 3 dB in the transmission band and the high attenuation of 27 dB in the stop band.
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84.40.Az Waveguides, transmission lines, striplines

Size and surface effects on transient photoconductivity in CdS nanobelts probed by time-resolved terahertz spectroscopy

Mingjie Li, Bo Wu, Sandy Adhitia Ekahana, Muhammad Iqbal Bakti Utama, Guichuan Xing, Qihua Xiong, Tze Chien Sum, and Xinhai Zhang

Appl. Phys. Lett. 101, 091104 (2012); http://dx.doi.org/10.1063/1.4748300 (5 pages)

Online Publication Date: 27 August 2012

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Ultrafast optical-pump terahertz probe spectroscopy was performed over a graduated size distribution of CdS nanobelts to investigate the size and surface effects on the transient photoconductivity. It was found that the nanobelt size has a profound influence on the carrier localization and photoconductivity dynamics, brought about by the carrier trapping at surface defects. The strong carrier localization in the nanobelt is ascribed to the internal surface boundaries arising from the surface depletion layer. The increased thickness of surface depletion layer due to a continuous trapping of photocarriers at surface defects results in more pronounced carrier localization after photoexcitation.
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73.63.Bd Nanocrystalline materials
78.47.D- Time resolved spectroscopy (>1 psec)
72.40.+w Photoconduction and photovoltaic effects
78.70.Gq Microwave and radio-frequency interactions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.25.+i Surface conductivity and carrier phenomena

Control of reflectance and transmittance in scattering and curvilinear hyperbolic metamaterials

T. U. Tumkur, J. K. Kitur, B. Chu, Lei Gu, V. A. Podolskiy, E. E. Narimanov, and M. A. Noginov

Appl. Phys. Lett. 101, 091105 (2012); http://dx.doi.org/10.1063/1.4746387 (4 pages) | Cited 2 times

Online Publication Date: 27 August 2012

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We demonstrate reduced reflectance in curvilinear lamellar hyperbolic metamaterials as well as planar hyperbolic metamaterials consisting of metal/dielectric multilayers, with scatterers deposited on the top. The reduced reflectance is accompanied by a significant enhancement in transmission along with non-reciprocity of transmittance in forward and backward propagating directions. The observed experimental behavior is qualitatively similar to the results of numerical solutions of Maxwell equations. The findings of this study pave the way to a variety of important applications, including broadband enhancement of light trapping in photovoltaic devices.
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81.05.Xj Metamaterials for chiral, bianisotropic and other complex media
42.70.-a Optical materials
42.79.Wc Optical coatings
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

Spontaneous emission control of single quantum dots by electromechanical tuning of a photonic crystal cavity

L. Midolo, F. Pagliano, T. B. Hoang, T. Xia, F. W. M. van Otten, L. H. Li, E. H. Linfield, M. Lermer, S. Höfling, and A. Fiore

Appl. Phys. Lett. 101, 091106 (2012); http://dx.doi.org/10.1063/1.4748302 (4 pages) | Cited 1 time

Online Publication Date: 28 August 2012

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We demonstrate the control of the spontaneous emission rate of single InAs quantum dots embedded in a double-membrane photonic crystal cavity by the electromechanical tuning of the cavity resonance. Controlling the separation between the two membranes with an electrostatic field, we obtain the real-time spectral alignment of the cavity mode to the excitonic line and we observe an enhancement of the spontaneous emission rate at resonance. The cavity has been tuned over 13 nm without shifting the exciton energies. A spontaneous emission enhancement of ≈ 4.5 has been achieved with a coupling efficiency of the dot to the mode β ≈ 92%.
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73.21.La Quantum dots
73.63.Kv Quantum dots
78.67.Hc Quantum dots
71.35.-y Excitons and related phenomena
78.47.jd Time resolved luminescence
42.70.Qs Photonic bandgap materials

Ultralow-power local laser control of the dimer density in alkali-metal vapors through photodesorption

Pankaj K. Jha, Konstantin E. Dorfman, Zhenhuan Yi, Luqi Yuan, Vladimir A. Sautenkov, Yuri V. Rostovtsev, George R. Welch, Aleksei M. Zheltikov, and Marlan O. Scully

Appl. Phys. Lett. 101, 091107 (2012); http://dx.doi.org/10.1063/1.4747537 (4 pages) | Cited 1 time

Online Publication Date: 28 August 2012

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Ultralow-power diode-laser radiation is employed to induce photodesorption of cesium from a partially transparent thin-film cesium adsorbate on a solid surface. Using resonant Raman spectroscopy, we demonstrate that this photodesorption process enables an accurate local optical control of the density of dimer molecules in alkali-metal vapors.
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68.43.Nr Desorption kinetics
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
68.43.Mn Adsorption kinetics
78.30.Er Solid metals and alloys
78.66.Bz Metals and metallic alloys
82.50.Nd Control of photochemical reactions

Glancing angle Talbot-Lau grating interferometers for phase contrast imaging at high x-ray energy

D. Stutman and M. Finkenthal

Appl. Phys. Lett. 101, 091108 (2012); http://dx.doi.org/10.1063/1.4748882 (5 pages)

Online Publication Date: 28 August 2012

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A Talbot-Lau interferometer is demonstrated using micro-periodic gratings inclined at a glancing angle along the light propagation direction. Due to the increase in the effective thickness of the absorption gratings, the device enables differential phase contrast imaging at high x-ray energy, with improved fringe visibility (contrast). For instance, at 28° glancing angle, we obtain up to ∼35% overall interferometer contrast with a spectrum having ∼43 keV mean energy, suitable for medical applications. In addition, glancing angle interferometers could provide high contrast at energies above 100 keV, enabling industrial and security applications of phase contrast imaging.
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87.85.Pq Biomedical imaging
07.85.-m X- and γ-ray instruments
42.25.Fx Diffraction and scattering
42.79.Dj Gratings
87.59.-e X-ray imaging

Terahertz imaging of inhomogeneous electrodynamics in single-layer graphene embedded in dielectrics

M. J. Paul, J. L. Tomaino, J. W. Kevek, T. DeBorde, Z. J. Thompson, E. D. Minot, and Yun-Shik Lee

Appl. Phys. Lett. 101, 091109 (2012); http://dx.doi.org/10.1063/1.4749280 (3 pages) | Cited 1 time

Online Publication Date: 29 August 2012

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We investigate electron transport properties in large-area, single-layer graphene embedded in dielectric media, using free-space terahertz (THz) imaging and time-domain spectroscopy. Sandwiched between a thin polymethyl methacrylate (PMMA) layer and a Si substrate, graphene layers of different growth recipes exhibit distinctive spatial inhomogeneity of sheet conductivity. The non-contacting, non-destructive THz probe reveals that the PMMA layer induces a small, yet noticeable reduction in conductivity.
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72.80.Vp Electronic transport in graphene
78.70.Gq Microwave and radio-frequency interactions

Low-threshold blue lasing from silk fibroin thin films

Stefano Toffanin, Sunghwan Kim, Susanna Cavallini, Marco Natali, Valentina Benfenati, Jason J. Amsden, David L. Kaplan, Roberto Zamboni, Michele Muccini, and Fiorenzo G. Omenetto

Appl. Phys. Lett. 101, 091110 (2012); http://dx.doi.org/10.1063/1.4748120 (4 pages)

Online Publication Date: 29 August 2012

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Silk is a natural biocompatible material that can be integrated in a variety of photonic systems and optoelectronic devices. The silk replication of patterned substrates with features down to tens of nanometers is exploited to realize highly transparent, mechanically stable, and free-standing structures with optical wavelength size. We demonstrate organic lasing from a blue-emitting stilbene-doped silk film spin-coated onto a one-dimensional distributed feedback grating (DFB). The lasing threshold is lower than that of organic DFB lasers based on the same active dye. These findings pave the way to the development of an optically active biocompatible technological platform based on silk.
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42.55.Mv Dye lasers
42.60.By Design of specific laser systems

Cavity enhanced plasma self-absorption spectroscopy

Anton Walsh, Dongfeng Zhao (赵东锋), and Harold Linnartz

Appl. Phys. Lett. 101, 091111 (2012); http://dx.doi.org/10.1063/1.4748125 (4 pages) | Cited 1 time

Online Publication Date: 29 August 2012

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We introduce cavity enhanced plasma self-absorption spectroscopy (CEpSAS), a sensitive spectroscopic diagnostic tool that is used here for plasma analysis, but can also be used for any light emitting sample. It works without an additional external light source. In CEpSAS, plasma is located in an optically stable cavity consisting of two high reflectivity mirrors, and here it acts both as light source and absorbing medium. We present proof of principle results to illustrate the performance of this technique that literally combines “sense and simplicity.” Quantitative absorption experiments are described on a supersonically expanding hydrocarbon plasma.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
07.60.Rd Visible and ultraviolet spectrometers

Simple visible supercontinuum light source with true continuous-wave output power

I. Shavrin, S. Novotny, A. G. Savelyev, S. C. Buchter, and H. Ludvigsen

Appl. Phys. Lett. 101, 091112 (2012); http://dx.doi.org/10.1063/1.4748327 (4 pages) | Cited 1 time

Online Publication Date: 29 August 2012

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We present the concept and both the experimental and computational study of a simple supercontinuum light source emitting at temporally highly stable output powers. The principle of the light source is based on a standard pulsed supercontinuum source combined with fiber-based dispersive time-stretching. This approach allows for tailored spectral emission in the visible at a power stability of below 1%. Furthermore, the computation indicates that highly stable light emission with this concept does not necessarily require highest possible input pulse repetition rates and longest dispersive fiber lengths.
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42.81.Dp Propagation, scattering, and losses; solitons
42.65.-k Nonlinear optics
42.72.-g Optical sources and standards
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Strong reddish-orange light emission from stress-activated Srn+1SnnO3n+1:Sm3+ (n = 1, 2, ∞) with perovskite-related structures

Sunao Kamimura, Hiroshi Yamada, and Chao-Nan Xu

Appl. Phys. Lett. 101, 091113 (2012); http://dx.doi.org/10.1063/1.4749807 (4 pages) | Cited 1 time

Online Publication Date: 30 August 2012

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We report mechanoluminescence (ML) in Sm3+-doped Srn+1SnnO3n+1 (n = 1, 2, ∞) phosphors with perovskite-related structures, which consist of layered units depending on the number of n. The intensity of the ML was strongly dependent on the layered structure; the ML intensity for Sr3Sn2O7:Sm3+ was three orders of magnitude higher than that for SrSnO3:Sm3+. The charge transfer state (CTS) band in the photoluminescence excitation spectra was observed for Sr3Sn2O7:Sm3+ and Sr2SnO4:Sm3+, indicating that the efficient energy transfers from the host to the Sm3+ ions. The formation of CTS and the layered structure may be responsible for this ML enhancement.
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78.60.Mq Sonoluminescence, triboluminescence
71.70.-d Level splitting and interactions
78.55.Hx Other solid inorganic materials

Integrating a plasmonic coupler to photo detector of terahertz frequency

Zhihai Wang, Koji Ishibashi, S. Komiyama, N. Nagai, and K. Hirakawa

Appl. Phys. Lett. 101, 091114 (2012); http://dx.doi.org/10.1063/1.4748581 (3 pages) | Cited 1 time

Online Publication Date: 31 August 2012

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Projection type photo lithography and electroplating techniques were applied to fabricate a plasmonic coupler, and to integrate the coupler on top of a photo detector for terahertz frequency. The coupler is a metallic disk with a sub-wavelength aperture surrounded by concentric gratings. The period and height of the gratings are about 200 μm and 20 μm, respectively. The photo detector is 2-dimensional electron gas in perpendicular magnetic field. The photo signal is change of longitudinal resistance, due to cyclotron absorption of photons. Enhancement of photo signal, due to presence of the plasmonic coupler, was observed.
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42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Dj Gratings
84.40.-x Radiowave and microwave (including millimeter wave) technology
42.82.Cr Fabrication techniques; lithography, pattern transfer

Observation of In-related collective spontaneous emission (superfluorescence) in Cd0.8Zn0.2Te:In crystal

C. R. Ding, Z. L. Li, Z. R. Qiu, Z. C. Feng, and P. Becla

Appl. Phys. Lett. 101, 091115 (2012); http://dx.doi.org/10.1063/1.4748883 (5 pages)

Online Publication Date: 31 August 2012

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The In-related superfluorescence at 788 nm from Cd0.8Zn0.2Te:In single crystal has been observed and characterized by the time-resolved photoluminescence comparing with undoped Cd0.8Zn0.2Te. The peak intensity scales Nc2 and the emitted pulse width scales 1/Nc, where Nc is the coherent excited state population. The detected emission pulse shows delay of 43 ps with respect to the pump pulse and has a pulse width of 60 ps. The observation of superfluorescence from Cd0.8Zn0.2Te:In single crystal extends characteristic studies of CdZnTe as one of materials for making superfluorescence sources.
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78.45.+h Stimulated emission
78.55.Et II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
78.47.jd Time resolved luminescence
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Asymmetric interfacial abruptness in N-polar and Ga-polar GaN/AlN/GaN heterostructures

B. Mazumder, M. H. Wong, C. A. Hurni, J. Y. Zhang, U. K. Mishra, and J. S. Speck

Appl. Phys. Lett. 101, 091601 (2012); http://dx.doi.org/10.1063/1.4748116 (5 pages) | Cited 1 time

Online Publication Date: 27 August 2012

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In this letter, we report on the interfacial abruptness of GaN/AlN/GaN heterostructures with pulsed laser atom probe tomography (APT). The samples were grown by plasma-assisted molecular beam epitaxy (MBE) under both metal-rich and N-rich conditions on both Ga-polar (0001) GaN templates and N-polar (000math) GaN substrates. An NH3 assisted MBE technique was involved to grow similar Ga-polar and N-polar structures on GaN:Fe substrates and GaN/Al2O3 templates, respectively, for a comparison study. We find in all cases the interface with net positive polarization charge was chemically abrupt, whereas the interface with net negative polarization charge was diffuse. We discuss the implications on device design and performance. These data validate the efficiency of APT in studying interfaces for better performance in devices.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
66.30.-h Diffusion in solids
68.35.Ct Interface structure and roughness

Near dispersion-less surface plasmon polariton resonances at a metal-dielectric interface with patterned dielectric on top

Sachin Kasture, P. Mandal, Amandev Singh, Andrew Ramsay, A. S. Vengurlekar, S. Dutta Gupta, Vladimir Belotelov, and Achanta Venu Gopal

Appl. Phys. Lett. 101, 091602 (2012); http://dx.doi.org/10.1063/1.4749277 (4 pages)

Online Publication Date: 29 August 2012

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We report possibility of surface plasmon polariton modes that can be excited by incident light of a fixed frequency coming at wide angles. We experimentally show such modes in structures with smooth dielectric-metal-dielectric interfaces having 2-D dielectric patterns on top. Calculated field profile establishes the field localization at the metal-dielectric interfaces. We show that the position and dispersion of the excited modes can be controlled by the excitation geometry and the 2-D pattern.
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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)
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Excimer laser ablation of thick SiOx-films: Etch rate measurements and simulation of the ablation threshold

J. Ihlemann, J. Meinertz, and G. Danev

Appl. Phys. Lett. 101, 091901 (2012); http://dx.doi.org/10.1063/1.4748127 (4 pages)

Online Publication Date: 27 August 2012

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Excimer laser ablation of 4.5 μm thick SiOx-films with x ≈ 1 is investigated at 193 nm, 248 nm, and 308 nm. Strong absorption enables precisely tunable removal depths. The ablation rates correlate with laser penetration depths calculated from low level absorption coefficients. The experimental ablation thresholds are in agreement with numerical simulations on the basis of linear absorption and one-dimensional heat flow. This behaviour is similar to that of strongly UV-absorbing polymers, leading to well controllable micro machining prospects. After laser processing, SiOx can be converted to SiO2, opening a route to laser based fabrication of micro optical components.
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81.65.Cf Surface cleaning, etching, patterning
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
66.30.Xj Thermal diffusivity
42.55.Lt Gas lasers including excimer and metal-vapor lasers
79.20.Eb Laser ablation
02.60.Cb Numerical simulation; solution of equations

Bond lengths and lattice structure of InP0.52Sb0.48 grown on GaAs

Chen-Jun Wu, Zhe-Chuan Feng, Wen-Ming Chang, Chih-Chung Yang, and Hao-Hsiung Lin

Appl. Phys. Lett. 101, 091902 (2012); http://dx.doi.org/10.1063/1.4748295 (4 pages) | Cited 1 time

Online Publication Date: 27 August 2012

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We performed reciprocal space mapping (RSM) and extended x-ray absorption fine structure (EXAFS) measurements to investigate the lattice structure of InP0.52Sb0.48 grown on GaAs. The RSM data reveal the existence of residual strain in the 1-μm-thick epilayer. The average vertical to horizontal lattice constant ratio, az/axy, is 1.009. We used a valence force field model to calculate the distortion energy and bond lengths of InPSb supercells with different az/axy ratio. The calculated InP and InSb bond lengths are in good agreement with the results of EXAFS. Both bond lengths are close to those in corresponding end-point binaries. We attributed the residual strain to the non-vanishing distortion energy resulting from the bond length mismatch between InP and InSb bonds.
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68.55.ag Semiconductors
78.70.Dm X-ray absorption spectra

High cyclic stability of the elastocaloric effect in sputtered TiNiCu shape memory films

C. Bechtold, C. Chluba, R. Lima de Miranda, and E. Quandt

Appl. Phys. Lett. 101, 091903 (2012); http://dx.doi.org/10.1063/1.4748307 (4 pages) | Cited 2 times

Online Publication Date: 27 August 2012

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The elastocaloric effect that occurs during the stress-induced martensitic transformation in shape memory alloys is a promising mechanism in view of solid state cooling applications. It also allows for downscaling to feature sizes in the μm range, thus, being attractive for micro-cooling applications using thin film materials. In this study, elastocaloric properties of TiNi and TiNiCu films and their relation to functional fatigue were investigated. Both materials show similar effect sizes, their fatigue behavior is however different. While the temperature change in TiNi degrades by a factor of two within 150 cycles, no significant elastocaloric fatigue was found in TiNiCu.
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81.30.Kf Martensitic transformations
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
81.40.Lm Deformation, plasticity, and creep
62.20.me Fatigue
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.fg Shape-memory effect; yield stress; superelasticity

Width-to-thickness ratio dependence on photoplastic effect of ZnS nanobelt

Y. Wei, L. H. Xu, Y. W. Tao, X. J. Zheng, J. H. Yang, D. F. Zou, and S. X. Mao

Appl. Phys. Lett. 101, 091904 (2012); http://dx.doi.org/10.1063/1.4749273 (4 pages)

Online Publication Date: 28 August 2012

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Photoplastic effect (PPE) of individual ZnS nanobelt with different width-to-thickness (w/t) ratios was investigated by using a nanoindenter in conjunction with an incident ultraviolet light source system. The results show that the positive and negative PPEs are observed for the w/t ratios 4.9–9.6 and 3.2–4.1. At the peak indentation loads 20–50 μN, the positive and negative PPEs occur for the w/t ratios 4.9 and 3.2, however, they disappear at 60 μN. PPE is determined by w/t ratio not peak indentation load, and it is interpreted by the competing mechanisms of increase of Peierls barrier and radiation enhanced dislocation glide.
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62.20.fq Plasticity and superplasticity
81.40.Lm Deformation, plasticity, and creep
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
62.25.Mn Fracture/brittleness

Single-crystalline laterally graded GeSn on insulator structures by segregation controlled rapid-melting growth

Masashi Kurosawa, Yuki Tojo, Ryo Matsumura, Taizoh Sadoh, and Masanobu Miyao

Appl. Phys. Lett. 101, 091905 (2012); http://dx.doi.org/10.1063/1.4748328 (4 pages)

Online Publication Date: 28 August 2012

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Single-crystalline laterally graded GeSn-on-insulator (GeSnOI) structures are essential to achieve novel device-arrays with various direct-energy-band gaps, which can be merged with high-density Si large-scale-integrated-circuits. We investigate the seeding rapid-melting-growth of narrow stripes with a-Ge/Sn/a-Ge stacked-structures. This achieves laterally graded GeSn crystalline layers on Si substrates covered with SiO2 films. Stripe-length dependent GeSn lateral-profiles are quantitatively explained by Scheil equation, which enables precise designing of GeSn lateral-profiles. High-crystallinity GeSn stripes without dislocations or stacking faults are also demonstrated.
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81.10.Fq Growth from melts; zone melting and refining
64.75.Qr Phase separation and segregation in semiconductors

Ultra-fast calorimetry study of Ge2Sb2Te5 crystallization between dielectric layers

J. Orava, A. L. Greer, B. Gholipour, D. W. Hewak, and C. E. Smith

Appl. Phys. Lett. 101, 091906 (2012); http://dx.doi.org/10.1063/1.4748881 (4 pages) | Cited 1 time

Online Publication Date: 28 August 2012

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Phase changes in chalcogenides such as Ge2Sb2Te5 can be exploited in non-volatile random-access memory, with fast crystallization crucial for device operation. Ultra-fast differential scanning calorimetry, heating at rates up to 40 000 K s−1, has been used to study the crystallization of amorphous Ge2Sb2Te5 with and without sandwich layers of ZnS-SiO2. At heating rates up to 1000 K s−1, the sandwich layers retard crystallization, an effect attributed to crystallization-induced stress. At greater heating rates (≥5000 K s−1), and consequently higher crystallization temperatures, the stress is relaxed, and sandwich layers catalyze crystallization. Implications for memory-device performance are discussed.
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64.70.kg Semiconductors
64.70.kj Glasses
81.40.Gh Other heat and thermomechanical treatments
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Dielectric elastomer actuators with elastomeric electrodes

Michael Bozlar, Christian Punckt, Sibel Korkut, Jian Zhu, Choon Chiang Foo, Zhigang Suo, and Ilhan A. Aksay

Appl. Phys. Lett. 101, 091907 (2012); http://dx.doi.org/10.1063/1.4748114 (5 pages)

Online Publication Date: 29 August 2012

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For many applications of dielectric elastomer actuators, it is desirable to replace the carbon-grease electrodes with stretchable, solid-state electrodes. Here, we attach thin layers of a conducting silicone elastomer to prestrained films of an acrylic dielectric elastomer and achieve voltage-actuated areal strains over 70%. The influence of the stiffness of the electrodes and the prestrain of the dielectric films is studied experimentally and theoretically.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
77.55.-g Dielectric thin films

Electrical and Fourier transform infrared properties of epitaxial SmNiO3 tensile strained thin film

Badr Torriss, Mohamed Chaker, and Joëlle Margot

Appl. Phys. Lett. 101, 091908 (2012); http://dx.doi.org/10.1063/1.4748982 (3 pages)

Online Publication Date: 29 August 2012

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We have grown epitaxial SmNiO3 thin films under tensile strain on SrTiO3 (001) substrate by pulsed laser deposition. A metal-insulator transition is found at about 394 K similar to observations made in bulk samples. The x-ray reciprocal space map suggests that the film undergoes partial strain relaxation, stabilizing the structure SmNiO3 with lower oxygen vacancies. The corresponding mid-infrared transmittance decreases when passing through the metal-insulator transition.
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73.61.Ng Insulators
78.66.Nk Insulators
78.30.Hv Other nonmetallic inorganics
71.30.+h Metal-insulator transitions and other electronic transitions
81.15.Fg Pulsed laser ablation deposition
81.15.Kk Vapor phase epitaxy; growth from vapor phase
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