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20 Apr 2009

Volume 94, Issue 16, Articles (16xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 94, 161105 (2009); http://dx.doi.org/10.1063/1.3119666 (3 pages)

Artur R. Davoyan, Ilya V. Shadrivov, Andrey A. Sukhorukov, and Yuri S. Kivshar
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Field dependent electroluminescence from amorphous Si/SiNx multilayer structure

Hengping Dong, Danqing Wang, Kunji Chen, Jian Huang, Hongcheng Sun, Wei Li, Jun Xu, and Zhongyuan Ma

Appl. Phys. Lett. 94, 161101 (2009); http://dx.doi.org/10.1063/1.3120226 (3 pages) | Cited 4 times

Online Publication Date: 20 April 2009

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We report field dependent electroluminescence (EL) from as-deposited amorphous Si/SiNx multilayer structure, where a-Si well layer thickness ranges from 1 to 4 nm, while SiNx barrier layer thickness is fixed at 3 nm. When the sample is applied by a low forward voltage Vbias (<6 V, i.e., 2.5 MV/cm), the dominant peak of EL is located at the lower energy region from 740 nm shifted to 660 nm with reducing the thickness of the a-Si well layer from 4 to 1 nm. However, under a high applied Vbias(>6 V), another EL band at the higher energy region is observed to be peaked at about 530 nm, which is independent of the well layer thickness. Photoluminescence (PL) investigation performed under optically pumped by the 325 nm line and the 488 nm line, respectively, also demonstrates the pump energy dependence of PL peaks. We interpreted these interesting phenomena of electrical and optical pump energy dependence of light emission by using different luminescence mechanisms in the a-Si/SiNx multilayer structure.
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78.60.Fi Electroluminescence
78.55.Qr Amorphous materials; glasses and other disordered solids
78.47.J- Ultrafast spectroscopy (<1 psec)
81.07.St Quantum wells
78.67.De Quantum wells
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

Widely tunable distributed-feedback lasers with chirped gratings

Liang Xue, S. R. J. Brueck, and R. Kaspi

Appl. Phys. Lett. 94, 161102 (2009); http://dx.doi.org/10.1063/1.3123813 (3 pages) | Cited 1 time

Online Publication Date: 20 April 2009

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A quasicontinuous tuning range of 65 nm at 3.2 μm was obtained for continuous wave, single-longitudinal-mode operation at 77 K of an optically pumped distributed-feedback laser with a chirped grating. Interferometric lithography with spherical wavefronts was used to fabricate a large-area chirped grating whose period varied continuously in the direction of the grating lines. Tuning was achieved by translating the optical pump stripe relative to the device to activate regions with different grating periods. Methane absorption spectra, obtained using this tunable distributed-feedback laser, closely match the high-resolution transmission molecular absorption database simulations.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.79.Dj Gratings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Picosecond optical pulse generation from self-pulsating bisectional GaN-based blue-violet laser diodes

Takao Miyajima, Hideki Watanabe, Masao Ikeda, and Hiroyuki Yokoyama

Appl. Phys. Lett. 94, 161103 (2009); http://dx.doi.org/10.1063/1.3106055 (3 pages) | Cited 14 times

Online Publication Date: 20 April 2009

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Self-pulsations of 407 nm emitting GaN-based blue-violet laser diodes with bisectional (BS) electrodes were demonstrated by applying a reverse bias (VSA) to the subelectrode of the saturable absorber (SA) section. By increasing the injected current to the main electrode of the gain section with a reverse bias of VSA = −12 V, the optical pulses shortened to 30 ps. The optical peak output power was as high as 2.4 W with a pulse width of 30 ps and a repetition frequency of 0.9 GHz. This is so far the shortest pulse width from a self-pulsating BS GaN-based laser diode achieved by applying a reverse bias to the SA section.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Surface plasmon enhanced photoconductance of gold nanoparticle arrays with incorporated alkane linkers

M. A. Mangold, C. Weiss, M. Calame, and A. W. Holleitner

Appl. Phys. Lett. 94, 161104 (2009); http://dx.doi.org/10.1063/1.3116148 (3 pages) | Cited 13 times

Online Publication Date: 20 April 2009

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We report on a photoconductive gain effect in two-dimensional arrays of gold nanoparticles (NPs) in which alkane molecules are inserted. The NP arrays are formed by a self-assembly process from alkanethiol-coated gold NPs, and subsequently they are patterned on a Si/SiO2 chip by a microcontact printing technique. We find that the photoconductance of the arrays is strongly enhanced at the frequency of the surface plasmon of the NPs. We interpret the observation as a bolometric enhancement in the conductance of the NP arrays upon excitation of the surface plasmon resonance.
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73.63.Bd Nanocrystalline materials
73.22.Lp Collective excitations
72.40.+w Photoconduction and photovoltaic effects
81.16.Dn Self-assembly

Plasmonic Bloch oscillations in chirped metal-dielectric structures

Artur R. Davoyan, Ilya V. Shadrivov, Andrey A. Sukhorukov, and Yuri S. Kivshar

Appl. Phys. Lett. 94, 161105 (2009); http://dx.doi.org/10.1063/1.3119666 (3 pages) | Cited 16 times

Online Publication Date: 21 April 2009

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We study the propagation of plasmon polaritons in one-dimensional chirped metal-dielectric layered structures. We find an optical Wannier–Stark ladder in the mode spectrum and analyze Bloch oscillations associated with the coupling of surface plasmons localized at the metal-dielectric interfaces. For long structures, we find that the energy flow may dramatically change its direction, thus providing possibilities for the beam steering in the transmission band.
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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)

High-speed InGaAs/InP-based single-photon detector with high efficiency

Lilin Xu, E Wu, Xiaorong Gu, Yi Jian, Guang Wu, and Heping Zeng

Appl. Phys. Lett. 94, 161106 (2009); http://dx.doi.org/10.1063/1.3120224 (3 pages) | Cited 11 times

Online Publication Date: 21 April 2009

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An efficient single-photon detector at telecom wavelength of 1.55 μm was realized with an InGaAs/InP avalanche photodiode at −30 °C. By implementing a short gating pulse and optimizing the self-differencing circuit, a detection efficiency of 29.3% was achieved with an error count probability of 6% at the gating frequency of 200 MHz, paving the way for the high-efficiency and low-noise fast detection of the infrared single photons.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors

GaN-based light-emitting diode with textured indium tin oxide transparent layer coated with Al2O3 powder

T. K. Kim, S. H. Kim, S. S. Yang, J. K. Son, K. H. Lee, Y. G. Hong, K. H. Shim, J. W. Yang, K. Y. Lim, S. J. Bae, and G. M. Yang

Appl. Phys. Lett. 94, 161107 (2009); http://dx.doi.org/10.1063/1.3120222 (3 pages) | Cited 16 times

Online Publication Date: 22 April 2009

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Surface-textured InGaN/GaN light-emitting diodes (LEDs) coated with transparent Al2O3 powder were fabricated by natural lithography combined with inductively coupled plasma etching. For surface texturing, 300 nm size Al2O3 powder is used as an etching mask by simply coating the surface using a spin-coating process. Also, the powders are left on the surface after surface texturing to further increase extraction efficiency. At 20 mA, the light output power of the textured indium tin oxide (ITO) InGaN/GaN LEDs coated with the Al2O3 powder is enhanced by ∼ 112% compared with the conventional nontextured ITO LED. The enhanced light output power is attributed to the improved extraction efficiency resulting from an overall decrease in the total internal reflection due to the textured surface and the Al2O3 powder coating.
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85.60.Jb Light-emitting devices
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.16.Nd Micro- and nanolithography
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning

Highly stretchable, conductive, and transparent nanotube thin films

Liangbing Hu, Wei Yuan, Paul Brochu, George Gruner, and Qibing Pei

Appl. Phys. Lett. 94, 161108 (2009); http://dx.doi.org/10.1063/1.3114463 (3 pages) | Cited 34 times

Online Publication Date: 22 April 2009

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We have studied the electrical and optical properties of transparent and conductive nanotube thin films subjected to extremely large strains, both isotropic and anisotropic. The films maintain electrical conductivity for strains up to 700% and the eventual loss of conductivity is due primarily to the buildup of cracks in the nanotube films. We also measured the change in optical transmittance and explain the observed haziness of the films by considering the micrometer sized cluster. This study of transparent nanotube films as stretchable electrodes is crucial for many applications, in particular, for medical implantation of electronic devices.
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78.66.Tr Fullerenes and related materials
73.61.Wp Fullerenes and related materials
62.20.mt Cracks
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
68.60.Bs Mechanical and acoustical properties

Defect reduction in (11math2) semipolar GaN grown on m-plane sapphire using ScN interlayers

C. F. Johnston, M. A. Moram, M. J. Kappers, and C. J. Humphreys

Appl. Phys. Lett. 94, 161109 (2009); http://dx.doi.org/10.1063/1.3119321 (3 pages) | Cited 10 times

Online Publication Date: 22 April 2009

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The effect of ScN interlayer thickness on the defect density of (11math2) semipolar GaN grown on m-plane sapphire was studied by transmission electron microscopy. The interlayers comprised Sc metal deposited on a GaN seedlayer that was nitrided before GaN overgrowth by metal-organic vapor-phase epitaxy. Both interlayer thicknesses reduced the dislocation density by a factor of 100 to low-108 cm−2. The 8.5 nm interlayer produced regions that were free from basal plane stacking faults (BSF) and dislocations. The overall BSF density here was reduced by a factor of 5, to (6.49±0.07)×104 cm−1, without the need for an ex situ mask patterning step.
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68.65.Ac Multilayers
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.Nn Stacking faults and other planar or extended defects

Optofluidic evanescent dye laser based on a distributed feedback circular grating

Wuzhou Song, Andreas E. Vasdekis, Zhenyu Li, and Demetri Psaltis

Appl. Phys. Lett. 94, 161110 (2009); http://dx.doi.org/10.1063/1.3124652 (3 pages) | Cited 24 times

Online Publication Date: 24 April 2009

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We demonstrate an optofluidic evanescent laser based on a solid circular distributed feedback grating with the dye solution acting as the cladding layer. The laser mode is confined within the grating and experiences optical gain via the interaction between its evanescent component with the dye solution. Above a pump energy of 9.5 μJ/pulse, the laser exhibited single mode operation at 571 nm. Stable, narrow-linewidth emission was observed for a wide range of fluid refractive indices, even for those lower than of polydimethylsiloxane. We attribute this property to the evanescent coupling of the laser mode with the fluidic gain.
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42.55.Mv Dye lasers
42.79.Dj Gratings
42.60.By Design of specific laser systems

Near-infrared intersubband absorption in molecular-beam epitaxy-grown lattice-matched InAlN/GaN superlattices

O. Malis, C. Edmunds, M. J. Manfra, and D. L. Sivco

Appl. Phys. Lett. 94, 161111 (2009); http://dx.doi.org/10.1063/1.3120551 (3 pages) | Cited 9 times

Online Publication Date: 24 April 2009

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Strong near-infrared intersubband absorption is observed directly at room temperature in silicon-doped lattice-matched InAlN/GaN superlattices grown by molecular-beam epitaxy on GaN templates grown by hydride vapor-phase epitaxy. X-ray diffraction characterization of the heterostructures indicates excellent layer thickness uniformity and low interface roughness. For 2–4.5 nm quantum wells, the intersubband transition energies span the technologically relevant range between 2.3 and 2.9 μm. The experimental results are in good agreement with calculations of the transition energies using a conduction band offset of 1 eV and spontaneous polarization of 3 MV/cm.
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68.65.Cd Superlattices
61.72.uj III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.Fg Quantum wells

Retrieval of satellite pulses of single isolated attosecond pulses

Michael Chini, He Wang, Sabih D. Khan, Shouyuan Chen, and Zenghu Chang

Appl. Phys. Lett. 94, 161112 (2009); http://dx.doi.org/10.1063/1.3125247 (3 pages) | Cited 14 times

Online Publication Date: 24 April 2009

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When isolated attosecond pulses are reconstructed from an ideal streaked photoelectron spectrogram, the relative amplitude of accompanying satellite pulses can be identified from their interference. However, the interference pattern in the spectrogram can be smeared by variation of the streaking laser intensity in the focal volume and by interpolation when using large delay steps acquiring the spectrogram, making accurate measurement of the relative intensity of the satellite pulses difficult. We investigate these effects on the reconstruction of satellite pulses with full- and half-cycle separations. Our simulations show that satellite pulses with full-cycle separation are largely unaffected by these issues.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
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Large-area metamaterials on thin membranes for multilayer and curved applications at terahertz and higher frequencies

X. G. Peralta, M. C. Wanke, C. L. Arrington, J. D. Williams, I. Brener, A. Strikwerda, R. D. Averitt, W. J. Padilla, E. Smirnova, A. J. Taylor, and J. F. O’Hara

Appl. Phys. Lett. 94, 161113 (2009); http://dx.doi.org/10.1063/1.3114416 (3 pages) | Cited 16 times

Online Publication Date: 24 April 2009

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A possible path for fabricating three-dimensional metamaterials with curved geometries at optical and infrared frequencies is to stack flexible metamaterial layers. We have fabricated highly uniform metamaterials at terahertz frequencies on large-area, low-stress, free-standing 1 μm thick silicon nitride membranes. Their response remains comparable to that of similar structures on thick substrates as measured by the quality factor of the resonances. Transmission measurements with a Fourier transform infrared spectrometer highlight the advantage of fabricating high frequency metamaterials on thin membranes as etalon effects are eliminated. Releasing the membranes enables layering schemes and placement onto curved surfaces in order to create three-dimensional structures.
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42.70.-a Optical materials
84.40.-x Radiowave and microwave (including millimeter wave) technology
82.45.Mp Thin layers, films, monolayers, membranes
78.30.-j Infrared and Raman spectra

Gain measurements in strain-compensated quantum cascade laser

Tobias Gresch, Jérôme Faist, and Marcella Giovannini

Appl. Phys. Lett. 94, 161114 (2009); http://dx.doi.org/10.1063/1.3123390 (3 pages) | Cited 6 times

Online Publication Date: 24 April 2009

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Spectrally resolved gain measurements of a strain-compensated quantum cascade laser, emitting at 4.8 μm, are presented. Measurements have been acquired using a multisection cavity technique. The shape of the gain is compared with electroluminescence measurements whereas gain coefficients are compared to values obtained from laser data, studying the dependence of the laser threshold current with cavity length. Gain coefficients of 9.9 cm kA−1 at 80 K and 3.2 cm kA−1 at 322 K are found and we show that the temperature dependence of the gain coefficient is governed by optical phonon scattering.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
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Disinfection of E. coli by nonthermal microplasma electrolysis in normal saline solution

Yukinori Sakiyama, Takaaki Tomai, Masaru Miyano, and David B. Graves

Appl. Phys. Lett. 94, 161501 (2009); http://dx.doi.org/10.1063/1.3122148 (3 pages) | Cited 23 times

Online Publication Date: 20 April 2009

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We present a unique method to inactivate microorganisms in 0.9% NaCl solution (normal saline solution) by means of microplasmas. The device consists of a thin titanium wire covered by a glass tube for insulation except the tip and a ground electrode. Application of an asymmetric high-frequency, high voltage results in the formation of microbubbles at both electrodes. Repetitive light emission is observed in the vicinity of the powered electrode. We employed E. coli bacteria to investigate the disinfection efficiency of the device. More than 99.5% of E. coli were deactivated in 180 s. The survival curve showed biphasic behavior.
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87.80.Kc Electrochemical techniques
82.80.-d Chemical analysis and related physical methods of analysis
82.45.Hk Electrolysis
82.45.Fk Electrodes
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Ab initio calculations of elastic properties of Ru1−xNixAl superalloys

I. D. Bleskov, E. A. Smirnova, Yu. Kh. Vekilov, P. A. Korzhavyi, B. Johansson, M. Katsnelson, L. Vitos, I. A. Abrikosov, and E. I. Isaev

Appl. Phys. Lett. 94, 161901 (2009); http://dx.doi.org/10.1063/1.3120543 (3 pages) | Cited 6 times

Online Publication Date: 20 April 2009

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Ab initio total energy calculations based on the exact muffin-tin orbitals method, combined with the coherent potential approximation, have been used to study the thermodynamical and elastic properties of substitutional refractory Ru1−xNixAl alloys. We have found that the elastic constants C′ and C11 exhibit pronounced peculiarities near the concentration of about 40 at. % Ni, which we ascribe to electronic topological transitions. Our suggestion is supported by the Fermi surface calculations in the whole concentration range. Results of our calculations show that one can design Ru–Ni–Al alloys substituting Ru by Ni (up to 40 at. %) with almost invariable elastic constants and reduced density.
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71.15.Nc Total energy and cohesive energy calculations
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
62.20.dq Other elastic constants

Doping and characterization of boron atoms in nanocrystalline silicon particles

Keisuke Sato, Naoki Fukata, and Kenji Hirakuri

Appl. Phys. Lett. 94, 161902 (2009); http://dx.doi.org/10.1063/1.3120768 (3 pages) | Cited 9 times

Online Publication Date: 20 April 2009

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Boron (B) doping into nanocrystalline-silicon (nc-Si) particles was achieved by cosputtering of Si chips/B chips/silica disk targets and subsequent annealing at 1100 °C. The average diameter of B-doped particles was less than 4.3 nm, and the content of B was about 14.3 at. %. The observation of EELS spectrum of B-K edge and x-ray photoelectron spectroscopy spectra of B 1s, and that of B local vibrational peaks and the Fano effect by micro-Raman scattering measurements clearly demonstrate that B atoms were doped and electrically activated in the particles, indicating the formation of electrically active p-type nc-Si particles.
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61.72.U- Doping and impurity implantation
61.72.Cc Kinetics of defect formation and annealing
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
81.07.Bc Nanocrystalline materials
82.45.Yz Nanostructured materials in electrochemistry
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Migration of species in a prototype diffusion barrier: Cu, O, and H in TiN

L. Tsetseris, S. Logothetidis, and S. T. Pantelides

Appl. Phys. Lett. 94, 161903 (2009); http://dx.doi.org/10.1063/1.3122344 (3 pages) | Cited 5 times

Online Publication Date: 20 April 2009

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Experimental data on the migration of Cu impurities in TiN and in similar diffusion-barriers used in electronic devices have led to conflicting suggestions about the underlying physical mechanisms. Here we use results of first-principles calculations, which are in agreement with measured activations energies, to elucidate the atomic-scale processes of moderate and rapid diffusion of Cu through the bulk and intergrain voids of TiN films, respectively. We also find that O and H impurities are fast diffusers in TiN. The results offer an assessment for the efficiency of TiN diffusion-barriers with respect to properties, such as nature of impurities, stoichiometry, and crystallinity.
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66.30.Ny Chemical interdiffusion; diffusion barriers
66.30.Lw Diffusion of other defects
61.72.sh Impurity distribution
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.66.Bi Elemental solids
61.66.Dk Alloys

Splitting of transmission peak due to the hole symmetry breaking

Xiao-gang Yin, Cheng-ping Huang, Zhi-qiang Shen, Qian-jin Wang, and Yong-yuan Zhu

Appl. Phys. Lett. 94, 161904 (2009); http://dx.doi.org/10.1063/1.3111162 (3 pages) | Cited 6 times

Online Publication Date: 20 April 2009

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We studied experimentally and theoretically the optical transmission through asymmetrical holes of a metal film, which is constructed by introducing small protuberances to the sides of individual square holes. Due to the symmetry breaking of the hole shape, an interesting transmission feature appears: both the Ag-glass (1, 0) and Ag-glass (1, 1) peaks split distinctly. Detailed studies indicate that the peak splitting is actually associated with the two asymmetrical waveguide surface-plasmon (WSP) modes confined on the surface of opposite hole walls. The finding demonstrates the crucial role of WSP modes and enriches our understanding of the phenomenon.
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78.66.Bz Metals and metallic alloys
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.55.-a Thin film structure and morphology

Spin-charge-lattice coupling through resonant multimagnon excitations in multiferroic BiFeO3

M. O. Ramirez, A. Kumar, S. A. Denev, Y. H. Chu, J. Seidel, L. W. Martin, S.-Y. Yang, R. C. Rai, X. S. Xue, J. F. Ihlefeld, N. J. Podraza, E. Saiz, S. Lee, J. Klug, S. W. Cheong, et al.

Appl. Phys. Lett. 94, 161905 (2009); http://dx.doi.org/10.1063/1.3118576 (3 pages) | Cited 10 times

Online Publication Date: 21 April 2009

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Spin-charge-lattice coupling mediated by multimagnon processes is demonstrated in multiferroic BiFeO3. Experimental evidence of two- and three-magnon excitations as well as multimagnon coupling at electronic energy scales and high temperatures are reported. Temperature dependent Raman experiments show up to five resonant enhancements of the two-magnon excitation below the Néel temperature. These are shown to be collective interactions between on-site Fe d-d electronic resonance, phonons, and multimagnons.
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77.80.B- Phase transitions and Curie point
63.20.kk Phonon interactions with other quasiparticles
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
78.30.Hv Other nonmetallic inorganics

Selective area wavelength tuning of InAs/GaAs quantum dots obtained by TiO2 and SiO2 layer patterning

H. S. Lee, A. Rastelli, S. Kiravittaya, P. Atkinson, C. C. Bof Bufon, I. Mönch, and O. G. Schmidt

Appl. Phys. Lett. 94, 161906 (2009); http://dx.doi.org/10.1063/1.3120229 (3 pages) | Cited 4 times

Online Publication Date: 22 April 2009

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Selective area wavelength tuning of InAs quantum dots (QDs) in GaAs matrix is achieved by patterning TiO2 and SiO2 layers on the sample surface followed by rapid thermal processing. After heat treatment, the QD emission under the SiO2 capped areas shows pronounced blueshifts compared with regions capped with TiO2/SiO2, where interdiffusion is strongly suppressed. Finite element calculations of the strain generated by the different thermal expansion coefficients of GaAs, SiO2, and TiO2 at high temperature are used to interpret the results. This method may provide a simple route to achieve monolithic integration of optoelectronic devices based on QDs.
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73.21.La Quantum dots
66.30.Pa Diffusion in nanoscale solids
81.07.Ta Quantum dots
66.30.Ny Chemical interdiffusion; diffusion barriers
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
65.40.De Thermal expansion; thermomechanical effects
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems

In-plane anisotropy of polarized photoluminescence in M-plane (10math0) ZnO and MgZnO/ZnO multiple quantum wells

Hiroaki Matsui and Hitoshi Tabata

Appl. Phys. Lett. 94, 161907 (2009); http://dx.doi.org/10.1063/1.3124243 (3 pages) | Cited 13 times

Online Publication Date: 22 April 2009

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Highly polarized photoluminescence (PL) from M-plane ZnO layers and MgZnO/ZnO quantum wells (QWs) grown on ZnO substrates were observed. The energy difference between PL peaks of E⊥c and E∥c corresponded to that between A- and C-excitonic transitions. The polarization degree (P = 0.43) at 300 K in QWs was slightly low due to confinement-induced admixture of the Pz orbital to A-excitonic states compared with the ZnO layers (P = 0.49). Furthermore, layers with anisotropic compressive strains also showed high polarization anisotropy (P = 0.55) at 300 K due to bounded excitonic emissions that reflected the selection rule.
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78.67.De Quantum wells
78.55.Et II-VI semiconductors
73.21.Fg Quantum wells
71.35.-y Excitons and related phenomena

Theoretical prediction of shape memory behavior and ferrimagnetism in Mn2NiIn

Aparna Chakrabarti and S. R. Barman

Appl. Phys. Lett. 94, 161908 (2009); http://dx.doi.org/10.1063/1.3116618 (3 pages) | Cited 17 times

Online Publication Date: 23 April 2009

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Using density functional theory, we show that in Mn2NiIn a phase transition from cubic to tetragonal structure results in a lowering of the total energy, indicating occurrence of martensitic phase transition. The structural phase transition is nearly volume conserving, which is a characteristic of a shape memory alloy. The magnetic ground state is ferrimagnetic with antiparallel Mn spin moments and the total spin magnetization is 0.51μB in the martensitic phase. Thus, we predict that Mn2NiIn would behave like a magnetic shape memory alloy. The electronic structure and magnetic properties are explained by the spin polarized density of states.
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81.30.Kf Martensitic transformations
64.70.kd Metals and alloys
75.50.Gg Ferrimagnetics
71.20.Gj Other 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

Analysis of wave propagation and localization in periodic/disordered layered composite structures by a mass-spring model

Zhi-Zhong Yan, Chuanzeng Zhang, and Yue-Sheng Wang

Appl. Phys. Lett. 94, 161909 (2009); http://dx.doi.org/10.1063/1.3119206 (3 pages) | Cited 4 times

Online Publication Date: 23 April 2009

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The band structure and the displacement field of elastic waves in periodic/disordered layered composite structures of finite width are investigated by a simple mass-spring model. In the case of comparable stiffness, the density contrast plays a dominant role for the center layer disorder to obtain localized wave modes within the band gap. On the other hand, in the case of comparable density contrast, the number and the position of the localized modes can be adjusted by changing the stiffness of the center layer. Compared to the soft and nearly cracked disorders situated between two layers with a lower density, the band structure and the displacement are quite different from the case between two layers with a higher density.
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62.30.+d Mechanical and elastic waves; vibrations
71.20.-b Electron density of states and band structure of crystalline solids
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.dq Other elastic constants
71.23.An Theories and models; localized states
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.mt Cracks
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Detection of Ga suboxides and their impact on III-V passivation and Fermi-level pinning

C. L. Hinkle, M. Milojevic, B. Brennan, A. M. Sonnet, F. S. Aguirre-Tostado, G. J. Hughes, E. M. Vogel, and R. M. Wallace

Appl. Phys. Lett. 94, 162101 (2009); http://dx.doi.org/10.1063/1.3120546 (3 pages) | Cited 70 times

Online Publication Date: 20 April 2009

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Show Abstract
The passivation of interface states remains an important problem for III-V based semiconductor devices. The role of the most stable bound native oxides GaOx (0.5 ≤ x ≤ 1.5) is of particular interest. Using monochromatic x-ray photoelectron spectroscopy in conjunction with controlled GaAs(100) and InGaAs(100) surfaces, a stable suboxide (Ga2O) bond is detected at the interface but does not appear to be detrimental to device characteristics. In contrast, the removal of the Ga 3+ oxidation state (Ga2O3) is shown to result in the reduction of frequency dispersion in capacitors and greatly improved performance in III-V based devices.
Show PACS
84.32.Tt Capacitors
81.65.Rv Passivation
73.20.At Surface states, band structure, electron density of states
79.60.Bm Clean metal, semiconductor, and insulator surfaces
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