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16 Jan 2006

Volume 88, Issue 3, Articles (03xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 034101 (2006); http://dx.doi.org/10.1063/1.2164910 (3 pages)

W. K. Hensinger, S. Olmschenk, D. Stick, D. Hucul, M. Yeo, M. Acton, L. Deslauriers, C. Monroe, and J. Rabchuk
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Guided modes supported by plasmonic films with a periodic arrangement of subwavelength slits

Peter B. Catrysse, Georgios Veronis, Hocheol Shin, Jung-Tsung Shen, and Shanhui Fan

Appl. Phys. Lett. 88, 031101 (2006); http://dx.doi.org/10.1063/1.2164905 (3 pages) | Cited 13 times

Online Publication Date: 17 January 2006

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We calculate the guided band diagram of a metallic film with a one-dimensional periodic arrangement of cut-through subwavelength slits. We find that this system supports two distinct types of guided modes propagating in a direction perpendicular to the slits when the metal obeys a plasmonic dispersion model. The first type is a well-known surface mode. The second type results from the presence of a subwavelength electromagnetic resonance inside the slits and closely resembles waveguide modes in a dielectric slab. We refer to them as effective dielectric slab modes. We show how the behavior of both modes is affected by film thickness and surface properties.
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78.66.Bz Metals and metallic alloys
78.68.+m Optical properties of surfaces
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Fabrication and design of an integrable subwavelength ultrabroadband dielectric mirror

Lu Chen, Michael C. Y. Huang, Carlos F. R. Mateus, Connie J. Chang-Hasnain, and Y. Suzuki

Appl. Phys. Lett. 88, 031102 (2006); http://dx.doi.org/10.1063/1.2164920 (3 pages) | Cited 17 times

Online Publication Date: 17 January 2006

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We have designed and fabricated a subwavelength grating (SWG) broadband mirror whose performance depends on key factors, including SWG period, duty cycle, and angle of incident light. The fabricated SWGs exhibit high reflectivity ( ≥ 96%), when the grating periods are varied from 650 to 750 nm and duty cycles are varied from 55% to 65%. The bandwidth and reflectivity of these mirrors are remarkably robust to variations in design and fabrication. The SWGs can be designed as broadband mirrors from microwave to visible wavelengths.
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42.25.Fx Diffraction and scattering
42.25.Gy Edge and boundary effects; reflection and refraction
42.25.Hz Interference
42.25.Ja Polarization
42.79.Dj Gratings
42.79.Fm Reflectors, beam splitters, and deflectors
42.79.Hp Optical processors, correlators, and modulators

Widely tunable type-II interband cascade laser

Sergey Suchalkin, Mikhail V. Kisin, Serge Luryi, Gregory Belenky, Fred J. Towner, John D. Bruno, Carlos Monroy, and Richard L. Tober

Appl. Phys. Lett. 88, 031103 (2006); http://dx.doi.org/10.1063/1.2165289 (3 pages) | Cited 11 times

Online Publication Date: 17 January 2006

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We discuss an ultrawide, voltage-tunable type-II mid-IR interband cascade laser. Its design has a charge accumulation layers outside of the optically active quantum wells that unclamps the electron-hole concentrations and facilitates above-threshold Stark shifts. Our results demonstrate laser tuning of 120 nm (120 cm−1).
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.60.By Design of specific laser systems
42.72.Ai Infrared sources

Engineering the imaging properties of a metallic photonic-crystal slab lens

Shuai Feng, Zhi-Yuan Li, Zhi-Fang Feng, Bing-Ying Cheng, and Dao-Zhong Zhang

Appl. Phys. Lett. 88, 031104 (2006); http://dx.doi.org/10.1063/1.2166470 (3 pages) | Cited 5 times

Online Publication Date: 18 January 2006

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Focusing properties of a two-dimensional metallic photonic crystal (PC) slab lens are studied through the finite-difference time-domain technique. The PC consists of a square lattice of metallic cylinders immersed in a dielectric background. A good-quality image can form in the opposite side of the slab in both the lowest and second higher transverse magnetic-polarized photonic bands, consistent with the analysis of equifrequency-surface contours. The all-angle negative refraction can be realized and controlled by simply adjusting the background material permittivity,.
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42.70.Qs Photonic bandgap materials
42.79.Bh Lenses, prisms and mirrors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Rf-plasma-assisted molecular-beam epitaxy of β-Ga2O3

Encarnación G. Víllora, Kiyoshi Shimamura, Kenji Kitamura, and Kazuo Aoki

Appl. Phys. Lett. 88, 031105 (2006); http://dx.doi.org/10.1063/1.2164407 (3 pages) | Cited 13 times

Online Publication Date: 18 January 2006

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Epitaxial growth of β-Ga2O3 thin films by the rf-plasma-assisted molecular-beam epitaxy technique is demonstrated. Growth on (1 0 0) β-Ga2O3 substrates leads to very smooth epilayers, while (2 0 math) and (1 0 0) oriented β-Ga2O3 films are obtained on (0 0 1) sapphire and (1 0 0) MgO substrates, respectively. Internal transmittance, refractive index and direct bandgaps are determined.
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81.05.Hd Other semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
78.66.Li Other semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
71.20.Nr Semiconductor compounds

Optical phase characterization of active semiconductor microdisk resonators in transmission

Andrew Stapleton, Stephen Farrell, Hooman Akhavan, Roshanak Shafiiha, Zhen Peng, Seung-June Choi, John O’Brien, P. Daniel Dapkus, and William Marshall

Appl. Phys. Lett. 88, 031106 (2006); http://dx.doi.org/10.1063/1.2165286 (3 pages) | Cited 5 times

Online Publication Date: 18 January 2006

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The optical phase characteristics of an indium phosphide (InP) vertically coupled microdisk were experimentally demonstrated. Overcoming the material losses by injecting current into the active quantum well microdisk layer has allowed us to observe the phase behavior in all three coupling regimes. The ability to tune the resonant wavelength of this device makes it suitable for use as a phase modulator or tunable optical delay element.
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42.79.Hp Optical processors, correlators, and modulators
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.30.De Semiconductor-device characterization, design, and modeling

High Q (33 000) all-epitaxial microcavity for quantum dot vertical-cavity surface-emitting lasers and quantum light sources

Andreas Muller, Chih-Kang Shih, Jaemin Ahn, Dingyuan Lu, Deepa Gazula, and Dennis G. Deppe

Appl. Phys. Lett. 88, 031107 (2006); http://dx.doi.org/10.1063/1.2158519 (3 pages) | Cited 10 times

Online Publication Date: 19 January 2006

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Data are presented on the modal and lasing characteristics of a new type of vertical-cavity surface-emitting laser that uses an intracavity mesa to confine the optical mode, with the mesa also confining the quantum dot active region. The quantum dot active region is lithographically isolated within the intracavity mesa using etching and epitaxial regrowth to form an all-epitaxial microcavity light source. Cavity quality factors as high as 33 000 are measured, and ground state lasing is demonstrated with a single quantum dot active layer for temperatures up to ∼ 110 K.
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42.55.Sa Microcavity and microdisk lasers
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Highly directional stadium-shaped polymer microlasers

M. Lebental, J. S. Lauret, R. Hierle, and J. Zyss

Appl. Phys. Lett. 88, 031108 (2006); http://dx.doi.org/10.1063/1.2159099 (3 pages) | Cited 48 times

Online Publication Date: 19 January 2006

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The far-field emission of two-dimensional stadium-shaped microlasers is investigated. Stadium-shaped microcavities based on a laser dye embedded in a polymer matrix have been elaborated. Such stadium-shaped microresonators, made by lithography and reactive ion etching have displayed quality factors greater than 6000 and a high output power. The highly directional far-field pattern of the emitted beam (full width at half maximum ∼ 15°) reflects the symmetries of the stadium shape.
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42.60.By Design of specific laser systems
42.55.Mv Dye lasers
42.55.Sa Microcavity and microdisk lasers

Predictive aberration correction for multilayer optical data storage

Martin J. Booth, Michael Schwertner, Tony Wilson, Masaharu Nakano, Yoshimasa Kawata, Masahito Nakabayashi, and Sou Miyata

Appl. Phys. Lett. 88, 031109 (2006); http://dx.doi.org/10.1063/1.2166684 (3 pages) | Cited 8 times

Online Publication Date: 19 January 2006

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The recording of data in multiple layers, rather than a single layer, permits a significant increase in the capacity of optical data storage devices. However, focusing to the different layers introduces different amounts of depth-dependent aberrations. Variable aberration correction is therefore necessary to maintain diffraction-limited operation. We demonstrate the use of adaptive optics to predict and correct these aberrations for both the recording and read-out of such media.
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42.79.Vb Optical storage systems, optical disks
42.15.Fr Aberrations

Actively tuned and spatially trapped polaritons

R. B. Balili, D. W. Snoke, L. Pfeiffer, and K. West

Appl. Phys. Lett. 88, 031110 (2006); http://dx.doi.org/10.1063/1.2164431 (3 pages) | Cited 28 times

Online Publication Date: 19 January 2006

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We report active tuning of the polariton resonance of quantum well excitons in a semiconductor microcavity using applied stress. Starting with the quantum well exciton energy higher than the cavity photon mode, we use stress to reduce the exciton energy and bring it into resonance with the photon mode. At the point of zero detuning, line narrowing and strong increase of the photoluminescence are seen. By the same means, we create an in-plane harmonic potential for the polaritons, which allows trapping, potentially making possible Bose-Einstein condensation of polaritons analogous to trapped atoms. We demonstrate drift of the polaritons into this trap.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.21.Fg Quantum wells
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
78.55.Cr III-V semiconductors

Visible resonant modes in GaN-based photonic crystal membrane cavities

Cedrik Meier, Kevin Hennessy, Elaine D. Haberer, Rajat Sharma, Yong-Seok Choi, Kelly McGroddy, Stacia Keller, Steven P. DenBaars, Shuji Nakamura, and Evelyn L. Hu

Appl. Phys. Lett. 88, 031111 (2006); http://dx.doi.org/10.1063/1.2166680 (3 pages) | Cited 21 times

Online Publication Date: 20 January 2006

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Photonic crystal membrane cavities play a key role as building blocks in the realization of several applications, including quantum information and photonic circuits. Thus far, there has been no work on defect cavities with active layers emitting in the UV to green range of the spectrum based on the (Al,In,Ga)N material system. While this material system has great potential for a new generation of optoelectronic devices, there are several obstacles for the fabrication of GaN-based membrane cavities, including the absence of a conventional selective chemical wet etch. Here, we demonstrate the first fabrication of fully undercut GaN photonic crystal membranes containing an InGaN multiquantum well layer, fabricated using band-gap-selective photoelectrochemical etching. A postfabrication coating of Ta2O5 is used to tune the cavity modes into resonance with the quantum well emission, and the fabricated membranes exhibit resonant modes with Q = 300.
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78.30.−j
78.35.+c Brillouin and Rayleigh scattering; other light scattering
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
77.22.−d
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Thermal conductivity of Fe nanofluids depending on the cluster size of nanoparticles

K. S. Hong, Tae-Keun Hong, and Ho-Soon Yang

Appl. Phys. Lett. 88, 031901 (2006); http://dx.doi.org/10.1063/1.2166199 (3 pages) | Cited 16 times

Online Publication Date: 17 January 2006

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Nanofluids have been attractive for the last few years with the enormous potential to improve the efficiency of heat transfer fluids. This work focuses on the effect of the clustering of nanoparticles on the thermal conductivity of nanofluids. Large enhancement of the thermal conductivity is observed in Fe nanofluids sonicated with high powered pulses. The average size of the nanoclusters and thermal conductivity of sonicated nanofluids are measured as time passes after the sonication stopped. It is found from the variations of the nanocluster size and thermal conductivity that the reduction of the thermal conductivity of nanofluids is directly related to the agglomeration of nanoparticles. The thermal conductivity of Fe nanofluids increases nonlinearly as the volume fraction of nanoparticles increases. The nonlinearity is attributed to the rapid clustering of nanoparticles in condensed nanofluids. The thermal conductivities of Fe nanofluids with the three lowest concentrations are fitted to a linear function. The Fe nanofluids show a more rapid increase of the thermal conductivity than Cu nanofluids as the volume fraction of the nanoparticles increases.
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66.90.+r Other topics in nonelectronic transport properties of condensed matter (restricted to new topics in section 66)
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Failure mechanism of AlN nanocaps used to protect rare earth-implanted GaN during high temperature annealing

E. Nogales, R. W. Martin, K. P. O’Donnell, K. Lorenz, E. Alves, S. Ruffenach, and O. Briot

Appl. Phys. Lett. 88, 031902 (2006); http://dx.doi.org/10.1063/1.2162797 (3 pages) | Cited 7 times

Online Publication Date: 17 January 2006

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The structural properties of nanometric AlN caps, grown on GaN to prevent dissociation during high temperature annealing after Eu implantation, have been characterized by scanning electron microscopy and electron probe microanalysis. The caps provide good protection up to annealing temperatures of at least 1300 °C, but show localized failure in the form of irregularly shaped holes with a lateral size of 1–2 μm which extend through the cap into the GaN layer beneath. Compositional micrographs, obtained using wavelength dispersive x-ray analysis, suggest that these holes form when GaN dissociates and ejects through cracks already present in the as-grown AlN caps due to the large lattice mismatch between the two materials. Implantation damage enhances the formation of the holes during annealing. Simultaneous room temperature cathodoluminescence mapping showed that the Eu luminescence is reduced in N-poor regions. Hence, exposed GaN dissociates first by outdiffusion of nitrogen through AlN cracks, thereby opening a hole in the cap through which Ga subsequently evaporates.
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81.07.Bc Nanocrystalline materials
81.05.Ea III-V semiconductors
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials
61.72.uj III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing

Pressure-induced structural transitions in Tb-pyrochlore oxides

Ravhi S. Kumar, Andrew L. Cornelius, Malcolm F. Nicol, Kinson C. Kam, Anthony K. Cheetham, and Jason S. Gardner

Appl. Phys. Lett. 88, 031903 (2006); http://dx.doi.org/10.1063/1.2165212 (3 pages) | Cited 13 times

Online Publication Date: 17 January 2006

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The structure of Tb2Ti2O7, Tb2Sn2O7, and Tb2TiSnO7 were studied at high pressures (P<1 Mbar) using synchrotron radiation and angular dispersive x-ray diffraction. The cubic lattice was shown to distort into a monoclinic phase before exhibiting total structural disorder (amorphization) in all three samples. Our experiments demonstrate that partial replacement of Sn with Ti significantly enhances the bulk modulus and increases the structural stability (crystalline state) to much higher pressures. Furthermore, pressure induces anion before cation disorder during the order-disorder transition. These results are compared to radiation damage studies that show order-disorder transitions.
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62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity

Surface microstructure analysis of cubic boron nitride films by transmission electron microscopy

X. M. Meng, W. J. Zhang, C. Y. Chan, C. S. Lee, I. Bello, and S. T. Lee

Appl. Phys. Lett. 88, 031904 (2006); http://dx.doi.org/10.1063/1.2165288 (3 pages) | Cited 4 times

Online Publication Date: 17 January 2006

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A simple coating technique was introduced to preserve the surface structure of samples for transmission electron microscopy (TEM) characterization, and used to study boron nitride (BN) films. A gold film precoated on the surface of BN films served to protect the BN surface against ion damages during sample preparation, and to separate and distinguish the film surface structure from the TEM glue. The technique enabled the observation of detailed surface microstructures of cubic BN (cBN) films, which provided direct evidences for understanding cBN growth mechanisms. The TEM sample technique is expected to be generally applicable to other film systems, particularly those with an amorphous topmost layer.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Lp Transmission electron microscopy (TEM)
81.65.-b Surface treatments

Nickel-induced enhancement of photoluminescence from Si-rich silica films

Y. He, K. Ma, L. Bi, J. Y. Feng, and Z. J. Zhang

Appl. Phys. Lett. 88, 031905 (2006); http://dx.doi.org/10.1063/1.2165292 (3 pages)

Online Publication Date: 17 January 2006

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The effect of Ni on the near-infrared luminescence emitting from silicon nanocrystals embedded in SiO2 matrix has been investigated. According to the thermodynamics calculation, nickel can give additional driving force to the phase separation process. The photoluminescence intensity increases with the increasing annealing temperature because of the crystallization of amorphous silicon in SiOx films. The intensity of near-infrared emission of SiO1.56/Ni/Si is stronger by a factor of 5 than that of regular specimen after annealing at 1000 or 1100 °C due to the increase of the density of Si nanocrystals.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
64.75.-g Phase equilibria
65.40.G- Other thermodynamical quantities
78.55.-m Photoluminescence, properties and materials
61.72.Cc Kinetics of defect formation and annealing
64.70.K- Solid-solid transitions

Density determination of focused-electron-beam-induced deposits with simple cantilever-based method

I. Utke, V. Friedli, J. Michler, T. Bret, X. Multone, and P. Hoffmann

Appl. Phys. Lett. 88, 031906 (2006); http://dx.doi.org/10.1063/1.2158516 (3 pages) | Cited 19 times

Online Publication Date: 18 January 2006

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Freestanding deposits are grown on a silicon cantilever from a precursor gas by an electron induced process. Deposit mass determination is performed with an atomic force microscopy setup, where the cantilever resonance frequency shift, resulting from mechanical removal of the deposit, is measured. Deposits from hexafluoroacetylacetonato–Cu(I)–vinyltrimethylsilane show densities ranging from 2.05±0.45 to 3.75±0.55 g/cm3. Deposits from tetramethoxysilane have a constant density of (1.9±0.3) g/cm3. Densities of deposits from Co2(CO)8 and [RhCl(PF3)2]2 are linearly related to their composition. The ratio of impinging electrons per deposited atom, beam heating, and thermal stability of the precursor molecule determine the density and composition in focused-electron-beam-induced deposits.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
68.60.Dv Thermal stability; thermal effects

Modeling of band gap properties of GaInNP alloys lattice matched to GaAs

I. A. Buyanova, M. Izadifard, W. M. Chen, Y. G. Hong, and C. W. Tu

Appl. Phys. Lett. 88, 031907 (2006); http://dx.doi.org/10.1063/1.2164433 (3 pages) | Cited 8 times

Online Publication Date: 18 January 2006

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Compositional and temperature dependences of the band gap energies of GaInNP alloys, which are lattice matched to GaAs, are determined and modeled by a band anticrossing (BAC) interaction between the localized state of the isolated NP and extended host states. The BAC parameters are deduced as EN = 2.1±0.1 eV and CMN = 1.7±0.2 eV. The low value of the coupling parameter CMN implies weaker coupling of the N level with the host matrix, presumably due to short range ordering effects, similar to the case of GaInNAs alloys with a high In content. The obtained information is important for future modeling of the electronic structure of the alloys.
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71.20.Nr Semiconductor compounds

Metamaterial with randomized patterns for negative refraction of electromagnetic waves

H. Chen, L. Ran, D. Wang, J. Huangfu, Q. Jiang, and J. A. Kong

Appl. Phys. Lett. 88, 031908 (2006); http://dx.doi.org/10.1063/1.2165088 (3 pages) | Cited 14 times

Online Publication Date: 18 January 2006

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Artificial metamaterials made to date are all periodic in structure. Here we show that by randomizing contour patterns deposited lithographically on circuit board materials, a metamaterial characterized by a constitutive relation with negative constitutive parameters is produced in solid-state form. We clearly demonstrate the phenomenon of negative refraction to show that it is not produced by periodicity. This underlines the importance of using constitutive relations for media characterization in electromagnetic theory and suggests that metamaterials could be realized with composite materials or fabricated with various techniques by using versatile hosting materials.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Real-time monitoring of plasma oxidation dynamics of subnanometer Al2O3 barriers for magnetic tunnel junctions

C. G. C. H. M. Fabrie, K. Knechten, J. T. Kohlhepp, H. J. M. Swagten, B. Koopmans, and W. J. M. de Jonge

Appl. Phys. Lett. 88, 031909 (2006); http://dx.doi.org/10.1063/1.2166696 (3 pages)

Online Publication Date: 19 January 2006

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We show that over-oxidation of sub-nm thin Al2O3 barriers of magnetic tunnel junctions can be observed in real time using in situ differential ellipsometry measurements. The change in ellipsometry signal of Al layers grown on CoFe films is proportional to the amount of oxidized metallic material. As a result, the derivative of this signal is a direct measure of the oxidation rate. Further analysis of this oxidation rate allows us to determine the onset of the CoFe oxidation. We found the onset to be proportional to the deposited Al layer thickness. The amount of CoO determined from in situ x-ray photoelectron spectroscopy data on identical samples was found to be proportional to that obtained from ellipsometry.
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81.65.Mq Oxidation
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
79.60.Jv Interfaces; heterostructures; nanostructures

Ion scattering and electron spectroscopy of the chemical species at a HF-prepared Si(211) surface

M. Jaime-Vasquez, M. Martinka, M. Groenert, and J. Dinan

Appl. Phys. Lett. 88, 031910 (2006); http://dx.doi.org/10.1063/1.2166682 (3 pages) | Cited 2 times

Online Publication Date: 19 January 2006

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The species and the nature of their chemical bonds at the surface of a hydrogen-terminated Si(211) wafer were characterized using temperature desorption spectroscopy, ion scattering spectroscopy, and electron spectroscopy. The surface region is dominated by monohydride species with dihydrides present in small amounts. Fluorine is distributed across the top layer as largely a physisorbed species to the Si substrate. Low-energy math ions remove the H and F species with only minimal damage to the underlying region.
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68.43.Vx Thermal desorption
61.80.Jh Ion radiation effects
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

ZnO p-n junction light-emitting diodes fabricated on sapphire substrates

S. J. Jiao, Z. Z. Zhang, Y. M. Lu, D. Z. Shen, B. Yao, J. Y. Zhang, B. H. Li, D. X. Zhao, X. W. Fan, and Z. K. Tang

Appl. Phys. Lett. 88, 031911 (2006); http://dx.doi.org/10.1063/1.2166686 (3 pages) | Cited 120 times

Online Publication Date: 19 January 2006

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A ZnO p-n junction light-emitting diode (LED) was fabricated on a-plane Al2O3 substrate by plasma-assisted molecular-beam epitaxy. NO plasma activated by a radio frequency atomic source was used to grow the p-type ZnO layer of the LED. The current-voltage measurements at low temperatures showed a typical diode characteristic with a threshold voltage of about 4.0 V under forward bias. With increasing temperature, the rectification characteristic was degraded gradually, and faded away at room temperature. Electroluminescence band of the ZnO p-n junction LED was located at the blue-violet region and was weakened significantly with increase of temperature. This thermal quenching of the electroluminescence was attributed to the degradation of the diode characteristic with temperature.
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85.60.Jb Light-emitting devices
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Generation of misfit dislocations and stacking faults in supercritical thickness strained-Si/SiGe heterostructures

Y. Kimura, N. Sugii, S. Kimura, K. Inui, and W. Hirasawa

Appl. Phys. Lett. 88, 031912 (2006); http://dx.doi.org/10.1063/1.2167391 (3 pages) | Cited 13 times

Online Publication Date: 19 January 2006

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Defects in the supercritical thickness strained-Si layer grown on a fully relaxed SiGe buffer layer were investigated by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The AFM observation of chemically etched surfaces showed that etch pits having a crosshatch pattern due to misfit dislocations decrease and segments and deep valley profiles increase with an increase in the strain energy of the Si. We found that the segment corresponds to an extended dislocation, of which a 30° partial is in the strained-Si layer and a 90° partial is in the SiGe layer, and the deep valley corresponds to a stacking fault found by a high-resolution TEM observation. A model of the generation of the stacking fault related to development of the misfit dislocation is also discussed here.
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81.05.Cy Elemental semiconductors
81.05.Hd Other semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Nn Stacking faults and other planar or extended defects
68.55.-a Thin film structure and morphology

First-principles calculations of structural and mechanical properties of Cu6Sn5

N. T. S. Lee, V. B. C. Tan, and K. M. Lim

Appl. Phys. Lett. 88, 031913 (2006); http://dx.doi.org/10.1063/1.2165280 (3 pages) | Cited 23 times

Online Publication Date: 19 January 2006

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The elastic constants of polycrystalline Cu6Sn5—an intermetallic in lead-free alternatives of several material systems—are presented. The results are obtained by applying: (i) Reported crystallographic structure of monoclinic single crystal Cu6Sn5, (ii) structure optimization and determination of single crystal elastic constants from first principle calculations, and (iii) limit analysis of polycrystal stiffness based on single crystal properties. The agreement between the calculated Young’s modulus (120 GPa) and those from nanoindentation experiments (112–125 GPa), and the tight bounds on the predicted polycrystal values give a measure of confidence in other calculated properties for which experimental data are unavailable.
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61.66.Dk Alloys
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.D- Elasticity
62.20.M- Structural failure of materials
62.20.Qp Friction, tribology, and hardness

Elastic properties of MFe3N (M = Ni, Pd, Pt) studied by ab initio calculations

Denis Music and Jochen M. Schneider

Appl. Phys. Lett. 88, 031914 (2006); http://dx.doi.org/10.1063/1.2165285 (3 pages) | Cited 37 times

Online Publication Date: 19 January 2006

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Using ab initio calculations, we have studied the correlation between the electronic structure and elastic properties of MFe3N phases (M = Ni, Pd, Pt). These ternary nitrides possess a bulk-modulus-to-C44 ratio from 2.3 to 2.9, a rather unusual ratio for nitrides. This may be understood based on the electronic structure: Predominantly covalent-ionic Fe–N layers are interleaved with predominantly metallic Fe–M layers. We propose that the unusually large bulk-modulus-to-C44 ratio is a consequence of weak coupling between the Fe–N and Fe–M layers (giving rise to a low C44) as well as strong coupling within Fe–N layers (giving rise to a large bulk modulus).
Show PACS
81.05.-t Specific materials: fabrication, treatment, testing, and analysis
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
71.15.-m Methods of electronic structure calculations
71.20.Ps Other inorganic compounds
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