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21 Sep 2009

Volume 95, Issue 12, Articles (12xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 95, 121104 (2009); http://dx.doi.org/10.1063/1.3231448 (3 pages)

E. H. Khoo, I. Ahmed, and E. P. Li
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Experimental measurement of negative index in an all-dielectric metamaterial

T. Lepetit, É. Akmansoy, and J.-P. Ganne

Appl. Phys. Lett. 95, 121101 (2009); http://dx.doi.org/10.1063/1.3232222 (3 pages) | Cited 3 times

Online Publication Date: 21 September 2009

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We designed and fabricated an all-dielectric metamaterial which exhibits negative index of refraction. This metamaterial consists of one layer made up of two sets of high permittivity resonators. We experimentally showed that this metamaterial exhibits resonant effective permeability and permittivity issued from the first two modes of Mie resonances, respectively, and that matching both these parameters results in negative effective index.
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42.70.-a Optical materials
42.25.Fx Diffraction and scattering
42.25.-p Wave optics

Relaxation and emission of Bragg-mode and cavity-mode polaritons in a ZnO microcavity at room temperature

S. Faure, C. Brimont, T. Guillet, T. Bretagnon, B. Gil, F. Médard, D. Lagarde, P. Disseix, J. Leymarie, J. Zúñiga-Pérez, M. Leroux, E. Frayssinet, J. C. Moreno, F. Semond, and S. Bouchoule

Appl. Phys. Lett. 95, 121102 (2009); http://dx.doi.org/10.1063/1.3232228 (3 pages) | Cited 10 times

Online Publication Date: 21 September 2009

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The strong coupling regime in a ZnO microcavity is investigated through room temperature photoluminescence and reflectivity experiments. The simultaneous strong coupling of excitons to the cavity mode and the first Bragg mode is demonstrated at room temperature. The polariton relaxation is followed as a function of the excitation density, showing a nonthermal polariton distribution. A relaxation bottleneck is evidenced in the Bragg-mode polariton branch. It is partly broken under strong excitation density, so that the emission from this branch dominates the one from cavity-mode polaritons.
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71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena

Transmission interference tuned by an external static magnetic field in a two-slit structure

Bin Hu, Ben-Yuan Gu, Yan Zhang, and Ming Liu

Appl. Phys. Lett. 95, 121103 (2009); http://dx.doi.org/10.1063/1.3232227 (3 pages) | Cited 1 time

Online Publication Date: 21 September 2009

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We present a near-field analysis of transmitted field interference tuned by an external static magnetic field on an n-doped semiconductor film drilled by two slits at terahertz frequency. It is found that the peak magnetic field intensity of the interference pattern between the two slits can be strengthened twice as against that of zero external static magnetic field. The physical origin comes from the interaction between surface plasmon polaritons (SPPs) and radiative evanescent field components launched by each slit on the transmitted surface, and also from the considerable alteration of the SPPs, caused by the external static magnetic field.
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78.66.-w Optical properties of specific thin films
78.70.Gq Microwave and radio-frequency interactions
77.22.Ch Permittivity (dielectric function)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
68.55.ag Semiconductors

Enhancement of light energy extraction from elliptical microcavity using external magnetic field for switching applications

E. H. Khoo, I. Ahmed, and E. P. Li

Appl. Phys. Lett. 95, 121104 (2009); http://dx.doi.org/10.1063/1.3231448 (3 pages) | Cited 2 times

Online Publication Date: 21 September 2009

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In this letter, the extraction efficiency of light energy from an elliptically shaped microcavity laser is enhanced with external magnetic field. The magnetic field causes electrons to accumulate on the minor arc edge of the elliptical microcavity due to Lorentz force. As a result, the field amplitude at the minor arc edge is higher, and this improves light energy tunneling mechanism from the edge. The extraction efficiency from the microcavity increases by more than 30% after the application of magnetic field. Alternating the direction of the magnetic field allows the elliptical microcavity to function as a switching device.
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42.55.Sa Microcavity and microdisk lasers
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.55.Px Semiconductor lasers; laser diodes

Metallic nanoparticles as intermediate reflectors in tandem solar cells

Stephan Fahr, Carsten Rockstuhl, and Falk Lederer

Appl. Phys. Lett. 95, 121105 (2009); http://dx.doi.org/10.1063/1.3232230 (3 pages) | Cited 17 times

Online Publication Date: 22 September 2009

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Tandem thin film solar cells made of amorphous and microcrystalline silicon offer the potential for high conversion efficiencies at low costs. However, their finite thickness imposed by intrinsic materials properties hinders the complete absorption of light and requires smart photon management. We reveal a genuine strategy to use metallic nanoparticles, appropriately tailored to provide a spectrally selective reflection, as an intermediate reflector. It enhances foremost light absorption in the top cell. We show that the current density for an optimized cell can be 1.16 times larger when compared to a cell without a spectrally selective intermediate reflector.
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84.60.Jt Photoelectric conversion
68.55.-a Thin film structure and morphology
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.07.Bc Nanocrystalline materials

Enhanced absorption of metals over ultrabroad electromagnetic spectrum

A. Y. Vorobyev, A. N. Topkov, O. V. Gurin, V. A. Svich, and Chunlei Guo

Appl. Phys. Lett. 95, 121106 (2009); http://dx.doi.org/10.1063/1.3227668 (3 pages) | Cited 10 times

Online Publication Date: 22 September 2009

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Metals are usually highly reflective for electromagnetic waves, especially at far-infrared and terahertz frequencies. Using a femtosecond laser structuring technique, near-perfectly reflective metals are transformed to highly absorptive over an ultrabroad electromagnetic spectrum, ranging from ultraviolet to terahertz. Absorptance of the processed metal is directly measured in the terahertz region using a calorimetry technique, and the measurements show that absorptance of the processed metal is enhanced by more than thirty times over its intrinsic value.
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78.70.Gq Microwave and radio-frequency interactions
78.47.-p Spectroscopy of solid state dynamics
78.30.Er Solid metals and alloys
78.40.Kc Metals, semimetals, and alloys

Efficiency retention at high current injection levels in m-plane InGaN light emitting diodes

X. Li, X. Ni, J. Lee, M. Wu, Ü. Özgür, H. Morkoç, T. Paskova, G. Mulholland, and K. R. Evans

Appl. Phys. Lett. 95, 121107 (2009); http://dx.doi.org/10.1063/1.3236538 (3 pages) | Cited 20 times

Online Publication Date: 22 September 2009

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We investigated the internal quantum efficiency (IQE) and the relative external quantum efficiency (EQE) of m-plane InGaN light emitting diodes (LEDs) grown on m-plane freestanding GaN emitting at ∼ 400 nm for current densities up to 2500 A/cm2. IQE values extracted from intensity and temperature dependent photoluminescence measurements were consistently higher, by some 30%, for the m-plane LEDs than for reference c-plane LEDs having the same structure, e.g., 80% versus 60% at an injected steady-state carrier concentration of 1.2×1018 cm−3. With increasing current injection up to 2500 A/cm2, the maximum EQE is nearly retained in m-plane LEDs, whereas c-plane LEDs exhibit approximately 25% droop. The negligible droop in m-plane LEDs is consistent with the reported enhanced hole carrier concentration and light holes in m-plane orientation, thereby enhanced hole transport throughout the active region, and lack of polarization induced field. A high quantum efficiency and in particular its retention at high injection levels bode well for m-plane LEDs as candidates for general lighting applications.
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85.60.Jb Light-emitting devices
72.20.-i Conductivity phenomena in semiconductors and insulators
78.55.Cr III-V semiconductors

Nanoscale optical tomography using volume-scanning near-field microscopy

Jin Sun, John C. Schotland, Rainer Hillenbrand, and P. Scott Carney

Appl. Phys. Lett. 95, 121108 (2009); http://dx.doi.org/10.1063/1.3224177 (3 pages) | Cited 7 times

Online Publication Date: 23 September 2009

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The relationship between sample structure and data in volume-scanning backscattering mode near-field optical microscopy is investigated. It is shown that the three-dimensional structure of a dielectric sample is encoded in the phase and amplitude of the scattered field and that an approximate reconstruction of the sample structure may be obtained.
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42.30.Wb Image reconstruction; tomography

Mach–Zehnder–Fano interferometer

Andrey E. Miroshnichenko and Yuri S. Kivshar

Appl. Phys. Lett. 95, 121109 (2009); http://dx.doi.org/10.1063/1.3232224 (3 pages) | Cited 7 times

Online Publication Date: 24 September 2009

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We introduce a concept of the Mach–Zehnder–Fano interferometer by inserting a cavity exhibiting Fano resonance into a conventional interferometer. By employing the scattering-matrix approach, we demonstrate that the transmission becomes sensitive to a position of the cavity such that an asymmetric structure exhibits a series of narrow resonances with almost perfect reflection. We discuss how to implement this novel geometry in two-dimensional photonic crystals and use direct numerical simulations to demonstrate novel regimes of the resonant transmission and reflection.
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42.70.Qs Photonic bandgap materials
07.60.Ly Interferometers
02.10.Yn Matrix theory

The effect of absorber doping on electrical and optical properties of nBn based type-II InAs/GaSb strained layer superlattice infrared detectors

Stephen Myers, Elena Plis, Arezou Khoshakhlagh, Ha Sul Kim, Yagya Sharma, Ralph Dawson, Sanjay Krishna, and Aaron Gin

Appl. Phys. Lett. 95, 121110 (2009); http://dx.doi.org/10.1063/1.3230069 (3 pages) | Cited 2 times

Online Publication Date: 24 September 2009

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We have investigated the electrical and optical properties of a nBn based InAs/GaSb strained layer superlattice detector as a function of absorber region background carrier concentration. Temperature dependent dark current, responsivity, and detectivity were measured. The device with a nonintentionally doped absorption region demonstrated the lowest dark current density with a specific detectivity at zero bias equal to 1.2×1011 cm Hz1/2/W at 77 K. This value decreased to 6×1010 cm Hz1/2/W at 150 K. This contrasts significantly with p-i-n diodes, in which the D∗ decreases by over two orders of magnitude from 77 to 150 K, making nBn devices promising for higher operating temperatures.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.30.Kk Junction diodes
61.72.uj III-V and II-VI semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
73.63.-b Electronic transport in nanoscale materials and structures
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

Strain effects in group-III nitrides: Deformation potentials for AlN, GaN, and InN

Qimin Yan, Patrick Rinke, Matthias Scheffler, and Chris G. Van de Walle

Appl. Phys. Lett. 95, 121111 (2009); http://dx.doi.org/10.1063/1.3236533 (3 pages) | Cited 37 times

Online Publication Date: 24 September 2009

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A systematic density functional theory study of strain effects on the electronic band structure of the group-III nitrides (AlN, GaN, and InN) is presented. To overcome the deficiencies of the local-density and generalized gradient approximations the Heyd–Scuseria–Ernzerhof (HSE) hybrid functional is used. Cross checks for GaN demonstrate good agreement between HSE and exact-exchange based G0W0 calculations. We observe a pronounced nonlinear dependence of band-energy differences on strain. For realistic strain conditions in the linear regime around the experimental equilibrium volume a consistent and complete set of deformation potentials is derived.
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71.20.Nr Semiconductor compounds
81.05.Ea III-V semiconductors
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Photocarrier recombination dynamics in highly excited SrTiO3 studied by transient absorption and photoluminescence spectroscopy

Yasuhiro Yamada, Hideki Yasuda, Takeshi Tayagaki, and Yoshihiko Kanemitsu

Appl. Phys. Lett. 95, 121112 (2009); http://dx.doi.org/10.1063/1.3238269 (3 pages) | Cited 9 times

Online Publication Date: 25 September 2009

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We studied photocarrier recombination processes in highly excited SrTiO3 crystals using pump-probe transient absorption (TA) and photoluminescence (PL) spectroscopy at room temperature. TA signals of nondoped SrTiO3 crystals clearly appear in the visible and infrared spectral region under intense interband photoexcitation, and TA spectra show Drude-like photon-energy dependence. Both TA and PL decay curves are well explained by the same simple rate equation including three-body Auger recombination and single-carrier trapping.
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72.40.+w Photoconduction and photovoltaic effects
72.80.Sk Insulators
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.40.Ha Other nonmetallic inorganics
78.30.Hv Other nonmetallic inorganics
78.55.Hx Other solid inorganic materials
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Branched carbon treelike structures grown in direct current plasmas

F. Ding, X. D. Zhu, R. J. Zhan, T. L. Ni, B. Ke, H. Y. Zhou, M. D. Chen, and X. H. Wen

Appl. Phys. Lett. 95, 121501 (2009); http://dx.doi.org/10.1063/1.3232229 (3 pages) | Cited 3 times

Online Publication Date: 21 September 2009

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The growth of centimeter-scale treelike carbon structures in a hydrocarbon direct current (dc) plasma without the help of catalyst particles is reported. Starting from the edge of the anode, the carbon trees have a tendency to grow toward the cathode along the direction of the electric field. It is found that the trees exhibit graphitelike characteristics, or have a diamond body with a graphitelike core depending on the formation conditions. A growth model is proposed for the unusual growths, where powders formed in the dc plasma play a crucial role.
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52.77.-j Plasma applications
52.80.-s Electric discharges
52.77.Dq Plasma-based ion implantation and deposition

High average power second harmonic generation in air

Martynas Beresna, Peter G. Kazansky, Yuri Svirko, Martynas Barkauskas, and Romas Danielius

Appl. Phys. Lett. 95, 121502 (2009); http://dx.doi.org/10.1063/1.3232235 (3 pages) | Cited 4 times

Online Publication Date: 22 September 2009

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We demonstrate second harmonic vortex generation in atmospheric pressure air using tightly focused femtosecond laser beam. The circularly polarized ring-shaped beam of the second harmonic is generated in the air by fundamental beam of the same circular polarization, while the linear polarized beam produces two-lobe beam at the second harmonic frequency. The achieved normalized conversion efficiency and average second harmonic power are two orders of magnitude higher compared to those previously reported and can be increased up to 20 times by external gas flow. We demonstrate that the frequency doubling originates from the gradient of photoexcited free electrons created by pondermotive force.
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52.30.-q Plasma dynamics and flow
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Selecting a single orientation for millimeter sized graphene sheets

R. van Gastel, A. T. N’Diaye, D. Wall, J. Coraux, C. Busse, N. M. Buckanie, F.-J. Meyer zu Heringdorf, M. Horn von Hoegen, T. Michely, and B. Poelsema

Appl. Phys. Lett. 95, 121901 (2009); http://dx.doi.org/10.1063/1.3225554 (3 pages) | Cited 15 times

Online Publication Date: 21 September 2009

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We have used low energy electron microscopy and photo emission electron microscopy to study and improve the quality of graphene films grown on Ir(111) using chemical vapor deposition (CVD). CVD at elevated temperature already yields graphene sheets that are uniform and of monatomic thickness. Besides domains that are aligned with respect to the substrate, other rotational variants grow. Cyclic growth exploiting the faster growth and etch rates of the rotational variants, yields films that are 99% composed of aligned domains. Precovering the substrate with a high density of graphene nuclei prior to CVD yields pure films of aligned domains extending over millimeters. Such films can be used to prepare cluster-graphene hybrid materials for catalysis or nanomagnetism and can potentially be combined with lift-off techniques to yield high-quality, graphene based, electronic devices.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.Cf Surface cleaning, etching, patterning
68.55.A- Nucleation and growth
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
81.05.ub Fullerenes and related materials

Stress influence on band-edge luminescence properties of 4H-AlN

Y. C. Cheng, X. L. Wu, S. H. Li, and Paul K. Chu

Appl. Phys. Lett. 95, 121902 (2009); http://dx.doi.org/10.1063/1.3232218 (3 pages)

Online Publication Date: 21 September 2009

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The band-edge luminescence properties of 4H-AlN under biaxial and uniaxial stress are studied using the first-principle method. In equilibrium, excitons B and C have energies 92 and 14 meV lower than exciton A, respectively. When the uniaxial tensile strain exceeds ∼ 0.95%, the top valence band is the B exciton state. Its band-edge emission is no longer prohibited and changes to E⊥c. The shift in the A exciton energy is similar to that of 2H-AlN under stress of −5 to 5 GPa. When the compressive biaxial strain is larger than 5 GPa, the band structure of 4H-AlN becomes indirect.
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78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
71.35.-y Excitons and related phenomena
71.20.Nr Semiconductor compounds
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.15.-m Methods of electronic structure calculations
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Time-resolved photoluminescence analysis of two-peak emission behavior in Sr2Si5N8:Eu2+

Kee-Sun Sohn, Sangjun Lee, Rong-Jun Xie, and Naoto Hirosaki

Appl. Phys. Lett. 95, 121903 (2009); http://dx.doi.org/10.1063/1.3233972 (3 pages) | Cited 13 times

Online Publication Date: 21 September 2009

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Sr2Si5N8:Eu2+, one of the most recently developed phosphors for use in white light emitting diodes, exhibits a two-peak emission. Namely, the emission band of Sr2Si5N8:Eu2+ is deconvoluted into two Gaussian peaks irrespective of the Eu2+ concentration. We examined the two-peak emission of Sr2Si5N8:Eu2+ by analyzing the time-resolved photoluminescence spectra. We revealed that the two-peak emission was closely associated with the energy transfer taking place between Eu2+ activators located at two different crystallographic sites in the Sr2Si5N8 structure. The experimental results coincided well with the rate equation model involving the crystallographic information of the host.
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78.55.Hx Other solid inorganic materials
61.72.up Other materials
78.47.D- Time resolved spectroscopy (>1 psec)
78.47.jd Time resolved luminescence
85.60.Jb Light-emitting devices

Lightweight sodium alanate thin films grown by reactive sputtering

M. Filippi, J. H. Rector, R. Gremaud, M. J. van Setten, and B. Dam

Appl. Phys. Lett. 95, 121904 (2009); http://dx.doi.org/10.1063/1.3236525 (3 pages) | Cited 3 times

Online Publication Date: 21 September 2009

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We report the preparation of sodium alanate, a promising hydrogen storage material, in a thin film form using cosputtering in a reactive atmosphere of atomic hydrogen. We study the phase formation and distribution, and the hydrogen desorption, with a combination of optical and infrared transmission spectroscopy. We show that the hydrogen desorption, the phase segregation, and the role of the dopants in these complex metal hydrides can be monitored with optical measurements. This result shows that a thin film approach can be used for a model study of technologically relevant lightweight metal hydrides.
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81.15.Cd Deposition by sputtering
68.55.aj Insulators
84.60.-h Direct energy conversion and storage
68.43.Nr Desorption kinetics
81.05.-t Specific materials: fabrication, treatment, testing, and analysis
64.75.St Phase separation and segregation in thin films
78.66.Nk Insulators
78.30.Hv Other nonmetallic inorganics

The strong influence of heat losses on the accurate measurement of thermal diffusivity using lock-in thermography

Agustín Salazar, Arantza Mendioroz, and Raquel Fuente

Appl. Phys. Lett. 95, 121905 (2009); http://dx.doi.org/10.1063/1.3236782 (3 pages) | Cited 3 times

Online Publication Date: 23 September 2009

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In modulated photothermal experiments the lateral thermal diffusivity can be obtained from the slope of the linear relation between the phase of the surface temperature and the distance to the heating spot. However, this slope is greatly affected by heat losses so that the measured thermal diffusivity is overestimated, especially for thin samples of poor thermal conducting materials. In this paper we definitely identify the physical mechanism responsible for the overestimation of the diffusivity as heat conduction to the surrounding gas. Accurate measurements of the thermal diffusivity using the “slope method” have been obtained by keeping the sample in vacuum.
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07.20.-n Thermal instruments and apparatus
07.60.Dq Photometers, radiometers, and colorimeters
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Study of the free energy of the La1−xCaxMnO3 manganites based on the temperature dependence of the crystal cell volume

G. D. Tang, S. P. Liu, X. Zhao, Y. G. Zhang, D. H. Ji, Y. F. Li, W. H. Qi, W. Chen, and D. L. Hou

Appl. Phys. Lett. 95, 121906 (2009); http://dx.doi.org/10.1063/1.3233934 (3 pages) | Cited 4 times

Online Publication Date: 23 September 2009

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A study of the free energy of the perovskite manganites was performed by fitting experimental results for the temperature dependence of the crystal cell volume using a detailed semiclassical model of the free energy. The fitted results coincide with the experimental results for the samples La1−xCaxMnO3 (x = 0.2, 0.25, 0.3, and 0.5). The free energy includes the energy corresponding to thermal vibration of the crystal lattice, the ionic cohesive energy, and additional energies produced by electrical carriers from the double exchange mechanism and the thermal activation of small polarons.
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63.20.-e Phonons in crystal lattices
65.40.G- Other thermodynamical quantities
75.50.Dd Nonmetallic ferromagnetic materials
72.80.Sk Insulators
72.20.Fr Low-field transport and mobility; piezoresistance
61.50.Lt Crystal binding; cohesive energy

In-depth resolved Raman scattering analysis of secondary phases in Cu-poor CuInSe2 based thin films

X. Fontané, V. Izquierdo-Roca, L. Calvo-Barrio, J. Álvarez-Garcia, A. Pérez-Rodríguez, J. R. Morante, and W. Witte

Appl. Phys. Lett. 95, 121907 (2009); http://dx.doi.org/10.1063/1.3236770 (3 pages) | Cited 6 times

Online Publication Date: 24 September 2009

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Raman scattering analysis of Cu-poor CuInSe2 layers shows the coexistence of the ordered vacancy compound (OVC), CuAu–CuInSe2 and chalcopyrite (CH) CuInSe2 phases as function of the Cu/In content ratio x. In-depth resolved measurements from layers with x ≤ 0.57 show a strong inhibition in the relative intensity of the CH-CuInSe2 mode at the back region. Micro-Raman spectra directly measured at different regions from the layers with 0.66 ≤ x ≤ 0.71 also suggest a higher content of the OVC phase at this back region. These data suggest an enhancement in the formation of OVC at this region in the layers.
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78.30.Hv Other nonmetallic inorganics
78.66.Li Other semiconductors
81.05.Hd Other semiconductors

Orientation control and self-assembled nanopyramid structure of LaFeO3 films epitaxially grown on SrTiO3(001) substrates

Lei Bi, Hyun-Suk Kim, Gerald F. Dionne, C. A. Ross, Hanjong Paik, and Yun Chang Park

Appl. Phys. Lett. 95, 121908 (2009); http://dx.doi.org/10.1063/1.3222912 (3 pages) | Cited 2 times

Online Publication Date: 24 September 2009

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Epitaxial films of LaFeO3 (LFO) were grown on SrTiO3(001) (STO) substrates using pulsed laser deposition. Two epitaxial orientations were observed: α where LFO(110)∥STO(100) and β where LFO(001)∥STO(100). By controlling the deposition conditions, LaFeO3 films could be grown with just the α orientation or with simultaneous α and β orientations in which the film consisted of a self-assembled array of nanoscale β pyramids embedded in a matrix of α. The microstructure and growth mechanism of the films and their exchange-bias with a Co overlayer are discussed.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Cc Other ferromagnetic metals and alloys
75.50.Ee Antiferromagnetics
81.15.Fg Pulsed laser ablation deposition
81.16.Dn Self-assembly

A superlens for the deep ultraviolet

Alina Schilling, Joerg Schilling, Carsten Reinhardt, and Boris Chichkov

Appl. Phys. Lett. 95, 121909 (2009); http://dx.doi.org/10.1063/1.3226101 (3 pages) | Cited 4 times

Online Publication Date: 24 September 2009

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A superlens based on a single aluminum layer operating at deep ultraviolet (UV) wavelengths is investigated both, theoretically and experimentally. Using a wavelength of 157 nm double slits with a center-to-center separation of only 70 nm were experimentally resolved and simulations indicate a possible resolution down to 29 nm with experimentally feasible arrangements. The results demonstrate the significance of aluminum as plasmonic material for the deep UV.
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68.55.-a Thin film structure and morphology
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
42.79.Bh Lenses, prisms and mirrors
42.70.-a Optical materials

Nitridating r-plane sapphire to improve crystal qualities and surface morphologies of a-plane GaN grown by metalorganic vapor phase epitaxy

Bei Ma, Weiguo Hu, Hideto Miyake, and Kazumasa Hiramatsu

Appl. Phys. Lett. 95, 121910 (2009); http://dx.doi.org/10.1063/1.3237164 (3 pages) | Cited 5 times

Online Publication Date: 25 September 2009

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Effects of the nitridation of the r-plane sapphire were investigated on the growth of a-plane GaN. Surface morphology and crystal quality were very sensitive to the nitridated time. A high quality a-plane GaN with a pit free-surface was obtained with nitridation at 1100 °C for 5 min, compared with under- or overnitridation. Nitridated layer were identified as AlN grains with 〈11math0〉 preferred orientation, which acted as the nuclearation layers for a-plane GaN growth. Moreover, the qualities improvements were attributed to enhancing grain uniformity and size with 5 min nitridation.
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81.10.Bk Growth from vapor
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.47.Fg Semiconductor surfaces
68.35.bg Semiconductors
61.66.Fn Inorganic compounds

Structural relaxation and crystallization of NiTi thin film metallic glasses

Xu Huang and A. G. Ramirez

Appl. Phys. Lett. 95, 121911 (2009); http://dx.doi.org/10.1063/1.3236544 (3 pages) | Cited 6 times

Online Publication Date: 25 September 2009

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This letter demonstrates the effects of structural relaxation on the crystallization and phase transformation behavior of NiTi thin films. Heat treatments below the glass transformation temperature produce films with a greater hardness than as-deposited films. The reduction in free volume occurring during film relaxation plays a role. Using scanning electron microscopy, structural relaxation was found to decrease the overall crystallization time and increase the nucleation rate, thus modifying the resulting microstructures. Structural relaxation had little effect on the phase transformation temperatures of fully crystallized films, but slightly increased the resulting actuation force during transformation.
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61.43.Fs Glasses
68.55.-a Thin film structure and morphology
62.20.Qp Friction, tribology, and hardness
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
64.70.kj Glasses
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
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