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21 Mar 2005

Volume 86, Issue 12, Articles (12xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 86, 123102 (2005); http://dx.doi.org/10.1063/1.1885187 (3 pages)

Jong H. Na, Robert A. Taylor, James H. Rice, James W. Robinson, Kwan H. Lee, Young S. Park, Chang M. Park, and Tae W. Kang
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White polymeric light-emitting diode based on a fluorene polymer∕Ir complex blend system

Hameed A. Al Attar, Andy P. Monkman, Mustafa Tavasli, Sylvia Bettington, and Martin R. Bryce

Appl. Phys. Lett. 86, 121101 (2005); http://dx.doi.org/10.1063/1.1873046 (3 pages) | Cited 77 times

Online Publication Date: 14 March 2005

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Efficient white-polymeric light-emitting diodes (PLED) were fabricated as a single active layer containing blue-emitting poly(9,9-bis(2-ethylhexyl)fluorene-2,7-diyl) endcapped with bis(4-methylphenyl)phenylamine; (PF2∕6am4), and yellow-orange-emitting iridium [tri-fluorenyl] pyridine complex [Ir(Fl3Py)3]. The fluorene-like ligands in the blended device prevent phase segregation and also enhance energy transfer from the polymer host to the guest due to efficient overlap of wave function (Dexter process) and host singlet emission and guest absorption bands (Förster process) which reduces the loading level required to produce white emission. The two emitted colors complement each other and doping levels of 2%–3% produce white emission. Above a certain current density, depending on the doping level, the device Commission Internationale de L’Eclairage (CIE) coordinates become bias independent and a stabilized white emission can be obtained. A white-emitting PLED (coordinates 0.348, 0.367) of peak external quantum efficiency of 2.8%, and luminance of 16000 cd/m2 at applied voltage of 5 V (i.e., 4.57 cd/A) was obtained.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
61.72.S- Impurities in crystals

Ultrafast all-optical switching in two-dimensional organic photonic crystal

Xiaoyong Hu, Yuanhao Liu, Jie Tian, Bingying Cheng, and Daozhong Zhang

Appl. Phys. Lett. 86, 121102 (2005); http://dx.doi.org/10.1063/1.1884254 (3 pages) | Cited 27 times

Online Publication Date: 14 March 2005

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An all-optical switching with high switch efficiency is realized based on two-dimensional nonlinear photonic crystal made of polystyrene. The prism-film coupling method is used to couple energy of probe light into photonic crystal waveguide. High transmittance contrast of more than 60% is realized for the probe light. Time response of the optical switching is around l0 ps. The dynamical shifts of photonic gap induced by pump light are measured and analyzed in detail. The photonic gap shifts l0 nm under the excitation of 16.7 GW/cm2 pump intensity, which is in agreement with the theoretical predictions.
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42.70.Qs Photonic bandgap materials
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.65.Wi Nonlinear waveguides
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.82.Et Waveguides, couplers, and arrays
42.79.Bh Lenses, prisms and mirrors

Creating all-angle negative refraction by using insertion

Xiangdong Zhang and Lie-Ming Li

Appl. Phys. Lett. 86, 121103 (2005); http://dx.doi.org/10.1063/1.1887838 (3 pages) | Cited 22 times

Online Publication Date: 14 March 2005

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The all-angle negative refraction (AANR) is generally very important to design a microsuperlens. However, it is usually absent from some two-dimensional (2D) photonic crystals (PCs). In this letter, we present a method to create and enlarge the AANR region by using insertion. For some 2D dielectric PC systems without the AANR, the AANR region can be created by adding a fraction of a metallic component to the center of each dielectric cylinder. At the same time, the AANR region can be enlarged by adjusting the size of the metal cylinder. To illustrate this phenomenon, the microsuperlens is designed and numerically demonstrated.
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42.79.Bh Lenses, prisms and mirrors
42.70.Qs Photonic bandgap materials

Simple scheme for rapid three-dimensional orientation determination of the emission dipole of single molecules

Johannes Hohlbein and Christian G. Hübner

Appl. Phys. Lett. 86, 121104 (2005); http://dx.doi.org/10.1063/1.1888040 (3 pages) | Cited 13 times

Online Publication Date: 14 March 2005

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One of the unique features of single molecule absorption and emission is their anisotropy due to the well-defined transition dipole(s) for both processes allowing the determination of the molecule’s orientation. While polarization-resolved techniques are usually capable of detecting only a projection of the transition dipole, several methods have been proposed in order to determine the full three-dimensional orientation. Here, we report on a detection scheme that allows for a shot-noise limited determination of the emission dipole orientation utilizing an annular mirror, a polarizing beam splitter in conjunction with three detectors in a scanning confocal optical microscope.
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87.64.mk Confocal
07.60.Pb Conventional optical microscopes
87.15.M- Spectra of biomolecules

Unpolarized narrow-band filtering with resonant gratings

Anne-Laure Fehrembach and Anne Sentenac

Appl. Phys. Lett. 86, 121105 (2005); http://dx.doi.org/10.1063/1.1886895 (3 pages) | Cited 23 times

Online Publication Date: 15 March 2005

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Periodically corrugated planar waveguides present sharp peaks in their reflectivity spectrum due to the excitation, by the incident beam, of an eigenmode of the structure. This property can be used to design free-space narrow-band filters. However, the extreme sensitivity of the resonances with respect to the angle and polarization under oblique incidence, has prevented, up to now, the development of efficient filters with this approach. We succeed in getting round these limitations by exiting four eigenmodes at the same time, and by modifying deeply the eigenmodes properties with an appropriate periodic corrugation.
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42.79.Ci Filters, zone plates, and polarizers
42.79.Gn Optical waveguides and couplers
42.79.Dj Gratings

Photonic band structure of colloidal crystal self-assembled in hollow core optical fiber

Y. Lin, P. R. Herman, C. E. Valdivia, J. Li, V. Kitaev, and G. A. Ozin

Appl. Phys. Lett. 86, 121106 (2005); http://dx.doi.org/10.1063/1.1887814 (3 pages) | Cited 5 times

Online Publication Date: 15 March 2005

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We report detailed stop-band measurements in colloidal photonic crystals, and a comparison with photonic band structure calculations. An achieved growth of colloidal photonic crystals in a hollow core optical fiber provides an optically accessible self-assembled system with controllable crystal orientations. The stop band is measured through optical transmissions as a function of incident angles relative to main crystallographic directions, revealing critical band structure information and indicating the high quality of the crystal formed.
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42.70.Qs Photonic bandgap materials
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.81.-i Fiber optics

Extraordinarily high-contrast and wide-view liquid-crystal displays

Qi Hong, Thomas X. Wu, Xinyu Zhu, Ruibo Lu, and Shin-Tson Wu

Appl. Phys. Lett. 86, 121107 (2005); http://dx.doi.org/10.1063/1.1887815 (3 pages) | Cited 35 times

Online Publication Date: 15 March 2005

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A computer simulation model based on oblique-angle Jones matrix and Poincaré sphere is developed for optimizing the design of film-compensated multidomain vertical-alignment liquid crystal display (VA-LCD). According to this design, a contrast ratio higher than 10 000:1 is predicted over the entire ±85° viewing cone for the four-domain VA-LCD. Potential application for liquid-crystal display television is emphasized.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems
85.60.Bt Optoelectronic device characterization, design, and modeling

Quasi-periodic planar metamaterial substrates

Hongqiang Li, Zhihong Hang, Yaqin Qin, Zeyong Wei, Lei Zhou, Yewen Zhang, Hong Chen, and C. T. Chan

Appl. Phys. Lett. 86, 121108 (2005); http://dx.doi.org/10.1063/1.1887822 (3 pages) | Cited 5 times

Online Publication Date: 15 March 2005

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We report our experimental and theoretical studies on a metamaterial substrate consisting of a quasi-periodic metallic planr pattern and a flat metal sheet, interconnected through metallic vias. We show that this structure possesses multiple in-phase reflection frequency regimes and spectral gaps for transverse-magnetic surface waves, whereas the transverse-electric surface waves are suppressed in all frequencies. In particular, an antenna put on top of this planar structure radiates with very high directivity (D = 240) at some frequencies. This phenomenon is mainly governed by the inhomogeneity of the structure, which is a collective effect of perfect magnetic and electric conductors operating simultaneously at the frequency.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
84.40.Ba Antennas: theory, components and accessories

Waveguide structures in heavy metal oxide glass written with femtosecond laser pulses above the critical self-focusing threshold

J. Siegel, J. M. Fernández-Navarro, A. García-Navarro, V. Diez-Blanco, O. Sanz, J. Solis, F. Vega, and J Armengol

Appl. Phys. Lett. 86, 121109 (2005); http://dx.doi.org/10.1063/1.1888032 (3 pages) | Cited 23 times

Online Publication Date: 15 March 2005

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We study the feasibility of femtosecond laser writing of optical waveguides in bulk 35PbO∙35Bi2O3∙15Ga2O3∙15GeO2 glass, motivated by the extended transparency interval of heavy metal oxide glasses in the mid-infrared regime. Its large linear and nonlinear refractive indices cause critical self-focusing to occur even at low laser energies, leading to filamentary propagation and material damage. However, the vicinity of the laser-damaged region shows a considerable increase in the refractive index, which we attribute to a collateral, stress-induced densification due to the high pressures generated in the focal region. These regions of increased refractive index are strongly birefringent and sufficiently large to support efficient light propagation in transversally written structures. Optical waveguides with a refractive index increase ≥ 10−3 and minimal mode ellipticity have been obtained.
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42.79.Gn Optical waveguides and couplers
42.62.-b Laser applications
42.65.Wi Nonlinear waveguides
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.70.Ce Glasses, quartz
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Effect of template morphology on the efficiency of InGaN/GaN quantum wells and light-emitting diodes grown by molecular-beam epitaxy

H. Tang, S. Haffouz, A. Powell, J. A. Bardwell, and J. Webb

Appl. Phys. Lett. 86, 121110 (2005); http://dx.doi.org/10.1063/1.1884745 (3 pages) | Cited 5 times

Online Publication Date: 16 March 2005

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The pronounced enhancement of indium incorporation efficiency for InGaN/GaN quantum wells due to the rough, faceted surface of the GaN template grown in situ by ammonia-molecular-beam epitaxy is reported. The InGaN/GaN quantum wells are grown by plasma-assisted molecular-beam epitaxy. Unlike the smooth (0002) surface of GaN template layers grown by metalorganic chemical vapor deposition, the surface of the template layers grown by ammonia-molecular-beam epitaxy is defined by {10-1m} pyramidal facets causing significant surface roughness. The drastically enhanced indium incorporation rate associated with the rough templates allows the InGaN/GaN quantum wells to be grown at higher temperatures as it compensates for the increased thermal decomposition. High luminescence efficiency is achieved as a result. Using such efficient InGaN/GaN quantum wells, light-emitting diodes have been grown entirely by molecular-beam epitaxy on sapphire substrates, demonstrating output power of 0.22 mW for 20 mA injection current.
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81.05.Ea III-V semiconductors
81.07.St Quantum wells
85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
68.65.Fg Quantum wells
68.35.Ct Interface structure and roughness
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.67.De Quantum wells
78.55.Cr III-V semiconductors
78.60.Fi Electroluminescence
52.77.Dq Plasma-based ion implantation and deposition

Propagation losses of silicon nitride waveguides in the near-infrared range

M. Melchiorri, N. Daldosso, F. Sbrana, L. Pavesi, G. Pucker, C. Kompocholis, P. Bellutti, and A. Lui

Appl. Phys. Lett. 86, 121111 (2005); http://dx.doi.org/10.1063/1.1889242 (3 pages) | Cited 10 times

Online Publication Date: 16 March 2005

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Si3N4/SiO2 waveguides have been fabricated by low pressure chemical vapor deposition within a complementary metal–oxide–semiconductor fabrication pilot line. Propagation losses for different waveguide geometries (channel and rib loaded) have been measured in the near infrared as a function of polarization, waveguide width, and light wavelength. A maximum thickness of single Si3N4 of 250 nm is allowed by the large stress between Si3N4 and SiO2. This small thickness turns into significant propagation losses at 1544 nm of about 4.5 dB/cm because of the poor optical mode confinement factor. Strain release and control is possible by using multilayer waveguides by alternating Si3N4 and SiO2 layers. In this way, propagation losses of about 1.5 dB/cm have been demonstrated thanks to an improved optical mode confinement factor and the good quality of the interfaces in the waveguide.
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42.82.Et Waveguides, couplers, and arrays
85.60.Bt Optoelectronic device characterization, design, and modeling
42.79.Gn Optical waveguides and couplers
42.79.Wc Optical coatings

Optical nonlinearity in PbO–SiO2 glass: Kramers–Kronig analyses

K. Tanaka and N. Minamikawa

Appl. Phys. Lett. 86, 121112 (2005); http://dx.doi.org/10.1063/1.1891269 (3 pages) | Cited 3 times

Online Publication Date: 16 March 2005

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Relationship between nonlinear refractivity and two-photon absorption has been studied for PbO–SiO2 glasses using a nonlinear Kramers–Kronig relation. Nonlinear refractive indices, which are determined with z-scan measurements, are consistent with those which are calculated using the relation from two-photon absorption spectra. This consistency suggests that large intensity-dependent refractivity in this glass system arises from resonant two-photon electronic transitions from oxygen 2p to lead 6p states.
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42.70.Ce Glasses, quartz
42.65.-k Nonlinear optics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Ultrabroadband (>2500 cm−1) multiplex coherent anti-Stokes Raman scattering microspectroscopy using a supercontinuum generated from a photonic crystal fiber

Hideaki Kano and Hiro-o Hamaguchi

Appl. Phys. Lett. 86, 121113 (2005); http://dx.doi.org/10.1063/1.1883714 (3 pages) | Cited 39 times

Online Publication Date: 16 March 2005

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We have developed ultrabroadband multiplex coherent anti-Stokes Raman scattering (CARS) microspectroscopy using a coherent supercontinuum in the near-infrared region generated from a photonic crystal fiber. Owing to the ultrabroadband Stokes radiation obtained from the supercontinuum, multiple vibrational modes can be excited simultaneously in the wave-number range of more than 2500 cm−1. A CARS imaging of a lipid vesicle is demonstrated with a high vibrational contrast.
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42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
87.64.K- Spectroscopy
42.62.Be Biological and medical applications
87.16.D- Membranes, bilayers, and vesicles
87.14.Cc Lipids

High-intensity terahertz radiation from a microstructured large-area photoconductor

A. Dreyhaupt, S. Winnerl, T. Dekorsy, and M. Helm

Appl. Phys. Lett. 86, 121114 (2005); http://dx.doi.org/10.1063/1.1891304 (3 pages) | Cited 88 times

Online Publication Date: 17 March 2005

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We present a planar large-area photoconducting emitter for impulsive generation of terahertz (THz) radiation. The device consists of an interdigitated electrode metal-semiconductor-metal (MSM) structure which is masked by a second metallization layer isolated from the MSM electrodes. The second layer blocks optical excitation in every second period of the MSM finger structure. Hence charge carriers are excited only in those periods of the MSM structure which exhibit a unidirectional electric field. Constructive interference of the THz emission from accelerated carriers leads to THz electric field amplitudes up to 85 V/cm when excited with fs optical pulses from a Ti:sapphire oscillator with an average power of 100 mW at a bias voltage of 65 V applied to the MSM structure. The proposed device structure has a large potential for large-area high-power THz emitters.
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84.40.-x Radiowave and microwave (including millimeter wave) technology
85.60.Ha Photomultipliers; phototubes and photocathodes
85.40.Ls Metallization, contacts, interconnects; device isolation
73.40.Sx Metal-semiconductor-metal structures
73.50.Pz Photoconduction and photovoltaic effects

Polarized transmission spectra of the fiber-microsphere system

G. Guan and F. Vollmer

Appl. Phys. Lett. 86, 121115 (2005); http://dx.doi.org/10.1063/1.1890465 (3 pages) | Cited 2 times

Online Publication Date: 18 March 2005

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The polarized transmission spectra of a fiber-microsphere system was investigated. Light from an optical fiber was side coupled into the dielectric microsphere through optical tunneling. It was found that the polarization of some of the light coupled into the microsphere and back into the fiber changed by 90°. The experiments showed a level of high signal-to-noise ratio peaks at the resonant frequencies in the polarized spectra and the possibility of discriminating between TE and TM modes of the microsphere.
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42.81.Wg Other fiber-optical devices
42.81.Gs Birefringence, polarization
42.79.-e Optical elements, devices, and systems

High resistance narrow band quantum cascade photodetectors

L. Gendron, C. Koeniguer, V. Berger, and X. Marcadet

Appl. Phys. Lett. 86, 121116 (2005); http://dx.doi.org/10.1063/1.1884257 (3 pages) | Cited 28 times

Online Publication Date: 18 March 2005

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A high resistance narrow band quantum cascade photodetector (QCD) is presented. Leakage current has been suppressed, increasing the resistivity, thanks to a design in which coupling barriers have been thickened. Useless cross transitions have been eliminated finally leading to a Johnson noise detectivity at 50 K comparable to quantum well infrared photodetectors. Because they work with no dark current, QCDs are very promising for small pixel and large focal plane array applications.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.63.Hs Quantum wells
73.50.Td Noise processes and phenomena
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Anisotropic Mg incorporation in GaN growth on nonplanar templates

Dawei Ren and P. Daniel Dapkus

Appl. Phys. Lett. 86, 121901 (2005); http://dx.doi.org/10.1063/1.1870121 (3 pages) | Cited 8 times

Online Publication Date: 14 March 2005

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Anisotropic Mg incorporation has been observed in the growth of p-type GaN on nonplanar GaN templates. As shown by cross-sectional scanning electron microscopy and cathodoluminescence spectroscopy, Mg-doped GaN grown on (0001) mesa tops is observed to have higher Mg concentration than the counterpart layers grown on {11math2} sidewalls. The origin of this anisotropic Mg incorporation is believed to be associated with local surface structure on the different surface facets. More importantly, this unique structure of Mg-doped GaN provides a natural lateral current confinement that paves a promising path to fabrication of InGaN∕GaN buried heterostructure lasers on these nonplanar templates.
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81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.A- Nucleation and growth
61.72.uj III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
61.72.S- Impurities in crystals
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Local environment of Mn dopant in ZnO by near-edge x-ray absorption fine structure analysis

Masahiro Kunisu, Fumiyasu Oba, Hidekazu Ikeno, Isao Tanaka, and Tomoyuki Yamamoto

Appl. Phys. Lett. 86, 121902 (2005); http://dx.doi.org/10.1063/1.1885175 (3 pages) | Cited 25 times

Online Publication Date: 14 March 2005

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High-resolution near-edge x-ray absorption fine structure (NEXAFS) at Mn K edge is employed to probe the local environment of Mn dopant in ZnO. First-principles supercell calculations are systematically made to obtain theoretical NEXAFS. Mn is found to substitute for Zn up to 5 at.%Mn in polycrystalline samples sintered at 1623 K in air. Presence of Mn3O4 is apparent for samples with higher Mn content. The NEXAFS does not change in the range of Mn concentration from 0.01 to 5 at. %, indicating the absence of Mn precipitates. The results are confirmed by examining the polarization dependence of the NEXAFS for a 5 at. %-doped ZnO thin film.
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75.50.Pp Magnetic semiconductors
61.72.S- Impurities in crystals
81.05.Dz II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.70.Dm X-ray absorption spectra
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Solid-state dewetting for ordered arrays of crystallographically oriented metal particles

Amanda L. Giermann and Carl V. Thompson

Appl. Phys. Lett. 86, 121903 (2005); http://dx.doi.org/10.1063/1.1885180 (3 pages) | Cited 57 times

Online Publication Date: 14 March 2005

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We demonstrate that topographically modified substrates can be used as templates to control solid-state dewetting of thin films by creating a periodic variation in the initial curvature of the film. The dewetting of gold films on oxidized silicon surfaces patterned with arrays of inverted pyramid shaped pits is investigated. For specific ranges of relative film thickness and topographic dimension, dewetting results in arrays of submicrometer-scale particles with uniform periodic spacing and nearly uniform size and crystallographic orientation.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology

Revealing hidden pore structure in nanoporous thin films using positronium annihilation lifetime spectroscopy

Hua-Gen Peng, William E. Frieze, Richard S. Vallery, David W. Gidley, Darren L. Moore, and Richard J. Carter

Appl. Phys. Lett. 86, 121904 (2005); http://dx.doi.org/10.1063/1.1886905 (3 pages) | Cited 7 times

Online Publication Date: 14 March 2005

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The highly inhomogeneous pore morphology of a plasma-enhanced-chemical-vapor-deposited ultralow-k dielectric film (k = 2.2) has been revealed using depth-profiled positronium annihilation lifetime spectroscopy (PALS) combined with progressive etch back of the film surface. The film is found to have a dense surface layer, an intermediate layer of 1.8 nm diameter mesopores, and a deep region of ∼ 3 nm diameter mesopores. After successively etching of the sealing layer and the isolated 1.8 nm pore region, PALS reveals that the underlying large pores are highly interconnected. This inhomogeneous pore structure is proposed to account for observed difficulties in film integration.
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81.05.Rm Porous materials; granular materials
81.07.Bc Nanocrystalline materials
77.84.Jd Polymers; organic compounds
61.43.Gt Powders, porous materials
77.55.-g Dielectric thin films
61.46.-w Structure of nanoscale materials
81.65.Cf Surface cleaning, etching, patterning
78.70.Bj Positron annihilation
78.66.Nk Insulators
68.55.-a Thin film structure and morphology

Fluorine segregation and incorporation during solid-phase epitaxy of Si

S. Mirabella, G. Impellizzeri, E. Bruno, L. Romano, M. G. Grimaldi, F. Priolo, E. Napolitani, and A. Carnera

Appl. Phys. Lett. 86, 121905 (2005); http://dx.doi.org/10.1063/1.1886907 (3 pages) | Cited 16 times

Online Publication Date: 14 March 2005

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We report on the F incorporation into Si during solid-phase epitaxy (SPE) at 580 °C and with the presence of B and∕or As, clarifying the F incorporation mechanism into Si. A strong segregation of F at the moving amorphous–crystalline interface has been characterized, leading to a SPE rate retardation and to a significant loss of F atoms through the surface. In B- or As-doped samples, an enhanced, local F incorporation is observed, whereas in the case of B and As co-implantation (leading to compensating dopant effect), a much lower F incorporation is achieved at the dopant peak. The F enhanced incorporation with the presence of B or As is shown to be a kinetic effect related to the SPE rate modification by doping, whereas the hypothesis of a F–B or F–As chemical bonding is refused. These results shed new light on the application of F in the fabrication of ultrashallow junctions in future generation devices.
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81.05.Cy Elemental semiconductors
68.55.A- Nucleation and growth
68.35.Dv Composition, segregation; defects and impurities
81.15.Np Solid phase epitaxy; growth from solid phases
61.72.uf Ge and Si
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.S- Impurities in crystals

Refractive indices of ZnSiN2 on r-plane sapphire

B. P. Cook, H. O. Everitt, I. Avrutsky, A. Osinsky, A. Cai, and J. F. Muth

Appl. Phys. Lett. 86, 121906 (2005); http://dx.doi.org/10.1063/1.1865325 (3 pages) | Cited 3 times

Online Publication Date: 14 March 2005

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II–IV–N2 wide band gap semiconductors such as ZnSiN2, ZnGeN2, and ZnSiGeN2 have potential uses for nonlinear materials and as lattice matching compounds for the growth of SiC and GaN devices. In this study, the dispersion of the TE and TM indices of refraction has been measured systematically using the prism coupling technique for an orthorhombic ZnSiN2 epitaxial layer grown on r-plane sapphire. The resulting index dispersion is extracted from the measured optical modes using a layered biaxial waveguide analysis, which shows that although the ZnSiN2 crystal is orthorhombic, for practical purposes it can be treated as a uniaxial material.
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68.55.-a Thin film structure and morphology
78.66.Li Other semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Fy Semiconductors

Oxidation kinetics of ion-amorphized (0001) 6H–SiC: Competition between oxidation and recrystallization processes

A. Poggi, A. Parisini, R. Nipoti, and S. Solmi

Appl. Phys. Lett. 86, 121907 (2005); http://dx.doi.org/10.1063/1.1887820 (3 pages) | Cited 5 times

Online Publication Date: 15 March 2005

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The wet oxidation of (0001) Si face 6H–SiC preamorphized by Ar+ implantation has been investigated in the temperature range between 750 and 950 °C. Electron microscopy analysis has been performed to obtain information on the evolution of the amorphous layer during the oxidation process. The oxidation rate of the amorphous substrate is linear in time and assumes the value VOx(α) = 3.8×107 exp(−1.6/kT) nm/min. Due to the concomitant oxidation and recrystallization processes occurring at the two opposite faces of the amorphous layer, this expression is valid up to about 910 °C for amorphous layer thickness of a few hundreds nanometer and processing time of a few tens of minutes. At higher temperatures, our oxidation data support the existence of a sudden increasing of the recrystallization that strongly reduces the time of surviving of the amorphous region and, consequently, the oxide thickness. The procedure to determine, for any fixed amorphous thickness, the most suitable experimental conditions giving rise to the maximum oxide thickness (i.e., the temperature at which corresponds the shortest oxidation time), preserving at the same time the flatness of the oxidized surface, is reported.
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81.05.Gc Amorphous semiconductors
81.65.Mq Oxidation
61.72.up Other materials
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
61.43.Dq Amorphous semiconductors, metals, and alloys
68.37.Lp Transmission electron microscopy (TEM)

Identification of vacancies in the ordered intermetallic compound B2–Ru46Al54

E. Partyka, W. Sprengel, H. Weigand, H.-E. Schaefer, F. Krogh, and G. Kostorz

Appl. Phys. Lett. 86, 121908 (2005); http://dx.doi.org/10.1063/1.1885176 (3 pages) | Cited 2 times

Online Publication Date: 16 March 2005

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For the identification of vacant lattice sites in the high-temperature intermetallic compound Ru46Al54, positron lifetime measurements as well as coincident measurements of the two Doppler-broadened positron-electron annihilation photons have been employed. These data demonstrate that thermal vacancies are formed on the Ru metal sublattice similar to FeAl and NiAl where the thermal vacancies are also formed on the transition metal sublattice.
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61.72.J- Point defects and defect clusters
78.70.Bj Positron annihilation
61.80.Fe Electron and positron radiation effects
61.82.Bg Metals and alloys

Thermal decomposition of sputtered thin PtOx layers used in super-resolution optical disks

A. V. Kolobov, F. Wilhelm, A. Rogalev, T. Shima, and J. Tominaga

Appl. Phys. Lett. 86, 121909 (2005); http://dx.doi.org/10.1063/1.1886255 (3 pages) | Cited 2 times

Online Publication Date: 16 March 2005

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Decomposition of sputtered PtOx layers has been studied by x-ray absorption spectroscopy. X-ray absorption fine structure measurements demonstrated that as-deposited films possess a composition of PtOx (x = 1.1–1.7). Upon annealing, the metallic platinum phase is formed. The formation of the metallic Pt phase starts at very early stages of the decomposition process. The decomposition is not monotonic and slows down at the final stage. The structure at intermediate stages of decomposition is a mixture of the starting phase and metallic Pt.
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68.55.-a Thin film structure and morphology
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
78.70.Dm X-ray absorption spectra
68.55.Nq Composition and phase identification
81.40.Gh Other heat and thermomechanical treatments
42.79.Vb Optical storage systems, optical disks
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