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12 Jun 2006

Volume 88, Issue 24, Articles (24xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 243101 (2006); http://dx.doi.org/10.1063/1.2211007 (3 pages)

G. H. Du, F. Xu, Z. Y. Yuan, and G. Van Tendeloo
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Electrical-optical hybrid pulse-heating method for rapid measurement of high-temperature thermal diffusivity

Hiromichi Watanabe and Tetsuya Baba

Appl. Phys. Lett. 88, 241901 (2006); http://dx.doi.org/10.1063/1.2211985 (3 pages) | Cited 1 time

Online Publication Date: 12 June 2006

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An electrical-optical hybrid pulse-heating method has been developed for measuring the thermal diffusivity of conductive materials up to very high temperatures. This method is an integration of the laser flash method and the feedback-controlled current-pulse heating technique. This method can measure the thermal diffusivity even at temperatures above 2500 K in less than 1 s for a sample initially held at room temperature. The resulting short exposure to high temperature can minimize the contamination of the sample and apparatus. To demonstrate the performance of this method, the thermal diffusivities of molybdenum from 2000 to 2600 K have been determined.
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72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
07.20.-n Thermal instruments and apparatus

Strong sub-band-gap infrared absorption in silicon supersaturated with sulfur

T. G. Kim, Jeffrey M. Warrender, and Michael J. Aziz

Appl. Phys. Lett. 88, 241902 (2006); http://dx.doi.org/10.1063/1.2212051 (3 pages) | Cited 21 times

Online Publication Date: 12 June 2006

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Silicon supersaturated with up to 0.6 at. % sulfur in solid solution was fabricated by ion implantation and pulsed-laser-melting-induced rapid solidification. The optical absorption coefficient over the range of 1200–2500 nm is uniformly high at ∼ 2.5×104/cm, which is at least an order of magnitude greater than the maximum value attributable to free carriers. High crystal quality was confirmed by transmission electron microscopy and ion channeling. The absorption coefficient decreases markedly with subsequent furnace annealing over the range of 200–600 °C. We propose that the high absorptivity is due to a broad distribution of sulfur-related localized states within the band gap.
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78.30.Am Elemental semiconductors and insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.20.Mq Elemental semiconductors
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
61.72.uf Ge and Si
81.30.Fb Solidification

Atomic scale characterization of shear bands in an amorphous metal

Qi-Kai Li and Mo Li

Appl. Phys. Lett. 88, 241903 (2006); http://dx.doi.org/10.1063/1.2212059 (3 pages) | Cited 59 times

Online Publication Date: 12 June 2006

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The shear bands in a model amorphous CuZr metallic glass are examined using atomistic simulations. The localized shear zones are characterized at atomic scales by the nearest-neighbor atomic bond rotation angle, the nearest-neighbor atomic bond length, the atomic volume, and the potential energy. It is shown that the shear band is indeed a region with a liquidlike structure and different thermomechanical properties. Shear band formation could be a result from both local heating and free volume generation. The variation of shear band properties with temperature and strain rate is also briefly reported.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
61.43.Fs Glasses
81.40.Gh Other heat and thermomechanical treatments
33.15.Dj Interatomic distances and angles
34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions

Nitrogen ion beam synthesis of InN in InP(100) at elevated temperature

S. Dhara, P. Magudapathy, R. Kesavamoorthy, S. Kalavathi, V. S. Sastry, K. G. M. Nair, G. M. Hsu, L. C. Chen, K. H. Chen, K. Santhakumar, and T. Soga

Appl. Phys. Lett. 88, 241904 (2006); http://dx.doi.org/10.1063/1.2186101 (3 pages) | Cited 3 times

Online Publication Date: 12 June 2006

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The InN phase is grown in crystalline InP(100) substrates by 50 keV N+ implantation at an elevated temperature of 400 °C followed by annealing at 525 °C in N2 ambient. Crystallographic structural and Raman scattering studies are performed for the characterization of grown phases. Temperature- and power-dependent photoluminescence studies show direct band-to-band transition peak ∼ 1.06 eV at temperatures ⩽ 150 K. Implantations at an elevated temperature with a low ion beam current and subsequent low temperature annealing step are found responsible for the growth of high-quality InN phase.
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61.80.Jh Ion radiation effects
61.72.Cc Kinetics of defect formation and annealing
78.30.Fs III-V and II-VI semiconductors
78.55.Cr III-V semiconductors

Anomalous blueshift in emission spectra of ZnO nanorods with sizes beyond quantum confinement regime

Chun-Wei Chen, Kuei-Hsien Chen, Ching-Hsing Shen, Abhijit Ganguly, Li-Chyong Chen, Jih-Jen Wu, Hui-I Wen, and Way-Faung Pong

Appl. Phys. Lett. 88, 241905 (2006); http://dx.doi.org/10.1063/1.2211047 (3 pages) | Cited 61 times

Online Publication Date: 12 June 2006

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Cathodoluminescence (CL) spectroscopy has been employed to study the electronic and optical properties of well-aligned ZnO nanorods with diameters ranging from 50 to 180 nm. Single-nanorod CL studies reveal that the emission peak moves toward higher energy as the diameter of the ZnO nanorod decreases, despite that their sizes are far beyond the quantum confinement regime. Blueshift of several tens of meV in the CL peak of these nanorods has been observed. Moreover, this anomalous energy shift shows a linear relation with the inverse of the rod diameter. Possible existence of a surface resonance band is suggested and an empirical formula for this surface effect is proposed to explain the size dependence of the CL data.
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78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.60.Hk Cathodoluminescence, ionoluminescence
61.46.-w Structure of nanoscale materials
81.05.Dz II-VI semiconductors

Morphological stability of the Stranski-Krastanow systems under an electric field

C.-h. Chiu, C. T. Poh, and Z. Huang

Appl. Phys. Lett. 88, 241906 (2006); http://dx.doi.org/10.1063/1.2212052 (3 pages) | Cited 4 times

Online Publication Date: 12 June 2006

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The morphological stability of the Stranski-Krastanow (SK) system against surface undulation is investigated for the case where the SK system consists of a conductor film and a thick substrate and it is under the influence of an electric field induced by an electrode above the film. It is shown that a flat electrode reduces the critical thickness below which the SK system is completely stable against surface undulation. Applying a wavy electrode to the completely stable system, on the other hand, causes the flat film surface to develop into an equilibrium ripple profile.
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68.35.B- Structure of clean surfaces (and surface reconstruction)

Growth mode and structural characterization of GaSb on Si (001) substrate: A transmission electron microscopy study

Y. H. Kim, J. Y. Lee, Y. G. Noh, M. D. Kim, S. M. Cho, Y. J. Kwon, and J. E. Oh

Appl. Phys. Lett. 88, 241907 (2006); http://dx.doi.org/10.1063/1.2209714 (3 pages) | Cited 14 times

Online Publication Date: 13 June 2006

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Growth mode and structural properties of GaSb layers grown on silicon substrate by molecular beam epitaxy method are investigated by transmission electron microscopy. It is found that the GaSb grows to three-dimensional islands and grains are tilted to reduce a lattice mismatch through twin boundaries when they are directly grown on Si substrate. A low-temperature (LT) AlSb buffer plays a key role in transferring the growth mode from a three-dimensional island to a layer-by-layer structure. When the LT AlSb layer is used as a buffer, 90° misfit dislocations, with the Burgers vector b of 1/2a 〈110〉, are observed on the interface.
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68.47.Fg Semiconductor surfaces
68.37.Lp Transmission electron microscopy (TEM)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology

Photoluminescence properties peculiar to the Mn-related transition in a lightly alloyed ZnMnO thin film grown by pulsed laser deposition

M. Nakayama, H. Tanaka, K. Masuko, T. Fukushima, A. Ashida, and N. Fujimura

Appl. Phys. Lett. 88, 241908 (2006); http://dx.doi.org/10.1063/1.2209719 (3 pages) | Cited 8 times

Online Publication Date: 13 June 2006

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We have investigated photoluminescence properties of ZnO and Zn0.95Mn0.05O thin films at 10 K grown on a (000math) ZnO crystal substrate by pulsed laser deposition. The structural characterization with x-ray diffraction and atomic force microscopy demonstrates the pseudomorphic growth of the Zn0.95Mn0.05O thin film and the atomically smooth surface. It has been found that a photoluminescence band originating from the d-d transition of Mn2+ in the Zn0.95Mn0.05O thin film appears in the energy region of deep-level transitions in a ZnO crystal: The photoluminescence-decay time is in the order of sub-milliseconds. The photoluminescence-excitation spectrum of the Mn-related transition exhibits a peaky structure with a broad profile at the energy lower than the A-exciton energy by ∼ 100 meV. This indicates that the light incorporation of Mn to ZnO leads to a negative energy shift of the band-gap energy. The broad profile of the band-edge transition observed in the photoluminescence-excitation spectrum suggests that the incorporation of Mn produces remarkable random-potential fluctuations.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
71.55.Gs II-VI semiconductors

Photorefractive effects in magnesium doped lithium niobate whispering gallery mode resonators

Anatoliy A. Savchenkov, Andrey B. Matsko, Dmitry Strekalov, Vladimir S. Ilchenko, and Lute Maleki

Appl. Phys. Lett. 88, 241909 (2006); http://dx.doi.org/10.1063/1.2212055 (3 pages) | Cited 3 times

Online Publication Date: 14 June 2006

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We report on the study of near-infrared photorefractivity in highly Mg doped as-grown congruent LiNbO3 forming a whispering gallery mode resonator. The resonator is pumped with 780 nm light. We have observed a change of the ordinary index of refraction of the material exceeding 8×10−5. We show that the basic features of the photorefraction in this type of crystal is different from the photorefraction in nominally pure as-grown congruent LiNbO3 and explain the origin of this difference.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.70.Gi Light-sensitive materials

Mg–Ti–H thin films for smart solar collectors

D. M. Borsa, A. Baldi, M. Pasturel, H. Schreuders, B. Dam, R. Griessen, P. Vermeulen, and P. H. L. Notten

Appl. Phys. Lett. 88, 241910 (2006); http://dx.doi.org/10.1063/1.2212287 (3 pages) | Cited 35 times

Online Publication Date: 14 June 2006

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Mg–Ti–H thin films are found to have very attractive optical properties: they absorb 87% of the solar radiation in the hydrogenated state and only 32% in the metallic state. Furthermore, in the absorbing state Mg–Ti–H has a low emissivity; at 400 K only 10% of blackbody radiation is emitted. The transition between both optical states is fast, robust, and reversible. The sum of these properties highlights the applicability of such materials as switchable smart coatings in solar collectors.
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42.79.Ek Solar collectors and concentrators
78.66.Bz Metals and metallic alloys
42.70.-a Optical materials

GaAs quantum dots with a high density on a GaAs (111)A substrate

Jong Su Kim, Mun Seok Jeong, Clare C. Byeon, Do-Kyeong Ko, Jongmin Lee, Jin Soo Kim, In-Soo Kim, and Nobuyuki Koguchi

Appl. Phys. Lett. 88, 241911 (2006); http://dx.doi.org/10.1063/1.2213012 (3 pages) | Cited 5 times

Online Publication Date: 14 June 2006

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The GaAs quantum dots (QDs) on an AlGaAs/GaAs (111)A surface grown by a droplet epitaxy have a density of 1.6×1011/cm2, which is relatively higher than those (1.3×1010/cm2) on an AlGaAs/GaAs (001) surface. The formation of highly dense GaAs QDs on the (111)A surface can be explained by the relatively short surface migration of Ga atoms. The GaAs QDs on AlGaAs/GaAs (111)A showed the intense photoluminescence (PL) and a relatively narrower PL linewidth compared to that of the GaAs QDs on AlGaAs/GaAs (001), indicating that the QDs on the GaAs (111)A substrate have a high crystal quality and high uniformity than those on GaAs (001).
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68.65.Hb Quantum dots (patterned in quantum wells)
78.67.Hc Quantum dots
66.30.J- Diffusion of impurities
78.55.Cr III-V semiconductors

Determination of transformation stresses of shape memory alloy thin films: A method based on spherical indentation

Wenyi Yan, Qingping Sun, Xi-Qiao Feng, and Linmao Qian

Appl. Phys. Lett. 88, 241912 (2006); http://dx.doi.org/10.1063/1.2213018 (3 pages) | Cited 8 times

Online Publication Date: 14 June 2006

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The forward and reverse transformation processes of superelastic shape memory alloys (SMAs) under spherical indentation are analyzed. We found that there exist two characteristic points, the bifurcating point and the returning point, in an indentation curve. The corresponding bifurcation force and return force, respectively, rely on the forward transformation stress and the reverse transformation stress. A method to determine the transformation stresses of SMA from the measure of the bifurcation and return forces is proposed. Additionally, we suggest a slope approach to determine the values of the two forces with high accuracy.
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68.60.Bs Mechanical and acoustical properties
64.70.K- Solid-solid transitions
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
62.20.M- Structural failure of materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Design of Cu8Zr5-based bulk metallic glasses

L. Yang, J. H. Xia, Q. Wang, C. Dong, L. Y. Chen, X. Ou, J. F. Liu, J. Z. Jiang, K. Klementiev, K. Saksl, H. Franz, J. R. Schneider, and L. Gerward

Appl. Phys. Lett. 88, 241913 (2006); http://dx.doi.org/10.1063/1.2213020 (3 pages) | Cited 28 times

Online Publication Date: 14 June 2006

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Basic polyhedral clusters have been derived from intermetallic compounds at near-eutectic composition by considering a dense packing and random arrangement of atoms at shell sites. Using such building units, bulk metallic glasses can be formed. This strategy was verified in the Cu–Zr binary system, where we have demonstrated the existence of Cu8Zr5 icosahedral clusters in Cu61.8Zr38.2, Cu64Zr36, and Cu64.5Zr35.5 amorphous alloys. Furthermore, ternary bulk metallic glasses can be developed by doping the basic Cu–Zr alloy with a minority element. This hypothesis was confirmed in systems (Cu0.618Zr0.382)100−xNbx, where x = 1.5 and 2.5 at. %, and (Cu0.618Zr0.382)98Sn2. The present results may open a route to prepare amorphous alloys with improved glass forming ability.
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81.05.Kf Glasses (including metallic glasses)
61.43.Fs Glasses
61.72.S- Impurities in crystals

High quality thin GaN templates grown by hydride vapor phase epitaxy on sapphire substrates

D. Martin, J. Napierala, M. Ilegems, R. Butté, and N. Grandjean

Appl. Phys. Lett. 88, 241914 (2006); http://dx.doi.org/10.1063/1.2213175 (3 pages) | Cited 10 times

Online Publication Date: 14 June 2006

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The growth by hydride vapor phase epitaxy (HVPE) of high quality thin GaN layers (d = 8 μm) on c-plane sapphire substrates with dislocation densities lower than 2×108 cm−2 is demonstrated using a two-step process similar to that of metal organic vapor phase epitaxy (MOVPE). Ex situ surface preparation and nucleation layer thickness are shown to be critical factors in achieving these high quality epilayers as they allow controlling the polarity and the dislocation density, respectively. Furthermore, we demonstrate that in situ reflectivity monitoring applied to HVPE is a powerful technique for rapidly optimizing the growth parameters. As a result, thin HVPE-grown GaN layers with state of the art MOVPE GaN quality are obtained as demonstrated through structural and optical characterizations.
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81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Fd III-V semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology

Crystallographic anisotropy of wear on a polycrystalline diamond surface

Bassem S. El-Dasher, Jeremy J. Gray, Joseph W. Tringe, Juergen Biener, Alex V. Hamza, Christoph Wild, Eckhard Wörner, and Peter Koidl

Appl. Phys. Lett. 88, 241915 (2006); http://dx.doi.org/10.1063/1.2213180 (3 pages) | Cited 7 times

Online Publication Date: 14 June 2006

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We correlate topography and diffraction measurements to demonstrate that grain orientation profoundly influences polishing rates in polycrystalline diamond synthesized by chemical vapor deposition. Grains oriented with {111} or {100} planes perpendicular to the surface normal polish at significantly lower rates compared with grains of all other orientations when the surface is polished in continuously varying in-plane directions. These observations agree with predictions of the periodic bond chain vector model, developed previously for single crystals, and indicate that the polishing rate depends strongly on the number of periodic bond chain vectors that are within 10° of the exposed surface plane.
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81.05.U- Carbon/carbon-based materials
81.40.Pq Friction, lubrication, and wear
62.20.Qp Friction, tribology, and hardness
68.35.Gy Mechanical properties; surface strains
68.35.B- Structure of clean surfaces (and surface reconstruction)

Direct measurement of spatial distortions of charge density waves in K0.3MoO3

Chao-hung Du, Yen-Ru Lee, Chung-Yu Lo, Hsiu-Hau Lin, Shih-Lin Chang, Mau-Tsu Tang, Yuri P. Stetsko, and Jey-Jau Lee

Appl. Phys. Lett. 88, 241916 (2006); http://dx.doi.org/10.1063/1.2213198 (3 pages) | Cited 2 times

Online Publication Date: 14 June 2006

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Using x-ray scattering and multiple diffraction on a charge density wave (CDW) material, K0.3MoO3, under applied voltages, we demonstrate that the occurrence of nonlinear conductivity caused by the periodic media is through the internal deformation of the CDW lattice, i.e., a phase jump of 2π, as the applied voltage exceeds the threshold. From the evolution of the measured peak width of satellite reflections as a function of the field strength, we also report that the CDW lattice can be driven to move and undergo a dynamic phase transition from the disordered pinning state to ordered moving solid state and then to disordered moving liquid.
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71.45.Lr Charge-density-wave systems
78.70.Ck X-ray scattering
72.80.Sk Insulators
81.40.Lm Deformation, plasticity, and creep
64.70.K- Solid-solid transitions
64.70.D- Solid-liquid transitions

Role of edge dislocations in enhancing the yellow luminescence of n-type GaN

D. G. Zhao, D. S. Jiang, Hui Yang, J. J. Zhu, Z. S. Liu, S. M. Zhang, J. W. Liang, X. Li, X. Y. Li, and H. M. Gong

Appl. Phys. Lett. 88, 241917 (2006); http://dx.doi.org/10.1063/1.2213509 (3 pages) | Cited 17 times

Online Publication Date: 14 June 2006

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We investigate the origin of yellow luminescence in n-type GaN. It is found that the relative intensity of yellow luminescence increases as the full width at half maximum of the x-ray diffraction rocking curve at the (102) plane increases. This indicates that the yellow luminescence is related to the edge dislocation density. In addition, the relative intensity of yellow luminescence is confirmed to increase with increasing Si doping for the high quality GaN we have obtained. We propose that the yellow luminescence is effectively enhanced by the transition from donor impurities such as Si to acceptors around the edge dislocations in n-type GaN.
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78.55.Cr III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.S- Impurities in crystals
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Spatial imaging and mechanical control of spin coherence in strained GaAs epilayers

H. Knotz, A. W. Holleitner, J. Stephens, R. C. Myers, and D. D. Awschalom

Appl. Phys. Lett. 88, 241918 (2006); http://dx.doi.org/10.1063/1.2210794 (3 pages) | Cited 11 times

Online Publication Date: 14 June 2006

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The effect of uniaxial tensile strain on spin coherence in n-type GaAs epilayers is probed using time-resolved Kerr rotation, photoluminescence, and optically detected nuclear magnetic resonance spectroscopies. The band gap, electron spin lifetime, electron g factor, and nuclear quadrupole splitting are simultaneously imaged over millimeter scale areas of the epilayers for continuously varying values of strain. All-optical nuclear magnetic resonance techniques allow access to the strain-induced nuclear quadrupolar resonance splitting in field regimes not easily addressable using conventional optically detected nuclear magnetic resonance.
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68.60.Bs Mechanical and acoustical properties
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
76.60.-k Nuclear magnetic resonance and relaxation
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Stability of electron-beam poling in N or Ge-doped H:SiO2 films

Q. Liu, B. Poumellec, R. Blum, G. Girard, J.-E. Bourée, A. Kudlinski, and G. Martinelli

Appl. Phys. Lett. 88, 241919 (2006); http://dx.doi.org/10.1063/1.2208960 (3 pages) | Cited 5 times

Online Publication Date: 14 June 2006

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We study the thermal stability of the second-harmonic signal in electron-beam poled silica based thin films developed for this application. Effects of N or Ge concentration as dopant, on one hand, and hydroxyl species, on the other hand, are tested. We conclude that water molecules inducing an ionic conductivity are detrimental to the e-beam poling efficiency and have to be avoided. Nevertheless, despite such precaution, the stability of the second-harmonic signal in an e-beam poled sample is worse than in a thermally poled sample.
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78.66.Nk Insulators
66.30.H- Self-diffusion and ionic conduction in nonmetals
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
61.80.Fe Electron and positron radiation effects
61.72.S- Impurities in crystals

Tetrastack: Colloidal diamond-inspired structure with omnidirectional photonic band gap for low refractive index contrast

T. T. Ngo, C. M. Liddell, M. Ghebrebrhan, and J. D. Joannopoulos

Appl. Phys. Lett. 88, 241920 (2006); http://dx.doi.org/10.1063/1.2206111 (3 pages) | Cited 22 times

Online Publication Date: 15 June 2006

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Omnidirectional photonic band gaps opening at low values of refractive index contrast have been found for a nonspherical colloid-based photonic crystal structure. A mechanically stable design is described for the diamondlike photonic crystal composed of colloidal tetrahedra. The proposed tetrastack structure displays omnidirectional 2–3 band gap over a large range of filling fractions, refractive index contrasts, and building block orientations. The threshold refractive index for the inverted tetrastack structure was 1.94. A gap width of 25.3% relative to the center frequency was obtained for an inverted tetrastack with a 0.21 filling fraction of silicon.
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42.70.Qs Photonic bandgap materials
82.70.Dd Colloids
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Neutron-enhanced annealing of radiation damage formed by self-ion implantation in silicon

A. Kinomura, A. Chayahara, Y. Mokuno, N. Tsubouchi, Y. Horino, T. Yoshiie, Y. Hayashi, Q. Xu, Y. Ito, R. Ishigami, and K. Yasuda

Appl. Phys. Lett. 88, 241921 (2006); http://dx.doi.org/10.1063/1.2211927 (3 pages)

Online Publication Date: 15 June 2006

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The annealing effect of neutron irradiation has been observed for radiation damage in self-ion implanted silicon. Si samples implanted with (0.5–2)×1015 Si/cm2 were neutron irradiated at 400 °C with the total number of displacements of 8.8×10−3 dpa. A heavily disordered (not amorphized) sample clearly showed damage annealing enhanced by the neutron irradiation. The annealing efficiency (the ratio of annealed defects to atomic displacements) was calculated to be 1.3 defects/displacement. This annealing efficiency was compared with the results of previous ion beam annealing studies.
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61.72.Cc Kinetics of defect formation and annealing
61.82.Fk Semiconductors
61.80.Hg Neutron radiation effects
61.80.Jh Ion radiation effects
61.72.uf Ge and Si

Structural analysis of cubic boron nitride films by ultraviolet Raman spectroscopy

K. M. Leung, H. Q. Li, Y. S. Zou, K. L. Ma, Y. M. Chong, Q. Ye, W. J. Zhang, S. T. Lee, and I. Bello

Appl. Phys. Lett. 88, 241922 (2006); http://dx.doi.org/10.1063/1.2207994 (3 pages) | Cited 6 times

Online Publication Date: 15 June 2006

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Cubic boron nitride (BN) films with improved crystallinity are deposited by physical vapor deposition at an extremely low substrate bias (−35 V). The films are characterized by UV Raman in association with Fourier transformed infrared (FTIR) spectroscopy. The influences of bias voltage and film thickness on the characterizations are investigated. UV Raman, in contrast to FTIR, is demonstrated to be a more powerful tool with high sensitivity for quantitative and/or qualitative evaluation of the phase purity and crystallinity, especially as the film thickness increases. Hexagonal BN inclusions (less than 1%), not evident in FTIR, are clearly revealed by UV Raman analysis.
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81.05.Hd Other semiconductors
68.55.-a Thin film structure and morphology
78.66.Li Other semiconductors
78.30.Hv Other nonmetallic inorganics
78.40.Fy Semiconductors
81.15.Cd Deposition by sputtering

Enhanced luminescence in GaInNAsSb quantum wells through variation of the arsenic and antimony fluxes

Seth R. Bank, Homan B. Yuen, Hopil Bae, Mark A. Wistey, Akihiro Moto, and James S. Harris

Appl. Phys. Lett. 88, 241923 (2006); http://dx.doi.org/10.1063/1.2213176 (3 pages) | Cited 6 times

Online Publication Date: 16 June 2006

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Photoluminescence efficiency was enhanced in molecular-beam-epitaxial-grown 1.55-μm GaInNAsSb single quantum wells through modulation of the arsenic and antimony fluxes. The arsenic-to-antimony flux ratio was found to be a key consideration at reduced group-V fluxes in maintaining the beneficial effects of antimony while reducing the number of point defects, most likely arsenic antisites. Samples were also characterized by high-resolution x-ray diffraction, secondary ion mass spectrometry, and low-temperature photoluminescence. These findings offer a means to substantially reduce dilute-nitride laser threshold current densities.
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81.07.St Quantum wells
81.05.Ea III-V semiconductors
78.67.De Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.J- Point defects and defect clusters
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Dynamic strength of metals in shock deformation

Alison Kubota, David B. Reisman, and Wilhelm G. Wolfer

Appl. Phys. Lett. 88, 241924 (2006); http://dx.doi.org/10.1063/1.2210799 (2 pages) | Cited 5 times

Online Publication Date: 16 June 2006

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The Hugoniot and critical shear strength of shock-compressed metals can be obtained directly from molecular dynamics simulations without recourse to surface velocity profiles and their analyses. Results from simulations in aluminum containing an initial distribution of microscopic defects are shown to agree with experimental results.
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62.50.-p High-pressure effects in solids and liquids
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
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