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6 Apr 2009

Volume 94, Issue 14, Articles (14xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 94, 141901 (2009); http://dx.doi.org/10.1063/1.3111813 (3 pages)

G. S. Huang (黄高山), S. Kiravittaya, V. A. Bolaños Quiñones, F. Ding (丁飞), M. Benyoucef, A. Rastelli, Y. F. Mei (梅永丰), and O. G. Schmidt
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Effect of hollow-core photonic crystal fiber microstructure on transverse optical trapping

P. Domachuk, N. Wolchover, M. Cronin-Golomb, and F. G. Omenetto

Appl. Phys. Lett. 94, 141101 (2009); http://dx.doi.org/10.1063/1.3099935 (3 pages) | Cited 5 times

Online Publication Date: 6 April 2009

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We investigate numerically and experimentally all-optical control of particles inside water filled, silica, hollow-core photonic crystal fiber (HC-PCF). We use an optical trapping beam focused outside the fiber, through its microstructure, perpendicular to the HC-PCF and independent of the guided fiber core mode. Finite difference time domain simulations model trapping through HC-PCF microstructure: trapping along the length of the HC-PCF is well maintained despite the significant effects due to scattering of the HC-PCF core structure. Trapped silica microspheres inside a HC-PCF is demonstrated experimentally as a reversible, reliable technique to control particles in fiber independent of the guided fiber mode. We observe a broadband attenuation of the HC-PCF transmission upon loading a silica microsphere into the fiber core.
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42.81.-i Fiber optics
42.50.Wk Mechanical effects of light on material media, microstructures and particles
42.70.Qs Photonic bandgap materials

Separation of surface plasmon polariton from nonconfined cylindrical wave launched from single slits

H. W. Kihm, J. H. Kang, J. S. Kyoung, K. G. Lee, M. A. Seo, and K. J. Ahn

Appl. Phys. Lett. 94, 141102 (2009); http://dx.doi.org/10.1063/1.3115028 (3 pages) | Cited 4 times

Online Publication Date: 6 April 2009

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We theoretically investigate the separation positions of surface plasmon polariton (SPP) from the cylindrical nonconfined diffracted light launched from a single slit. Through an analysis of the finite difference time domain calculations and the analytical solution of a line source on a metal surface, we find the wavelength dependent SPP separation positions defined as the lateral distance from the slit with two different criteria. These results show that the SPP separation positions can be approximated by a simple relationship given by the permittivity of the metal and by the wavelength regardless of how the criteria are chosen.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Electromagnetically induced transparency in acetylene molecules with counterpropagating beams in V and Λ schemes

P. S. Light, F. Benabid, G. J. Pearce, F. Couny, and D. M. Bird

Appl. Phys. Lett. 94, 141103 (2009); http://dx.doi.org/10.1063/1.3115143 (3 pages) | Cited 7 times

Online Publication Date: 6 April 2009

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We report on the experimental observation of electromagnetically induced transparency in V and Λ energy level schemes using counterpropagating coupling and probe beam geometry. The observation was achieved using an acetylene photonic microcell. The conditions required for this observation are explored theoretically, and we show that the use of counterpropagating beams in electromagnetically induced transparency may have applications as a spectroscopic technique where velocity discrimination is desirable.
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33.57.+c Magneto-optical and electro-optical spectra and effects
42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption
42.50.Hz Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift
51.70.+f Optical and dielectric properties

Vertical coupling between short range surface plasmon polariton mode and dielectric waveguide mode

Ruiyuan Wan, Fang Liu, Xuan Tang, Yidong Huang, and Jiangde Peng

Appl. Phys. Lett. 94, 141104 (2009); http://dx.doi.org/10.1063/1.3111001 (3 pages) | Cited 13 times

Online Publication Date: 7 April 2009

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Coupling performance between a short range surface plasmon polariton (SRSPP) mode and a conventional dielectric waveguide mode is demonstrated numerically. Simulation results show that the coupling length, as short as tens of microns, can be realized because the field of SRSPP extremely concentrates to the metal surface. SRSPP-based hybrid coupler provides not only an approach to realize highly compact functional devices, such as the TE-pass polarizer with high performance, but also an integratable route for efficiently exciting SRSPP mode, which is very useful in the SRSPP-based biosensor or SRSPP-assisted emission enhancement devices.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
84.40.Az Waveguides, transmission lines, striplines
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
78.68.+m Optical properties of surfaces
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Ultralow noise microwave generation with fiber-based optical frequency comb and application to atomic fountain clock

J. Millo, M. Abgrall, M. Lours, E. M. L. English, H. Jiang, J. Guéna, A. Clairon, M. E. Tobar, S. Bize, Y. Le Coq, and G. Santarelli

Appl. Phys. Lett. 94, 141105 (2009); http://dx.doi.org/10.1063/1.3112574 (3 pages) | Cited 15 times

Online Publication Date: 8 April 2009

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We demonstrate the use of a fiber-based femtosecond laser locked onto an ultrastable optical cavity to generate a low-noise microwave reference signal. Comparison with both a cryogenic sapphire oscillator (CSO) and a titanium-sapphire-based optical frequency comb system exhibit a stability of about 3×10−15 between 1 and 10 s. The microwave signal from the fiber system is used to perform Ramsey spectroscopy in a state-of-the-art cesium fountain clock. The resulting clock is compared to the CSO and exhibits a stability of 3.5×10−14τ−1/2.
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42.55.Wd Fiber lasers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Fc Modulation, tuning, and mode locking
42.60.By Design of specific laser systems

Highly efficient and air-stable near infrared emission in erbium/bismuth codoped zeolites

Hong-Tao Sun, Takashi Hasegawa, Minoru Fujii, Fumiaki Shimaoka, Zhenhua Bai, Minoru Mizuhata, Shinji Hayashi, and Shigehito Deki

Appl. Phys. Lett. 94, 141106 (2009); http://dx.doi.org/10.1063/1.3115034 (3 pages) | Cited 9 times

Online Publication Date: 9 April 2009

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We have shown that highly efficient and air-stable 1531 nm emission can be realized in erbium/bismuth codoped zeolites. The luminescence lifetime of Er3+ at 1531 nm can reach up to 4.2 ms. Bismuth compounds formed by high temperature annealing can act as blockages of selectively closing down the “in-out windows” of water molecules, i.e., Er3+ ions are sealed in a low-vibrational environment by bismuth agglomerates even when the samples contain a large amount of water. This finding may pave the way for the applications of active ions doped porous materials in infrared photonics.
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78.55.Mb Porous materials
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Doping nanocrystals by in situ layer-by-layer overcoating

Hsueh-Shih Chen, Ramachandran Vasant Kumar, and Hsin-Yen Hong

Appl. Phys. Lett. 94, 141107 (2009); http://dx.doi.org/10.1063/1.3115035 (3 pages) | Cited 3 times

Online Publication Date: 9 April 2009

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We demonstrate that internally doped nanocrystals can be obtained by an in situ overcoating process. In the case of ZnSe doped with iodine, ZnSe cores are overcoated by interlaced iodine layers and ZnSe layers to incorporate the iodine atoms into the ZnSe matrix. Photoluminescence from the ZnSe band edge is gradually depressed, while emission from the deep-level recombination caused by iodine is dramatically improved up to fourfolds with increasing number of iodine/ZnSe overcoats. This result suggests that the impurity atoms are incorporated into the host matrix.
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61.72.uj III-V and II-VI semiconductors
78.55.Et II-VI semiconductors
81.05.Dz II-VI semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
71.55.Gs II-VI semiconductors

Transparent amorphous silicon channel waveguides with silicon nitride intercladding layer

Rong Sun, Kevin McComber, Jing Cheng, Daniel K. Sparacin, Mark Beals, Jurgen Michel, and Lionel C. Kimerling

Appl. Phys. Lett. 94, 141108 (2009); http://dx.doi.org/10.1063/1.3117363 (3 pages) | Cited 11 times

Online Publication Date: 9 April 2009

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We have experimentally demonstrated single mode amorphous silicon channel waveguides with low optical transmission loss of 2.7±0.4 dB/cm for TE mode in the 1550 nm range. This result was achieved by using hydrogen passivation of a-Si dangling bonds and a thin, low loss silicon nitride intercladding layer prepared by plasma enhanced chemical vapor deposition between the waveguide core and the oxide cladding layer. The silicon nitride intercladding layer reduces waveguide sidewall roughness scattering and preserves the hydrogen passivation.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.Rv Passivation

High speed pulsed electrical spin injection in spin-light emitting diode

V. G. Truong, P.-H. Binh, P. Renucci, M. Tran, Y. Lu, H. Jaffrès, J.-M. George, C. Deranlot, A. Lemaître, T. Amand, and X. Marie

Appl. Phys. Lett. 94, 141109 (2009); http://dx.doi.org/10.1063/1.3110990 (3 pages) | Cited 6 times

Online Publication Date: 10 April 2009

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We demonstrate high speed pulsed electrical spin injection from a CoFeB/MgO spin injector into a AlGaAs/GaAs semiconductor light emitting diode. Under pulsed electrical excitation, time-resolved electroluminescence on nanosecond time scale exhibits a plateau of circular polarization degree as high as 15% under a 0.8 T magnetic field. It follows an initial decay that could be due to electron spin-relaxation process in the quantum well embedded in the intrinsic region of the diode. The temporal buildup of the electronic spin polarization degree in the quantum well is much faster than the rise time of electroluminescence intensity.
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72.25.Hg Electrical injection of spin polarized carriers
85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.47.jd Time resolved luminescence
78.67.De Quantum wells

Photonic crystal heteroslab-edge microcavity with high quality factor surface mode for index sensing

Tsan-Wen Lu, Yi-Hua Hsiao, Wei-De Ho, and Po-Tsung Lee

Appl. Phys. Lett. 94, 141110 (2009); http://dx.doi.org/10.1063/1.3117225 (3 pages) | Cited 9 times

Online Publication Date: 10 April 2009

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In this report, we propose a photonic crystal heteroslab-edge microcavity design for optical index sensing, where the high quality (Q) surface mode is confined by mode-gap effect. By optimizing the barrier region of the microcavity, high Q factor of 6.6×105 is obtained in simulations. Lasing actions with high Q factor and low threshold of 6400 and 0.55 mW are obtained from the real devices. High index sensing response and small detectable index variation of 625 nm per refractive index unit and 3.6×10−6 are obtained in simulations.
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07.60.Hv Refractometers and reflectometers
42.15.Eq Optical system design
42.55.Sa Microcavity and microdisk lasers
42.55.Tv Photonic crystal lasers and coherent effects
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy

High output power density from GaN-based two-dimensional nanorod light-emitting diode arrays

Ya-Ju Lee, Shawn-Yu Lin, Ching-Hua Chiu, Tien-Chang Lu, Hao-Chung Kuo, Shing-Chung Wang, Sameer Chhajed, Jong Kyu Kim, and E. Fred Schubert

Appl. Phys. Lett. 94, 141111 (2009); http://dx.doi.org/10.1063/1.3119192 (3 pages) | Cited 15 times

Online Publication Date: 10 April 2009

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Here we propose and realize a scheme for making a direct contact to a two-dimensional nanorod light-emitting diode (LED) array using the oblique-angle deposition approach. And, more importantly, we demonstrate highly efficient electrical carrier injection into the nanorods. As a result, we show that at a 20 mA dc current injection, the light output power density of our nanorod LED array is 3700 mW cm−2. More general, this contact scheme will pave the ways for making direct contacts to other kinds of nanoscale optoelectronic devices.
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85.60.Jb Light-emitting devices
81.16.-c Methods of micro- and nanofabrication and processing
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
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Fast imaging of laser-blow-off plume: Lateral confinement in ambient environment

Sony George, Ajai Kumar, R. K. Singh, and V. P. N. Nampoori

Appl. Phys. Lett. 94, 141501 (2009); http://dx.doi.org/10.1063/1.3111441 (3 pages) | Cited 7 times

Online Publication Date: 7 April 2009

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The dynamics of plasma plume, formed by the laser-blow-off of multicomponent LiF-C thin film under various ambient pressures ranging from high vacuum to argon pressure of 3 Torr, has been studied using fast imaging technique. In vacuum, the plume has ellipsoidal shape. With the increase in the ambient pressure, sharp plume boundary is developed showing a focusing-like (confinement in the lateral space) behavior in the front end, which persists for long times. At higher ambient pressure (>10−1 Torr), structures are developed in the plasma plume due to hydrodynamic instability/turbulences.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.40.Hf Plasma-material interactions; boundary layer effects
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
79.20.Ds Laser-beam impact phenomena

Bacterial inactivation using atmospheric pressure single pin electrode microplasma jet with a ground ring

Sun Ja Kim, T. H. Chung, S. H. Bae, and S. H. Leem

Appl. Phys. Lett. 94, 141502 (2009); http://dx.doi.org/10.1063/1.3114407 (3 pages) | Cited 20 times

Online Publication Date: 8 April 2009

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Bacterial inactivation experiment was performed using atmospheric pressure microplasma jets driven by radio-frequency wave of 13.56 MHz and by low frequency wave of several kilohertz. With addition of a ground ring electrode, the discharge current, the optical emission intensities from reactive radicals, and the sterilization efficiency were enhanced significantly. When oxygen gas was added to helium at the flow rate of 5 SCCM, the sterilization efficiency was enhanced. From the survival curve of Escherichia coli, the primary role in the inactivation was played by reactive species with minor aid from heat, UV photons, charged particles, and electric fields.
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87.53.-j Effects of ionizing radiation on biological systems
52.75.-d Plasma devices
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Optical properties of rolled-up tubular microcavities from shaped nanomembranes

G. S. Huang (黄高山), S. Kiravittaya, V. A. Bolaños Quiñones, F. Ding (丁飞), M. Benyoucef, A. Rastelli, Y. F. Mei (梅永丰), and O. G. Schmidt

Appl. Phys. Lett. 94, 141901 (2009); http://dx.doi.org/10.1063/1.3111813 (3 pages) | Cited 21 times

Online Publication Date: 6 April 2009

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Tubular optical microcavities have been fabricated by releasing prestressed SiO/SiO2 bilayer nanomembranes from polymer sacrificial layers, and their geometrical structure is well controlled by defining the shape of nanomembranes via photolithography. Optical measurements at room temperature demonstrate that resonant modes of microtubular cavities rolled up from circular shapes can be tuned in peak energy and relative intensity along the tube axes compared to those from square patterns. The resonant modes shift to higher energy with decreasing number of tube wall rotations and thickness, which fits well to finite-difference time-domain simulations. Polarization resolved measurements of the resonant modes indicate that their polarization axes are parallel to the tube axis, independent of the polarization of the excitation laser.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Hx Other solid inorganic materials

Room temperature photoluminescence of tensile-strained Ge/Si0.13Ge0.87 quantum wells grown on silicon-based germanium virtual substrate

Yanghua Chen, Cheng Li, Zhiwen Zhou, Hongkai Lai, Songyan Chen, Wuchang Ding, Buwen Cheng, and Yude Yu

Appl. Phys. Lett. 94, 141902 (2009); http://dx.doi.org/10.1063/1.3114408 (3 pages) | Cited 8 times

Online Publication Date: 6 April 2009

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We report a room temperature study of the direct band gap photoluminescence of tensile-strained Ge/Si0.13Ge0.87 multiple quantum wells grown on Si-based germanium virtual substrates by ultrahigh vacuum chemical vapor deposition. Blueshifts of the luminescence peak energy from the Ge quantum wells in comparison with the Ge virtual substrate are in good agreement with the theoretical prediction when we attribute the luminescence from the quantum well to the cΓ1-HH1 direct band transition. The reduction in direct band gap in the tensile strained Ge epilayer and the quantum confinement effect in the Ge/Si0.13Ge0.87 quantum wells are directly demonstrated by room temperature photoluminescence.
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78.67.De Quantum wells
71.20.Mq Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.21.Fg Quantum wells
81.07.St Quantum wells
78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors

Ab initio molecular dynamics study of the hydrogen-deuterium exchange in bulk lithiumborohydride (LiBH4)

M. Ramzan and R. Ahuja

Appl. Phys. Lett. 94, 141903 (2009); http://dx.doi.org/10.1063/1.3115032 (2 pages) | Cited 6 times

Online Publication Date: 6 April 2009

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The hydrogen storage is still a challenge for mobile applications. The diffusion of hydrogen in solids is considered as a general model system but there is limited knowledge available for the dynamics of hydrogen in complex hydrides. In this letter, we present a systematic approach to study the hydrogen-deuterium exchange in bulk LiBH4 based on ab initio molecular dynamics. Our results predict the single hydrogen (deuterium) exchange in LiBH4, which supports the experimental results. The self-diffusion constant 〈D〉 of deuterium in LiBH4 is around 1.42×10−8 m2 s−1.
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84.60.-h Direct energy conversion and storage
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations
66.30.H- Self-diffusion and ionic conduction in nonmetals

Structural and optical investigations of periodically polarity inverted ZnO heterostructures on (0001) Al2O3

J. S. Park, T. Goto, S. K. Hong, S. H. Lee, J. W. Lee, T. Minegishi, S. H. Park, J. H. Chang, D. C. Oh, J. Y. Lee, and T. Yao

Appl. Phys. Lett. 94, 141904 (2009); http://dx.doi.org/10.1063/1.3114989 (3 pages) | Cited 4 times

Online Publication Date: 7 April 2009

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We report the structural and optical properties of one-dimensional grating of ZnO consisting of periodically polarity inverted structures on (0001) Al2O3 substrates. The inversion domain boundaries (IDBs) between the Zn- and the O-polar ZnO regions were clearly observed by transmission electronic microscopy. The investigation of spatially resolved local photoluminescence (PL) revealed strong excitonic emission at the interfacial region including the IDBs. The possible mechanism of strong PL has been discussed by the consideration of atomic configuration and carrier collection including its lifetime and diffusion process in Zn- and O-polar regions. Therefore the authors conclude that the IDBs can be active for the strong emission not a nonradiative center.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
66.30.H- Self-diffusion and ionic conduction in nonmetals
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
73.61.Ga II-VI semiconductors
68.55.-a Thin film structure and morphology

Direct observation of ion exchange in mechanically activated LiH+MgB2 system using ultrahigh field nuclear magnetic resonance spectroscopy

Jian Zhi Hu, Ja Hun Kwak, Zhenguo Yang, Xuefei Wan, and Leon L. Shaw

Appl. Phys. Lett. 94, 141905 (2009); http://dx.doi.org/10.1063/1.3110966 (3 pages) | Cited 6 times

Online Publication Date: 8 April 2009

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The LiBH4+MgH2 system has great potential for hydrogen vehicle applications. In this study, the reported solid-state hydrogenation system made of LiH+1/2MgB2 has been investigated using ultrahigh field nuclear magnetic resonance spectroscopy. It is found that Mg–Li ion exchange occurs within MgB2 during ball milling to form a compound of (Mg1−xLi2x)B2, which facilitates the formation of LiBH4 in the subsequent hydriding reaction. This discovery offers a scientific foundation for investigating the detailed mechanisms of solid-state hydrogenation and dehydrogenation of the LiBH4+MgH2 system in the future.
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82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
84.60.-h Direct energy conversion and storage
76.60.-k Nuclear magnetic resonance and relaxation

The influence of nanoscale atomic-layer-deposited alumina coating on the fatigue behavior of polycrystalline silicon thin films

M. Budnitzki and O. Pierron

Appl. Phys. Lett. 94, 141906 (2009); http://dx.doi.org/10.1063/1.3112565 (3 pages) | Cited 6 times

Online Publication Date: 8 April 2009

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The influence of atomic-layer-deposited alumina surface coatings on the fatigue of polycrystalline silicon thin films was investigated. Tests were performed on 2-μm-thick notched cantilever-beam structures actuated at resonance ( ∼ 40 kHz) that were coated with ∼ 20 nm of alumina deposited at 100 °C. The coated devices show a drastically different frequency evolution behavior as compared to uncoated specimens, while no surface oxide thickening during cycling is observed in bright-field transmission electron microscopy. Both results are consistent with a surface degradation mechanism for polycrystalline silicon fatigue such as the reaction-layer mechanism. The improved frequency evolution has the potential of increasing the performance of resonator-based microelectromechanical system sensors.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.me Fatigue
62.25.-g Mechanical properties of nanoscale systems

Optical and electronic properties of one-dimensional Ca3Co2O6 thin films: Influence of the oxygen pressure

R. Moubah, S. Colis, G. Schmerber, J. Petersen, and A. Dinia

Appl. Phys. Lett. 94, 141907 (2009); http://dx.doi.org/10.1063/1.3114373 (3 pages) | Cited 7 times

Online Publication Date: 8 April 2009

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Thin films of Ca3Co2O6 were fabricated on c-cut sapphire substrates by pulsed laser deposition. The films are polycrystalline and can be grown in a large interval of oxygen pressure with significant influence on the film texture. X-ray photoelectron spectroscopy analyses indicated that only Co3+ ions are present in our samples for both octahedral and trigonal prismatic sites. The band gap measured by ultraviolet-visible light absorption experiments was found about 1.35 eV and slightly larger when the oxygen partial pressure during the deposition is increased from 10−3 to 7×10−2 mbar. Temperature dependent transport measurements showed a semiconducting behavior of the films and the associated band gap was found similar to the one evaluated by optical measurements and reported by theoretical studies.
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78.66.Nk Insulators
78.40.Ha Other nonmetallic inorganics
71.20.-b Electron density of states and band structure of crystalline solids
79.60.Dp Adsorbed layers and thin films
81.15.Fg Pulsed laser ablation deposition
68.55.jm Texture

Electronic and structural properties of molybdenum thin films as determined by real-time spectroscopic ellipsometry

J. D. Walker, H. Khatri, V. Ranjan, Jian Li, R. W. Collins, and S. Marsillac

Appl. Phys. Lett. 94, 141908 (2009); http://dx.doi.org/10.1063/1.3117222 (3 pages) | Cited 6 times

Online Publication Date: 8 April 2009

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Real-time spectroscopic ellipsometry (RTSE) is shown to be an effective contactless probe of radio frequency magnetron sputtered molybdenum thin films used as the back electrode in chalcopyrite [Cu(In,Ga)Se2] solar cells. A series of Mo thin films was sputtered onto soda-lime glass substrates at Ar pressures ranging from 4 to 20 mTorr. RTSE measurements reveal how Ar pressure affects the nucleation and growth mechanisms that influence the films’ ultimate grain structure and properties. Determinations of the free electron relaxation times at optical frequencies reveal that higher pressures lead to a smaller average grain size and increased void volume fraction.
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68.55.A- Nucleation and growth
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
72.15.Lh Relaxation times and mean free paths
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.At Metal and metallic alloys
81.15.Cd Deposition by sputtering

SiGe nanorings by ultrahigh vacuum chemical vapor deposition

C.-H. Lee, Y.-Y. Shen, C. W. Liu, S. W. Lee, B.-H. Lin, and C.-H. Hsu

Appl. Phys. Lett. 94, 141909 (2009); http://dx.doi.org/10.1063/1.3116619 (3 pages) | Cited 8 times

Online Publication Date: 9 April 2009

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Formation of SiGe nanorings from Si capped Si0.1Ge0.9 quantum dots (QDs) grown at 500 °C by ultrahigh vacuum chemical vapor deposition was investigated. SiGe nanorings have average diameter, width, and depth of 185, 30, and 9 nm, respectively. Based on both Raman and x-ray diffraction results, the formation of SiGe nanorings can be attributed to Ge outdiffusion from central SiGe QDs during in situ annealing. Moreover, the depth of SiGe nanorings can be controlled by Si cap thickness. The Si cap is essential for nanorings formation.
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81.16.-c Methods of micro- and nanofabrication and processing
61.05.C- X-ray diffraction and scattering
61.72.Cc Kinetics of defect formation and annealing
66.30.H- Self-diffusion and ionic conduction in nonmetals
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.65.Hb Quantum dots (patterned in quantum wells)

On the influence of elastic strain on the accommodation of carbon atoms into substitutional sites in strained Si:C layers grown on Si substrates

N. Cherkashin, M. J. Hÿtch, F. Houdellier, F. Hüe, V Paillard, A. Claverie, A. Gouyé, O. Kermarrec, D. Rouchon, M. Burdin, and P. Holliger

Appl. Phys. Lett. 94, 141910 (2009); http://dx.doi.org/10.1063/1.3116648 (3 pages) | Cited 4 times

Online Publication Date: 9 April 2009

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Measurements of strain and composition are reported in tensile strained 10- and 30-nm-thick Si:C layers grown by chemical vapor deposition on a Si (001) substrate. Total carbon concentration varies from 0.62% to 1.97%. Strain measurements were realized by high-resolution x-ray diffraction, convergent-beam electron diffraction, and geometric phase analysis of high-resolution transmission electron microscopy cross-sectional images. Raman spectroscopy was used for the deduction of the substitutional concentration. We demonstrate that in addition to the growth conditions, strain accumulating during deposition, thus depending on a layer thickness, has an influence on the final substitutional carbon composition within a strained Si:C layer.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.30.Hv Other nonmetallic inorganics
73.61.Le Other inorganic semiconductors
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep

Band offsets at the Ge/GeO2 interface through hybrid density functionals

Peter Broqvist, Jan Felix Binder, and Alfredo Pasquarello

Appl. Phys. Lett. 94, 141911 (2009); http://dx.doi.org/10.1063/1.3116612 (3 pages) | Cited 20 times

Online Publication Date: 10 April 2009

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Band offsets of the Ge/GeO2 interface are calculated through a hybrid density functional scheme. We first generate a model of disordered GeO2 through ab initio molecular dynamics to describe the oxide component. For addressing the interface, we then consider an atomistic model in which amorphous GeO2 is connected to crystalline Ge through a suboxide transition region showing regular structural parameters. The band offsets are obtained through the application of an alignment scheme, which reproduces the experimental band gaps of the interface components. The calculated valence band offset of 3.7 eV favors the low-energy side of the range of measured offsets.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Nr Semiconductor compounds
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations

Experimental and computational studies on structural transitions in the LiBH4–LiI pseudobinary system

H. Oguchi, M. Matsuo, J. S. Hummelshøj, T. Vegge, J. K. Nørskov, T. Sato, Y. Miura, H. Takamura, H. Maekawa, and S. Orimo

Appl. Phys. Lett. 94, 141912 (2009); http://dx.doi.org/10.1063/1.3117227 (3 pages) | Cited 21 times

Online Publication Date: 10 April 2009

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Structural transition properties of the LiBH4+xLiI (x = 0–1.00) pseudobinary system were examined by powder x-ray diffraction and differential scanning calorimetry combined with periodic density functional theory calculations. We experimentally and computationally confirmed the stabilization of the high-temperature [hexagonal, lithium super(fast-)ionic conduction] phase of LiBH4 with x = 0.33 and 1.00, and the results also imply the existence of intermediate phases with x = 0.07–0.20. The studies are of importance for further development of LiBH4 and the derived hydrides as solid-state electrolytes.
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64.70.K- Solid-solid transitions
81.70.Pg Thermal analysis, differential thermal analysis (DTA), differential thermogravimetric analysis
82.45.Gj Electrolytes
66.30.H- Self-diffusion and ionic conduction in nonmetals
65.40.gk Electrochemical properties
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