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29 Jan 2007

Volume 90, Issue 5, Articles (05xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 90, 052503 (2007); http://dx.doi.org/10.1063/1.2436715 (3 pages)

Biqin Huang, Igor Altfeder, and Ian Appelbaum
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Influence of uniaxial stress on stimulated terahertz emission from phosphor and antimony donors in silicon

R. Kh. Zhukavin, V. V. Tsyplenkov, K. A. Kovalevsky, V. N. Shastin, S. G. Pavlov, U. Böttger, H.-W. Hübers, H. Riemann, N. V. Abrosimov, and N. Nötzel

Appl. Phys. Lett. 90, 051101 (2007); http://dx.doi.org/10.1063/1.2431568 (3 pages) | Cited 6 times

Online Publication Date: 29 January 2007

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The effect of uniaxial stress on terahertz stimulated emission from phosphor and antimony donors in silicon excited by CO2 laser radiation was studied. The laser action originates from 2p0→1s(T2) intracenter transitions. A compressive force applied to the silicon crystal decreases the laser threshold by one order of magnitude. The output power depends nonmonotonically on the stress, while the emission frequency does not change. The results are explained by changes of the donor electronic structure, which do not affect the energy gap between the laser states, and a resonant interaction with acoustic f-TA and g-TA phonons that disappears with increasing stress.
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78.45.+h Stimulated emission
63.20.K- Phonon interactions
71.55.Cn Elemental semiconductors
78.70.Gq Microwave and radio-frequency interactions

Ultrashort pulse generation in lasers by nonlinear pulse amplification and compression

L. M. Zhao, D. Y. Tang, T. H. Cheng, and C. Lu

Appl. Phys. Lett. 90, 051102 (2007); http://dx.doi.org/10.1063/1.2437124 (3 pages) | Cited 1 time

Online Publication Date: 29 January 2007

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Generation of ultrashort, transform-limited pulses in a laser resonator by means of nonlinear pulse amplification and compression is observed both numerically and experimentally; this constitutes another type of pulse shaping mechanism in the mode-locked lasers. It is shown that as a result of nonlinear pulse compression, mode-locked pulse with pulse width beyond the gain bandwidth limitation could be directly generated in a laser.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Technique for measuring the rotational velocity of a single cell

Toshiki Yasokawa, Ichirou Ishimaru, Katsumi Ishizaki, Kazuhiro Gesyo, Shigeki Kuriyama, Tsutomu Masaki, Kaoru Takegawa, and Naotaka Tanaka

Appl. Phys. Lett. 90, 051103 (2007); http://dx.doi.org/10.1063/1.2437129 (3 pages)

Online Publication Date: 30 January 2007

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A method for measuring the rotational velocity of a cell is presented. In this method, a parallel pencil beam illuminates the cell and the reflected light intensity distribution from the cell surface is observed using an objective lens. In the Fourier transform plane of the lens, this light intensity distribution is translated by an amount that corresponds to the rotational velocity of the cell. This translational velocity can be converted into the rotational velocity. The authors confirmed that the rotational velocity of a cell could be measured using this method by rotating a cancer cell using light pressure.
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87.63.L- Visual imaging
87.17.-d Cell processes
87.19.X- Diseases
42.30.Kq Fourier optics

Kinetic study of Al-mole fraction in AlxGa1−xN grown on c-plane sapphire and AlN bulk substrates by metal-organic vapor-phase epitaxy

Y. A. Xi, K. X. Chen, F. W. Mont, J. K. Kim, W. Lee, E. F. Schubert, W. Liu, X. Li, and J. A. Smart

Appl. Phys. Lett. 90, 051104 (2007); http://dx.doi.org/10.1063/1.2437681 (3 pages) | Cited 2 times

Online Publication Date: 30 January 2007

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A systematic study is performed on the dependence of the Al-mole fraction in AlxGa1−xN on the organometallic group-III precursor flow during metal-organic vapor-phase epitaxy. When keeping the total organometallic volume flow constant, a nonlinear concave bowing relationship is found between the Al-mole fraction (for 0 ⩽ x ⩽ 1) and the relative trimethylaluminum volume flow. A kinetic model, which takes into account the growth rate ratio between GaN and AlN (gGaN/gAlN), is developed to explain such concave bowing relationship. The experimental data are in excellent agreement with the theoretical model. For AlxGa1−xN growth on AlN bulk substrates, it is found that the Al-mole fraction is smaller and the growth rate ratio is larger than on sapphire substrates. The authors also investigate the incorporation of Al in AlxGa1−xN as a function of the group-III precursor molar flow rate. A positive convex bowing relationship is found between Al-mole fraction and the relative trimethylaluminum molar flow, which is consistent with our model.
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68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Ea III-V semiconductors

Enhanced photoresponse of a metal-oxide-semiconductor photodetector with silicon nanocrystals embedded in the oxide layer

Jia-Min Shieh, Yi-Fan Lai, Wei-Xin Ni, Hao-Chung Kuo, Chih-Yao Fang, Jung Y. Huang, and Ci-Ling Pan

Appl. Phys. Lett. 90, 051105 (2007); http://dx.doi.org/10.1063/1.2450653 (3 pages) | Cited 14 times

Online Publication Date: 30 January 2007

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The authors report a two-terminal metal-oxide-semiconductor photodetector for which light is absorbed in a capping layer of silicon nanocrystals embedded in a mesoporous silica matrix on p-type silicon substrates. Operated at reverse bias, enhanced photoresponse from 300 to 700 nm was observed. The highest optoelectronic conversion efficiency is as high as 200%. The enhancements were explained by a transistorlike mechanism, in which the inversion layer acts as the emitter and trapped positive charges in the mesoporous dielectric layer assist carrier injection from the inversion layer to the contact, such that the primary photocurrent could be amplified.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.30.Tv Field effect devices

Blue light emitting diodes based on fluorescent CdSe/ZnS nanocrystals

Aurora Rizzo, Yanqin Li, Stefan Kudera, Fabio Della Sala, Marco Zanella, Wolfgang J. Parak, Roberto Cingolani, Liberato Manna, and Giuseppe Gigli

Appl. Phys. Lett. 90, 051106 (2007); http://dx.doi.org/10.1063/1.2426899 (3 pages) | Cited 28 times

Online Publication Date: 30 January 2007

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The authors report on the blue electroluminescence from CdSe/ZnS core/shell nanocrystals prepared from ultrasmall, magic size CdSe clusters that have a diameter of less than 2 nm. The light emitting device consists of an active layer of nanocrystals blended with 4,4′,N,N′- diphenylcarbazole and an evaporated electron transporting/hole blocking layer made of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline. A blue, stable electroluminescence at 485 nm from the hybrid device was observed, in good agreement with the photoluminescence spectra of a solid film of the same nanocrystals used for the device.
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85.60.Jb Light-emitting devices

Polariton parametric luminescence in a single micropillar

D. Bajoni, E. Peter, P. Senellart, J. L. Smirr, I. Sagnes, A. Lemaître, and J. Bloch

Appl. Phys. Lett. 90, 051107 (2007); http://dx.doi.org/10.1063/1.2435515 (3 pages) | Cited 14 times

Online Publication Date: 31 January 2007

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The authors report on parametric luminescence in a single pillar semiconductor microcavity. Nonresonant photoluminescence measurements at 10 K show that micropillars operate in the exciton-photon strong coupling regime. Under resonant excitation, polariton parametric scattering is observed: signal and idler beams are of comparable intensities, a promising result in the framework of quantum optics with correlated photon pairs.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
71.35.-y Excitons and related phenomena
42.50.-p Quantum optics

Wavelength- and material-dependent absorption in GaAs and AlGaAs microcavities

C. P. Michael, K. Srinivasan, T. J. Johnson, O. Painter, K. H. Lee, K. Hennessy, H. Kim, and E. Hu

Appl. Phys. Lett. 90, 051108 (2007); http://dx.doi.org/10.1063/1.2435608 (3 pages) | Cited 22 times

Online Publication Date: 31 January 2007

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The quality factors of modes in nearly identical GaAs and Al0.18Ga0.82As microdisks are tracked over three wavelength ranges centered at 980, 1460, and 1600 nm, with quality factors measured as high as 6.62×105 in the 1600 nm band. After accounting for surface scattering, the remaining loss is due to sub-band-gap absorption in the bulk and on the surfaces. The observed absorption is, on average, 80% greater in AlGaAs than in GaAs and is 540% higher in both materials at 980 nm than at 1600 nm.
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78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors

Extrahigh color rendering white light-emitting diode lamps using oxynitride and nitride phosphors excited by blue light-emitting diode

Naoki Kimura, Ken Sakuma, Syunichiro Hirafune, Kenichiro Asano, Naoto Hirosaki, and Rong-Jun Xie

Appl. Phys. Lett. 90, 051109 (2007); http://dx.doi.org/10.1063/1.2437090 (3 pages) | Cited 71 times

Online Publication Date: 1 February 2007

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The blue-light-excitation-type white light-emitting diode (LED) lamps are considered to be very suitable for lighting for art objects, shop window displays, and medical applications because they do not give infrared ray and ultraviolet ray. But their color rendering indices are needed to be improved for such applications. In this letter, the authors have fabricated white LED lamps with a broad range of color temperatures, and realized extrahigh color rendering index Ra values of 95–98 in them, using four oxynitride/nitride phosphors and a blue LED die. It means UV LED die is not always necessary for high color rendering white LED lamps. The luminous efficacies of white LED lamps are 28–35 lm/W, which are sufficiently high for extremely high color rendering white LED lamps.
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85.60.Jb Light-emitting devices
42.72.Bj Visible and ultraviolet sources

Excitation dynamics of the 1.54 μm emission in Er doped GaN synthesized by metal organic chemical vapor deposition

C. Ugolini, N. Nepal, J. Y. Lin, H. X. Jiang, and J. M. Zavada

Appl. Phys. Lett. 90, 051110 (2007); http://dx.doi.org/10.1063/1.2450641 (3 pages) | Cited 20 times

Online Publication Date: 1 February 2007

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The authors report on the excitation dynamics of the photoluminescence (PL) emission of Er doped GaN thin films synthesized by metal organic chemical vapor deposition. Using the frequency tripled output from a Ti:sapphire laser, the authors obtained PL spectra covering the ultraviolet (UV) to the infrared regions. In the UV, a dominant band edge emission at 3.23 eV was observed at room temperature; this is redshifted by 0.19 eV from the band edge emission of undoped GaN. An activation energy of 191 meV was obtained from the thermal quenching of the integrated intensity of the 1.54 μm emission line. This value coincides with the redshift of the band edge emission and is assigned to the ErGa-VN complex level.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.40.Gh Other heat and thermomechanical treatments
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Short-wavelength (λ ≈ 3.05 μm) InP-based strain-compensated quantum-cascade laser

M. P. Semtsiv, M. Wienold, S. Dressler, and W. T. Masselink

Appl. Phys. Lett. 90, 051111 (2007); http://dx.doi.org/10.1063/1.2437108 (3 pages) | Cited 35 times

Online Publication Date: 2 February 2007

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The design and implementation of a short-wavelength quantum-cascade laser based on the strain-compensated In0.73Ga0.27As–In0.55Al0.45As–AlAs heterosystem on InP is described. Lasers with a reduced level of doping in the active region require a larger bias voltage and emit at shorter wavelength; the emission wavelength is 3.05 μm at T ≈ 80 K. The lasers operate up to T ≈ 150 K and electroluminescence persists up to room temperature, where the peak position is close to 3.3 μm. The short-wavelength limit of such lasers is evaluated based on the dependence of their maximum operation temperatures and on the probable energies of the indirect valleys in the active region.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Excitation dependences of gain and carrier-induced refractive index change in quantum-dot lasers

M. Lorke, F. Jahnke, and W. W. Chow

Appl. Phys. Lett. 90, 051112 (2007); http://dx.doi.org/10.1063/1.2437670 (3 pages) | Cited 11 times

Online Publication Date: 2 February 2007

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The excitation-density dependence of optical gain and refractive index changes in quantum-dot active media is investigated on the basis of a microscopic theory. Carrier-carrier Coulomb interaction and carrier-phonon interaction are treated on the level of a quantum-kinetic description. In the range of small optical gain the authors find small values of the α factor, while in the regime of gain saturation ∣α∣ increases drastically.
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42.55.Px Semiconductor lasers; laser diodes
63.20.K- Phonon interactions
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Off-axis directional beaming of optical field diffracted by a single subwavelength metal slit with asymmetric dielectric surface gratings

Seyoon Kim, Hwi Kim, Yongjun Lim, and Byoungho Lee

Appl. Phys. Lett. 90, 051113 (2007); http://dx.doi.org/10.1063/1.2437730 (3 pages) | Cited 49 times

Online Publication Date: 2 February 2007

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The authors propose a method for the off-axis directional beaming of optical field diffracted by a single subwavelength metal slit with dielectric surface gratings. In the proposed method, dielectric gratings are optimally designed to directionally couple the surface plasmon polariton modes induced by the metal slit into surrounding medium along a specific off-axis direction. Design of the gratings and the analysis are conducted based on the rigorous coupled wave analysis method. Their simulation shows the off-axis directional beaming of the oblique angle, 20.2°, with respect to the on axis by the proposed method. The beaming angle can be changed by adjusting the grating periods.
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42.79.Gn Optical waveguides and couplers
42.79.Dj Gratings
42.15.Eq Optical system design
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)

Measured limits of detection based on thermal-mechanical frequency noise in micromechanical sensors

T. H. Stievater, W. S. Rabinovich, N. A. Papanicolaou, R. Bass, and J. B. Boos

Appl. Phys. Lett. 90, 051114 (2007); http://dx.doi.org/10.1063/1.2450643 (3 pages) | Cited 6 times

Online Publication Date: 2 February 2007

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The authors have fabricated and tested all-optical micromechanical resonators that sense the presence of analyte molecules by monitoring the shift in the resonant frequency of a mechani-cal mode of vibration. An analysis of the measured frequency noise at the fundamental flexural mode shows that it is dominated by thermal-mechanical noise. This result demonstrates that thermal-mechanical frequency noise can set the limit of detection in actual micromechanical or nanomechanical resonance-based sensors.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.80.-d Chemical analysis and related physical methods of analysis

High power continuous-wave green light generation by quasiphase matching in Mg stoichiometric lithium tantalate

Sergey V. Tovstonog, Sunao Kurimura, and Kenji Kitamura

Appl. Phys. Lett. 90, 051115 (2007); http://dx.doi.org/10.1063/1.2450648 (3 pages) | Cited 27 times

Online Publication Date: 2 February 2007

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Single-pass second-harmonic generation of 7 W continuous wave of 542 nm radiation with 35.4% efficiency was achieved by quasiphase matching in periodically poled Mg-doped stoichiometric lithium tantalate at room temperature. The effects of laser beam quality and linewidth on the second-harmonic generation efficiency were investigated using a Yb-doped fiber laser.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Mp Nonlinear optical crystals
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Viewing angle switching of vertical alignment liquid crystal displays by controlling birefringence of homogenously aligned liquid crystal layer

Eun Jeong, Young Jin Lim, John Moon Rhee, Seung Hee Lee, Gi-Dong Lee, Kyoung Ho Park, and Hyun Chul Choi

Appl. Phys. Lett. 90, 051116 (2007); http://dx.doi.org/10.1063/1.2435693 (3 pages) | Cited 24 times

Online Publication Date: 2 February 2007

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Viewing angle switching from a wide viewing angle to a narrow viewing angle has been studied. Conventional multidomain vertical alignment (VA) mode offers the advantages of a high contrast ratio (CR) not only in the front view but also in the wide viewing directions only if compensation films such as a negative C plate and a positive A plate are used. The positive A plate can be replaced by a homogeneous aligned (HA) liquid crystal layer, and the retardation of the HA layer at the off axis can be controlled by applying an electric field while keeping the retardation value at zero in the normal direction. Consequently, the viewing angle range of a VA device can be controlled from a wide viewing mode (over 170° in terms of CR = 10) to a narrow viewing angle mode (approximately 60° in terms of CR = 2) in the horizontal direction while keeping a high image quality at the normal direction.
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42.79.Kr Display devices, liquid-crystal devices
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Motion characteristics of long ac arcs in atmospheric air

Shanqiang Gu, Jinliang He, Rong Zeng, Bo Zhang, Guozheng Xu, and Weijiang Chen

Appl. Phys. Lett. 90, 051501 (2007); http://dx.doi.org/10.1063/1.2435622 (3 pages) | Cited 2 times

Online Publication Date: 31 January 2007

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Experiments on the motion of long alternating current arcs in atmospheric air show that the anode and cathode arc roots have different motion characteristics because of different formation mechanisms. During a half cycle of the arc current, the anode arc root moves towards the direction of magnetic force and occasionally has a jumping motion, while the cathode arc root moves sufficiently slow to consider it stationary and hardly has any jump. The arc column has a complex shape and moves under the drive of the magnetic force and is also quickened by the lower arc root.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.25.Fi Transport properties

Electrohydrodynamic force and scaling laws in surface dielectric barrier discharges

Y. Lagmich, Th. Callegari, Th. Unfer, L. C. Pitchford, and J. P. Boeuf

Appl. Phys. Lett. 90, 051502 (2007); http://dx.doi.org/10.1063/1.2435349 (3 pages) | Cited 12 times

Online Publication Date: 1 February 2007

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The electrohydrodynamic force generated by surface dielectric barrier discharges is analyzed with a fluid mode under conditions where the electrode above the dielectric surface is the anode.. The calculated current is composed of successive large pulses associated with filamentary discharges spreading along the dielectric surface, separated by low current periods where the discharge is in a transient “coronalike” regime. The contribution of the corona discharges to the overall force is by far dominant. An important result is that the extension of the region above the surface where the electrohydrodynamic force is significant depends on the product of the dielectric layer capacitance and the rate of voltage increase (spatial extension is larger when this parameter is smaller), but that the total, integrated force is not very sensitive to these parameters.
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52.80.Hc Glow; corona
52.65.Kj Magnetohydrodynamic and fluid equation

Ethynyl (C2H): A major player in the chemical vapor deposition of diamond

Peter Deák, Antal Kováts, Peter Csíkváry, István Maros, and György Hárs

Appl. Phys. Lett. 90, 051503 (2007); http://dx.doi.org/10.1063/1.2437718 (3 pages) | Cited 1 time

Online Publication Date: 2 February 2007

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In situ mass spectrometry of the near-surface composition—with special emphasis on radicals—has been carried out during diamond deposition from a microwave plasma in a CH4/H2 mixture at 25 and 100 mbars. The most abundant species in the former case are C2H2 and CH3, together giving 65% of the hydrocarbon content. At 100 mbars, this value drops to 15%, while the C2H content rises to 76%. The factor of ∼ 8 increase in the C2H ratio is accompanied by a similar increase in the growth rate, indicating a major role of C2H in diamond growth.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
81.05.U- Carbon/carbon-based materials

Atmospheric-pressure argon/oxygen plasma-discharge source with a stepped electrode

Jin-Pyo Lim, Han S. Uhm, and Shou-Zhe Li

Appl. Phys. Lett. 90, 051504 (2007); http://dx.doi.org/10.1063/1.2450654 (3 pages) | Cited 14 times

Online Publication Date: 2 February 2007

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The nonequilibrium glow discharge in argon mixed with oxygen at atmospheric pressure was generated in a parallel plate reactor with a stepped electrode powered by a 13.56 MHz radio-frequency power supplier. The stepped-electrode reactor consists of a narrow and wide gap structure. A strong electric field occurred at the narrow gap region preionizes Ar/O2 gas and assists to generate a large volumetric plasma in the wide gap region. Therefore, the stepped-electrode reactor makes it easy to operate Ar/O2 glow discharge, providing a stable, uniform, and broad plasma jet at atmospheric pressure.
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52.50.Dg Plasma sources
52.80.Hc Glow; corona
52.25.Jm Ionization of plasmas
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Enhanced interface mixing of Fe/Si bilayers on preamorphized silicon substrates

N. Bibić, V. Milinović, K. P. Lieb, M. Milosavljević, and F. Schrempel

Appl. Phys. Lett. 90, 051901 (2007); http://dx.doi.org/10.1063/1.2432952 (3 pages) | Cited 5 times

Online Publication Date: 29 January 2007

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Ion-beam mixing of Fe/Si bilayers, induced at room temperature by 100 keV 40Ar+, 180 keV 86Kr+, and 250 keV 132Xe+ ions, was investigated. The study focuses on the influence of the preamorphization of the Si(100) substrates by 1.0 keV Ar-ion irradiation. Rutherford backscattering spectroscopy as well as scanning and transmission electron microscopies were applied for structural characterization. The mixing rate across the preamorphized Fe/Si interface was, on average, by 76% higher than that of crystalline Si.
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64.75.-g Phase equilibria
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
61.82.Fk Semiconductors
61.82.Bg Metals and alloys
61.80.Jh Ion radiation effects

Recombination processes in undoped and rare-earth doped MAl2O4 (M = Ca,Sr) persistent phosphors investigated by optically detected magnetic resonance

Stefan Schweizer, Bastian Henke, Uldis Rogulis, and William M. Yen

Appl. Phys. Lett. 90, 051902 (2007); http://dx.doi.org/10.1063/1.2437099 (3 pages) | Cited 1 time

Online Publication Date: 29 January 2007

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The authors present magneto-optical measurements on single-crystal MAl2O4 (M = Ca and Sr) persistent phosphors that are nominally pure or doped with Eu and Nd or Dy, respectively. Their recombination luminescence (RL) and microwave-induced changes in the RL in a high magnetic field (RL-EPR) were investigated after ultraviolet excitation at low temperatures. Wavelength dependent RL-EPR measurements indicate that only one intrinsic donor but at least two different intrinsic acceptors are involved in the recombination process. The donor-acceptor recombination energy is either emitted directly (undoped samples) or almost completely transferred to the rare-earth activators (doped samples).
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.60.-b Other luminescence and radiative recombination
71.55.Ht Other nonmetals
78.20.Ls Magneto-optical effects

Efficient focusing of hard x rays to 25 nm by a total reflection mirror

Hidekazu Mimura, Hirokatsu Yumoto, Satoshi Matsuyama, Yasuhisa Sano, Kazuya Yamamura, Yuzo Mori, Makina Yabashi, Yoshinori Nishino, Kenji Tamasaku, Tetsuya Ishikawa, and Kazuto Yamauchi

Appl. Phys. Lett. 90, 051903 (2007); http://dx.doi.org/10.1063/1.2436469 (3 pages) | Cited 69 times

Online Publication Date: 29 January 2007

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Nanofocused x rays are indispensable because they can provide high spatial resolution and high sensitivity for x-ray nanoscopy/spectroscopy. A focusing system using total reflection mirrors is one of the most promising methods for producing nanofocused x rays due to its high efficiency and energy-tunable focusing. The authors have developed a fabrication system for hard x-ray mirrors by developing elastic emission machining, microstitching interferometry, and relative angle determinable stitching interferometry. By using an ultraprecisely figured mirror, they realized hard x-ray line focusing with a beam width of 25 nm at 15 keV. The focusing test was performed at the 1-km-long beamline of SPring-8.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
41.50.+h X-ray beams and x-ray optics
42.79.Bh Lenses, prisms and mirrors

Interface modulated structure of highly epitaxial (Pb,Sr)TiO3 thin films on (001) MgO

J. C. Jiang, E. I. Meletis, Z. Yuan, and C. L. Chen

Appl. Phys. Lett. 90, 051904 (2007); http://dx.doi.org/10.1063/1.2436631 (3 pages) | Cited 10 times

Online Publication Date: 29 January 2007

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The interface of epitaxial (Pb0.35Sr0.65)TiO3 films on MgO substrates grown by pulsed laser ablation was studied using transmission electron microscopy (TEM). Cross-section TEM studies revealed that the epitaxial films have a lattice mismatch of −6.2% with respect to the substrates. Electron diffraction pattern and high-resolution TEM image of the plan-view (Pb0.35Sr0.65)TiO3/MgO interface present evidence of a modulated structure on the film plane. This allowed obtaining the actual lattice mismatch of −7.14% at the interface. Plan-view TEM of the interface is able to provide fundamental information that cannot be obtained by the cross-section TEM alone, and its advantages in studying such epitaxial films are addressed.
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68.35.Ct Interface structure and roughness
68.55.-a Thin film structure and morphology
68.37.Lp Transmission electron microscopy (TEM)

X-ray diffraction and continuum measurements in silicon crystals shocked below the elastic limit

Stefan J. Turneaure and Y. M. Gupta

Appl. Phys. Lett. 90, 051905 (2007); http://dx.doi.org/10.1063/1.2436638 (3 pages) | Cited 5 times

Online Publication Date: 29 January 2007

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The shock wave response of silicon, compressed along [100] and [111], was examined at both the lattice and continuum scales. Peak stresses were below the Hugoniot elastic limit and ranged between 2.8 and 6.9 GPa. X-ray diffraction measurements provided the interplaner spacing changes along the shock loading direction. The continuum response was determined by using laser interferometry to measure the rear surface velocity histories. In contrast to earlier results, both the lattice and continuum results were consistent with the known nonlinear elastic constants of silicon. Additionally, the diffracted intensity in the shocked state was considerably larger than the intensity in the ambient state.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
62.20.D- Elasticity
62.20.F- Deformation and plasticity
62.50.-p High-pressure effects in solids and liquids
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