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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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Stimulated Raman scattering from individual single-wall carbon nanotubes

B. P. Zhang, K. Shimazaki, T. Shiokawa, M. Suzuki, K. Ishibashi, and R. Saito

Appl. Phys. Lett. 88, 241101 (2006); http://dx.doi.org/10.1063/1.2211054 (3 pages) | Cited 5 times

Online Publication Date: 12 June 2006

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Individual single-wall carbon nanotubes (SWNTs) exhibited continuous-wave stimulated Raman scattering (SRS). The Raman gain is a few orders higher, and the threshold power is a few orders lower, than values ever reported for other bulk materials and is explained as the result of both the large nonlinear property and efficient electron-phonon interaction in the SWNT. The laser-induced variation of the peak position of the SRS line was likely to depend on the linewidth or tube quality. The results demonstrate the high potential of SWNTs in applications of nanoscale nonlinear optical devices such as wide-range tuneable Raman lasers.
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78.67.Ch Nanotubes
78.30.Hv Other nonmetallic inorganics
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
42.55.Ye Raman lasers

Laser-induced air ionization microscopy

Y. Zhao, N. Zhang, J. Yang, and X. Zhu

Appl. Phys. Lett. 88, 241102 (2006); http://dx.doi.org/10.1063/1.2209715 (3 pages) | Cited 4 times

Online Publication Date: 13 June 2006

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A nonlinear scanning imaging method is introduced that uses the highly localized air ionization initiated by photoelectrons from the sample surface under irradiation of femtosecond laser pulses as the microprobe. This type of microscopy with realizable subdiffraction spatial resolution has the unique advantages of being highly sensitive to both elemental and topographical properties of the samples of interest. Microscopic images of a femtosecond laser ablated micropattern, the cross section and the side view profile of an optical fiber, and a fresh mulberry leaf are obtained with this imaging technique, which demonstrate this technique’s broad applicability in microscopic studies of different materials.
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79.60.-i Photoemission and photoelectron spectra
07.60.-j Optical instruments and equipment
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
06.60.Jn High-speed techniques (microsecond to femtosecond)
42.62.-b Laser applications

Wide-band transmission of nondistorted slow waves in one-dimensional optical superlattices

M. Ghulinyan, M. Galli, C. Toninelli, J. Bertolotti, S. Gottardo, F. Marabelli, D. S. Wiersma, L. Pavesi, and L. C. Andreani

Appl. Phys. Lett. 88, 241103 (2006); http://dx.doi.org/10.1063/1.2209716 (3 pages) | Cited 11 times

Online Publication Date: 13 June 2006

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Few micron-thick one-dimensional optical superlattices were designed and grown, in which an optimized choice of external dielectric layers allows the formation of a wide and high transmission miniband of coupled cavity states. In such structures a reduction in light group velocity and minimal line shape distortion of propagating optical signal was observed. Group velocity reduction by a factor of 5, obtained both from phase (white-light interferometry) and from time-resolved measurements, is in reasonably good agreement with those calculated through a transfer matrix approach. Time-resolved experiments confirm the minimal line shape distortion for optical pulses of 1.8 THz bandwidth at λ = 1.5 μm wavelength.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.47.-p Spectroscopy of solid state dynamics

Terahertz frequency comb by multifrequency-heterodyning photoconductive detection for high-accuracy, high-resolution terahertz spectroscopy

Takeshi Yasui, Yasuhiro Kabetani, Eisuke Saneyoshi, Shuko Yokoyama, and Tsutomu Araki

Appl. Phys. Lett. 88, 241104 (2006); http://dx.doi.org/10.1063/1.2209718 (3 pages) | Cited 34 times

Online Publication Date: 13 June 2006

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We report a terahertz spectroscopy technique based on a stable terahertz frequency comb from a photoconductive terahertz emitter driven by a stabilized femtosecond laser. To this end, a photocurrent frequency comb is induced in a photoconductive terahertz detector by instantaneous photogating with another detuned femtosecond laser and is applied to read out the terahertz frequency comb. The detailed structure of the terahertz frequency comb was clearly observed with frequency accuracy of 2.5×10−7 and resolution of 81.8 MHz using multifrequency-heterodyning photoconductive detection, which in turn is caused by the slightly mismatched frequency spacing between terahertz and photocurrent frequency combs.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Subpicosecond pulse generation at 134 GHz using a quantum-dash-based Fabry-Perot laser emitting at 1.56 μm

C. Gosset, K. Merghem, A. Martinez, G. Moreau, G. Patriarche, G. Aubin, A. Ramdane, J. Landreau, and F. Lelarge

Appl. Phys. Lett. 88, 241105 (2006); http://dx.doi.org/10.1063/1.2213007 (3 pages) | Cited 29 times

Online Publication Date: 13 June 2006

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We demonstrate passive mode locking in one-section monolithic semiconductor laser diodes based on quantum-dash active layer at very high repetition rate in the 1.5 μm window. Transform-limited pulses are generated at 134 GHz with subpicosecond width, without any pulse compression scheme. A 50 kHz linewidth of the radio-frequency spectrum is also demonstrated at 42 GHz, the lowest value reported for any passively mode-locked semiconductor laser. We further show that the saturable absorption section in two-section devices has no significant impact on the mode-locking behavior.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes

Wavelength conversion in nonlinear optical polymer waveguides

Jung Jin Ju, Seung Koo Park, Suntak Park, Jongbae Kim, Min-su Kim, Myung-Hyun Lee, and Jung Yun Do

Appl. Phys. Lett. 88, 241106 (2006); http://dx.doi.org/10.1063/1.2213008 (3 pages) | Cited 4 times

Online Publication Date: 13 June 2006

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We developed a polyimide side-chain polymer under the key guidelines of low losses at interacting wavelengths and high nonlinearity as well as thermal stability and fabricated quasi-phase-matched waveguide devices for second harmonic generation (SHG) and difference frequency generation (DFG). In addition, waveguide structures and periodic poling electrode widths were optimized for large mode overlap and efficient phase matching between the interacting optical fields (0.775 and 1.55 μm), respectively. The polymeric waveguide (1 cm length) records a normalized SHG efficiency of 5.4% W−1 cm−2 and demonstrates DFG with −50 dB conversion efficiency for an input pump power of 10 mW (cw) at room temperature.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers

Redshift phenomenon of the excitation light of long life emission phosphor

Liyan Liu, Chengyu Li, Shubin Wang, and Qiang Su

Appl. Phys. Lett. 88, 241107 (2006); http://dx.doi.org/10.1063/1.2213184 (3 pages) | Cited 6 times

Online Publication Date: 13 June 2006

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We observed that the SrMg2(PO4)2:Eu phosphor could emit long life phosphorescence with the excitation light whose wavelength was shorter than 420 nm, however, when La, Ce, or Gd was codoped, the wavelength of the excitation light to cause the phosphorescence had a redshift of 40 nm. A possible mechanism and related discussion for this redshift phenomenon of the excitation light was given. It was suggested that the threshold between the trap and valence band was decreased with the addition of the codopants.
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78.60.-b Other luminescence and radiative recombination

Next generation of oxide photonic devices: ZnO-based ultraviolet light emitting diodes

Yungryel Ryu, Tae-Seok Lee, Jorge A. Lubguban, Henry W. White, Bong-Jin Kim, Yoon-Soo Park, and Chang-Joo Youn

Appl. Phys. Lett. 88, 241108 (2006); http://dx.doi.org/10.1063/1.2210452 (3 pages) | Cited 136 times

Online Publication Date: 13 June 2006

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Results are presented for ZnO-based ultraviolet light emitting diodes (LEDs) that employ a BeZnO/ZnO active layer comprised of seven quantum wells. Arsenic and gallium are used for p-type and n-type layers. The ZnO-based LEDs show two dominant electroluminescence peaks located in the ultraviolet spectral region between 360 and 390 nm, as well as a broad peak at 550 nm.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Electron-lattice coupling in bound-to-continuum THz quantum-cascade lasers

Miriam S. Vitiello, Gaetano Scamarcio, Vincenzo Spagnolo, Tonia Losco, Richard P. Green, Alessandro Tredicucci, Harvey E. Beere, and David A. Ritchie

Appl. Phys. Lett. 88, 241109 (2006); http://dx.doi.org/10.1063/1.2211301 (3 pages) | Cited 22 times

Online Publication Date: 14 June 2006

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We measured the thermal resistance (R = 20.1 K/W) and the electrical power dependence of the electronic temperature (Re = 27.0 K/W) of THz quantum-cascade lasers (QCLs) with bound-to-continuum active region scheme in the lattice temperature range of 30–100 K. This information, obtained from the analysis of microprobe photoluminescence spectra for QCLs operating at 2.5 THz, gives an electron-lattice energy relaxation rate (0.1 ps−1) ∼ 50 times lower than THz QCLs with resonant-phonon active region scheme.
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42.55.Px Semiconductor lasers; laser diodes

Low threshold amplified spontaneous emission from near-infrared dye-doped polymeric waveguide

K. Yamashita, T. Kuro, K. Oe, and H. Yanagi

Appl. Phys. Lett. 88, 241110 (2006); http://dx.doi.org/10.1063/1.2211303 (3 pages) | Cited 17 times

Online Publication Date: 14 June 2006

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We have investigated near-infrared light amplification in a dye-doped polymeric waveguide structure under optical pumping. Amplified spontaneous emission (ASE) at ∼ 800 nm was observed in poly(vinyl-pyrrolidone) thin film with organic dye LDS798. The ASE threshold energy was as low as ∼ 12 μJ/cm2, which is about one-tenth of previously reported values for infrared-dye-doped polymeric waveguides. This low threshold ASE comes from a large Stokes shift of LDS798, in which the self-absorption of emission is suppressed.
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42.55.Mv Dye lasers
42.60.By Design of specific laser systems
42.55.Rz Doped-insulator lasers and other solid state lasers

Optical switching in graded plasmonic waveguides

J. J. Xiao, K. Yakubo, and K. W. Yu

Appl. Phys. Lett. 88, 241111 (2006); http://dx.doi.org/10.1063/1.2210287 (3 pages) | Cited 10 times

Online Publication Date: 14 June 2006

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A mechanism of longitudinal confinement of optical energy via coupled plasmon modes is proposed in chains of noble metal nanoparticles embedded in a graded dielectric medium, which is analogous to the confinement of electrons in semiconductor quantum wells. In these systems, one can control the transmission of optical energy by varying the graded refractive index of the host medium or the separation between the nanoparticles to realize the photonic analog of electronic transistors. Possible passband tunability by nanoparticle spacing and modulation of the refractive index in the host medium have been presented explicitly and compared favorably with numerical calculations.
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42.65.Wi Nonlinear waveguides
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Gn Optical waveguides and couplers
42.79.Ry Gradient-index (GRIN) devices
73.22.Lp Collective excitations

Sol-gel synthesis and photoluminescence of p-type semiconductor Cr2O3 nanowires

Huaqiang Cao, Xianqing Qiu, Yu Liang, Meijuan Zhao, and Qiming Zhu

Appl. Phys. Lett. 88, 241112 (2006); http://dx.doi.org/10.1063/1.2213204 (3 pages) | Cited 2 times

Online Publication Date: 14 June 2006

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Rhombohedral structure p-type semiconductor Cr2O3 nanowires were generated by sol-gel template technology with the diameters in the range of 100–300 nm and the lengths ca. 10 μm. A sharp ultraviolet photoluminescence band (full width at half maximum = 13.8 nm) at the wavelength of 385 nm (3.22 eV in photon energy) was observed, which was attributed to the transition involving 3d3 electron of the Cr3+ ions.
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81.07.Vb Quantum wires
68.65.La Quantum wires (patterned in quantum wells)
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
78.55.Hx Other solid inorganic materials
78.67.Lt Quantum wires
61.46.-w Structure of nanoscale materials

Form birefringence of oxidized porous silicon

L. A. Golovan, D. A. Ivanov, V. A. Melnikov, V. Yu. Timoshenko, A. M. Zheltikov, P. K. Kashkarov, G. I. Petrov, and V. V. Yakovlev

Appl. Phys. Lett. 88, 241113 (2006); http://dx.doi.org/10.1063/1.2212534 (3 pages) | Cited 6 times

Online Publication Date: 15 June 2006

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A network of preferentially oriented pores is shown to induce anisotropy of linear and nonlinear optical properties of oxidized porous silicon (OPS) films. Although the x-ray diffraction indicates the presence of amorphous phase in OPS samples, the near-infrared and visible transmission measurements reveal a strong in-plane anisotropy exceeding that for the crystalline quartz. This anisotropy modifies dramatically polarization properties of the nonlinear optical properties resulting in a strong anisotropy of the third-harmonic signal generated from these films.
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78.66.Db Elemental semiconductors and insulators
78.20.Fm Birefringence
78.66.Jg Amorphous semiconductors; glasses
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Design of microlens illuminated aperture array fabricated by aligned ultraviolet imprinting process for optical read only memory card system

Hongmin Kim, Jeeseung Lee, Jiseok Lim, Seok-Min Kim, Shinill Kang, Young-Joo Kim, and Christopher Busch

Appl. Phys. Lett. 88, 241114 (2006); http://dx.doi.org/10.1063/1.2208688 (3 pages) | Cited 3 times

Online Publication Date: 15 June 2006

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A microlens illuminated aperture array (MLIAA) was designed for the multiprobe optical read only memory card system. As a method to integrate the microlens array (MLA) with the aperture array containing 1000×1000 apertures, an aligned ultraviolet imprinting process was used to satisfy the system objectives of reduced focal length and reduced spot size. An analysis using diffraction theory was performed to obtain the design tolerances for both MLIAA and the imprinting process. The maximum intensity of the optical probes at the Talbot [Philos. Mag. 9, 401 (1836) ] position from the fabricated MLIAA was 12 times higher than that from the aperture array without a MLA.
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42.15.Eq Optical system design
42.79.Bh Lenses, prisms and mirrors
42.86.+b Optical workshop techniques
42.79.Vb Optical storage systems, optical disks

Energy-tunable transmission x-ray microscope for differential contrast imaging with near 60 nm resolution tomography

Gung-Chian Yin, Mau-Tsu Tang, Yen-Fang Song, Fu-Rong Chen, Keng S. Liang, Frederick W. Duewer, Wenbing Yun, Chen-Hao Ko, and Han-Ping D. Shieh

Appl. Phys. Lett. 88, 241115 (2006); http://dx.doi.org/10.1063/1.2211300 (3 pages) | Cited 29 times

Online Publication Date: 15 June 2006

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An energy-tunable transmission hard x-ray microscope with close to 60 nm spatial resolution in three dimensions (3D) has been developed. With a cone beam illumination, a zone plate of 50 nm outmost zone width, a stable mechanical design, and software feedback, we obtained tomographic data sets that are close to 60 nm spatial resolution. Meanwhile, the element specific imaging was also obtained by a differential absorption contrast technique used below and above the absorption of the element. Examples of advanced intergraded circuit devices are used to demonstrate the element selectivity and spatial resolution in 3D of the microscope.
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07.85.Tt X-ray microscopes

Tunable organic thin-film laser pumped by an inorganic violet diode laser

T. Riedl, T. Rabe, H.-H. Johannes, W. Kowalsky, J. Wang, T. Weimann, P. Hinze, B. Nehls, T. Farrell, and U. Scherf

Appl. Phys. Lett. 88, 241116 (2006); http://dx.doi.org/10.1063/1.2211947 (3 pages) | Cited 47 times

Online Publication Date: 15 June 2006

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We demonstrate an organic thin-film distributed feedback (DFB) laser pumped by an inorganic violet laser diode (λ = 406 nm). The active organic medium consists of a highly efficient, modified poly(9,9-dioctylfluorene) derivative containing 12% of statistical intrachain 6,6′-(2,2′-octyloxy-1,1′-binaphthalene) binaphthyl spacer groups. The polymer is doped with 4 wt % of the stilbene dye 1,4-bis(2-(4-(N,N-di(p-tolyl)amino)phenyl)vinylbenzene). This guest-host system features minimum lasing threshold energy densities below 1 μJ/cm2 for second order DFB resonator geometries and significant absorption (7.3×104 cm−1) at the wavelength of the pumping diode laser. The entire setup states an extremely compact and cost effective, laser source tunable between 496 and 516 nm.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.55.Xi Diode-pumped lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Comparison between multilayered InAs quantum dot lasers with different dot densities

Hitoshi Shimizu, Shanmugam Saravanan, Junji Yoshida, Sayoko Ibe, and Noriyuki Yokouchi

Appl. Phys. Lett. 88, 241117 (2006); http://dx.doi.org/10.1063/1.2213520 (3 pages) | Cited 3 times

Online Publication Date: 15 June 2006

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This letter describes the dependence of the dot density per layer on laser performance for 1.3-μm range multilayered InAs quantum dot (QD) lasers having 12-QD layer in order to increase the maximum modal gain of the ground state (GS). Twelve-QD lasers with almost identical photoluminescence (PL) intensities and full width at half maximum (FWHM) were prepared, with a dot density per layer in the range of (1.4–3.0)×1010 cm−2. Results for the undoped 12-QD lasers reveal that the lasers with almost the same PL intensity and FWHM have an almost identical relationship between the threshold current density (Jth) and the mirror loss and have much the same maximum mirror loss from which lasers can oscillate from the GS. This is probably due to the fact that the Jth of dot lasers fabricated by the self-assembled method are strongly dominated by the gain width that is governed by the nonuniformity of QDs.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
81.16.Dn Self-assembly

InP-based quantum cascade detectors in the mid-infrared

Marcel Graf, Nicolas Hoyler, Marcella Giovannini, Jérôme Faist, and Daniel Hofstetter

Appl. Phys. Lett. 88, 241118 (2006); http://dx.doi.org/10.1063/1.2210088 (3 pages) | Cited 23 times

Online Publication Date: 16 June 2006

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We present two InP-based quantum cascade detectors (QCDs) in the mid-infrared wavelength range. Their narrow band detection spectra are centered at 5.3 and 9 μm. A vertical intersubband transition followed by a carefully designed extraction cascade, which is adapted to the LO-phonon energy, leads to 10 K responsivities R of 3.2 and 9.0 mA/W and background limited detectivities DBLIP* of 2×108 and 3×109 Jones, for the 5.3 and the 9 μm devices, respectively. Detection has been observed up to device temperatures of 300 K (RT), albeit reasonable performance is restricted to temperatures below 150 K (5.3 μm) and 70 K (9 μm). Designed for zero bias operation, QCDs do not produce any dark current and therefore do not suffer from dark current noise and capacitance saturation at long integration times, making them ideal devices for large focal plane arrays.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.79.Pw Imaging detectors and sensors
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
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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.
Show PACS
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
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