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10 Jun 2002

Volume 80, Issue 23, pp. 4291-4461

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Enlargement of omnidirectional total reflection frequency range in one-dimensional photonic crystals by using photonic heterostructures

Xin Wang, Xinhua Hu, Yizhou Li, Wulin Jia, Chun Xu, Xiaohan Liu, and Jian Zi

Appl. Phys. Lett. 80, 4291 (2002); http://dx.doi.org/10.1063/1.1484547 (3 pages) | Cited 69 times

Online Publication Date: 31 May 2002

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We show theoretically that the omnidirectional total reflection frequency range of a multilayer dielectric reflector can be substantially enlarged as desired by using photonic heterostructures. This photonic heterostructure consists of different one-dimensional (1D) photonic crystals. The constituent 1D photonic crystals have to be properly chosen such that their omnidirectional photonic band gaps of the adjacent photonic crystals overlap each other. © 2002 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
78.40.Ha Other nonmetallic inorganics

Tunable microfluidic optical fiber

P. Mach, M. Dolinski, K. W. Baldwin, J. A. Rogers, C. Kerbage, R. S. Windeler, and B. J. Eggleton

Appl. Phys. Lett. 80, 4294 (2002); http://dx.doi.org/10.1063/1.1483384 (3 pages) | Cited 49 times

Online Publication Date: 31 May 2002

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We describe a class of active, tunable optical fiber that incorporates multiple microfluidic plugs into interior fiber microchannels. The propagation characteristics of certain optical modes of these fiber waveguides can be usefully manipulated by controlling the positions and optical properties of these plugs, using actuators and pumps formed on the fiber surface. These hybrid microfluidic/silica structures offer versatile tuning capabilities in a format that preserves the advantages of conventional, passive optical fiber. As an example, we report an all-fiber, narrowband filter, whose transmission wavelength and attenuation are independently adjustable via microfluidic tuning. © 2002 American Institute of Physics.
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42.81.Wg Other fiber-optical devices
42.79.Ci Filters, zone plates, and polarizers
42.82.Gw Other integrated-optical elements and systems
47.85.Np Fluidics

Light-triggered molecular devices based on photochromic oligothiophene substituted chromenes

A. Yassar, F. Garnier, H. Jaafari, N. Rebière-Galy, M. Frigoli, C. Moustrou, A. Samat, and R. Guglielmetti

Appl. Phys. Lett. 80, 4297 (2002); http://dx.doi.org/10.1063/1.1481240 (3 pages) | Cited 6 times

Online Publication Date: 31 May 2002

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An original concept for the realization of a molecular photoswitch is proposed, based on photochrochromic oligothiophene-substituted chromenes. When optically excited, these compounds undergo a structural change passing from a neutral state (closed form) to a strongly polarized one (open form). This photochromism process is also accompanied by a large increase in the electrical conductivity. © 2002 American Institute of Physics.
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85.65.+h Molecular electronic devices

Luminescence enhancement of core-shell ZnS:Mn/ZnS nanoparticles

Lixin Cao, Jiahua Zhang, Shanling Ren, and Shihua Huang

Appl. Phys. Lett. 80, 4300 (2002); http://dx.doi.org/10.1063/1.1483113 (3 pages) | Cited 50 times

Online Publication Date: 31 May 2002

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Mn2+-doped ZnS nanoparticles and Mn2+-doped ZnS nanoparticles coated with a shell of ZnS were prepared in reverse micelles. Mn2+ emission at 580 nm in the coated nanoparticles was seven times stronger than that in the uncoated ones. Ultraviolet light treatment enhanced the luminescence at 580 nm in the uncoated nanoparticles, but led to no luminescence enhancement in the coated ones. Some calculations indicated that Mn2+ ions were not randomly distributed in the particle, but preferred to occupy the sites close to the surface. The experiment results indicated that ZnS shell and UV treatment could block the nonradiative transition paths and led to the enhancement of luminescence. © 2002 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Et II-VI semiconductors
78.40.Fy Semiconductors
61.46.-w Structure of nanoscale materials

Nonequilibrium optical phonon generation by steady-state electron transport in quantum-cascade lasers

Vincenzo Spagnolo, Gaetano Scamarcio, Mariano Troccoli, Federico Capasso, Claire Gmachl, A. Michael Sergent, Albert L. Hutchinson, Deborah L. Sivco, and Alfred Y. Cho

Appl. Phys. Lett. 80, 4303 (2002); http://dx.doi.org/10.1063/1.1481186 (3 pages) | Cited 10 times

Online Publication Date: 31 May 2002

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Observation of the nonequilibrium optical phonons population associated with electron transport in quantum-cascade lasers is reported. The phonon occupation number was measured in the range 75–280 K by using a combination of microprobe photoluminescence and Stokes/anti-Stokes Raman spectroscopy. The excess phonon population is observed to decrease as the lattice temperature increases. From the nonequilibrium phonon population, we extracted interface phonon lifetimes of 5 ps at 75 K and 2 ps at 280 K. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.67.De Quantum wells
78.55.Cr III-V semiconductors
78.30.Fs III-V and II-VI semiconductors

Experimental observation of complete chaos synchronization in semiconductor lasers

Y. Liu, Y. Takiguchi, P. Davis, T. Aida, S. Saito, and J. M. Liu

Appl. Phys. Lett. 80, 4306 (2002); http://dx.doi.org/10.1063/1.1485127 (3 pages) | Cited 36 times

Online Publication Date: 31 May 2002

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We experimentally demonstrate the complete synchronization of a semiconductor laser to the injection of a chaotic oscillating optical signal that is generated by a similar semiconductor laser with external optical feedback. The synchronization is characterized by sensitive dependencies on frequency detuning and injection strength and a time lag that varies reversely with the variation of the delay time in the external optical feedback of the master laser. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.65.Sf Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics
05.45.Xt Synchronization; coupled oscillators
42.60.Mi Dynamical laser instabilities; noisy laser behavior

1064 nm laser emission of highly doped Nd: Yttrium aluminum garnet under 885 nm diode laser pumping

V. Lupei, N. Pavel, and T. Taira

Appl. Phys. Lett. 80, 4309 (2002); http://dx.doi.org/10.1063/1.1483926 (3 pages) | Cited 28 times

Online Publication Date: 31 May 2002

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Highly efficient 1064 nm continuous-wave laser emission under 885 nm diode pumping in concentrated Nd: Yttrium aluminum garnet (YAG) crystals (up to 3.5 at. % Nd) and ceramics (up to 3.8 at. % Nd) is reported. A highly doped (2.4 at. %) Nd:YAG laser, passively Q switched by a Cr4+:YAG saturable absorber, is demonstrated. © 2002 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Pk Continuous operation
42.60.By Design of specific laser systems
42.70.Hj Laser materials
42.55.Px Semiconductor lasers; laser diodes
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

Intersubband staircase laser

Nicolaus Ulbrich, Giuseppe Scarpa, Gerhard Böhm, Gerhard Abstreiter, and Markus-Christian Amann

Appl. Phys. Lett. 80, 4312 (2002); http://dx.doi.org/10.1063/1.1484245 (3 pages) | Cited 7 times

Online Publication Date: 31 May 2002

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A quantum-cascade laser is presented in which the injection minibands are omitted. The intersubband laser operates as a four-level staircase and has potential for higher gain devices due to an increased confinement factor compared to conventional quantum-cascade lasers. A high threshold current density of 5.9 kA/cm2 with peak output powers of 230 mW at 77 K is observed. A large wavelength shift from 9.3 to 10 μm and broadband emission are observed at higher bias fields. This modification to existing quantum-cascade laser designs has potential for higher gain devices, but problems with thermal backfilling and doping limit the operating temperature currently to 200 K. © 2002 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
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Optical emission investigation of laser-produced MgB2 plume expanding in an Ar buffer gas

S. Amoruso, R. Bruzzese, N. Spinelli, R. Velotta, X. Wang, and C. Ferdeghini

Appl. Phys. Lett. 80, 4315 (2002); http://dx.doi.org/10.1063/1.1484549 (3 pages) | Cited 12 times

Online Publication Date: 31 May 2002

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Optical emission spectroscopy is used to study the dynamics of the plasma generated by pulsed-laser irradiation of a MgB2 target, both in a vacuum and at different Ar buffer gas pressures. The analysis of the time-resolved emission of selected species shows that the Ar background gas strongly influences the plasma dynamics. Above a fixed pressure, plasma propagation into Ar leads to the formation of blast waves causing both a considerable increase of the fraction of excited Mg atoms and a simultaneous reduction of their kinetic flux energy. These results can be particularly useful for optimizing MgB2 thin-film deposition processes. © 2002 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Microairplane propelled by laser driven exotic target

T. Yabe, C. Phipps, M. Yamaguchi, R. Nakagawa, K. Aoki, H. Mine, Y. Ogata, C. Baasandash, M. Nakagawa, E. Fujiwara, K. Yoshida, A. Nishiguchi, and I. Kajiwara

Appl. Phys. Lett. 80, 4318 (2002); http://dx.doi.org/10.1063/1.1485313 (3 pages) | Cited 30 times

Online Publication Date: 31 May 2002

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We propose a propulsion concept to drive a microairplane by laser that can be used for observation of climate and volcanic eruption. Since it does not have to develop thrust for vertical takeoff, and it has no engine in the normal sense, the microairplane can be very light, with its payload consisting only of observation and communication equipment. In order to demonstrate the concept, we succeeded in flying a paper microairplane driven by a 590 mJ, 5 ns pulse yttrium–aluminum–garnet laser that impinges on a double-layer “exotic target.” The coupling efficiency agrees well with simulations and with experiments. © 2002 American Institute of Physics.
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89.40.-a Transportation
42.62.Cf Industrial applications
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Origins of micropipes in SiC crystals

S. Mahajan

Appl. Phys. Lett. 80, 4321 (2002); http://dx.doi.org/10.1063/1.1484555 (3 pages) | Cited 6 times

Online Publication Date: 31 May 2002

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It is argued that micropipes in SiC crystals grown by the physical vapor transport process form independently of screw dislocations. A mechanism involving liquid droplets of silicon containing some carbon or graphite particles is proposed to explain the formation of micropipes. The observed strain fields associated with micropipes are attributed to the presence of screw dislocations in their vicinity. An expression is developed that relates the change in radius of a micropipe to the number of screw dislocations that are eliminated during its expansion. © 2002 American Institute of Physics.
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61.72.Lk Linear defects: dislocations, disclinations
81.10.Bk Growth from vapor

Electrostatic force microscopy using a quartz tuning fork

Yongho Seo, Wonho Jhe, and Cheol Seong Hwang

Appl. Phys. Lett. 80, 4324 (2002); http://dx.doi.org/10.1063/1.1485312 (3 pages) | Cited 11 times

Online Publication Date: 31 May 2002

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We demonstrate an electrostatic force microscopy based on a quartz tuning fork with 50 nm spatial resolution and 1 pN force sensitivity. We use a tuning fork with a spring constant of 1300 N/m and a Q factor of 3000. A sharpened nickel tip is attached to a prong of the tuning fork as well as electrically connected to the electrode of the prong. By applying a dc bias to the tip, ferroelectric domain patterns are recorded and read out on piezoelectric thin film. © 2002 American Institute of Physics.
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07.79.-v Scanning probe microscopes and components
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.80.Dj Domain structure; hysteresis
77.55.-g Dielectric thin films
77.65.-j Piezoelectricity and electromechanical effects

Nanodomains of pyrochlore formed by Ti ion implantation in yttria-stabilized zirconia

S. Zhu, X. T. Zu, L. M. Wang, and R. C. Ewing

Appl. Phys. Lett. 80, 4327 (2002); http://dx.doi.org/10.1063/1.1482784 (3 pages) | Cited 8 times

Online Publication Date: 31 May 2002

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The microstructural evolution of a single crystal of yttria-stabilized zirconia (YSZ) implanted with Ti has been studied by cross-sectional transmission electron microscopy (TEM). The implantation of 180 keV Ti ions to a dose of 1×1017 ions/cm2 was completed at room temperature. After annealing at 1100 °C in an Ar atmosphere for 2 h, a phase transition from the fluorite structure of ZrO2 to an isometric pyrochlore structure-type, A2B2O7, occurred due to cation ordering. High-resolution TEM revealed nanodomains of pyrochlore, Y2(TixZr1−x)2O7, with a ≅ 10.24±0.05 Å. The nanodomains of the pyrochlore phase, embedded within the YSZ fluorite substrate, occurred in a depth range from 45 to 105 nm below the surface, which corresponds to Ti concentrations from ∼10 to ∼15 at. %. The nanoscale pyrochlore precipitates and the YSZ matrix have a completely coherent orientation. © 2002 American Institute of Physics.
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61.72.up Other materials
61.80.Jh Ion radiation effects
61.82.Ms Insulators
61.72.Cc Kinetics of defect formation and annealing
61.46.-w Structure of nanoscale materials
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation

Anisotropic surface etching of 6H–SiC(0001) induced by reaction with oxygen molecules

O. Kubo, T. Kobayashi, N. Yamaoka, S. Itou, M. Katayama, K. Oura, and H. Ohkado

Appl. Phys. Lett. 80, 4330 (2002); http://dx.doi.org/10.1063/1.1485136 (3 pages)

Online Publication Date: 31 May 2002

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The initial reactions of the 6H–SiC(0001)√×√ surface with O2 molecules at elevated temperatures have been investigated by scanning tunneling microscopy. As a result, two types of anisotropic features were observed. One was a dark parallelogram with √×√ periodic protrusions elongated in the 〈1math00〉 direction, which was observed only in the case of O2 exposure at 700 °C. The other was a dark line in the 〈1math00〉 direction, which was observed with O2 exposure at temperatures above 500 °C. Both features manifest anisotropic surface etching induced by O2 molecules. © 2002 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.20.-w Chemical kinetics and dynamics
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Dynamics of crystallization and phase transition in La0.5Sr0.5CoO3 thin films

Hauyee Chang, C. L. Chen, T. Garrett, X. H. Chen, X.-D. Xiang, C. W. Chu, Q. Y. Zhang, and C. Dong

Appl. Phys. Lett. 80, 4333 (2002); http://dx.doi.org/10.1063/1.1482417 (3 pages) | Cited 2 times

Online Publication Date: 31 May 2002

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Dynamics of crystallization and phase transitions were investigated in La0.5Sr0.5CoO3 films with four-probe resistance electrical measurements and x-ray diffraction. Nucleation of crystalline phases from the amorphous phase of La0.5Sr0.5CoO3 was found to start at a temperature of 325 °C. It is very interesting to note that the crystallization completes within a very narrow temperature range of 390–420 °C, and recrystallization occurs at 560 °C. In addition, electron–phonon, electron–grain boundary, and electron–defect interactions, as well as oxygen contents were found to be important factors in various temperature regions during the resistance measurement. The metallic phase La0.5Sr0.5CoO3 films can only be obtained if the films were directly heated to higher than 750 °C. The sequence and knowledge of phase transitions observed for La0.5Sr0.5CoO3 are expected to be ubiquitous for perovskite oxide compounds in general. © 2002 American Institute of Physics.
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68.55.A- Nucleation and growth
61.43.Dq Amorphous semiconductors, metals, and alloys
73.61.Jc Amorphous semiconductors; glasses
72.60.+g Mixed conductivity and conductivity transitions
73.61.At Metal and metallic alloys
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions
61.72.Mm Grain and twin boundaries
61.72.Cc Kinetics of defect formation and annealing

Silver photodoping into Al–ZnSe for application to white light emitters

Hyun-Yong Lee, Toshiaki Takai, and Takafumi Yao

Appl. Phys. Lett. 80, 4336 (2002); http://dx.doi.org/10.1063/1.1485135 (3 pages) | Cited 2 times

Online Publication Date: 31 May 2002

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Room-temperature Ag photodoping into crystalline Al-doped ZnSe grown by molecular-beam epitaxy (MBE) has been achieved. A promising approach to apply to a patterned white light emitter has also been proposed. An Al–ZnSe with Ag islands was illuminated with a HeCd laser at 300 K and annealed in the MBE chamber. Then, their photoluminescence characteristics were measured in real time. The self-activated (SA) emission, observed in as-grown Al–ZnSe, undergoes a considerable change in intensity and band energy position through Ag photodoping and subsequent annealing. The resultant emission bands centered at 2.145 eV and 2.250 eV are assigned as a donor-to-acceptor pair transition related with Ag impurities rather than SA centers. In addition, chromaticity can be controlled by an adjustment of photoirradiated Ag-doped area. © 2002 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
68.55.A- Nucleation and growth
81.05.Dz II-VI semiconductors
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.40.Gh Other heat and thermomechanical treatments
81.40.Tv Optical and dielectric properties related to treatment conditions

Formation mechanism of the multilayered-structure barrier of WNx/Si(100)

I. S. Choi, J. C. Park, J. T. Choi, H. J. Kim, and S. Y. Lee

Appl. Phys. Lett. 80, 4339 (2002); http://dx.doi.org/10.1063/1.1484542 (3 pages)

Online Publication Date: 31 May 2002

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The chemical bonding states, microstructure, and the formation mechanism of an interfacial layer between WNx/Si(100) treated by rapid thermal annealing at various temperatures were investigated. It was found that the ultrathin interfacial layer had the multilayered structure of SiO2/SiOxNy/nano-WSi2. The interfacial silicon nitride layer formed by lower annealing temperatures was converted into an oxide layer by increasing the annealing temperature. The thickness of the interfacial oxide layer increased from ∼34 to ∼50 Å with the annealing temperature. It was found that the interfacial layer played a role as a barrier against silicidation between W and Si(100) up to 1000 °C. © 2002 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
68.65.Ac Multilayers
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.72.Cc Kinetics of defect formation and annealing

Band filling and depletion through the doping of polyaniline thin films

B. Xu, Jaewu Choi, A. N. Caruso, and P. A. Dowben

Appl. Phys. Lett. 80, 4342 (2002); http://dx.doi.org/10.1063/1.1484247 (3 pages) | Cited 15 times

Online Publication Date: 31 May 2002

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The position of the molecular orbitals of polyaniline, relative to the Fermi level, shifts with the doping of polyaniline by both charge donor and charge acceptor species. Sodium as an electron donor, when added to the polyaniline system, results in an increase in electron population in the polyaniline bands but a decrease in density of states near EF. This is evident from the consistent shifts toward the greater binding energy of the occupied as well as unoccupied molecular orbitals, the valence bands and conduction band edges and characteristic core levels. In the case of iodine doping, an electron acceptor, all the states were shifted toward smaller binding energy. These results provide compelling evidence that the molecular orbitals of vapor deposited polyaniline thin films are delocalized. © 2002 American Institute of Physics.
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71.20.Rv Polymers and organic compounds
73.20.At Surface states, band structure, electron density of states

Cross-sectional scanning tunneling microscopy study of InGaAs quantum dots on GaAs(001) grown by heterogeneous droplet epitaxy

N. Liu, H. K. Lyeo, C. K. Shih, M. Oshima, T. Mano, and N. Koguchi

Appl. Phys. Lett. 80, 4345 (2002); http://dx.doi.org/10.1063/1.1479196 (3 pages) | Cited 10 times

Online Publication Date: 31 May 2002

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We present a cross-sectional scanning tunneling microscopy (STM) study of heterogeneous-droplet-epitaxy (HDE)-grown InGaAs quantum dots (QDs). We found that the structural properties of HDE-grown QDs such as size, shape, etc., are quite different from that of Stranski–Krastanov (SK)-grown InGaAs QDs. HDE-grown InGaAs QDs exhibit a reverse trapezoidal shape, opposite to the SK-grown QDs. In addition, the In concentration within individual HDE QDs is rather uniform, contrary to the case in SK QDs. These HDE QDs also show large size fluctuation. However, we found that there is a size dependence in the In concentration within the QD—the larger QD has lower In concentration, suggesting a self-compensation effect which gives rise to a sharp photoluminescence linewidth. © 2002 American Institute of Physics.
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68.65.Hb Quantum dots (patterned in quantum wells)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Invar-type effect induced by cold-rolling deformation in shape memory alloys

R. Kainuma, J. J. Wang, T. Omori, Y. Sutou, and K. Ishida

Appl. Phys. Lett. 80, 4348 (2002); http://dx.doi.org/10.1063/1.1485118 (3 pages) | Cited 10 times

Online Publication Date: 31 May 2002

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Since the discovery of Fe–Ni alloys showing low thermal expansion (LTE) in 1896, many Invar alloys have been developed based on magnetovolume effect where negative thermal expansion is induced by magnetic transformation. Herein, we show that the control of stress-induced martensitic transformation due to cold working of the Cu–Zn–Al polycrystalline alloy results in the LTE. This type of LTE material is easily fabricated by conventional cold rolling, and the coefficient of thermal expansion in the range from about 0 to 32×10−6 K−1 can be obtained by controlling the reduction ratio. The LTE effect due to the present method can also be obtained for other shape memory (SM) alloys such as Ni–Ti, Cu–Mn–Al and Ni–Al base alloys, which have high potential for various practical applications. © 2002 American Institute of Physics.
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65.40.De Thermal expansion; thermomechanical effects
81.30.Kf Martensitic transformations
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
64.70.K- Solid-solid transitions

Impurity-free disordering mechanisms in GaAs-based structures using doped spin-on silica layers

Prakash N. K. Deenapanray, Bin Gong, R. N. Lamb, A. Martin, L. Fu, H. H. Tan, and C. Jagadish

Appl. Phys. Lett. 80, 4351 (2002); http://dx.doi.org/10.1063/1.1484244 (3 pages) | Cited 10 times

Online Publication Date: 31 May 2002

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We have used photoluminescence, deep level transient spectroscopy and x-ray photoelectron spectroscopy to investigate the mechanisms of impurity-free disordering in GaAs-based structures using doped spin-on silica layers. We demonstrate that VGa is efficiently converted into arsenic-antisite, AsGa, related defects (EL2-type defects) when the GaAs layer is under compressive stress. We propose that the efficient formation of EL2-type defects reduces the efficiency of impurity-free interdiffusion of GaAs/AlGaAs quantum wells. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.55.Cr III-V semiconductors
78.67.De Quantum wells
68.35.Fx Diffusion; interface formation
61.72.J- Point defects and defect clusters

60Co gamma-irradiation-induced defects in n-GaN

G. A. Umana-Membreno, J. M. Dell, T. P. Hessler, B. D. Nener, G. Parish, L. Faraone, and U. K. Mishra

Appl. Phys. Lett. 80, 4354 (2002); http://dx.doi.org/10.1063/1.1483390 (3 pages) | Cited 5 times

Online Publication Date: 31 May 2002

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Transient capacitance measurements of Schottky diodes fabricated on nominally undoped n-type GaN exposed to 60Co gamma irradiation indicate the introduction of two defect levels with thermal activation energies of 89±6 and 132±11 meV. While the emission characteristics of these defects manifest significant broadening, their parameters are consistent with reported electron-irradiation-induced nitrogen-vacancy related centers. Three deep-level defects present before irradiation exposure with activation energies of 265, 355, and 581 meV were found to remain unaffected for cumulative gamma-ray doses up to 21 Mrad(Si). © 2002 American Institute of Physics.
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61.80.Ed γ-ray effects
61.82.Fk Semiconductors
71.55.Eq III-V semiconductors
81.05.Ea III-V semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species
85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Kk Junction diodes
61.72.J- Point defects and defect clusters
85.30.De Semiconductor-device characterization, design, and modeling

Comparison of strain relaxation in InGaAsN and InGaAs thin films

M. Adamcyk, J. H. Schmid, T. Tiedje, A. Koveshnikov, A. Chahboun, V. Fink, and K. L. Kavanagh

Appl. Phys. Lett. 80, 4357 (2002); http://dx.doi.org/10.1063/1.1485124 (3 pages) | Cited 10 times

Online Publication Date: 31 May 2002

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We compare the strain relaxation of In0.08Ga0.92As and In0.12Ga0.88As0.99N0.01 epitaxial thin films grown on GaAs (001) by elemental-source molecular-beam epitaxy. The epilayers we studied were essentially identical in their compressive lattice mismatch (0.62±0.02%), and thickness (600 nm). The strain state of the samples was determined by in situ substrate curvature monitoring, and by ex situ x-ray diffraction and plan-view transmission electron microscopy. We observe a slower rate of strain relaxation, and a 25% higher residual strain in the nitride. This is attributed to the presence of nitrogen interstitials in the InGaAsN epilayers and/or to the higher nitrogen bond strengths. © 2002 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
81.05.Ea III-V semiconductors
68.55.Nq Composition and phase identification
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.50.Lt Crystal binding; cohesive energy
61.72.J- Point defects and defect clusters

Determination of the phonon dispersion of zinc blende (3C) silicon carbide by inelastic x-ray scattering

J. Serrano, J. Strempfer, M. Cardona, M. Schwoerer-Böhning, H. Requardt, M. Lorenzen, B. Stojetz, P. Pavone, and W. J. Choyke

Appl. Phys. Lett. 80, 4360 (2002); http://dx.doi.org/10.1063/1.1484241 (3 pages) | Cited 10 times

Online Publication Date: 31 May 2002

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We present an experimental and theoretical investigation of the phonon dispersion relations in zinc blende (3C) SiC. The experimental data were obtained for the entire Brillouin zone by inelastic x-ray scattering (IXS) using a synchrotron radiation source. Eigenvector analysis is performed with the aid of state-of-the-art linear response first principles calculations based on density functional theory. The theoretical predictions reproduce the experimental phonon dispersion remarkably well. These results are compared with data obtained previously for the 〈111〉 direction by Raman spectroscopy using several SiC polytypes and the backfolding technique. IXS data for 4H modification along the c axis are also reported. © 2002 American Institute of Physics.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.70.Ck X-ray scattering
78.30.Hv Other nonmetallic inorganics
71.20.Nr Semiconductor compounds
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Channeling of low energy heavy ions: Er in Si〈111〉

S. M. Hogg, B. Pipeleers, A. Vantomme, and M. Swart

Appl. Phys. Lett. 80, 4363 (2002); http://dx.doi.org/10.1063/1.1485128 (3 pages) | Cited 9 times

Online Publication Date: 31 May 2002

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Channeled implantation of 80 keV Er ions into Si(111) has been investigated as a function of the angle between the ion beam and the 〈111〉 normal axis. The angular dependence of both the projected range and the crystalline quality of the resulting silicide shows excellent agreement with theoretical predictions and simulations. Simulations indicate that the critical angle for channeling is largely independent of substrate temperature. The postimplantation strain in the silicide layer is determined by irradiation-induced damage and therefore increases with the angle between the crystalline axis and the ion beam direction. © 2002 American Institute of Physics.
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61.72.uf Ge and Si
81.05.Cy Elemental semiconductors
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
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