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8 May 2000

Volume 76, Issue 19, pp. 2647-2800

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High-frequency electrical pulse generation using optical rectification in bulk GaAs

S. Graf, H. Sigg, and W. Bächtold

Appl. Phys. Lett. 76, 2647 (2000); http://dx.doi.org/10.1063/1.126432 (3 pages) | Cited 3 times

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We present the realization of a traveling-wave electrical pulse generator using pure nonresonant instantaneous optical rectification in bulk GaAs. The optical excitation was achieved by far-infrared pulses of 1–6 ps duration in the wavelength range from 8 to 15 μm, generated by a free-electron laser. The coupling of the optical rectification polarization into the fundamental mode of the microstrip transmission line is verified by angle-resolved measurements. Since optical femtosecond pulses are now becoming readily available, this alternative technique, which gains in efficiency at shorter pulses, may find growing importance for ultrafast pulse generation. © 2000 American Institute of Physics.
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42.79.-e Optical elements, devices, and systems
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
85.60.-q Optoelectronic devices

Efficient photon harvesting at high optical intensities in ultrathin organic double-heterostructure photovoltaic diodes

P. Peumans, V. Bulović, and S. R. Forrest

Appl. Phys. Lett. 76, 2650 (2000); http://dx.doi.org/10.1063/1.126433 (3 pages) | Cited 267 times

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We demonstrate a method for efficient photon harvesting in organic thin films, thereby increasing the efficiency of organic photovoltaic cells. By incorporating an exciton-blocking layer (EBL) inserted between the photoactive organic layers and the metal cathode, we achieved an external power conversion efficiency of 2.4%±0.3% in vacuum-deposited ultrathin organic bilayer photovoltaic (PV) cells employed in a simple light trapping geometry. Ultrathin (∼100 Å) cells incorporating the transparent, conductive EBL have an internal quantum efficiency as high as 33%±4% over a spectral region matched to the solar spectrum. The very thin organic layers have a low series resistance, allowing for efficient power conversion in organic PV cells under intense (>15 suns) AM1.5 illumination. This device structure demonstrates that control of exciton diffusion in solid-state organic devices leads to a significant increase in the photon-to-carrier conversion efficiency. © 2000 American Institute of Physics.
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84.60.Jt Photoelectric conversion
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
73.20.At Surface states, band structure, electron density of states

Effect of band gap renormalization on threshold current and efficiency of a distributed Bragg reflector laser

H. Wenzel, A. Klehr, G. Erbert, J. Sebastian, G. Tränkle, and M. F. Pereira

Appl. Phys. Lett. 76, 2653 (2000); http://dx.doi.org/10.1063/1.126434 (3 pages) | Cited 3 times

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The threshold current and the external efficiency of a three-section distributed Bragg reflector laser are investigated as a function of a forward electrical bias applied to the passive sections. Within a well-determined range, the threshold current increases and the external efficiency decreases with increasing bias. This effect is attributed to band gap renormalization. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes

Three-dimensional microfabrication by use of single-photon-absorbed polymerization

Shoji Maruo and Koji Ikuta

Appl. Phys. Lett. 76, 2656 (2000); http://dx.doi.org/10.1063/1.126742 (3 pages) | Cited 36 times

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We developed a promising method to fabricate three-dimensional microstructures by using single-photon-absorbed polymerization confined to the vicinity of a tightly focused spot. This localized polymerization is based on the nonlinear response of the photopolymerizable resin to optical intensity with sufficiently low exposure. The nonlinear response was verified by measuring polymerization exotherm at different light intensities. The proposed method enables us to make even movable microstructures without any of the supporting parts or sacrificial layers normally required with conventional micromachining. In the experiment reported here, we fabricated a microgear with an external diameter of 47 μm and an attached shaft. © 2000 American Institute of Physics.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
07.10.Cm Micromechanical devices and systems
81.20.Wk Machining, milling
82.35.-x Polymers: properties; reactions; polymerization
82.50.-m Photochemistry
82.60.Cx Enthalpies of combustion, reaction, and formation

Temperature dependence of intrinsic recombination coefficients in 1.3 μm InAsP/InP quantum-well semiconductor lasers

J. M. Pikal, C. S. Menoni, P. Thiagarajan, G. Y. Robinson, and H. Temkin

Appl. Phys. Lett. 76, 2659 (2000); http://dx.doi.org/10.1063/1.126435 (3 pages) | Cited 7 times

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In this letter, we report on the temperature dependence of the intrinsic recombination coefficients in long-wavelength quantum-well lasers. Unlike previous studies, we obtain the intrinsic recombination coefficients from carrier lifetime measurements with a correction for the carrier population in the barrier and separate confinement heterostructure region. Our results show that this carrier population not only affects the value of the recombination coefficients obtained but also their temperature dependence. We measure a significant increase in the intrinsic Auger coefficient with temperature indicating that the frequently reported temperature insensitivity of this coefficient is likely due to carriers spilling out of the wells at elevated temperatures and not an intrinsic property of the Auger process. © 2000 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.)
72.80.Ey III-V and II-VI semiconductors
73.61.Ey III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Temporal evolution of resonant Raman-scattering in ZnCdSe quantum dots

A. Kaschner, M. Strassburg, A. Hoffmann, C. Thomsen, M. Bartels, K. Lischka, and D. Schikora

Appl. Phys. Lett. 76, 2662 (2000); http://dx.doi.org/10.1063/1.126436 (3 pages) | Cited 3 times

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We investigated ZnCdSe/ZnSe quantum-dot structures which include planar and coherently strained three-dimensional islands with different sizes. Optical excitation of these islands well below the ZnSe band gap leads to a resonant enhancement of the Zn0.7Cd0.3Se longitudinal-optical (LO) phonon-scattering efficiency and makes the 2LO and 3LO multiphonon emission observable. Resonant excitation with a power density of about 1.3 MW/cm2 using a micro-Raman setup results in an exponential decrease of the 1LO, 2LO, and 3LO intensity with irradiation time. This decay behavior is not observed for pure ZnSe crystals and can be avoided for the ZnCdSe/ZnSe structures using much lower excitation densities. The decrease in intensity is accompanied by a shift of the LO mode to higher frequencies resulting from a lower cadmium concentration in the alloy. From these experimental findings, we conclude that resonant excitation at a certain power density leads to cadmium out-diffusion from the planar quantum dots, which shifts the resonance away from the excitation energy. © 2000 American Institute of Physics.
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78.30.Fs III-V and II-VI semiconductors
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

On the strong influence of the photoelastic effect in the collinear mirage deflection

A. Salazar, M. Gateshki, and A. Sánchez-Lavega

Appl. Phys. Lett. 76, 2665 (2000); http://dx.doi.org/10.1063/1.126437 (3 pages) | Cited 1 time

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We report in this letter on the strong influence of the polarization state of the probe beam in the amplitude and phase of the collinear mirage deflection. A model of the collinear mirage deflection that takes into account the photoelastic effect in the sample has been developed. The agreement between the model predictions and the experimental results is excellent. © 2000 American Institute of Physics.
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42.79.Fm Reflectors, beam splitters, and deflectors
42.30.-d Imaging and optical processing
42.25.Ja Polarization

Photofabrication of three-dimensional photonic crystals by multibeam laser interference into a photopolymerizable resin

Satoru Shoji and Satoshi Kawata

Appl. Phys. Lett. 76, 2668 (2000); http://dx.doi.org/10.1063/1.126438 (3 pages) | Cited 93 times

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Three-dimensional (3D) photonic crystal structures can be fabricated into photopolymerizable resins by using laser beam interference with high precision. Three laser beams interfere into a glass cell filled with a liquid photopolymerizable resin to form a hexagonal periodic structure. Rods are formed in a hexagonal arrangement after being photopolymerzed according to the 3D periodic light distribution which results from the laser’s interference. Two beams of another laser also interfere to form layers which cross perpendicular to the rod array. After photofabrication, the nonsolidified resin is removed by ethanol. The lattice constant can be selected by tuning the angles of the incident beams and the laser wavelength. We have fabricated a 500 μm×500 μm×150 μm photonic crystal structure, the lattice constant of which is 1 μm and contains 150 lateral layers. © 2000 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.86.+b Optical workshop techniques
82.35.-x Polymers: properties; reactions; polymerization
82.50.-m Photochemistry

Measurement of the linear electro-optic coefficients of sol-gel derived strontium barium niobate thin films using a two-beam polarization interferometer

Junmo Koo, Changho Lee, Jae Hyeok Jang, Kwangsoo No, and Byeong-Soo Bae

Appl. Phys. Lett. 76, 2671 (2000); http://dx.doi.org/10.1063/1.126439 (3 pages) | Cited 6 times

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A two-beam polarization interferometer in a reflection configuration is used to measure the electro-optic coefficients of highly oriented strontium barium niobate thin films prepared by a sol-gel method. The technique enables the determination of the electro-optic coefficients of films using a strong Fabry–Perot effect with automatic adjustment and maintenance of the operation point of the interferometer. The linear electro-optic coefficients increase with increasing Sr content in the films. © 2000 American Institute of Physics.
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78.20.Jq Electro-optical effects
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
07.60.Ly Interferometers
77.80.-e Ferroelectricity and antiferroelectricity
77.55.-g Dielectric thin films
78.66.Li Other semiconductors
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Interface structures in GaAs wafer bonding: Application to compliant substrates

R. R. Vanfleet, M. Shverdin, J. Silcox, Z. H. Zhu, and Y. H. Lo

Appl. Phys. Lett. 76, 2674 (2000); http://dx.doi.org/10.1063/1.126440 (3 pages) | Cited 5 times

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The interface of direct bonded GaAs to GaAs has been studied by scanning transmission electron microscopy and electron energy loss spectroscopy. Voids are seen along the boundary with most being partially filled with a gallium particle. Two general sizes of voids are seen. The large voids (d ∼ 45 nm) are distributed in an approximately linear relationship and the smaller (d ∼ 12 nm) randomly. In compliant substrates, one of the layers is made thin ( ⩽ 10 nm) and twisted ∼ 45°. The larger voids often extend past this thin compliant layer, but no evidence of granularity of the epitaxial film is observed. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.35.Ct Interface structure and roughness
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Structure and optical properties of Si/InAs/Si layers grown by molecular beam epitaxy on Si substrate

N. D. Zakharov, P. Werner, U. Gösele, R. Heitz, D. Bimberg, N. N. Ledentsov, V. M. Ustinov, B. V. Volovik, Zh. I. Alferov, N. K. Polyakov, V. N. Petrov, V. A. Egorov, and G. E. Cirlin

Appl. Phys. Lett. 76, 2677 (2000); http://dx.doi.org/10.1063/1.126441 (3 pages) | Cited 16 times

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Epitaxial Si/InAs/Si heterostructure grown on (001) Si substrate by molecular beam epitaxy and annealed at 800 °C was investigated by high resolution transmission electron microscopy. Extensive interdiffusion leads to the formation of an InAs solid solution in the Si cap layer. Additionally, InAs-enriched regions with extensions of ∼ 6 nm, which exhibit two kinds of ordering are observed. The ordering of InAs molecules has occurred, respectively, in (101) and (10math) planes inclined and (110) and (1math0) planes parallel to the [001] growth direction. It is attributed to the energy gain from the reduced number of mixed Si–As and Si–In bonds. The sample show photoluminescence in the 1.3 μm region, which is tentatively attributed to the recombination of excitons localized in the ordered regions. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
78.55.Ap Elemental semiconductors
78.55.Cr III-V semiconductors
78.66.Db Elemental semiconductors and insulators
78.66.Fd III-V semiconductors
71.35.-y Excitons and related phenomena

High-quality strain-relaxed SiGe alloy grown on implanted silicon–on–insulator substrate

F. Y. Huang, M. A. Chu, M. O. Tanner, K. L. Wang, G. D. U’Ren, and M. S. Goorsky

Appl. Phys. Lett. 76, 2680 (2000); http://dx.doi.org/10.1063/1.126442 (3 pages) | Cited 30 times

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We report on the growth and characterization of high-quality strain-relaxed SiGe alloys on a compliant silicon–on–insulator (SOI) substrate. The annealing temperature required for strain transfer has been reduced through boron implantation to the buried oxide, leading to a high quality SiGe alloy free from dislocations as evident from the near-band gap photoluminescence. Nearly complete strain relaxation (∼95%) for SiGe alloy of a thickness beyond the conventional critical thickness has been obtained. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
73.61.Le Other inorganic semiconductors
81.05.Hd Other semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.72.uf Ge and Si

Dependence of radiative lifetimes of porous silicon on excitation wavelength and intensity

Patrick J. Moyer, Andy Pridmore, Timothy Martin, Jan Schmidt, Tom Hasche, Lukas Eng, and James L. Gole

Appl. Phys. Lett. 76, 2683 (2000); http://dx.doi.org/10.1063/1.126443 (3 pages) | Cited 5 times

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Excited state radiative lifetime measurements are made on porous silicon as a function of excitation wavelength and excitation intensity. The results indicate that a simple quantum confinement model for the light absorption and emission mechanism is not suitable. We support our results by suggesting that a cascading energy transfer process among surface molecule-like states is most likely active and we provide a general indication of the density of energy transfer states. © 2000 American Institute of Physics.
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78.55.Ap Elemental semiconductors
78.55.Mb Porous materials

Nanopatterning of copper (111) vicinal surfaces by oxygen-induced mesoscopic faceting

S. Vollmer, A. Birkner, S. Lukas, G. Witte, and Ch. Wöll

Appl. Phys. Lett. 76, 2686 (2000); http://dx.doi.org/10.1063/1.126444 (3 pages) | Cited 15 times

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We report the preparation of periodic nanostripes on vicinal copper surfaces. For the investigated Cu(n,n,n−1) surfaces [n = 4,3,2], an oxygen-induced mesoscopic faceting of the regular monoatomic stepped surfaces into periodic nanostripes consisting of Cu(111) and Cu(110)–O(2×1) facets is observed. The width and thermal stability of these nanostripes increase with the terrace length of the initial vicinal surfaces. Stripe widths of 50, 20, and 12 nm were obtained for Cu(443), Cu(332), and Cu(221), respectively. Whereas on Cu(221) the nanostripes disappear above 450 K, they are stable up to 800 K on Cu(443). For the latter surface, the nanostructures are found to be unusually stable and could be observed ex situ by atomic force microscopy under ambient conditions. © 2000 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
61.46.-w Structure of nanoscale materials
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Mechanism for the anomalous degradation of silicon space solar cells

S. Zh. Karazhanov

Appl. Phys. Lett. 76, 2689 (2000); http://dx.doi.org/10.1063/1.126445 (3 pages) | Cited 11 times

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We propose a mechanism to explain the anomalous degradation of n+-p-p+ silicon space solar cells. Distinct from previously known mechanisms, it has been shown that the anomalous increase and abrupt decrease of short-circuit current are caused by corresponding changes of the minority carrier lifetime and a conversion of conductivity type. The majority carrier density decreases abruptly due to trapping by the radiation-induced deep donors, which results in an increase of carrier lifetime and resistance, conversion of conductivity type, and anomalous change of solar cell performance. Peak values of the carrier lifetime and short-circuit current decrease with increasing illumination intensity and are sensitive to variations of the weak optical illumination. © 2000 American Institute of Physics.
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84.60.Jt Photoelectric conversion

Formation of carbon nitride with sp3-bonded carbon in CNx/ZrN superlattice coatings

M. L. Wu, M. U. Guruz, V. P. Dravid, Y. W. Chung, S. Anders, F. L. Freire, and G. Mariotto

Appl. Phys. Lett. 76, 2692 (2000); http://dx.doi.org/10.1063/1.126743 (3 pages) | Cited 9 times

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A carbon nitride phase with primarily sp3-bonded carbon is stabilized in CNx/ZrN superlattice coatings. Rutherford backscattering spectrometry measurements give a N/C atomic ratio ∼ 1.3 for the CNx layers. High-resolution transmission electron microscopy and Z-contrast imaging from the superlattice show a well-defined layer structure. Raman and near-edge x-ray absorption fine structure spectroscopy results reveal the formation of sp3-bonded carbon atoms in short-period CNx/ZrN superlattices. © 2000 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators
78.70.Dm X-ray absorption spectra

Quantization energy mapping of single V-groove GaAs quantum wires by femtosecond near-field optics

M. Achermann, B. A. Nechay, U. Siegner, A. Hartmann, D. Oberli, E. Kapon, and U. Keller

Appl. Phys. Lett. 76, 2695 (2000); http://dx.doi.org/10.1063/1.126446 (3 pages) | Cited 8 times

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We demonstrate that femtosecond pump–probe spectroscopy in the optical near field is well suited to study the intrinsic properties of single V-groove GaAs quantum wires. Temporally and spatially resolved experiments show that the shape of near-field pump–probe traces sensitively depends on the detuning between the laser photon energy and the lowest exciton resonance of a quantum wire. This detuning dependence allows one to map the quantization energy fluctuations along a single quantum wire with 200 nm spatial resolution. We measure fluctuations of about 12 meV over 2 μm wire length, resulting from wire thickness variations of 1 ML. © 2000 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Diffuse x-ray rods and scattering from point defect clusters in ion implanted silicon

U. Beck, T. H. Metzger, J. Peisl, and J. R. Patel

Appl. Phys. Lett. 76, 2698 (2000); http://dx.doi.org/10.1063/1.126447 (3 pages) | Cited 14 times

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We have studied the early stages of annealing in boron implanted silicon. In a grazing incidence diffuse scattering investigation of implantation-induced defects, we have observed narrow diffuse rods of intensity along 〈111〉 directions. These diffuse streaks arise from stacking faults formed during annealing in the 1000 °C range. From the width of the diffuse streak the average size of the stacking fault is 71 nm in diameter. These intensity rods are distinct from the point defect or point defect cluster scattering in the tails of the Bragg peak (Huang scattering). From the q dependence of the scattered intensity in the Huang scattering region we find clear evidence for defect clusters with an average effective size of 4 nm, remarkably independent of the annealing temperature. These observations are discussed in the context of the enhanced diffusion of implanted boron over its bulk value referred to as transient enhanced diffusion. © 2000 American Institute of Physics.
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61.72.Nn Stacking faults and other planar or extended defects
66.30.J- Diffusion of impurities
78.70.Ck X-ray scattering
61.72.S- Impurities in crystals
61.72.Cc Kinetics of defect formation and annealing

Defect structure in selective area growth GaN pyramid on (111)Si substrate

Shigeyasu Tanaka, Yasutoshi Kawaguchi, Nobuhiko Sawaki, Michio Hibino, and Kazumasa Hiramatsu

Appl. Phys. Lett. 76, 2701 (2000); http://dx.doi.org/10.1063/1.126448 (3 pages) | Cited 29 times

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A GaN pyramid grown selectively on a (111)Si substrate with a patterned dot structure of a SiO2 mask, by metalorganic vapor phase epitaxy using AlGaN as an intermediate layer, was characterized by transmission electron microscopy. The dot pattern has an array of 5.0-μm-diameter window openings with a 10 μm period. The density of threading dislocations observed in the window region decreased gradually with increasing distance from the interface. This was mainly due to the dislocation reaction and bending of threading dislocations for the first 2 μm region from the interface and for the upper region, respectively. Dominantly observed defects in the lateral-growth part were dislocations parallel to the interface. An amorphous layer was formed at the interface in the window region. Nitride particles were observed at the interface in the mask region. © 2000 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Modification of the hole injection barrier in organic light-emitting devices studied by ultraviolet photoelectron spectroscopy

X. M. Ding, L. M. Hung, L. F. Cheng, Z. B. Deng, X. Y. Hou, C. S. Lee, and S. T. Lee

Appl. Phys. Lett. 76, 2704 (2000); http://dx.doi.org/10.1063/1.126449 (3 pages) | Cited 44 times

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Ultraviolet photoelectron spectroscopy has been applied to the investigation of modified hole injection barriers in organic light-emitting devices (OLEDs). Different from those reported previously, the indium tin oxide (ITO) surface treated in situ by oxygen plasma possesses a work function of 5.2 eV, and the organic ITO interface thereafter formed shows a 0.5 eV smaller hole injection barrier compared to that on untreated ITO. Insertion of an ultrathin SiO2 layer between the organic and ITO results in a similar reduction of the barrier. This indicates that improved hole injection favors efficient operation of OLEDs, as manifested by enhanced efficiency by the SiO2 insertion. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.30.+y Surface double layers, Schottky barriers, and work functions
81.65.-b Surface treatments
79.60.Jv Interfaces; heterostructures; nanostructures
73.20.At Surface states, band structure, electron density of states
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Near-surface InAs/GaAs quantum dots with sharp electronic shells

S. Fafard

Appl. Phys. Lett. 76, 2707 (2000); http://dx.doi.org/10.1063/1.126450 (3 pages) | Cited 16 times

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The interaction between zero-dimensional states and surface states is studied using near-surface quantum dot (QD) ensembles with well-defined electronic shells. The inhomogeneous broadening of self-assembled InAs/GaAs QDs increases from ∼ 30 to more than ∼ 46 meV as the distance of the QDs from the surface is changed from 100 to 5.0 nm. Simultaneously, a decrease of the radiative recombination intensity by ∼ 3 orders of magnitude, and a red-shift of ∼ 65 meV are observed. For QDs capped with less than ∼ 10 nm, remarkable charge transfers between the QD and surface states lead to optical memory effects lasting over time-scales of several minutes.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors

Predictive model for scanned probe oxidation kinetics

J. A. Dagata, F. Perez-Murano, G. Abadal, K. Morimoto, T. Inoue, J. Itoh, and H. Yokoyama

Appl. Phys. Lett. 76, 2710 (2000); http://dx.doi.org/10.1063/1.126451 (3 pages) | Cited 66 times

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Previous descriptions of scanned probe oxidation kinetics involved implicit assumptions that one-dimensional, steady-state models apply for arbitrary values of applied voltage and pulse duration. These assumptions have led to inconsistent interpretations regarding the fundamental processes that contribute to control of oxide growth rate. We propose a model that includes a temporal crossover of the system from transient to steady-state growth and a spatial crossover from predominantly vertical to coupled lateral growth. The model provides an excellent fit of available experimental data. © 2000 American Institute of Physics.
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81.65.Mq Oxidation
82.20.Wt Computational modeling; simulation
82.45.-h Electrochemistry and electrophoresis
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Analysis of x-ray reflectivity data from low-contrast polymer bilayer systems using a Fourier method

O. H. Seeck, I. D. Kaendler, M. Tolan, K. Shin, M. H. Rafailovich, J. Sokolov, and R. Kolb

Appl. Phys. Lett. 76, 2713 (2000); http://dx.doi.org/10.1063/1.126452 (3 pages) | Cited 24 times

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X-ray reflectivity data of polymer bilayer systems have been analyzed using a Fourier method which takes into account different limits of integration in q-space. It is demonstrated that the interfacial parameters can be determined with high accuracy although the difference in the electron density (the contrast) of the two polymers is extremely small. This method is not restricted to soft-matter thin films. It can be applied to any reflectivity data from low-contrast layer systems. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.41.+e Polymers, elastomers, and plastics
68.55.-a Thin film structure and morphology

Bi surfactant effects on ordering in GaInP grown by organometallic vapor-phase epitaxy

S. W. Jun, C. M. Fetzer, R. T. Lee, J. K. Shurtleff, and G. B. Stringfellow

Appl. Phys. Lett. 76, 2716 (2000); http://dx.doi.org/10.1063/1.126453 (3 pages) | Cited 8 times

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The effect of the isoelectronic surfactant Bi on surface structure and ordering has been studied for GaInP semiconductor alloys grown by organometallic vapor-phase epitaxy. A small amount of Bi (trimethylbismuth) added during growth is found to result in disordering for layers grown using conditions that would otherwise produce highly ordered materials. An order of magnitude increase in the step velocity was observed by atomic-force microscopy. Bi completely eliminates three-dimensional islands on the singular (001) surface. © 2000 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors

Plasma patterning of carbon nanotubes

Qidao Chen and Liming Dai

Appl. Phys. Lett. 76, 2719 (2000); http://dx.doi.org/10.1063/1.126454 (3 pages) | Cited 25 times

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We have prepared micropatterns of carbon nanotubes on a wide range of substrates either by patterned growth of aligned nanotubes on surfaces prepatterned with plasma polymers (e.g., n-hexane plasma polymer) or through region-specific adsorption of certain chemically modified carbon nanotubes (e.g., –COOH substituted nanotubes) onto surfaces prepatterned with various plasma-generated functionalities (e.g., –NH2). Micropatterns of carbon nanotubes prepared in both cases have resolutions on a micrometer scale, suitable for fabrication of various electronic and photonic devices. © 2000 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.05.ub Fullerenes and related materials
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
85.65.+h Molecular electronic devices
68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.40.Hp Lithography, masks and pattern transfer
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
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