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13 Jun 1994

Volume 64, Issue 24, pp. 3205-3350

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As capture and the growth of ultrathin InAs layers on InP

D. E. Aspnes, M. C. Tamargo, M. J. S. P. Brasil, R. E. Nahory, and S. A. Schwarz

Appl. Phys. Lett. 64, 3279 (1994); http://dx.doi.org/10.1063/1.111309 (3 pages) | Cited 10 times

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Capture of As by (001) InP surfaces exposed to As fluxes under chemical beam epitaxy conditions is investigated by virtual‐interface analysis of real‐time kinetic ellipsometric data. Intentional growth of ultrathin InAs layers is readily followed. Arsenic accumulated in the absence of growth can be completely removed by exposure to P, showing that As‐P exchange occurs only in the outermost layer.
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68.55.-a Thin film structure and morphology
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Photoluminescence of Sm doped porous silicon—evidence for light emission through luminescence centers in SiO2 layers

J. Lin, L. Z. Zhang, Y. M. Huang, B. R. Zhang, and G. G. Qin

Appl. Phys. Lett. 64, 3282 (1994); http://dx.doi.org/10.1063/1.111310 (3 pages) | Cited 20 times

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After oxidation promoted by gamma‐ray irradiation, in the photoluminescence (PL) spectra of Sm doped porous silicon (PS), there are three sharp peaks, superimposed on a broad band, with wavelengths near to those of the Sm doped SiO2 [R. Morimo, T. Mizushima, and H. Okumura, J. Electrochem. Soc. 137, 2340 (1990)]. The experimental results indicate that Sm‐related luminescence centers can be created within the oxide of porous silicon, and only in porous silicon with high porosity can the Sm‐related luminescence be found in the SiO2 layer. This experimental result can be explained by the fact that the excitation of electron‐hole pairs occurs in nanoscale silicon, and the recombination occurs at the Sm‐related luminescence centers in SiO2 layers covering nanoscale silicon.
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78.55.Hx Other solid inorganic materials
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Millisecond time‐resolved reflectance difference measurements of GaAs grown by short‐pulse supersonic nozzle beam epitaxy

Jie Cui, Suian Zhang, Akihiko Tanaka, and Yoshinobu Aoyagi

Appl. Phys. Lett. 64, 3285 (1994); http://dx.doi.org/10.1063/1.111311 (3 pages) | Cited 6 times

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We report the millisecond time‐resolved reflectance difference (RD) measurements during short‐pulse supersonic nozzle beam epitaxy of GaAs using trimethylgallium (TMG) and arsine (AsH3). A rapid rise of RD signal upon the injection of TMG short pulse was observed, and was assigned due to the density change of As dimers on the growing surface. With changes of the TMG pulse width and the substrate temperature, the corresponding changes of the rise time of the RD signal were observed. It is concluded that the rise in the RD signal is related to the As dimer annihilation caused by TMG decomposition, and As dimer formation. Our results also show that the growth amount under monolayer is proportional to the TMG molecular population in the TMG pulse.
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68.55.-a Thin film structure and morphology
78.47.-p Spectroscopy of solid state dynamics
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Observation of a negative electron affinity for heteroepitaxial AlN on α(6H)‐SiC(0001)

M. C. Benjamin, Cheng Wang, R. F. Davis, and R. J. Nemanich

Appl. Phys. Lett. 64, 3288 (1994); http://dx.doi.org/10.1063/1.111312 (3 pages) | Cited 123 times

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This study demonstrates the presence of a negative electron affinity (NEA) surface on AlN was grown on α(6H)‐SiC. Heteroepitaxial AlN was grown on α(6H)‐SiC(0001) substrates by molecular beam epitaxy techniques. The surface electronic states were characterized by ultraviolet photoemission obtained at surface normal. The observation of a sharp spectral feature at the lowest energy of the emitted electrons is an indication of a surface with a negative electron affinity. In addition, the trend of the NEA feature was examined as a function of annealing. The surface Fermi level is found to be near the middle of the AlN gap, and a possible band alignment between the AlN and SiC is presented.
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73.20.At Surface states, band structure, electron density of states
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Effect of an augmented oxygen implant on electron trapping in buried oxides

R. J. Lambert, T. N. Bhar, and H. L. Hughes

Appl. Phys. Lett. 64, 3291 (1994); http://dx.doi.org/10.1063/1.111313 (2 pages) | Cited 9 times

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Standard silicon on insulator wafers were prepared by separation by implantation of oxygen. The standard implant of 1.8×1018 O+ cm−2 was augmented by an additional implant of 1017 O+ cm−2. The effect of this augmented implantation of oxygen on electron trap density and cross section was investigated using avalanche injection of electrons into the buried oxide. The shift in the high‐frequency capacitance‐voltage curve was monitored as a function of injected charge. Analysis of the mid‐gap voltage shift versus charge shows no change in the effective density of electron traps. There is a factor of 6.8 decrease in the capture cross section for samples that received the supplemental oxygen implantation.
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61.72.up Other materials
61.72.uf Ge and Si
71.55.Ht Other nonmetals
61.80.Jh Ion radiation effects

Sintered aerosol masks for dry‐etched quantum dots

Knut Deppert, Ivan Maximov, Lars Samuelson, Hans‐Christen Hansson, and Alfred Weidensohler

Appl. Phys. Lett. 64, 3293 (1994); http://dx.doi.org/10.1063/1.111314 (3 pages) | Cited 18 times

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We report on a sintering step in producing ultra‐fine silver aerosol particles to serve as etch masks for semiconductor quantum‐dot structures. Our experiments found heating conditions that reshape the Ag particles, resulting in a spherical shape and very good size uniformities. Using this improved aerosol generation technology, we have dry etched InP columns with 24±5 nm diameter and with very good uniformity, with nearly every aerosol particle resulting in a column. Column arrays with a density as high as 3×109 cm−2 could be produced.
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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
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.65.-b Surface treatments

Far‐infrared study of a quasi‐one‐dimensional electron gas formed by molecular beam epitaxial regrowth on patterned GaAs

D. D. Arnone, J. H. Burroughes, M. Pepper, M. P. Grimshaw, D. A. Ritchie, and G. A. C. Jones

Appl. Phys. Lett. 64, 3296 (1994); http://dx.doi.org/10.1063/1.111315 (3 pages) | Cited 1 time

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A quasi‐one‐dimensional electron gas has been realized by using molecular beam epitaxy to grow a high electron mobility transistor (HEMT) on a patterned GaAs structure consisting of alternate layers of p‐GaAs and n‐GaAs. Independently contacting the p‐GaAs and n‐GaAs creates a patterned backgate, which is used to electrostatically induce a lateral modulation of the electron gas in the HEMT. Far‐infrared cyclotron resonance spectra demonstrate that lateral confinement energies over the range 1.3–3.3 meV may be selected via tuning of the biases applied to the p‐GaAs and n‐GaAs layers.
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68.55.-a Thin film structure and morphology
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.66.Fd III-V semiconductors

Growth of GaAs/AlAs trench‐buried multiple quantum wires by metalorganic chemical vapor deposition on V‐grooved substrates

T. Sogawa, S. Ando, and H. Kanbe

Appl. Phys. Lett. 64, 3299 (1994); http://dx.doi.org/10.1063/1.111972 (3 pages) | Cited 5 times

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We report the fabrication of GaAs/AlAs multiple trench‐buried quantum wires (TBWs) by metalorganic chemical vapor deposition on V‐grooved substrates. The shape of AlAs layers grown on the V‐grooves can be changed significantly from a V‐shape to U‐shape by varying growth temperatures and group‐V/III ratios. 30‐nm‐wide and 100‐nm‐deep AlAs trenches with nearly vertical sidewalls are formed at the growth temperature of 650 °C with the group‐V/III ratio of 165, while V‐shaped AlAs grooves are formed at 700 °C with the V/III ratio of 110. Vertically stacked double TBWs are formed using the 30‐nm‐wide trenches. The low‐temperature (15 K) photoluminescence spectrum for the double TBWs shows two distinct emission peaks corresponding to the 6.5‐ and 8.0‐nm‐thick wires.
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68.55.-a Thin film structure and morphology
78.55.Cr III-V semiconductors

Eliminating dopant diffusion after ion implantation by surface etching

Cynthia C. Lee, Michael D. Deal, and John C. Bravman

Appl. Phys. Lett. 64, 3302 (1994); http://dx.doi.org/10.1063/1.111319 (3 pages) | Cited 4 times

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Implantation damage is believed to play a significant role in dopant diffusion. Described here is an attempt to modify the point defect damage profile of a 40 keV, 29Si implant in GaAs by chemically etching away the top 100 Å of the sample after implantation. In these samples, no Si diffusion was observed after annealing, while significant Si redistribution did occur in a similar sample which received no post‐implant etch. trim simulations predict an excess Ga vacancy surface layer and excess Ga interstitials deeper in the sample. It is thought that by removing the vacancy‐rich surface layer, the etch alters the implant damage profile and thus the diffusion behavior of the Si. Surface effects from etching as related to the Si diffusion are shown to be consistent with a vacancy‐assisted diffusion mechanism. Evidence that this model may be applicable to B implants in Si is also shown.
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61.80.Jh Ion radiation effects
66.30.J- Diffusion of impurities
61.72.uj III-V and II-VI semiconductors
81.65.-b Surface treatments

On the nature of cross‐hatch patterns on compositionally graded Si1−xGex alloy layers

Sergey Yu. Shiryaev, Flemming Jensen, and Jon Wulff Petersen

Appl. Phys. Lett. 64, 3305 (1994); http://dx.doi.org/10.1063/1.111287 (3 pages) | Cited 79 times

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The effect of strain relaxation on the surface morphology of compositionally graded Si1−xGex layers grown at 550 °C has been investigated by a combination of transmission electron and atomic force microscopy. By annealing unrelaxed graded layers, we have found that shear displacements caused by dislocation glide roughen the surface dramatically. This effect is attributed to the formation of a network of dislocation clusters which give rise to the pronounced slip‐band pattern on the surface of the graded layers. It is shown that the surface plastic displacements produced by such a network during growth of the graded layer contribute significantly to the formation of the cross‐hatch patterns.
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68.55.-a Thin film structure and morphology
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Low temperature formation of Si(111)7×7 surfaces from chemically prepared H/Si(111)‐(1×1) surfaces

Le Thanh Vinh, M. Eddrief, C. A. Sébenne, P. Dumas, A. Taleb‐Ibrahimi, R. Gunther, Y. J. Chabal, and J. Derrien

Appl. Phys. Lett. 64, 3308 (1994); http://dx.doi.org/10.1063/1.111288 (3 pages) | Cited 31 times

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Reflection high energy and low energy electron diffraction, along with high resolution photoemission studies reveal that ideally H‐terminated Si(111) surfaces, H/Si(111)‐(1×1) prepared by wet chemical etching, transform in ultrahigh vacuum into atomically clean Si(111)7×7 surfaces upon hydrogen desorption at temperatures as low as 550 °C.
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81.65.-b Surface treatments
68.35.B- Structure of clean surfaces (and surface reconstruction)

Milliwatt output levels and superquadratic bias dependence in a low‐temperature‐grown GaAs photomixer

E. R. Brown, K. A. McIntosh, F. W. Smith, K. B. Nichols, M. J. Manfra, C. L. Dennis, and J. P. Mattia

Appl. Phys. Lett. 64, 3311 (1994); http://dx.doi.org/10.1063/1.111289 (3 pages) | Cited 42 times

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A cw output power up to 0.8 mW is obtained from a low‐temperature‐grown (LTG) GaAs, 0.3 μm gap, interdigitated‐electrode photomixer operating at room temperature and pumped by two modes of a Ti:Al2O3 laser separated in frequency by 0.2 GHz. The output power and associated optical‐to‐electrical conversion efficiency of 1% represent more than a sixfold increase over previous LTG‐GaAs photomixer results obtained at room temperature. A separate LTG‐GaAs photomixer having 0.6 μm gaps generated up to 0.1 mW at room temperature and up to 4 mW at 77 K. Low‐temperature operation is beneficial because it reduces the possibility of thermal burnout and it accentuates a nearly quartic dependence of output power on bias voltage at high bias. The quartic dependence is explained by space‐charge effects which result from the application of a very high electric field in the presence of recombination‐limited transport. These conditions yield a photocurrent‐voltage characteristic that is very similar in form to the well‐known Mott–Gurney square‐law current in trap‐free solids.
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42.55.Px Semiconductor lasers; laser diodes
78.66.Fd III-V semiconductors
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Photoreflectance study of surface Fermi level in molecular beam epitaxial grown InAlAs heterostructures

J. S. Hwang, S. L. Tyan, W. Y. Chou, M. L. Lee, David Weyburne, Z. Hang, H. H. Lin, and T. L. Lee

Appl. Phys. Lett. 64, 3314 (1994); http://dx.doi.org/10.1063/1.111294 (3 pages) | Cited 15 times

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We have studied the band gaps and the surface Fermi level positions of a series of In1−xAlxAs surface‐intrinsic‐n+ structures at room temperature by photoreflectance. Experiments demonstrated that over aluminum concentrations of 0.42–0.57, the surface Fermi level is not pinned at midgap, as commonly believed, but instead varies, respectively, from 0.50±0.01 to 0.81±0.01 eV below the conduction band edge.
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73.20.At Surface states, band structure, electron density of states
73.61.Ey III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.80.Ey III-V and II-VI semiconductors

Real time spectroellipsometry study of the interaction of hydrogen with ZnO during ZnO/a‐Si1−xCxH interface formation

Ilsin An, Yiwei Lu, C. R. Wronski, and R. W. Collins

Appl. Phys. Lett. 64, 3317 (1994); http://dx.doi.org/10.1063/1.111295 (3 pages) | Cited 17 times

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Using real time spectroellipsometry (SE), we have studied the interfacial interactions that occur when i‐ and p‐type hydrogenated amorphous silicon‐carbon alloys (a‐Si1−xCx:H) are deposited from hydride‐containing plasmas onto transparent, conducting films of ZnO. The SE spectra collected during the nucleation of a‐Si1−xCx:H onto ZnO reveal a widening of the near‐interface optical gap of ZnO by ∼0.1 eV, an effect attributed to the penetration of atomic H from the plasma. The SE data, along with ex situ secondary ion mass spectrometry, reveal that the H diffuses into ZnO to depths ≳200 Å. The defects that result from H incorporation in ZnO (e.g., O vacancies) lead to a shift in the near‐interface Fermi level higher into the ZnO conduction band and to an estimated enhancement in the electron concentration by ∼1020 cm−3.
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68.35.Fx Diffusion; interface formation
78.66.Hf II-VI semiconductors
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Sharp‐line photoluminescence of excitons localized at GaAs/AlGaAs quantum well inhomogeneities

K. Brunner, G. Abstreiter, G. Böhm, G. Tränkle, and G. Weimann

Appl. Phys. Lett. 64, 3320 (1994); http://dx.doi.org/10.1063/1.111265 (3 pages) | Cited 83 times

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GaAs/AlGaAs single quantum well samples have been investigated by photoluminescence spectroscopy using a probe size of about a micron at low temperature. Thin quantum wells fabricated by molecular beam epitaxy with growth interruptions at the interfaces reveal intense photoluminescence lines with spectral widths below 0.1 meV at the low‐energy side of the main luminescence. Mapping the quantum well by scanning the probe shows local emission of these sharp lines, which change in number and in energy with lateral probe position. The local source of the sharp lines, as well as their temperature and saturation behavior shows that they are caused by single excitons localized at sample inhomogeneities, like GaAs well width fluctuations.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
77.55.-g Dielectric thin films

Measurement of the velocity of current filaments in optically triggered, high gain GaAs switches

G. M. Loubriel, F. J. Zutavern, H. P. Hjalmarson, R. R. Gallegos, W. D. Helgeson, and M. W. O’Malley

Appl. Phys. Lett. 64, 3323 (1994); http://dx.doi.org/10.1063/1.111266 (3 pages) | Cited 6 times

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Pictures are presented of the time evolution of current filaments during optically triggered, high gain switching in GaAs. Two filaments are triggered with two laser diode arrays and the time delay between them is varied. When the filament that is triggered first crosses the switch the voltage drops and the other filament ceases to grow. By varying the delay between the lasers, the tip velocity is measured to be 2±1×109 cm/s, 100 times larger than the peak drift velocity of carriers in GaAs. This observation supports switching models that rely on carrier generation at the tip of the filament.
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72.20.Ht High-field and nonlinear effects
72.40.+w Photoconduction and photovoltaic effects
78.47.-p Spectroscopy of solid state dynamics
78.55.Et II-VI semiconductors

Surface resistance and penetration depth of YBa2Cu3O7−δ thin films on silicon at ultrahigh frequencies

Christian Jaekel, Christian Waschke, Hartmut G. Roskos, Heinrich Kurz, Werner Prusseit, and Helmut Kinder

Appl. Phys. Lett. 64, 3326 (1994); http://dx.doi.org/10.1063/1.111267 (3 pages) | Cited 8 times

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The surface resistance Rs and the absolute value of the magnetic penetration depth λ of ultrathin YBa2Cu3O7−δ films on silicon are determined by THz‐pulse transmission experiments. We find a minimal value of Rs for a film thickness of about 30 nm. The increase of Rs with film thickness above 30 nm reveals an increase of the density of weak links possibly associated with the formation of microfractures even below the critical film thickness of 50–70 nm.
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74.78.-w Superconducting films and low-dimensional structures
74.25.N- Response to electromagnetic fields
74.25.Op Mixed states, critical fields, and surface sheaths
74.72.-h Cuprate superconductors

Theory of YBa2Cu3O7−x/PrBa2Cu3O7−x superlattices as superconductor‐insulator multilayers

Jun Li, Ke qi Luo, and Chang de Gong

Appl. Phys. Lett. 64, 3329 (1994); http://dx.doi.org/10.1063/1.111268 (2 pages) | Cited 1 time

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The YBa2Cu3O7−xCu3O7−x superlattices are treated as superconductor‐insulator multilayers, where CuO2 planes in the YBa2Cu3O7−x layers are taken as two‐dimensional (2D) superconductors and CuO2 planes in the PrBa2Cu3O7−x layer are described by the 2D Mott–Hubbard insulator with large Coulomb repulsion. We obtain good Tc vs number of PrBa2Cu3O7−x unit cells in a single layer by using only one adjustable parameter and without assuming charge‐carrier‐transfer effect.
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74.72.-h Cuprate superconductors
74.78.Fk Multilayers, superlattices, heterostructures

Enhancement of persistent currents in Bi2Sr2CaCu2O8 tapes with splayed columnar defects induced with 0.8 GeV protons

L. Krusin‐Elbaum, J. R. Thompson, R. Wheeler, A. D. Marwick, C. Li, S. Patel, D. T. Shaw, P. Lisowski, and J. Ullmann

Appl. Phys. Lett. 64, 3331 (1994); http://dx.doi.org/10.1063/1.111269 (3 pages) | Cited 70 times

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Composite tapes of the superconductor Bi2Sr2CaCu2O8 on silver were irradiated with energetic light ions (0.8 GeV protons), creating extended splayed tracks ∼7 nm in diameter via fission of Bi nuclei. Magnetic hysteresis indicates large enhancements of persistent currents J, especially at high fields and temperatures, and substantial expansion of the irreversible regime. The technique may be suitable for large scale applications due to the long range (∼half meter) of fast protons.
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84.71.Mn Superconducting wires, fibers, and tapes
74.25.Sv Critical currents
61.80.Jh Ion radiation effects
74.72.-h Cuprate superconductors

Direct high‐resolution electron microscopy observations of sputtered a‐axis oriented YBa2Cu3O7 films prepared by a self‐template method on SrTiO3 substrates

J. G. Wen, S. Mahajan, W. Ito, T. Morishita, and N. Koshizuka

Appl. Phys. Lett. 64, 3334 (1994); http://dx.doi.org/10.1063/1.111270 (3 pages) | Cited 7 times

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A‐axis oriented YBa2Cu3O7 films grown on a SrTiO3 substrate with and without the template layer have been studied by high‐resolution electron microscopy. The self‐template layer was found to be very effective to obtain highly crystalline a‐axis oriented YBa2Cu3O7 film. A disordered cubic perovskite structure with a lattice parameter of 3.85 Å was found in the template layer which could be a good seed for further growth of a‐axis film. In the film without the self‐template layer, YBa4Cu3Ox cubic perovskite with lattice parameter 4.08 Å was observed to have grown at the interface as an island growth. Moreover, some faulted c‐axis film at the very beginning of the template layer was observed even at the rather lower deposition temperature of 640 °C.
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68.55.-a Thin film structure and morphology
74.78.-w Superconducting films and low-dimensional structures

(Pt/Co/Pt)/X multilayer films with high Kerr rotations and large perpendicular magnetic anisotropies

G. A. Bertero and R. Sinclair

Appl. Phys. Lett. 64, 3337 (1994); http://dx.doi.org/10.1063/1.111271 (3 pages) | Cited 15 times

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We have sputter‐deposited a series of (Pt/Co/Pt)/X multilayer structures with X=Pd,Ag,Cu displaying large Kerr rotations with improved perpendicular anisotropy and magnetic coercivity compared to the corresponding Co/X multilayers. In particular, Ar‐sputtered (Pt/Co/Pt)/Pd multilayers, with the Pt layer thicknesses corresponding to one atomic monolayer, present Kerr rotations of the order of 0.26°, perpendicular anisotropy energies of 33×106 ergs/cc (Co) or better, and magnetic coercivities as high as 8 kOe.
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75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.30.Gw Magnetic anisotropy
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
78.20.Ls Magneto-optical effects

Dynamics of laser‐ablated iron in nitrogen atmosphere

M. Ohkoshi, T. Yoshitake, and K. Tsushima

Appl. Phys. Lett. 64, 3340 (1994); http://dx.doi.org/10.1063/1.111272 (3 pages) | Cited 18 times

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Fast photography with a framing streak camera is applied to investigate the dynamics of ablated Fe particles by a pulsed excimer laser when a nitrogen atmosphere is present. Two stages of expansion are found in the generated plume. The first one starts just after the laser irradiation where the hemispherical and unidirectional plumes are found simultaneously. The dynamics of the unidirectional plume is described by a drag model for 300 ns. The second stage occurs at 300 ns, and the unidirectional plume expands again in agreement with a delayed blast wave model. The thickness distribution of the deposited Fe‐N film is well correlated with the change in the plume geometry, then with the nitrogen pressure.
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81.15.Fg Pulsed laser ablation deposition
79.20.Ds Laser-beam impact phenomena

Oxygen exchange between CO2 adsorbate and TiO2 surfaces

Y. Yanagisawa and T. Sumimoto

Appl. Phys. Lett. 64, 3343 (1994); http://dx.doi.org/10.1063/1.111273 (2 pages) | Cited 2 times

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Using temperature‐programmed desorption gas analysis, thermal desorptions of C18O2 and C16O18O with a small amount of C16O2 were observed in the temperature range 350–500 K after C18O2 was adsorbed on vacuum‐annealed TiO2 powders at room temperature. This indicates that oxygen isotope exchange takes place between C18O2 gas and TiO2 surfaces. After 16O2 exposure of the C18O2‐preadsorbed powders, the amount of C16O2 desorption increased, suggesting that isotope mixing may occur through a CO2‐O2 intermediate complex.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics

Effect of surface composition on the radiation pattern from a photonic‐crystal planar‐dipole antenna

E. R. Brown, C. D. Parker, and O. B. McMahon

Appl. Phys. Lett. 64, 3345 (1994); http://dx.doi.org/10.1063/1.111274 (3 pages) | Cited 29 times

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Radiation patterns are measured from a planar‐dipole antenna mounted on two {111}‐oriented surfaces of a face‐centered‐cubic photonic‐crystal substrate. The photonic crystal consists of nonspherical air atoms in a dielectric matrix having a permittivity of 12. The measurements are made at a frequency of 14.5 GHz in the middle of the photonic band gap. We find that the antenna pattern depends strongly on the fraction of the crystal surface occupied by dielectric material. A surface having a low dielectric fraction yields much narrower patterns in polar angle than one having a high fraction. We attribute this difference to the strong excitation of a TE mode by the dipole on the surface having a high dielectric fraction.
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42.25.-p Wave optics
42.79.-e Optical elements, devices, and systems

Maskless laser patterning of insulating films from salt solutions

R. J. von Gutfeld, D. R. Vigliotti, O. C. Wells, V. D. Khanna, and E. J. O’Sullivan

Appl. Phys. Lett. 64, 3348 (1994); http://dx.doi.org/10.1063/1.111275 (3 pages) | Cited 4 times

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Insulating thin‐film patterns have been deposited on a variety of metal surfaces using focused laser light incident on samples submerged in both electrolytic and electroless nickel solutions. Deposits occur only where the laser radiation is absorbed by the substrate. For a single scan, the patterned film can have dimensions as small as 25 nm in height, 4 μm in width. Scanning electron microscope and electrical probing measurements confirm the insulating nature of the films.  
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81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
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
68.55.-a Thin film structure and morphology
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