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16 Oct 1995

Volume 67, Issue 16, pp. 2263-2418

Page 2 of 3 Pages Previous Page Next Page | Jump to Page

Single hole quantum dot transistors in silicon

Effendi Leobandung, Lingjie Guo, and Stephen Y. Chou

Appl. Phys. Lett. 67, 2338 (1995); http://dx.doi.org/10.1063/1.114337 (3 pages) | Cited 38 times

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Novel p‐channel quantum‐dot transistors were fabricated in silicon‐on‐insulator. Strong oscillations in the drain current as a function of the gate voltage have been observed at temperatures over 81 K and drain biases over 66 mV. The oscillations are attributed to holes tunneling through the discrete single hole energy levels in the quantum dot. Measurements show that the average energy level spacing is ∼35 meV. Simple modeling indicates that about two thirds of the energy level spacing come from the Coulomb interaction between holes (i.e., hole Coulomb blockade) and one third from the quantum confinement effect. The realization of single hole quantum‐dot transistors opens new possibilities for innovative circuits that utilize complementary pairs of quantum‐dot transistors. © 1995 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Gk Tunneling
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Growth of hydrogenated Si clusters using a quadrupole ion trap

Hirohiko Murakami and Toshihiko Kanayama

Appl. Phys. Lett. 67, 2341 (1995); http://dx.doi.org/10.1063/1.114338 (3 pages) | Cited 26 times

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To investigate how stability of small Si clusters is affected by hydrogenation, SinH+xions (n=2–10) were grown from silane gas in a recently developed ion trap and the mass spectra were measured. Some compositions have been found to be particularly stable besides those already known for nonhydrogenated Si clusters such as Si6 and Si10. These clusters, Si5H10+, Si6H12+, and Si10H12–17+, are inferred to have the bulklike tetrahedrally coordinated structures whose dangling bonds are terminated by H atoms. © 1995 American Institute of Physics.
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36.40.Qv Stability and fragmentation of clusters
61.46.-w Structure of nanoscale materials

Interband transitions in Cd0.07Zn0.93Te/ZnTe strained single quantum wells grown by double‐well temperature‐gradient vapor deposition

J. H. Lee, H. L. Park, and T. W. Kim

Appl. Phys. Lett. 67, 2344 (1995); http://dx.doi.org/10.1063/1.114339 (3 pages) | Cited 2 times

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The electronic states in a Cd0.07Zn0.93Te/ZnTe strained single quantum well grown by the simple method of double‐well temperature‐gradient vapor deposition have been investigated both experimentally and theoretically. X‐ray diffractometry measurements were performed to characterize the structural properties of the Cd0.07Zn0.93Te/ZnTe quantum well. Reflectivity and photoreflectance measurements showed several resonant excitations in the Cd0.07Zn0.93Te quantum well, and photoluminescence measurements on the strained quantum well structures showed that the sharp excitonic transition from the first electron subband to the first heavy‐hole band. Interband transition energies in the Cd0.07Zn0.93Te were calculated by taking into account the strain effects, and these theoretical values are in reasonable agreement with the results from the experimental measurement. These results indicate that these Cd0.07Zn0.93Te/ZnTe strained quantum wells hold promise for the potential applications such as in optoelectronic devices in the blue‐green region of the spectrum. © 1995 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Band‐gap reduction and valence‐band splitting of ordered GaInP2

P. Ernst, C. Geng, F. Scholz, H. Schweizer, Yong Zhang, and A. Mascarenhas

Appl. Phys. Lett. 67, 2347 (1995); http://dx.doi.org/10.1063/1.114340 (3 pages) | Cited 121 times

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Low‐temperature photoluminescence excitation spectra are used to determine the order‐dependent parameters: valence‐band splitting and band‐gap reduction in spontaneously ordered GaInP2. Effects due to composition fluctuations between different samples and the associated strain, as well as the excitonic binding energies, have been properly taken into account to yield accurate band‐gap reduction and valence‐band splitting values. The results from recently published ab initio band structure calculations are used to extrapolate the band‐gap reduction from the strongest experimentally realized degree of ordering to perfect ordering. We find a total band‐gap reduction of 471±12 meV, which is very close to recent theoretical predictions. © 1995 American Institute of Physics.
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71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
78.30.Fs III-V and II-VI semiconductors
78.55.Cr III-V semiconductors

Study of surface Fermi level and surface state distribution in InAlAs surface‐intrinsic‐n+ structure by photoreflectance

J. S. Hwang, W. Y. Chou, S. L. Tyan, H. H. Lin, and T. L. Lee

Appl. Phys. Lett. 67, 2350 (1995); http://dx.doi.org/10.1063/1.114341 (3 pages) | Cited 15 times

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The built‐in electric field and surface Fermi level in the InAlAs surface‐intrinsic‐n+ structures were studied by room‐temperature photoreflectance. The samples were grown by molecular beam epitaxy with an undoped layer thickness of 1000 Å. The undoped layer was subsequently etched to 800, 600, 400, and 200 Å. Different chemical solutions were used in the etching process and the built‐in electric field is found independent of the etching process. While the surface Fermi level, in general, varies with the undoped layer thickness, there exists, for each Al concentration, a certain range of thicknesses within which the surface Fermi level is weakly pinned. From the dependence of electric field and surface Fermi level on the undoped layer thickness, we conclude that the surface states distribute over two separate regions within the energy band gap and the densities of surface states are as low as 1.02±0.05×1011 cm−2 for the distribution near the conduction band and 2.91±0.05×1011 cm−2 for the distribution near valence band. © 1995 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
78.66.Fd III-V semiconductors

Envelope‐function theorem in the high‐energy limit

Richard L. Liboff and Steven R. Seidman

Appl. Phys. Lett. 67, 2353 (1995); http://dx.doi.org/10.1063/1.114342 (2 pages)

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The envel/pe‐function theorem is considered in the ,imit that el%ctron energy far exceeds that of the characteristic height of the potgntial array which, in turn, is comprised of a slowly varying component and smaller amplitude rapidly varying component. Working in the nearly‐free‐electron model, it is found that ‘‘new’’ energies and wave functions at band edges are those related to the slowly varying component of the potential. Wave functions related to the rapidly varying potential component average to zero over a small function of a primitive cell. These properties comprise the envelope‐function theorem relevant to high‐energy charge carriers passing through a quantum well array. © 1995 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.-c Electronic transport in interface structures

Epitaxial electrodeposition of CdTe films on InP from aqueous solutions: Role of a chemically deposited CdS intermediate layer

D. Lincot, A. Kampmann, B. Mokili, J. Vedel, R. Cortes, and M. Froment

Appl. Phys. Lett. 67, 2355 (1995); http://dx.doi.org/10.1063/1.114343 (3 pages) | Cited 17 times

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Epitaxial (111) CdTe films have been grown on (1 1 1) InP single crystals by one step electrodeposition in aqueous acidic solution, at a temperature of 85 °C, and a growth rate of about 0.7 μm h−1. Reflexion high‐energy electron diffraction and five‐circle x‐ray diffraction techniques have been used to characterize the interface structure and epitaxial quality. The epitaxy of CdTe (fcc a=6.49 Å) takes place with a direct continuation of the InP lattice (fcc a=5.87 Å), with no rotation of the respective crystallographic directions. The epitaxy is markedly improved when the InP substrate is covered with a thin film (20–30 nm) of epitaxial CdS grown by chemical bath deposition which acts as an interfacial buffer layer. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.15.Pq Electrodeposition, electroplating

InGaAs/InP quantum wires grown by gas source molecular beam epitaxy onto V‐grooved InP substrates with (111)A facet sidewalls

J. Wang, B. J. Robinson, D. A. Thompson, and J. G. Simmons

Appl. Phys. Lett. 67, 2358 (1995); http://dx.doi.org/10.1063/1.114344 (3 pages) | Cited 8 times

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InGaAs/InP layers have been grown under optimized conditions by gas source molecular beam epitaxy on (100) InP substrates patterned with V grooves having (111)A facet sidewalls. Transmission electron microscopy shows that InGaAs/InP quantum wires are obtained with well thickness variation as high as a factor of 6 and that all epilayers are defect‐free. Lateral subband separations are estimated by a simple one‐dimensional parabolic potential model with the thickness determined by transmission electron microscopy. Photoluminescence from the InGaAs quantum wires is resolved with a selective etching technique. The quantum wire emission has a significant red shift compared to the adjacent quantum wells on the groove sidewalls and the (100) surface region between grooves. The red shift results from both the increased well thickness and compositional change due to adatom diffusion from sidewalls. © 1995 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.Fd III-V semiconductors

Formation of buried oxide in silicon using separation by plasma implantation of oxygen

Jingbao Liu, S. Sundar Kumar Iyer, Chenming Hu, Nathan W. Cheung, Ron Gronsky, Jing Min, and Paul Chu

Appl. Phys. Lett. 67, 2361 (1995); http://dx.doi.org/10.1063/1.114345 (3 pages) | Cited 41 times

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Plasma immersion ion implantation (PIII) is used to fabricate buried oxide layers in silicon. This ‘‘separation by plasma implantation of oxygen’’ (SPIMOX) technique can achieve a nominal oxygen atom dose of 2×1017 cm−2 in implantation time of about 3 min. SPIMOX is thus presented as a practical high‐throughput process for manufacturing silicon‐on‐insulator. In the SPIMOX samples prepared, three distinct modes of buried oxide microstructure formation are identified and related to the as‐implanted oxygen profiles. A first‐order model based on oxygen transport and oxide precipitation explains the formation mechanisms of these three types of SPIMOX layers. © 1995 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
61.72.uf Ge and Si
81.10.Jt Growth from solid phases (including multiphase diffusion and recrystallization)
81.65.-b Surface treatments

In situ observation of silicon hydrides on Si(100) surfaces during synchrotron‐radiation‐stimulated Si2H6 gas source molecular beam epitaxy

A. Yoshigoe, K. Mase, Y. Tsusaka, T. Urisu, Y. Kobayashi, and T. Ogino

Appl. Phys. Lett. 67, 2364 (1995); http://dx.doi.org/10.1063/1.114346 (3 pages) | Cited 12 times

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Silicon hydrides (SiHn) on the Si(100) surface during synchrotron‐radiation (SR) stimulated Si2H6 gas source molecular beam epitaxy has been observed in situ at low temperatures (≤400 °C), by means of infrared reflection absorption spectroscopy using CoSi2 buried metal layer substrates. At high temperatures (400 °C, 370 °C), SiH is a dominant surface species, while with temperature decrease from 275 to 50 °C, the number of SiH decreases, and, on the other hand, SiH2 and SiH3 appear and increase. This result explains the change of reflection high‐energy diffraction pattern from 2×1 to 1×1. The SiH in the bulk network has not been observed. SR irradiation on the film at 140 °C after deposition shows that SiH2 and SiH3 are easily decomposed to SiH and that SiH decomposes much more slowly than SiH2 and SiH3. © 1995 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Hf II-VI semiconductors
82.50.-m Photochemistry
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Au–Sn solder bumps with tungsten silicide based barrier metallization schemes

W. Pittroff, T. Reiche, J. Barnikow, A. Klein, U. Merkel, K. Vogel, and J. Würfl

Appl. Phys. Lett. 67, 2367 (1995); http://dx.doi.org/10.1063/1.114347 (3 pages) | Cited 9 times

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A homogeneous melting eutectic Au/Sn solder bump for flip‐chip application has been developed. The underbump metallization consists of a WSi0.4N0.2‐layer and a Ni‐wetting layer. The solder is deposited as a sequence of alternating Au and Sn layers. The bump can be exposed to multiple fluxless reflow cycles. The reflow of the solder as deposited starts with a phase forming process in the solid state which results in an eutecticlike phase and the near eutectic δ and ζ phases. The δ and ζ phases dissolve during the liquid state stage of the reflow at temperatures between 300 and 350 °C. © 1995 American Institute of Physics.
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85.40.Bh Computer-aided design of microcircuits; layout and modeling
85.40.Hp Lithography, masks and pattern transfer
85.40.Ls Metallization, contacts, interconnects; device isolation

Size dependence of band gaps in silicon nanostructures

B. Delley and E. F. Steigmeier

Appl. Phys. Lett. 67, 2370 (1995); http://dx.doi.org/10.1063/1.114348 (3 pages) | Cited 145 times

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The size dependence of the energy band gap for hydrogen saturated silicon clusters, wires and slabs are calculated using all electron density functional theory. The hydrogen saturation is considered as a model for a wider band gap insulator enclosing the silicon structures. With this perspective in mind, an effective mass model with finite barriers for both valence and conduction band is found to semiquantatively account for the numerical findings. © 1995 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
78.66.Db Elemental semiconductors and insulators

Relaxed Si0.7Ge0.3 buffer layers for high‐mobility devices

P. M. Mooney, J. L. Jordan‐Sweet, K. Ismail, J. O. Chu, R. M. Feenstra, and F. K. LeGoues

Appl. Phys. Lett. 67, 2373 (1995); http://dx.doi.org/10.1063/1.114349 (3 pages) | Cited 43 times

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The minimum epitaxial layer thickness required to produce relaxed, thermally stable, Si0.7Ge0.3 buffer layer structures for high electron‐ and hole‐mobility devices has been determined, using high resolution x‐ray diffraction. A 1.4‐μm‐thick layer, step graded to x=0.35, is sufficiently thick so that the residual strain in a uniform composition Si0.33Ge0.67 layer grown on top of it is essentially independent of thickness or growth temperature of the layer. Such structures are stable when annealed at 750 °C. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology
73.61.Le Other inorganic semiconductors

Paramagnetic resonance in GaN‐based light emitting diodes

W. E. Carlos, E. R. Glaser, T. A. Kennedy, and S. Nakamura

Appl. Phys. Lett. 67, 2376 (1995); http://dx.doi.org/10.1063/1.114350 (3 pages) | Cited 13 times

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Significant advances in GaN‐based materials and devices have prompted intense interest in the group III nitrides. In this letter, we report electroluminescence‐detected magnetic resonance (ELDMR) and electrically detected magnetic resonance (EDMR) results on InGaN/AlGaN double heterostructures which have an intense blue emission. The dominant feature detected by either technique is a broad resonance (ΔB∼21 mT) at g≊2.00. Our ELDMR measurements show that this is associated with the blue emission and we ascribe this resonance signal to a deep Zn‐related acceptor. A second resonance, resolved in EDMR, is tentatively identified as a deep donor trap. Based on our results we propose a model for the blue emission from these diodes. © 1995 American Institute of Physics.
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76.30.Mi Color centers and other defects
78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices

Diamond deposition from fluorinated precursors using microwave‐plasma chemical vapor deposition

Ciaran A. Fox, Mark C. McMaster, Wen L. Hsu, Michael A. Kelly, and Stig B. Hagstrom

Appl. Phys. Lett. 67, 2379 (1995); http://dx.doi.org/10.1063/1.114351 (3 pages) | Cited 15 times

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Diamond thin films were grown using fluorinated precursors by microwave plasma‐assisted chemical vapor deposition. Using CH4/H2, CH3F/H2, and CF4/H2 gas mixtures, films were grown at surface temperatures in the range 600–900 °C at constant microwave power, carbon mole fraction, and pressure. Growth activation energies for the CH4/H2, CH3F/H2, and CF4/H2 mixtures were 12.6±1.8, 13.7±1.2, and 12.4±1.1 kcal/mole, respectively. Argon ion etching in conjunction with x‐ray photoelectron spectroscopy indicated negligible fluorine incorporation into the films. These results are consistent with the hypothesis that diamond is grown from the same intermediates, namely methyl radicals and atomic hydrogen, for all of these mixtures. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Desegregation of boron at the grain boundaries of the in situ boron doped diamond films

J. T. Huang, C. S. Hu, J. Hwang, H. Chang, and L. J. Lee

Appl. Phys. Lett. 67, 2382 (1995); http://dx.doi.org/10.1063/1.114352 (3 pages) | Cited 9 times

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High quality in situ boron doped polycrystalline diamond films were grown on the scratched Si (100) substrate. A saturated deionized water solution of boron acid was chosen as a dopant source. The concentration profiles of boron, tantalum, and oxygen were examined by using scanning Auger nanoprobe and secondary ion mass spectroscopy. The boron atoms are uniformly distributed inside each diamond grain. However, no Auger signal from boron was observed at grain boundaries within the detection limit. In contrast, tantalum atoms are uniformly distributed across diamond grains and grain boundaries. A simple model was proposed in explaining the boron desegregation. © 1995 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Incorporation mechanism of N, Al, and B impurities in chemical vapor deposition of SiC

Tsunenobu Kimoto, Akira Itoh, and Hiroyuki Matsunami

Appl. Phys. Lett. 67, 2385 (1995); http://dx.doi.org/10.1063/1.114555 (3 pages) | Cited 25 times

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In situ doping characteristics of N, Al, and B in step‐controlled epitaxy of SiC have been investigated. Clear C/Si ratio dependence was observed in the growth on (0001)Si faces. Doping efficiency of N decreased and those of Al and B increased under the C‐rich condition, which agrees with a model proposed as ‘‘site‐competition epitaxy.’’ However, doping efficiencies were almost independent of the C/Si ratio on (0001)C faces. Based on the results, the incorporation mechanism is discussed. © 1995 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

The effect of a ZnTe buffer layer on the structural and optical properties of the CdTe/ZnTe/GaAs strained heterostructures grown by temperature‐gradient vapor‐transport deposition

T. W. Kim, H. L. Park, and J. Y. Lee

Appl. Phys. Lett. 67, 2388 (1995); http://dx.doi.org/10.1063/1.114556 (3 pages) | Cited 5 times

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Lattice‐mismatched CdTe epilayers on GaAs (100) substrates with and without ZnTe buffer layers were grown by the simple method of double‐well temperature gradient vapor‐transport deposition. X‐ray diffraction measurements were performed to investigate the structural properties of the epitaxial layers. Photoluminescence and transmission electron microscopy measurements showed that the crystallinity of the CdTe epilayers grown on the GaAs substrates was remarkably improved using the ZnTe buffer. The strain of the CdTe layer was determined from photoreflectance measurements. These results indicated that the CdTe epitaxial films grown on GaAs substrates with the ZnTe buffer can be used for applications as buffer layers for the growth of HgxCd1−xTe and CdxZn1−xTe. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology

Excited state spectroscopy of excitons in single quantum dots

D. Gammon, E. S. Snow, and D. S. Katzer

Appl. Phys. Lett. 67, 2391 (1995); http://dx.doi.org/10.1063/1.114557 (3 pages) | Cited 76 times

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We describe the results of a photoluminescence study of quantum dots which are formed by interface fluctuations in narrow GaAs/AlAs single quantum wells. The photoluminescence measurements were made with lateral spatial resolution ranging from the macroscopic down to the optical near‐field regime. For spatial resolution below a few square microns the photoluminescence from individual quantum dots is resolved. Photoluminescence excitation spectroscopy is used to study the excited state spectrum of an exciton bound in a single quantum dot. © 1995 American Institute of Physics.
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71.35.-y Excitons and related phenomena
78.55.Cr III-V semiconductors
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

Oscillations at liquid‐nitrogen temperatures in the transconductance of a silicon metal‐oxide‐semiconductor field‐effect transistor with a neck in the middle

Kan Takeuchi, Dai Hisamoto, and Masaaki Aoki

Appl. Phys. Lett. 67, 2394 (1995); http://dx.doi.org/10.1063/1.114558 (3 pages)

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The conductance of a silicon metal‐oxide‐semiconductor field‐effect transistor, the gate of which has a neck in the middle, was measured at liquid‐helium temperatures and liquid‐nitrogen temperatures. The channel width in the neck region configured by SiO2 isolation regions is below 50 nm. The transconductance at liquid‐nitrogen temperatures shows periodic oscillations that are accentuated by negative substrate bias. We explain the results based on the one‐dimensional subbands formed in the neck region. © 1995 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.Tv Field effect devices

Properties of YBa2Cu3O7−δ thick films on flexible buffered metallic substrates

X. D. Wu, S. R. Foltyn, P. N. Arendt, W. R. Blumenthal, I. H. Campbell, J. D. Cotton, J. Y. Coulter, W. L. Hults, M. P. Maley, H. F. Safar, and J. L. Smith

Appl. Phys. Lett. 67, 2397 (1995); http://dx.doi.org/10.1063/1.114559 (3 pages) | Cited 169 times

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We report superconducting and mechanical properties of YBa2Cu3O7−δ (YBCO) thick films on Ni‐based alloys with a textured yttria‐stabilized zirconia (YSZ) buffer layer. The YBCO and YSZ layers were deposited by pulsed laser deposition and ion beam assisted deposition, respectively. It was found that the transport critical current density (Jc) correlates very well with the YBCO mosaic spread. Jc over 1×10 6 A/cm2 at 75 K and ∼1×107 A/cm2 at 4 K were obtained in the 1‐μm thick YBCO films. Zero field critical current of 120 amps at 75 K was obtained in a 2‐μm‐thick and 1‐cm‐wide YBCO film. Angular dependence measurement revealed Jc peaks for both H∥c and H∥a‐b. The peak for H∥c implies additional pinning due to defects such as small angle grain boundaries or twin boundaries. Bending tests at 75 K showed that the YBCO thick films on the metallic substrates could sustain a strain of 0.4% and over 1% for tension and compression, respectively. © 1995 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Fg Pulsed laser ablation deposition

Damping of the oscillations of a permanent magnet levitating between high‐Tc superconductors

R. Grosser, J. Jäger, J. Betz, and W. Schoepe

Appl. Phys. Lett. 67, 2400 (1995); http://dx.doi.org/10.1063/1.114560 (3 pages) | Cited 7 times

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A permanent magnet (spherical shape, radius 100 μm) is levitating inside a superconducting parallel plate capacitor made of YBCO. Translational oscillations of the magnet at its resonance frequency (∼150 Hz) can be excited and detected. The damping of the oscillations is investigated as a function of temperature and oscillation amplitude. Close to Tc we observe a steep minimum of the damping. The data can be described by a linear frictional force which decreases near Tc, and a quadratic one which diverges at Tc. These frictional forces are attributed to flux flow phenomena in the high‐Tc superconductor. © 1995 American Institute of Physics.
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74.72.-h Cuprate superconductors
84.71.Ba Superconducting magnets; magnetic levitation devices

Phase intergrowth in Bi2Sr2Ca2Cu3Ox superconducting thin films prepared by single cylindrical‐sputtering gun

M. Ohkubo, J. Geerk, G. Linker, and O. Meyer

Appl. Phys. Lett. 67, 2403 (1995); http://dx.doi.org/10.1063/1.114561 (3 pages) | Cited 6 times

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Bi2Sr2Can−1CunOx thin films have been prepared in situ on MgO(100) by dc‐sputtering employing a single cylindrical target. The thin films are of almost pure Bi2Sr2Ca2Cu3Ox (2223) or intergrowth phases known as random stacking‐fault structures of two phases having adjacent n. Deviations from the sputtering conditions for the 2223 growth induce the phase intergrowth of 2212, 2223, and 2234. The phase intergrowth occurs in connection with film compositions. © 1995 American Institute of Physics.
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68.55.Nq Composition and phase identification
74.78.-w Superconducting films and low-dimensional structures
81.15.Cd Deposition by sputtering

High critical‐current density of Nd(Ba,Nd)2Cu3O7−δ single crystals

T. Egi, J. G. Wen, K. Kuroda, H. Unoki, and N. Koshizuka

Appl. Phys. Lett. 67, 2406 (1995); http://dx.doi.org/10.1063/1.114562 (3 pages) | Cited 87 times

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We have studied the superconducting properties of Nd(Ba1−xNdx)2Cu3O7−δ (Nd123, x≊0.1) single crystals grown by the traveling‐solvent floating‐zone method under 0.1% O2 in Ar atmosphere. An anomalous peak effect in the magnetization hysteresis (M–B) loop is observed in the Nd123 single crystals as well as in the Nd123 bulk crystals prepared by the oxygen‐controlled melt growth (OCMG) method. The critical current density (Jc) of the Nd123 single crystals is 70 600 A/cm2 in 1.0 T at 77 K for the applied field perpendicular to the a‐b plane. Uniform flux density distribution with the same shape as the sample is observed in the field perpendicular to the a‐b plane by the magneto‐optical flux‐density observation. Finely dispersed white regions in the dark‐field image due to Nd substitutions for Ba are observed in the Nd123 matrix by the transmission electron microscopy. The high Jc value of the Nd123 single crystals in the applied field is explained by the field‐induced pinning centers caused by the Nd–Ba substitutions in the Nd123 matrix. © 1995 American Institute of Physics.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)

Helical peniotron backward wave oscillators

A. T. Lin and Chih‐Chien Lin

Appl. Phys. Lett. 67, 2409 (1995); http://dx.doi.org/10.1063/1.114563 (3 pages) | Cited 1 time

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The performance of peniotron backward wave oscillators which utilize the axis‐encircling beam generated by a combined solenoidal and wiggler magnetic field was investigated through computer simulations. The potential advantages of this new configuration are that it is capable of converting both beam longitudinal and transverse energy into radiation and reducing the severity of mode competition. © 1995 American Institute of Physics.
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41.60.Cr Free-electron lasers
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