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17 Apr 1989

Volume 54, Issue 16, pp. 1489-1598

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Hole transport through minibands of a symmetrically strained GexSi1−x/Si superlattice

J. S. Park, R. P. G. Karunasiri, K. L. Wang, S. S. Rhee, and C. H. Chern

Appl. Phys. Lett. 54, 1564 (1989); http://dx.doi.org/10.1063/1.101314 (3 pages) | Cited 20 times

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The hole transport through the minibands of a GexSi1−x/Si superlattice is observed for the first time. The symmetrically strained, short‐period GexSi1−x/Si supperlattice is grown on a Gex/2Si1−x/2 /Si buffer layer. The current‐voltage and conductance‐voltage characteristics show two peaks which are attributed to the conduction of light holes through the first and second light hole minibands. The light hole miniband energies are estimated by thermionic emission analysis and are in good agreement with the calculated values using effective mass approximation.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Direct pattern replication in plasma deposited silicon nitride films by 193 nm ArF excimer laser‐induced suppression of etching

V. M. Donnelly and J. A. Mucha

Appl. Phys. Lett. 54, 1567 (1989); http://dx.doi.org/10.1063/1.101315 (3 pages) | Cited 2 times

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Exposure of plasma deposited silicon nitride to 193 nm ArF excimer laser radiation suppresses the etch rate in buffered HF solution by as much as a factor of 50. Using a contact mask, 0.23 μm lines and spaces were transferred into silicon nitride by this exposure and etching technique. The mechanism involves transient thermal annealing induced by the 15 ns laser pulses, which reduces the concentration of NH and SiH groups.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Phosphorus ion implantation induced intermixing of InGaAs‐InP quantum well structures

B. Tell, J. Shah, P. M. Thomas, K. F. Brown‐Goebeler, A. DiGiovanni, B. I. Miller, and U. Koren

Appl. Phys. Lett. 54, 1570 (1989); http://dx.doi.org/10.1063/1.101316 (3 pages) | Cited 31 times

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We have studied P ion implantation induced intermixing of In0.53Ga0.47As quantum wells embedded between InP barriers. Data are presented for both standard furnace anneals at 650 °C and rapid thermal anneals at 750 °C. Low‐temperature photoluminescence and quantitative Auger electron spectroscopy were performed for furnace‐annealed samples for which photoluminescence shifts of ∼200 meV were in excellent agreement with the calculated band gap for the lattice matched composition determined by Auger spectroscopy. Photoluminescence studies of rapid thermal annealed samples yield an energy gap shift of ∼150 meV for annealing times of at least 10 s.
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68.35.Fx Diffusion; interface formation
68.35.Dv Composition, segregation; defects and impurities
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
66.30.J- Diffusion of impurities

Oriented thin films of YBaCu(F)O with high Tc and Jc prepared by electron beam multilayer evaporation

X. K. Wang, K. C. Sheng, S. J. Lee, Y. H. Shen, S. N. Song, D. X. Li, R. P. H. Chang, and J. B. Ketterson

Appl. Phys. Lett. 54, 1573 (1989); http://dx.doi.org/10.1063/1.101317 (3 pages) | Cited 17 times

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Thin films of YBaCu(F)O were deposited on SrTiO3(100) substrates by multilayer deposition from three electron guns containing Y, BaF2, and Cu under a pressure of 5×10−5 Torr of O2. The films were later annealed in a separate chamber under a flowing O2‐H2O atmosphere. X‐ray diffraction studies reveal that the resulting structure is highly oriented with the a axis perpendicular to the substrate. Scanning electron micrographs show a morphology consisting of an array of orthogonal, interconnecting bars with well‐developed junctions. High‐resolution electron microscopy and electron diffraction patterns show that these junctions are atomically abrupt and that the associated c axes are mutually perpendicular. These epitaxial films show a sharp resistive transition with Tc(R=0) as high as 90 K. The zero field critical current density, determined from magnetization measurements, is 2.9×106 A/cm2 at 4.2 K and 5.0×104 A/cm2 at 77 K.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
68.55.-a Thin film structure and morphology
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Isolation of the 110 K superconducting phase of Bi‐Pb‐Sr‐Ca‐Cu‐O compounds

R. Escudero, E. Chavira, and D. Rios‐Jara

Appl. Phys. Lett. 54, 1576 (1989); http://dx.doi.org/10.1063/1.101318 (3 pages) | Cited 16 times

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We have prepared 90% single‐phase bulk samples of the 110 K superconducting phase of the Bi‐Sr‐Ca‐Cu‐O compounds with different Pb amounts. Critical superconducting temperatures (zero resistance) of up to 109 K were measured in the bulk samples. X‐ray powder diffraction patterns of the almost isolated 110 K phase are presented. Computer‐simulated diffractograms were obtained, which are in general agreement with the measured ones. A discussion of the role of Pb in the stability of the 110 K phase in this compound is presented.
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74.10.+v Occurrence, potential candidates
74.70.-b Superconducting materials other than cuprates
61.66.Fn Inorganic compounds
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Superlattice modulation and epitaxy of Tl2Ba2Ca2Cu3O10 thin films grown on MgO and SrTiO3 substrates

C. H. Chen, M. Hong, D. J. Werder, J. Kwo, S. H. Liou, and D. D. Bacon

Appl. Phys. Lett. 54, 1579 (1989); http://dx.doi.org/10.1063/1.101387 (3 pages) | Cited 7 times

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We compare the superlattice modulation, microstructure, and epitaxy of Tl2Ba2Ca2Cu3O10 thin films grown on MgO [100] and SrTiO3 [100] substrates by dc diode sputtering. Films grown on MgO were found to be quite clean with the c axis perpendicular to the substrate. However, no in‐plane orientational relationship to the substrate was found. Films grown on SrTiO3, on the other hand, showed very good epitaxy to the substrate despite the presence of second phases. Films grown on MgO also exhibited a longer coherence length of the superlattice modulation than those grown on SrTiO3 under identical conditions.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Kk Vapor phase epitaxy; growth from vapor phase
74.78.-w Superconducting films and low-dimensional structures
68.55.-a Thin film structure and morphology

Improvement of the critical current density in the silver sheathed Bi‐Pb‐Sr‐Ca‐Cu‐O superconducting tape

M. Mimura, H. Kumakura, K. Togano, and H. Maeda

Appl. Phys. Lett. 54, 1582 (1989); http://dx.doi.org/10.1063/1.101319 (3 pages) | Cited 16 times

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The critical current density (Jc) at 77 K and in 0 T of more than 3000 A/cm2 has been obtained in the silver sheathed Bi‐Pb‐Sr‐Ca‐Cu‐O tape fabricated by the combination process of sintering and intermediate cold working. The decrease of the Jc with increasing magnetic field is much smaller in the tape prepared by this process than that prepared by sintering only. The improvement of the Jc is attributed to the improvement of the coupling between the grains of the high Tc phase. The process enhances the formation of the high Tc phase and produces a highly oriented grain structure. These are considered to be responsible for the large improvement of the coupling.
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74.25.Sv Critical currents
61.72.Mm Grain and twin boundaries
74.70.-b Superconducting materials other than cuprates
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Synthesis of high‐density Ba1−xKxBiO3 superconducting samples

D. G. Hinks, A. W. Mitchell, Y. Zheng, D. R. Richards, and B. Dabrowski

Appl. Phys. Lett. 54, 1585 (1989); http://dx.doi.org/10.1063/1.101388 (3 pages) | Cited 28 times

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A synthesis procedure for producing high‐density Ba1−xKxBiO3 has been developed. A novel melt‐processing technique is described which yields strong, near 100% dense superconducting material. This material is much more amenable to experimental study than the powder samples produced by the previous synthesis methods.
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74.70.-b Superconducting materials other than cuprates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.40.Gh Other heat and thermomechanical treatments
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Effect of atmosphere on the formation of low Tc and high Tc phases in Bi‐Pb‐Sr‐Ca‐Cu‐O superconductors

Nong M. Hwang, Gun W. Bahng, Han G. Moon, and Jong C. Park

Appl. Phys. Lett. 54, 1588 (1989); http://dx.doi.org/10.1063/1.101320 (3 pages) | Cited 7 times

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Two kinds of sintering atmosphere, N2 and air, were used to study the effect of atmosphere on the formation of the low Tc phase and the high Tc phase. The annealing temperatures were 810 °C in N2 and 850 °C in air. The resistivity measurements and the x‐ray diffraction analysis showed that while the fraction of the high Tc phase continued to increase with sintering times in air, it did not increase in any appreciable amount even after 264 h of sintering in N2 atmosphere. Compared with air, N2 atmosphere enhanced the formation of the low Tc phase and inhibited the formation of the high Tc phase.
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74.70.-b Superconducting materials other than cuprates
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
64.70.K- Solid-solid transitions

Enhancing Tc in Bi2.1CaSr2Cu2O8+δ from 90 to 101 K by yttrium substitution

J. L. Tallon, R. G. Buckley, M. P. Staines, M. R. Presland, and P. W. Gilberd

Appl. Phys. Lett. 54, 1591 (1989); http://dx.doi.org/10.1063/1.101389 (3 pages) | Cited 6 times

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The Y and rare‐earth substitution for Ca in Bi2.1CaSr2Cu2O8+δ is described with particular emphasis on Y substitution. We have prepared single phase, fully substituted material which exhibits an 8.0×b‐axis incommensurate structure, rather larger than the 4.75× structure in the parent superconductor. The infrared absorption spectra of the insulating fully substituted material are shown to have features very similar to that for YBa2Cu3O7−δ. A solubility range is observed only at substitutions up to 5% at which point zero‐resistance Tc is raised from 90 to 101 K. This is shown to arise from 2 copper‐layer material and not from 3 copper‐layer material. Combined Y and Pb substitution yields n=2 material for which Tc remains fixed at 90 K, insensitive to annealing temperature and oxygen loading.
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74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.70.-b Superconducting materials other than cuprates
78.30.Hv Other nonmetallic inorganics

Observation of fast nonbolometric optical response of nongranular high Tc Y1Ba2Cu3O7−x superconducting thin films

A. Frenkel, M. A. Saifi, T. Venkatesan, Chinlon Lin, X. D. Wu, and A. Inam

Appl. Phys. Lett. 54, 1594 (1989); http://dx.doi.org/10.1063/1.101390 (3 pages) | Cited 41 times

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We report fast optical response measurements in predominantly c‐axis oriented crystalline Y1Ba2Cu3O7−x superconducting thin films at the wavelength of 1.06 μm. We identify two distinct components contributing to the optical response: a nonbolometric (as fast as 1 ns) and a bolometric component (several ns). The bolometric component is stronger at temperatures in the vicinity of the transition region to the normal state. The nonbolometric component is dominant at temperatures below the transition region showing weak temperature dependence and a linear dependence on the bias current. This nonbolometric component may be evidence for nonequilibrium effects (e.g., breaking of Cooper pairs and generation of quasiparticles or other mechanisms). These results suggest that with proper optimization of device parameters (its geometry, critical current density, etc.) high‐speed detectors with reasonable sensitivity covering a broad electromagnetic spectrum (visible and infrared) may be developed.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
74.25.N- Response to electromagnetic fields
85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices

New method of hot rolling for fabricating anisotropic Pr‐Fe‐B‐based magnets

T. Mukai and H. Sakamoto

Appl. Phys. Lett. 54, 1597 (1989); http://dx.doi.org/10.1063/1.101391 (2 pages) | Cited 5 times

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A unique method of hot rolling is described which fabricates high performance plate‐shaped magnets from a cast Pr17Fe76.5B5Cu1.5 alloy. A flat ingot of the alloy with fine‐scale columnar grains of a Pr2Fe14B phase is prepared by chill casting. The ingot is hot rolled in such a way that the roll pressure is applied perpendicular to the preferential growth direction of the columnar grains. A maximum energy product of 25.3 MG Oe has been obtained by this method.
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07.55.Db Generation of magnetic fields; magnets
85.70.-w Magnetic devices
81.05.Bx Metals, semimetals, and alloys
75.50.Bb Fe and its alloys
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
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