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21 May 1990

Volume 56, Issue 21, pp. 2059-2153

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InGaAs shallow junction fabrication using Langmuir–Blodgett film diffusion source

D. M. Shah, W. K. Chan, R. Bhat, H. M. Cox, N. E. Schlotter, and C. C. Chang

Appl. Phys. Lett. 56, 2132 (1990); http://dx.doi.org/10.1063/1.102994 (3 pages) | Cited 6 times

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A new source of cadmium diffusion in In0.53Ga0.47As has been developed. Langmuir–Blodgett (LB) deposited monolayers of cadmium arachidate have been used as a source of cadmium. The LB film has been characterized by grazing incidence infrared spectroscopy and Auger electron spectroscopy. Acceptor profiles obtained by differential Hall technique are presented. Highly doped (NA =2×1019 cm−3) shallow (xj ≊0.1–0.4 μm), p+‐n junctions are obtained. Mesa‐type p‐i‐n diodes with 125 μm diameter, ideality factor =1.3, Idark =5 nA at 20 V reverse bias, and Vbreakdown =30 V have been fabricated.
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61.72.U- Doping and impurity implantation
85.30.Kk Junction diodes
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
66.30.J- Diffusion of impurities

Formation of superconducting (Tl,Bi)Sr2CaCu2Oy thin films by rf sputtering and thallium diffusion

R. S. Liu, P. P. Edwards, P. D. Hunneyball, M. J. Bennett, D. Jedamzik, M. R. Harrison, and R. J. Horley

Appl. Phys. Lett. 56, 2135 (1990); http://dx.doi.org/10.1063/1.103236 (3 pages) | Cited 2 times

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We have prepared new high Tc superconducting thin films of (Tl,Bi)‐Sr‐Ca‐Cu‐O by combining low temperature (500 °C) rf sputtering of Bi‐Sr‐Ca‐Cu‐O precursor films and thallium diffusion. A typical film has Tc(onset) =80 K, Tc(midpoint) =79 K, and Tc(zero) =50 K. X‐ray diffraction and energy dispersive spectroscopic studies were carried out to determine the composition and crystal structure of the superconducting phase within the film. We identified a material with the chemical composition of (Tl0.7 Bi0.3 )Sr2CaCu2Oy and tetragonal symmetry (a=3.795 Å and c=12.095 Å), and propose that this phase is responsible for superconductivity around 80 K. The film also has a highly preferred orientation with the c axis perpendicular to the surface of the (100)MgO substrate.
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81.15.Cd Deposition by sputtering
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
74.78.-w Superconducting films and low-dimensional structures

Microstructure of epitaxial YBa2Cu3O7−x thin films

C. W. Nieh, L. Anthony, J. Y. Josefowicz, and F. G. Krajenbrink

Appl. Phys. Lett. 56, 2138 (1990); http://dx.doi.org/10.1063/1.103237 (3 pages) | Cited 39 times

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We have investigated the microstructure of epitaxial YBa2Cu3O7−x thin films on SrTiO3(100), LaGaO3(100), and LaAlO3 (100) with particular emphasis on how the final microstructure is developed. Cross‐sectional transmission electron microscopy as well as plan‐view transmission electron microscopy combined with sputter depth profiling were used to study the change in microstructure with the increase in film thickness. For a thin film or near the substrate/film interface of a thick film, the YBa2Cu3O7−x film is composed primarily of grains oriented with c axis normal to the substrate surface and a small volume fraction of grains with c axis parallel to the substrate surface. As the film grows thicker, the c‐axis parallel grains increase in size and grow over the top of the c‐axis normal grains. The volume fraction of c‐axis parallel grains increases rapidly as the film thickness increases and eventually the entire film surface is covered by c‐axis parallel grains. However, the number density of the c‐axis parallel grains remains constant throughout the whole film thickness. A growth model is proposed to explain the observed microstructure. Based on this model, a computer simulation is carried out. The simulated microstructure agrees well with the experimental result.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
74.70.-b Superconducting materials other than cuprates

Flexible superconducting whiskers of the Li‐doped Bi‐Sr‐Ca‐Cu oxide

Ichiro Matsubara, Hideo Tanigawa, Toru Ogura, Hiroshi Yamashita, Makoto Kinoshita, and Tomoji Kawai

Appl. Phys. Lett. 56, 2141 (1990); http://dx.doi.org/10.1063/1.103238 (3 pages) | Cited 13 times

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Flexible Li‐doped Bi‐Sr‐Ca‐Cu‐O superconducting whiskers have been prepared by heating a glassy melt‐quenched plate in a stream of O2 gas. The whiskers show a resistance drop at 110 K with a zero resistance at 81 K. These values are higher than those of the Pb‐doped Bi‐Sr‐Ca‐Cu‐O whiskers by 5 and 11 K, respectively. The doping of Li is effective to raise Tc for both the 2212 phase and the 2223 phase. The Jc values of the Li‐doped whiskers are 30 000 A/cm2 at 77 K and 300 000 A/cm2 at 66 K in a zero magnetic field.
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68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
68.35.B- Structure of clean surfaces (and surface reconstruction)

Particulates reduction in laser‐ablated YBa2Cu3O7−δ thin films by laser‐induced plume heating

G. Koren, R. J. Baseman, A. Gupta, M. I. Lutwyche, and R. B. Laibowitz

Appl. Phys. Lett. 56, 2144 (1990); http://dx.doi.org/10.1063/1.103239 (3 pages) | Cited 40 times

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Experimental demonstration of reduction in the number and size of particulates formed in the laser ablation deposition of YBa2Cu3O7−δ thin films is obtained by the use of a second laser which further heats and fragments the blowoff material in the plume formed by the first laser. This results in a smoother film with higher critical current density as compared to that obtained without the second laser irradiation of the plume.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
79.20.Ds Laser-beam impact phenomena
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Microwave surface resistance of magnetron‐sputtered Tl‐Ba‐Ca‐Cu‐O films on silver substrates

D. W. Cooke, E. R. Gray, P. N. Arendt, G. A. Reeves, R. J. Houlton, N. E. Elliott, and D. R. Brown

Appl. Phys. Lett. 56, 2147 (1990); http://dx.doi.org/10.1063/1.102954 (3 pages) | Cited 6 times

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Surface resistance measurements on Tl‐Ba‐Ca‐Cu‐O thick films (∼15 μm) magnetron sputtered onto BaF2‐buffered, silver‐based (Consil 995) substrates have been made at a microwave frequency of 22 GHz. The relatively large‐area films (∼5 cm2) are characterized by surface resistance values of 6.9±2 mΩ at 11.3 K and 30.2±1 mΩ at 77 K; the corresponding values for Cu are 10 and 22 mΩ, respectively. These results demonstrate that Tl‐Ba‐Ca‐Cu‐O can be deposited onto large‐area, metallic substrates with characteristic surface resistance values lower than Cu at 4 K. Orientation of the film should improve the surface resistance at 77 K, thereby making the fabrication of microwave cavities that are superior to Cu possible.
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74.70.-b Superconducting materials other than cuprates
74.25.N- Response to electromagnetic fields
74.78.-w Superconducting films and low-dimensional structures

Structural and chemical stability in nonrandom silver‐YBa2Cu3O7 composites in the presence of water

D. Veretnik and S. Reich

Appl. Phys. Lett. 56, 2150 (1990); http://dx.doi.org/10.1063/1.103240 (2 pages) | Cited 16 times

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Accelerated water and moisture degradation of YBa2Cu3O7(YBCO)‐silver nonrandom composites is studied. Oxygen evolution for these composites immersed in water at 65 °C was compared with that for regular YBCO ceramic material prepared under similar sintering conditions. Time evolution of the decay of crystalline structure was followed by x‐ray diffraction for the composite material and for the regular YBCO ceramic. We find that the nonrandom Ag‐YBCO composite exhibits high chemical and structural stability in the presence of water; this advantageous property is probably due to the encapsulation of the YBCO grains with silver in this composite material.
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82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
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

Origin of anomalous energy spreads in photoelectron beams

H.‐J. Drouhin and Ph. Bréchet

Appl. Phys. Lett. 56, 2152 (1990); http://dx.doi.org/10.1063/1.102955 (2 pages) | Cited 7 times

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The use of photocathodes as intense monoenergetic electron sources seems very promising. Yet, many experimenters have observed large energy spreads, increasing with the emitted current, which remained unexplained. Here, we analyze a mechanism which accounts well for these effects.
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41.75.Fr Electron and positron beams
29.25.Bx Electron sources
81.65.-b Surface treatments
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