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9 Dec 1991

Volume 59, Issue 24, pp. 3075-3191

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Compensation effects in nitrogen‐doped diamond thin films

J. Mort, M. A. Machonkin, and K. Okumura

Appl. Phys. Lett. 59, 3148 (1991); http://dx.doi.org/10.1063/1.105767 (3 pages) | Cited 56 times

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Diamond thin films have been doped with nitrogen during growth by the hot‐filament technique. For nitrogen concentrations in the films, determined by quantitative secondary ion‐mass spectroscopy (SIMS) exceeding about 3×1018 atoms/cc, a decrease of several orders of magnitude is observed in the electrical conductivity for temperatures at or above room temperature. Qualitatively, this decrease is as expected, assuming compensation of existing acceptor states in nominally undoped diamond thin films by substitutional nitrogen which is known to introduce a deep‐lying donor level.
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71.20.-b Electron density of states and band structure of crystalline solids
71.55.Ht Other nonmetals
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors

New method for determination of the peak‐velocity in epitaxial semiconductor structures by dc measurements on microbridges

Wlodzimierz Strupinski, Herbert Zirath, Hans Grönqvist, and Niklas Rorsman

Appl. Phys. Lett. 59, 3151 (1991); http://dx.doi.org/10.1063/1.105768 (3 pages)

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A simple current‐voltage measurement technique using microbridge patterns is described as a fast method for the determination of the effective peak electron velocity in III‐V semiconducting materials. The method is tested for GaAs samples. Microbridge patterns with different geometries were investigated and the influence of ‘‘self‐heating’’ by power dissipation was examined. Some other potential sources of errors deteriorating the accuracy of measurements were determined.
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72.20.Ht High-field and nonlinear effects
72.80.Ey III-V and II-VI semiconductors
73.61.Ey III-V semiconductors

Current imaging of cleaved silicon pn junctions with an ultrahigh vacuum scanning tunneling microscope

S. Kordić, E. J. van Loenen, and A. J. Walker

Appl. Phys. Lett. 59, 3154 (1991); http://dx.doi.org/10.1063/1.105769 (3 pages) | Cited 9 times

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Current imaging of cleaved two‐dimensional silicon pn junctions with an ultrahigh vacuum scanning tunneling microscope is presented. In order to be able to distinguish between p‐type material, n‐type material, and the depletion region a voltage ramp is applied to the p side of the junction, while the voltage on the n side is constant. At the same time standard topography and stabilization current plots give no indication of the presence of the pn junctions. The IV characteristics measured over different parts of the junctions are explained. The influence of the shape of the cleaved surface on the measurements is discussed.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.-z Semiconductor devices

Nanometer scale pattern replication using electron beam direct patterned SiO2 as the etching mask

X. Pan, D. R. Allee, A. N. Broers, Y. S. Tang, and C. W. Wilkinson

Appl. Phys. Lett. 59, 3157 (1991); http://dx.doi.org/10.1063/1.105770 (2 pages) | Cited 9 times

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Because of its unique properties and well‐established processing techniques, SiO2 has wide application in the integrated circuit industry. The ability to directly pattern SiO2 with nanometer resolution by electron beam irradiation is therefore of great importance in the fabrication of both ultrasmall conventional and quantum devices. In this letter we demonstrate the replication of trenches with feature sizes as small as 10 nm into polycrystalline silicon and single‐crystal and via reactive ion etching by using electron beam direct patterned SiO2 as the mask.
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85.40.Hp Lithography, masks and pattern transfer

Van der Waals bonding of GaAs on Pd leads to a permanent, solid‐phase‐topotaxial, metallurgical bond

E. Yablonovitch, T. Sands, D. M. Hwang, I. Schnitzer, T. J. Gmitter, S. K. Shastry, D. S. Hill, and J. C. C. Fan

Appl. Phys. Lett. 59, 3159 (1991); http://dx.doi.org/10.1063/1.105771 (3 pages) | Cited 32 times

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Various forms of wafer bonding have now emerged as a serious competitor to heteroepitaxy for optoelectronic integration of dissimilar semiconductor materials. Among the types of wafer bonding, perhaps the most flexible is that which employs free‐standing III–V films as created by epitaxial liftoff. For some purposes, weak Van der Waals forces provide an adequate bond between the native oxides of the III–V film and its new substrate. If the substrate is coated by palladium however, a low temperature solid‐phase‐topotaxial reaction occurs, producing oriented Pd4GaAs under the GaAs film. In effect, the topotaxy comes about through mechanical contact alone. The resulting metallurgical bond is an ohmic contact, a thermal contact and a robust, permanent, adherent contact.
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81.15.Np Solid phase epitaxy; growth from solid phases
68.35.Fx Diffusion; interface formation
68.35.B- Structure of clean surfaces (and surface reconstruction)

Temperature dependence of Si1−xGex epitaxial growth using very low pressure chemical vapor deposition

Syun‐Ming Jang and Rafael Reif

Appl. Phys. Lett. 59, 3162 (1991); http://dx.doi.org/10.1063/1.106399 (3 pages) | Cited 42 times

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We report measured Ge contents and growth rates for Si1−xGex films grown by very low pressure chemical vapor deposition between 570–700 °C. The ratio of Ge/Si was found to increase linearly with increasing the ratio of GeH4 flow rate to SiH4 flow rate. The nonlinear Arrhenius behavior of growth rate as a function of Ge fraction suggests that Ge enhances hydrogen desorption and modifies the activation energy for Si1−xGex growth. The growth rates of Si1−xGex show different dependencies on Ge content at different temperatures. The growth rate decreases with increasing Ge content at 700 °C, but increases monotonically with Ge at 570 °C. A peak in growth rate was observed at intermediate temperatures between 570 and 700 °C.
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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.)

Hydrogen diffusivities below room temperature in silicon evaluated from the photoinduced dissociation of hydrogen–carbon complexes

Yoichi Kamiura, Minoru Yoneta, and Fumio Hashimoto

Appl. Phys. Lett. 59, 3165 (1991); http://dx.doi.org/10.1063/1.105772 (3 pages) | Cited 7 times

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We have evaluated hydrogen and deuterium diffusivities in silicon below room temperature (220–270 K) by analyzing the kinetics of photoinduced dissociation of a chemical etching introduced hydrogen (deuterium)–carbon complex. Under sufficiently strong illumination, the annihilation rate of the complex was proportional to the phosphorus density, indicating that the rate‐determining step is the diffusion of hydrogen (deuterium) to phosphorus atoms. Applying the diffusion‐controlled reaction theory, we have evaluated the diffusion coefficients as 7×10−2exp(−0.54 eV/kT) cm2 s−1 for hydrogen and 5×10−3exp(−0.49 eV/kT) cm2 s−1 for deuterium, being in good agreement with the extrapolation of the high‐temperature diffusion data of A. Van Wieringen and N. Warmoltz [Physica 22, 849 (1956)].
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66.30.J- Diffusion of impurities
61.72.Bb Theories and models of crystal defects
71.55.Ht Other nonmetals
81.65.-b Surface treatments

Visible photoluminescence of Ge microcrystals embedded in SiO2 glassy matrices

Yoshihito Maeda, Nobuo Tsukamoto, Yoshiaki Yazawa, Yoshihiko Kanemitsu, and Yasuaki Masumoto

Appl. Phys. Lett. 59, 3168 (1991); http://dx.doi.org/10.1063/1.105773 (3 pages) | Cited 318 times

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Ge microcrystals embedded in SiO2 glassy matrices were formed by a radio‐frequency magnetron cosputtering technique and then annealed at 800 °C for 30 min. The average radius of the Ge microcrystals in SiO2 was determined to be about 3 nm by means of Raman spectroscopy and high resolution electron microscope. The annealed sample showed a strong room temperature luminescence with a peak at 2.18 eV. This is consistent with quantum confinement of electrons and holes.
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78.55.-m Photoluminescence, properties and materials
42.70.-a Optical materials
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
42.65.-k Nonlinear optics

Critical currents in silver‐sheathed (Bi,Pb)2Sr2Ca2Cu3O10−y superconducting tapes

Donglu Shi, S. Salem‐Sugui, Zuning Wang, L. F. Goodrich, S. X. Dou, H. K. Liu, Y. C. Guo, and C. C. Sorrell

Appl. Phys. Lett. 59, 3171 (1991); http://dx.doi.org/10.1063/1.105774 (3 pages) | Cited 7 times

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Nearly 95 vol % of the 110 K superconducting phase was formed by lead doping in a Bi–Sr–Ca–Cu–O system. The processed 110 K superconducting powders were used to produce long silver‐sheathed tapes with a highly textured microstructure by rolling and prolonged sintering. The transport critical current density was measured at 4.0 K to be 0.7×105 A/cm2 (the corresponding critical current is 74 A) at zero field and 1.6×104 A/cm2 at 12 T for H∥ab. At 76 K, the critical current density reached a value of ∼1×104 A/cm2 at zero field for H∥ab and gradually decreased to 419 A/cm2 at 1 T. Excellent grain alignment in the a–b plane led to greatly improved critical current densities under a magnetic field. The relationship between the transport properties and the microstructure of the tapes is discussed.
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84.71.Ba Superconducting magnets; magnetic levitation devices
74.25.Sv Critical currents
74.70.-b Superconducting materials other than cuprates
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties

Phase relationships in Cu‐O thin films prepared by sputtering

D. J. Miller, R. P. Chiarello, H. K. Kim, T. Roberts, H. You, R. T. Kampwirth, K. E. Gray, J. Q. Zheng, S. Williams, R. P. H. Chang, and J. B. Ketterson

Appl. Phys. Lett. 59, 3174 (1991); http://dx.doi.org/10.1063/1.105775 (3 pages) | Cited 4 times

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The conditions for deposition of Cu and Cu‐oxide thin films by reactive dc sputtering have been investigated by characterizing the crystal structure of growing films both during and immediately following deposition using an in situ x‐ray diffraction technique. The relationship between sputtering conditions and the phases deposited was established for a variety of conditions. At each temperature studied, increasing the oxygen pressure in the system resulted in a systematic change in the phases deposited. Of significant importance was the identification of temperature‐pressure regimes in which CuO was stable during deposition but reverted to Cu2O after the sputtering plasma was extinguished, suggesting a shift in the oxidizing potential in the plasma environment. These results also suggest that the in situ analysis technique may be ideally suited for the investigation of phase relationships and phase diagrams in other systems.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.Nq Composition and phase identification
81.15.Cd Deposition by sputtering

Microstructure and growth mechanism of thin sputtered films of YBa2Cu3O7 on MgO substrates

Ian D. Raistrick, Marilyn Hawley, Jerome G. Beery, Fernando H. Garzon, and Robert J. Houlton

Appl. Phys. Lett. 59, 3177 (1991); http://dx.doi.org/10.1063/1.105776 (3 pages) | Cited 21 times

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The microstructures of very thin sputtered films of YBa2Cu3O7 deposited on (100) faces of single‐crystal MgO, have been investigated using scanning tunneling and atomic force microscopies. By a thickness of 10 nm, the substrate is completely covered by a fine‐grained layer of the superconductor. The average grain size is about 100 nm. Many of these grains show evidence of a spiral growth mechanism. In somewhat thicker films (20 nm), the grain size has increased considerably (to about 200 nm), and this trend continues as the thickness is increased. The small grain size close to the interface suggests a possible origin for widely observed ion‐beam dechanneling in this region of the film.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology

Pressure dependence of Bi‐Sr‐Ca‐Cu‐O phases with laser deposition technique

E. Narumi, J. Lee, C. Li, S. Hosokawa, S. Patel, and D. T. Shaw

Appl. Phys. Lett. 59, 3180 (1991); http://dx.doi.org/10.1063/1.105753 (3 pages) | Cited 12 times

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Superconducting Bi2Sr2Can−1CunOx (n=1,2,3) films, with the c‐axis perpendicular to the films, were fabricated by laser deposition. Oxygen pressure was found to be important to control the phases, and a unique pressure dependence of Bi‐Sr‐Ca‐Cu‐O phases was shown by these films. Tc of 76 K and Jc of 1.5×105 A/cm2 at 40 K were achieved for the in situ Bi2Sr2CaCu2Ox film. The critical‐current densities in the external magnetic field up to 5 T with the fields parallel and perpendicular to the c‐axis of the film were measured.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.Nq Composition and phase identification

Flux creep in the Josephson mixed state of granular‐oriented YBa2Cu3O7−x thin thin films

E. C. Jones, D. K. Christen, C. E. Klabunde, J. R. Thompson, D. P. Norton, R. Feenstra, D. H. Lowndes, and J. D. Budai

Appl. Phys. Lett. 59, 3183 (1991); http://dx.doi.org/10.1063/1.105754 (3 pages) | Cited 9 times

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A self‐consistent critical current model in the Josephson mixed state is proposed for a series of c‐oriented, polycrystalline and for a series of epitaxial triaxially oriented YBCO thin films. The flux pinning activation energies were experimentally determined from electrical transport measurements over a wide range of temperatures and were found to behave quite differently for the two types of granular film. With these activation energies applied to a superconductor‐normal metal‐superconductor weak‐link system, thermally activated flux motion is shown to reproduce the experimentally measured critical current densities.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents
74.50.+r Tunneling phenomena; Josephson effects
74.78.-w Superconducting films and low-dimensional structures

Introduction of pinning centers into Tl‐(1223) phase of Tl–Sr–Ca–Cu–O systems

Kamo Tomoichi, Toshiya Doi, Atsuko Soeta, Toyotaka Yuasa, Naomi Inoue, Katsuzo Aihara, and Matsuda Shin‐Pei

Appl. Phys. Lett. 59, 3186 (1991); http://dx.doi.org/10.1063/1.105731 (3 pages) | Cited 46 times

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Pinning centers were successfully introduced into the (1223) phase of Tl–Sr–Ca–Cu–O system using its derivative (Tl/Pb)–(Sr/Ba)–Ca–Cu–O with the nominal composition of (0.5/0.5)−(1.6/0.4)–2–3. The bulk sample showed a strong flux pinning characteristics. The critical current density, Jc, was obtained from the magnetization measurement. The intragrain Jc was ∼43,000 A/cm2 at 77 K and 1 T. The transport Jc of a tape with the (1223) material in core was ∼500 A/cm2 at 77 K and 5 T.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents
74.70.-b Superconducting materials other than cuprates
84.71.Ba Superconducting magnets; magnetic levitation devices

Fluorescent micropattern formation on polymer surface by laser ablation

Tatsuya Uchida, Hiroyuki Sugimura, Klaus Kemnitz, Nobuo Shimo, and Hiroshi Masuhara

Appl. Phys. Lett. 59, 3189 (1991); http://dx.doi.org/10.1063/1.105732 (2 pages) | Cited 4 times

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248‐nm laser ablation of poly(methyl methacrylate) plates and soaking of the ablated plates in aqueous solution of rhodamine B resulted in fluorescent micropattern formation. A positive or negative fluorescent pattern of the dye was obtained by controlling the laser fluence. Incorporation mechanism of the dye into the ablated polymer is discussed.
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81.65.-b Surface treatments
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
79.20.Ds Laser-beam impact phenomena
FREE

Erratum: Electronic surface states confined to the boundary of periodic multiple quantum wells [Appl. Phys. Lett. 57, 1669 (1990)] and Tunneling resonance studies of electronic ministop gap mode in coupled semi‐infinity semiconductor superlattices [Appl. Phys. Lett. 57, 2199 (1990)]

F. Y. Huang

Appl. Phys. Lett. 59, 3191 (1991); http://dx.doi.org/10.1063/1.106425 (1 page)

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Abstract Unavailable
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
99.10.Cd Errata
FREE

Erratum: Excimer laser etching of transparent conducting oxides [Appl. Phys. Lett. 59, 647 (1991)]

J. G. Lunney, R. R. O’Neill, and K. Schulmeister

Appl. Phys. Lett. 59, 3191 (1991); http://dx.doi.org/10.1063/1.106374 (1 page)

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Abstract Unavailable
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81.65.-b Surface treatments
78.70.-g Interactions of particles and radiation with matter
99.10.Cd Errata
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