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24 Aug 1998

Volume 73, Issue 8, pp. 1017-1159

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The large magnetoresistance property of La0.5Sr0.5CoO3−x thin films prepared by pulsed laser deposition

J.-M. Liu and C. K. Ong

Appl. Phys. Lett. 73, 1047 (1998); http://dx.doi.org/10.1063/1.122080 (3 pages) | Cited 31 times

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High-quality (001) thin film La0.5Sr0.5CoO3−x (LSCO) has been prepared on (001) SrTiO3 substrates by pulsed laser deposition under different oxygen pressures with and without postannealing. C-axis expansion of the LSCO with reducing oxygen pressure was revealed. The electrical resistivity increased over five orders of magnitude when oxygen pressure varied from 1.0 mbar (plus postannealing) to 10−3 mbar. The negative magnetoresistance (n-MR) property as a function of temperature and oxygen pressure was investigated. Linear dependence of the n-MR ratio on magnetic field and temperature was found and significant effect of oxygen stoichiometry on the n-MR was demonstrated. The film prepared at 650 °C and 0.1 mbar oxygen shows a n-MR ratio of −16% at 81 K under a field of only 0.2 T. © 1998 American Institute of Physics.
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73.61.At Metal and metallic alloys
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Fq High-field and nonlinear effects
61.66.Bi Elemental solids
61.66.Dk Alloys
61.72.Cc Kinetics of defect formation and annealing

Chemical vapor deposition of diamond growth using a chemical precursor

Eric Leroy, Olivier M. Küttel, Louis Schlapbach, Luc Giraud, and Titus Jenny

Appl. Phys. Lett. 73, 1050 (1998); http://dx.doi.org/10.1063/1.122081 (3 pages) | Cited 5 times

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A nucleation method to form diamond on chemically pretreated silicon (111) surfaces is reported. The nucleation consisted of binding covalently 2,2-divinyladamantane molecules on the silicon substrate. Subsequently, low pressure diamond growth was performed via microwave plasma chemical vapor deposition in a tubular deposition system. The resulting diamond layers presented a good crystallinity and the Raman spectra showed a very sharp peak at 1331 cm−1. © 1998 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.05.ub Fullerenes and related materials
81.05.Cy Elemental semiconductors
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators

Si adatom surface migration biasing by elastic strain gradients during capping of Ge or Si1−xGex hut islands

L. Kubler, D. Dentel, J. L. Bischoff, C. Ghica, C. Ulhaq-Bouillet, and J. Werckmann

Appl. Phys. Lett. 73, 1053 (1998); http://dx.doi.org/10.1063/1.122082 (3 pages) | Cited 17 times

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Hut cluster formation during Ge or Si1−xGex solid source molecular beam epitaxial growth on Si(001) is a well-known kinetic pathway for partial strain relief. It results in undulated morphologies with {105} facets allowing a∥ lattice parameter relaxation on the island apexes. Here, we show how subsequent Si coverages, grown at 500 °C, avoid being tensile strained and impede further increase of stored elastic strain energy. Dominant inhomogeneous Si surface diffusions take place as proven by a Ge marker technique able to provide transmission electron microscopy or high-resolution transmission electron microscopy images of the initial Si morphology stages and by reflection high-energy electron diffraction examinations. This mechanism prevails for high enough Si growth rates, able to quench lateral Ge diffusion and limit chemical strain relief. Mediated by stress variations on the noncapped island curvatures, Si is depleted from the top of the islands and accumulates in the troughs of the ripples where it accommodates mostly unstrained. By this selective Si coverage, the surface undergoes a rapid smoothing and a∥ recovery toward the Si bulk value. When the Ge containing islands are completely buried, their strain, dictated by the Si buffer and cap layers, ends by being mainly along the growth direction or tetragonal (Δa∥ = 0). © 1998 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.05.Hd Other semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.35.Fx Diffusion; interface formation

Cooling by adiabatic pressure application in Pr1−xLaxNiO3

K. Alex Müller, François Fauth, Stephan Fischer, Max Koch, Albert Furrer, and Philippe Lacorre

Appl. Phys. Lett. 73, 1056 (1998); http://dx.doi.org/10.1063/1.122083 (3 pages) | Cited 22 times

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A novel principle for cooling by adiabatic pressure application in the mixed crystalline compound Pr1−xLaxNiO3 is described and experimentally verified. Cooling occurs in the vicinity of the structural phase transition where the electronic ground state of the Pr3+ ions changes from a singlet to a doublet state. By properly choosing the La concentration x, the cooling effect can be achieved down to some 100 mK. Furthermore, Pr1−xLaxNiO3 can be used for second and third stage cooling down to the μK region by classical paramagnetic and nuclear demagnetization techniques, respectively. © 1998 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
64.70.K- Solid-solid transitions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Preparation of atomically flat Co(110) films on Cu(110)

Christian Tölkes, Rainer Struck, Rudolf David, Peter Zeppenfeld, and George Comsa

Appl. Phys. Lett. 73, 1059 (1998); http://dx.doi.org/10.1063/1.122084 (3 pages) | Cited 17 times

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It is shown that the growth mode of cobalt on the Cu(110) surface at 350 K can be changed from three-dimensional to extended layer-by-layer growth by pre- and co-adsorption of oxygen. The shape and the intensity of the growth oscillations observed in thermal energy helium atom scattering experiments depends sensitively on the total oxygen coverage. Helium diffraction reveals that different oxygen induced surface reconstructions of the top-most Co layer are responsible for the presence or absence of layer-by-layer growth in an extended coverage range. © 1998 American Institute of Physics.
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81.05.Bx Metals, semimetals, and alloys
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Rh Phase transitions and critical phenomena

Reflective homeotropic mode in a twisted nematic liquid crystal

Seong-Woo Suh, J. S. Patel, and Sin-Doo Lee

Appl. Phys. Lett. 73, 1062 (1998); http://dx.doi.org/10.1063/1.122085 (3 pages) | Cited 1 time

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This letter reports on a novel liquid crystal (LC) display device capable of achromatic reflection in a twisted homeotropic configuration using a chiral nematic LC with negative dielectric anisotropy. Using the elastic continuum formalism, we arrived at simulated values for each parameter of interest, including external twist, cell gap, molecular chirality for the chiral pitch, and the surface anchoring energy. The experimental results correspond well with the calculated expectations, exhibiting EO properties that demonstrate excellent achromatic reflection, extinction, and a high contrast ratio. © 1998 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
85.60.Pg Display systems
78.20.Jq Electro-optical effects
61.30.-v Liquid crystals

Infrared analysis of deuterated carbon–nitrogen films obtained by dual-ion-beam-assisted-deposition

F. Alvarez, N. M. Victoria, P. Hammer, F. L. Freire, and M. C. dos Santos

Appl. Phys. Lett. 73, 1065 (1998); http://dx.doi.org/10.1063/1.122115 (3 pages) | Cited 42 times

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The isotopic effect on the infrared spectra is used to determine the existence of nitrogen–hydrogen bonds in amorphous carbon–nitrogen alloys (a-CNx) prepared by dual-ion-beam-assisted deposition. The deuteration experiments and the evolution of the infrared spectra upon atmospheric exposure show that hydroxyls are incorporated from atmospheric moisture. © 1998 American Institute of Physics.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
61.43.Er Other amorphous solids
68.55.-a Thin film structure and morphology
78.66.-w Optical properties of specific thin films

Characterization of dislocations in germanium substrates induced by mechanical stress

S. Gan, L. Li, and R. F. Hicks

Appl. Phys. Lett. 73, 1068 (1998); http://dx.doi.org/10.1063/1.122086 (3 pages) | Cited 4 times

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Dislocations are observed in germanium crystals (9° off axis toward the [011] direction) that have undergone plastic deformation. Optical microscopy reveals that the substrates exhibit a crosshatch pattern, consisting of ridges and trenches that extend in the [011] and [011] directions. Further characterization of these features with scanning tunneling microscopy shows that they consist of bands of steps. These bands are created when a group of dislocations emerge onto the crystal surface from the bulk. The dislocations are determined to be type (a/2)〈011〉. © 1998 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
62.20.F- Deformation and plasticity
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Coulomb blockade in Sb nanocrystals formed in thin, thermally grown SiO2 layers by low-energy ion implantation

Anri Nakajima, Hiroshi Nakao, Hiroaki Ueno, Toshiro Futatsugi, and Naoki Yokoyama

Appl. Phys. Lett. 73, 1071 (1998); http://dx.doi.org/10.1063/1.122087 (3 pages) | Cited 19 times

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Sb nanocrystals were formed in thin, thermally grown SiO2 layers using low-energy ion implantation followed by thermal annealing. These Sb nanocrystals have good size and position uniformity. Both the narrow as-implanted profile and the compressive strain that exists near the SiO2/Si interface supposedly contribute to the uniformity. The I–V characteristics of the diode structure show a Coulomb blockade region around 0 V and a Coulomb staircase at 4.2 K. The Coulomb blockade region was observed up to a temperature of 100 K. The technique offers the possibility of developing practical Si-based single-electron devices. © 1998 American Institute of Physics.
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73.23.Hk Coulomb blockade; single-electron tunneling
85.35.Ds Quantum interference devices
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.up Other materials
61.72.Cc Kinetics of defect formation and annealing
81.07.-b Nanoscale materials and structures: fabrication and characterization

Anisotropic misfit dislocation nucleation in two-dimensional grown InAs/GaAs(001) heterostructures

Achim Trampert, Klaus H. Ploog, and Eric Tournié

Appl. Phys. Lett. 73, 1074 (1998); http://dx.doi.org/10.1063/1.122088 (3 pages) | Cited 7 times

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We report on structural investigations of the plastic strain relief in the highly mismatched InAs/GaAs(001) system grown in the layer-by-layer growth mode. The misfit dislocation generation mechanism is observed to be anisotropic in the two perpendicular 〈110〉 directions. We explain this result by the interplay between the chemically inequivalent dislocation types present in compound semiconductors and the applied growth condition. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep

Stress-related interdiffusion in dc sputtered TiN/B–C–N multilayers

S. Fayeulle and M. Nastasi

Appl. Phys. Lett. 73, 1077 (1998); http://dx.doi.org/10.1063/1.122089 (3 pages) | Cited 1 time

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The diffusion in TiN/B–C–N multilayers during vacuum annealing at temperatures up to 1000 °C and/or 300 keV argon irradiation is studied. Changes in composition, stress field, bilayer repeat length, and interface quality are reported. The effect of stress on diffusion is proved by performing the same annealing or the same irradiation on a multilayer with and without compressive stress. During thermal annealing, demixing or phase separation is observed. On the contrary, during irradiation, mixing occurs. Both phenomena are enhanced in the presence of the stress field. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
64.75.-g Phase equilibria
61.80.Jh Ion radiation effects
61.82.Ms Insulators
61.72.Cc Kinetics of defect formation and annealing
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.30.Mh Solid-phase precipitation
68.35.Ct Interface structure and roughness

Properties of Ba(Mg1/3Ta2/3)O3 thin films prepared by metalorganic solution deposition technique for microwave applications

P. C. Joshi and S. B. Desu

Appl. Phys. Lett. 73, 1080 (1998); http://dx.doi.org/10.1063/1.122090 (3 pages) | Cited 13 times

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We report on the properties of Ba(Mg1/3Ta2/3)O3 thin films prepared by the metalorganic solution deposition technique. Bulk Ba(Mg1/3Ta2/3)O3 ceramics have shown excellent dielectric properties at microwave frequencies; however, the high sintering temperature of bulk material is the major obstacle in their use as dielectric resonators to miniaturize microwave circuits. It was possible to obtain an ordered-perovskite phase of 0.3-μm-thick Ba(Mg1/3Ta2/3)O3 films with trigonal symmetry at an annealing temperature of 700 °C, which is much lower than the bulk sintering temperatures. The electrical measurements were conducted on Pt/Ba(Mg1/3Ta2/3)O3/Pt capacitors. The typical measured small signal dielectric constant and dissipation factor at 100 kHz were 22.2 and 0.009, respectively. The dielectric constant of thin films was comparable to the typical values (ϵr ∼ 23.5–25) reported for bulk ceramics. The temperature coefficient of capacitance was −145 ppm/°C in the measured temperature range of 25–125 °C. The leakage current density was lower than 10−7 A/cm2 at an applied electric field of 0.5 MV/cm. The high dielectric constant, which is comparable to bulk, low dielectric loss, and good temperature and bias stability suggest the suitability of Ba(Mg1/3Ta2/3)O3 thin films for microwave communications and integrated capacitor applications. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.40.Lj Microwave integrated electronics
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.-a Thin film structure and morphology
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
84.32.Tt Capacitors

Temperature dependence of electromigration dynamics in Al interconnects by real-time microscopy

J. A. Prybyla, S. P. Riege, S. P. Grabowski, and A. W. Hunt

Appl. Phys. Lett. 73, 1083 (1998); http://dx.doi.org/10.1063/1.122091 (3 pages) | Cited 12 times

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Real-time transmission electron microscopy (TEM) was used to directly examine the temperature dependence of electromigration-induced void and failure dynamics over the range 200–350 °C. The studies were done using submicron Al interconnects and a special sample stage, which allowed TEM observations to be recorded while heating and passing current through the sample. A novel sample design dramatically minimized any Joule heating in the runners. Our experiments directly reveal that the mechanism responsible for void and failure dynamics at temperatures <250 °C is distinctly different from that at higher temperatures. These results have implications regarding methods used for predicting electromigration reliability at use conditions from accelerated test data. © 1998 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration
66.30.Lw Diffusion of other defects
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
61.72.Qq Microscopic defects (voids, inclusions, etc.)
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