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23 Sep 1996

Volume 69, Issue 13, pp. 1823-1980

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

Electroluminescence in vertically aligned quantum dot multilayer light‐emitting diodes fabricating by growth‐induced islanding

G. S. Solomon, M. C. Larson, and J. S. Harris

Appl. Phys. Lett. 69, 1897 (1996); http://dx.doi.org/10.1063/1.117614 (3 pages) | Cited 27 times

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A molecular beam epitaxy (MBE) growth‐induced islanding process has been used to form self‐organized multiple quantum dot layers, in which quantum dots from different layers are vertically aligned in columns and are electronically coupled. These structures are used as the active region in light‐emitting diodes operating at room temperature. Light‐emitting diodes are investigated using quantum dot columns containing single, 5 and 10 InAs quantum dots. These diodes emit light over a broad band with typical spectral linewidths of 120 nm, peaked between 1000 and 1100 nm. In addition to the quantum dot spectral feature, a spectral feature from a thin quantum well region, integral to the quantum dot formation process, is seen in the single quantum dot diode, but is eliminated in diodes with active regions containing columns of multiple quantum dots. © 1996 American Institute of Physics.
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78.66.Fd III-V semiconductors
85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence

Epitaxial growth of CuInS2 on sulphur terminated Si(111)

H. Metzner, Th. Hahn, J.‐H. Bremer, and J. Conrad

Appl. Phys. Lett. 69, 1900 (1996); http://dx.doi.org/10.1063/1.117615 (3 pages) | Cited 25 times

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We demonstrate the direct heteroepitaxial growth of the chalcopyrite semiconductor CuInS2 on silicon (111) substrates by means of three‐source molecular beam epitaxy. The pretreatment of the silicon wafers includes sulphur termination which leads to a new surface structure defining the starting condition for successful epitaxy. All stages of the growth process were controlled in situ using Auger electron spectroscopy and low energy electron diffraction. Furthermore, the epitaxial layers were characterized by means of x‐ray diffraction methods and by Rutherford backscattering spectrometry including channeling. X‐ray rocking curves showed a typical width of 0.2° while the minimum yield due to the channeling effect was found to be 56%. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis

Correlation between visible and infrared (1.54 μm) luminescence from Er‐implanted porous silicon

X. Wu, U. Hömmerich, F. Namavar, and A. M. Cremins‐Costa

Appl. Phys. Lett. 69, 1903 (1996); http://dx.doi.org/10.1063/1.117616 (3 pages) | Cited 20 times

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A photoluminescence excitation (PLE) study was performed of Er‐implanted porous Si with two different porosities. Erbium was implanted at a dose of 1×1015 cm−2 at 380 keV and the samples were annealed for 30 min at temperatures from 650 to 850 °C. We observed that PLE spectra from Er3+ at 1.54 μm are nearly identical to those from the visible‐emitting porous Si layers. Our results provide the first direct experimental evidence that infrared photoluminescence at 1.54 μm arises from Er3+ ions in porous Si and that ions are excited through the recombination of excess carriers spatially confined in Si nanograms. © 1996 American Institute of Physics.
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78.55.Mb Porous materials
61.72.uf Ge and Si

First order gain‐coupled GaInAs/GaAs distributed feedback laser diodes patterned by focused ion beam implantation

A. Orth, J. P. Reithmaier, R. Zeh, H. Doleschel, and A. Forchel

Appl. Phys. Lett. 69, 1906 (1996); http://dx.doi.org/10.1063/1.117617 (3 pages) | Cited 7 times

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Electrically pumped gain‐coupled distributed feedback lasers with first order gratings have been fabricated on a (Ga,In)As/(Al,Ga)As separate confinement heterostructure by focused ion beam implantation and epitaxial overgrowth. The lasers are operating at room temperature at wavelengths around 950 nm. All investigated devices show single longitudinal mode emission at all operating conditions. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.82.Cr Fabrication techniques; lithography, pattern transfer
61.72.uj III-V and II-VI semiconductors

Electric field dependent EL2 capture coefficient in semi‐insulating GaAs obtained from propagating high field domains

F. Piazza, P. C. M. Christianen, and J. C. Maan

Appl. Phys. Lett. 69, 1909 (1996); http://dx.doi.org/10.1063/1.117618 (3 pages) | Cited 18 times

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We have determined the electric field dependence of the carrier capture coefficient of the EL2 traps in semi‐insulating GaAs up to 7 kV/cm by means of the quantitative analysis of propagating high electric field domains. The experimental data show a trapping coefficient which is proportional to the electron drift velocity, supporting the microscopic model of electric field enhanced trapping of carriers over a configurational barrier. © 1996 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Ht High-field and nonlinear effects
71.55.Eq III-V semiconductors

Semiconducting Ge–Si–Fe alloy grown on Si(100) substrate by reactive deposition epitaxy

H. Chen, P. Han, X. D. Huang, L. Q. Hu, Y. Shi, and Y. D. Zheng

Appl. Phys. Lett. 69, 1912 (1996); http://dx.doi.org/10.1063/1.117619 (3 pages) | Cited 8 times

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In this letter, we report a semiconducting Ge–Si–Fe alloy thin film grown on Si(100) by reactive deposition epitaxy using high vacuum evaporation technique. This work is based on the idea that the band structure of β‐FeSi2 will be changed with part of the Si atoms in the lattice replaced by Ge atoms. An iron film was first deposited on a SiGe/Si(100) structure, then the alloy was formed during an annealing process. Auger electron spectroscopy and x‐ray diffraction results indicate that the new alloy film can be regarded as a distorted β‐FeSi2 thin film with the participation of Ge. The direct band gap of the Ge–Si–Fe alloy is determined to be 0.83 eV by optical transmission measurements, which indicate a redshift of the band gap with regard to that of β‐FeSi2 (Eg=0.87 eV) thin films. © 1996 American Institute of Physics.
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75.47.De Giant magnetoresistance
68.35.Ct Interface structure and roughness
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Synthesis of SiGe and SiGeC alloys formed by Ge and C implantation

Xiang Lu and Nathan W. Cheung

Appl. Phys. Lett. 69, 1915 (1996); http://dx.doi.org/10.1063/1.117620 (3 pages) | Cited 8 times

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In this study, near surface SiGe and SiGeC alloys with germanium peak composition up to 16 at.% were formed using high‐dose ion implantation and subsequent solid phase epitaxial growth. Rutherford backscattering spectroscopy (RBS) channeling spectra and cross‐sectional transmission electron microscopy (XTEM) studies showed that high quality Si0.92Ge0.08 and Si0.91Ge0.08C0.01 crystals were formed at the Si surface, while Si0.84Ge0.16 and Si0.82Ge0.16C0.02 layers had extended defects. X‐ray diffraction experiments demonstrated that carbon could reduce the lattice strain in SiGe alloys but without significant crystal quality improvement as detected by RBS channeling spectra or XTEM observations. © 1996 American Institute of Physics.
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61.72.uf Ge and Si
81.15.Np Solid phase epitaxy; growth from solid phases
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
85.40.Ry Impurity doping, diffusion and ion implantation technology

Functional InP/InGaAs lateral double barrier heterostructure resonant tunneling diodes by using etch and regrowth

T. P. E. Broekaert, J. N. Randall, E. A. Beam III, D. Jovanovic, A. C. Seabaugh, and B. D. Smith

Appl. Phys. Lett. 69, 1918 (1996); http://dx.doi.org/10.1063/1.117621 (3 pages) | Cited 1 time

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A planar integrated lateral double barrier heterostructure resonant tunneling diode is demonstrated. Resonances in the current–voltage (I–V) characteristics are observed that have peak‐to‐valley current ratios as high as 3.5 at 4.2 K and are attributed to resonant tunneling in a two‐dimensional/one‐dimensional/two‐dimensional system. The device structure consists of a lateral double barrier heterostructure embedded in an InP/InGaAs/InP modulation‐doped field‐effect transistor structure. The lateral heterostructure uses InP barriers and an InGaAs quantum well fabricated by epitaxial etch and regrowth techniques. This device and fabrication process forms the basis for lateral resonant tunneling transistors. © 1996 American Institute of Physics.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.40.Gk Tunneling

Offset of the electrical characteristics of alternating‐current thin‐film electroluminescent devices

S. Shih, P. D. Keir, J. Hitt, and J. F. Wager

Appl. Phys. Lett. 69, 1921 (1996); http://dx.doi.org/10.1063/1.117622 (3 pages) | Cited 2 times

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Offset is observed in the charge–voltage (Q–V) or internal charge–phosphor field (Q–Fp) characteristics of certain alternating‐current thin‐film electroluminescent (ACTFEL) devices. This offset arises from a displacement along the voltage axis of a transient curve measured across a sense capacitor in the electrical characterization setup. A procedure for adjusting this offset is proposed that allows ACTFEL devices manifesting offset to be meaningfully analyzed. Two possible sources of offset are deduced from simulation and are associated with an asymmetry in the interface state energy depths at the two phosphor–insulator interfaces or with an asymmetry in the location of space charge generation in the phosphor. © 1996 American Institute of Physics.
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78.60.Fi Electroluminescence
85.60.Pg Display systems
73.61.Ga II-VI semiconductors

Fabrication and characterization of modulation‐doped‐field‐effect‐transistors with antidot‐patterned passivation layers

S. W. Hwang, Y. S. Yu, W. I. Ha, T. G. Kim, C. K. Han, J. H. Park, M. S. Kim, E. K. Kim, and S. K. Min

Appl. Phys. Lett. 69, 1924 (1996); http://dx.doi.org/10.1063/1.117623 (3 pages)

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A gate passivation technique for modulation‐doped‐field‐effect‐transistors has been proposed and demonstrated. This technique incorporates an antidot‐patterned (net‐shaped), polymer passivation layer deposited between the gate metal and the heterojunction wafer. Characterization results of the device with the patterned passivation layer show that independent engineering of the threshold voltage and the transconductance has been achieved. © 1996 American Institute of Physics.
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85.30.Tv Field effect devices
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Thermal stability of engineered Schottky barriers in Al/Si/GaAs(001) diodes

L. Sorba, S. Yildirim, M. Lazzarino, A. Franciosi, D. Chiola, and F. Beltram

Appl. Phys. Lett. 69, 1927 (1996); http://dx.doi.org/10.1063/1.117624 (3 pages) | Cited 11 times

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Schottky barriers as high (low) as 1.0–1.1 eV (0.2–0.3 eV) obtained in Al/n‐GaAs(001) diodes by fabricating Si bilayers at the interface under an excess cation (anion) flux were subjected to sequential annealing cycles in the 100–450 °C temperature range. X‐ray photoemission and current–voltage studies indicate a higher stability for high‐barrier diodes, which retain 90% of the Si‐induced interface dipole after a 450 °C anneal, as compared to only 32% for the low‐barrier devices. Qualitatively different microscopic degradation mechanisms were identified in the two cases. © 1996 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
68.60.Dv Thermal stability; thermal effects
85.30.Hi Surface barrier, boundary, and point contact devices
79.60.Jv Interfaces; heterostructures; nanostructures

Optical determination of the direct bandgap energy of lead iodide crystals

A. Ferreira da Silva, N. Veissid, C. Y. An, I. Pepe, N. Barros de Oliveira, and A. V. Batista da Silva

Appl. Phys. Lett. 69, 1930 (1996); http://dx.doi.org/10.1063/1.117625 (3 pages) | Cited 21 times

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The optical bandgap energy of lead iodide PbI2, grown by Bridgman’s method, is obtained by photoacoustic spectroscopy. Due to its potential applications, as a room temperature, semiconductor material detector, which may be used as a photocell, or as a x‐ and γ‐ray radiation detector, the physical properties of PbI2 have attracted much attention. We computed, by different methods the bandgap energy. We found the energy in a range 2.301±0.038⩽〈Eg〉⩽2.359±0.037 eV. © 1996 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
81.10.Fq Growth from melts; zone melting and refining
81.05.Hd Other semiconductors

Far‐infrared study of a quasi‐one‐dimensional electron gas formed on (100)GaAs facets with hole gas sidegates on a (311)A GaAs substrate

D. D. Arnone, J. H. Burroughes, M. Pepper, C. Norman, R. J. Evans, T. Burke, D. A. Ritchie, and M. P. Grimshaw

Appl. Phys. Lett. 69, 1933 (1996); http://dx.doi.org/10.1063/1.117626 (3 pages) | Cited 4 times

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A new type of quasi‐one‐dimensional electron gas has been realized by using molecular beam epitaxy to grow a high mobility heterostructure on a (311)A GaAs substrate selectively etched to expose (100) facets. The electron gas formed on the (100) facets is confined in one lateral dimension by the p–n junctions formed with the adjacent two‐dimensional hole gases on (311)A, thereby forming a p–n–p structure. Far‐infrared cyclotron resonance spectra demonstrate the dimensionality of such structures and yield typical lateral confinement energies of 22.3 cm−1 and electronic widths of ∼900 nm. These estimates are supported by cathodoluminescence data. © 1996 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.30.Fs III-V and II-VI semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence

Radiative recombination lifetime measurements of InGaN single quantum well

C.‐K. Sun, S. Keller, G. Wang, M. S. Minsky, J. E. Bowers, and S. P. DenBaars

Appl. Phys. Lett. 69, 1936 (1996); http://dx.doi.org/10.1063/1.117627 (3 pages) | Cited 41 times

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We present results from a time‐resolved study of radiative recombination in InGaN quantum wells. The sample was grown by atmospheric pressure metal‐organic chemical‐vapor deposition. Time‐resolved photoluminescence measurements were performed from 7 K up to room temperature. The low temperature radiative lifetime was measured to be on the order of 250 ps at a generated carrier density of 1012 cm−2. The time‐resolved measurements show a bimolecular recombination characteristic. At 300 K, we observed a lifetime of 130 ps which, to the best of our knowledge, is the longest lifetime reported for any III–V nitride at room temperature. © 1996 American Institute of Physics.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.47.-p Spectroscopy of solid state dynamics
78.55.Cr III-V semiconductors
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Influence of AsH3 cracking temperature on the H passivation of C acceptors in In0.53Ga0.47As grown by beam epitaxy techniques

Steven L. Jackson, Judith E. Baker, and Gregory E. Stillman

Appl. Phys. Lett. 69, 1939 (1996); http://dx.doi.org/10.1063/1.117628 (3 pages) | Cited 1 time

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The influence of subhydride species generated in a low‐pressure Ta‐based AsH3 cracker on the degree of H passivation of C acceptors in heavily doped (p⩾3×1019 cm−3) In0.53Ga0.47As grown by gas source and metalorganic molecular beam epitaxy has been studied. A strong correlation has been observed between the relative abundance of AsH3, AsH, and H in quadrupole mass spectra and the degree of passivation. Enhanced effects were observed at reduced growth temperatures. Design of experiments techniques have been used to study the influence of hydride cracker temperature, substrate temperature, H2 pumping speed, group III sources, AsH3 flow rate and the second order interactions on the H passivation of C acceptors. The substrate temperature, hydride cracking temperature, and H2 pumping speed, were determined to have the dominant effects, while second order interactions were dominated by substrate temperature, H2 pumping speed, and AsH3 flow rate interactions with the hydride cracking temperature. Optimized parameters were determined that permit the growth of essentially unpassivated (⩽10%) C‐doped In0.53Ga0.47As with net hole concentrations as high as p=8×1019 cm−3 by both gas source and metalorganic molecular beam epitaxy techniques. © 1996 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.72.uj III-V and II-VI semiconductors

Twinning orientation in YBa2Cu3O7−x films deposited on YAlO3 substrates

C. Dubourdieu, J. P. Sénateur, O. Thomas, F. Weiss, B. P. Thrane, and M. Brunel

Appl. Phys. Lett. 69, 1942 (1996); http://dx.doi.org/10.1063/1.117629 (3 pages) | Cited 3 times

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An x‐ray diffraction study of YBa2Cu3O7−x (YBCO) films deposited on YAlO3 (001) substrates by metal organic chemical vapor deposition is reported. The twinning orientation of YBCO on YAlO3 is compared to the one observed for films deposited on MgO (001), SrTiO3 (001), and LaAlO3 (012) substrates. The ϕ scans performed on hhl type reflections and the grazing incidence x‐ray diffraction on the 020/200 reflections of YBCO reveal a particular epitaxial relationship on YAlO3: there is only one twinning direction relatively to the substrate. The [110] and [110] directions of YBCO are aligned with the [010] direction of YAlO3. This twinning geometry may be explained by coherency strains. © 1996 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
61.72.Mm Grain and twin boundaries
61.05.cm X-ray reflectometry (surfaces, interfaces, films)

X‐ray detection using a superconducting transition‐edge sensor microcalorimeter with electrothermal feedback

K. D. Irwin, G. C. Hilton, D. A. Wollman, and John M. Martinis

Appl. Phys. Lett. 69, 1945 (1996); http://dx.doi.org/10.1063/1.117630 (3 pages) | Cited 65 times

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We have developed a new type of x‐ray detector based on a superconducting transition‐edge thermometer operated near 100 mK. A superconducting quantum interference device is used to measure the current through the thermometer, and negative electrothermal feedback is used to improve the energy resolution and shorten the thermal time constant. We have used a detector mounted on a scanning electron microscope to measure the energy of titanium Kα (4.5 keV) fluorescence x rays with a resolution better than 14 eV full width at half‐maximum. Using two other devices, we have measured an energy resolution for Joule heat pulses of 2.6 eV at 1 keV and 0.2 eV at 4 eV, the best reported for any calorimeter. An electrical noise equivalent power of 3×10−18 W/√Hz was also measured, suggesting the use of these detectors as infrared bolometers.
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07.85.Nc X-ray and γ-ray spectrometers
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
29.40.Vj Calorimeters

Performance of YBa2Cu3O7−δ direct current SQUIDS with high‐resistance step‐edge junctions

F. Dillmann, V. N. Glyantsev, and M. Siegel

Appl. Phys. Lett. 69, 1948 (1996); http://dx.doi.org/10.1063/1.117631 (3 pages) | Cited 16 times

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We measured the performance of dc superconducting quantum interference devices (SQUIDs) fabricated from YBa2Cu3O7−δ films as a function of the SQUID inductance, L, and normal resistance, Rn, of step‐edge Josephson junctions and compared it to theoretical expectations. A process for adjusting critical currents and obtaining high normal resistances of junctions has been developed. All measurements were performed in liquid nitrogen, i.e., at 77 K. We could obtain controllably normal resistances of 5–10 Ω per junction at critical currents of 20–50 μA. A spectral density of white flux noise of SΦ1/2=2.5μΦ0/√Hz was obtained with a dc SQUID having L=50 pH, Rn=7 Ω per junction, βL=0.5 and ∂V/∂Φ=110 μV/Φ0. The best magnetic field resolution at 1 kHz was 20 fT/√Hz, with L=150 pH. © 1996 American Institute of Physics.
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74.72.-h Cuprate superconductors
85.25.Dq Superconducting quantum interference devices (SQUIDs)

Epitaxial growth of (Sr1−xCax)CuO2 thin film with the infinite‐layer structure by metal‐organic chemical vapor deposition

K.‐W. Chang, B. W. Wessels, D. Studebaker, and T. J. Marks

Appl. Phys. Lett. 69, 1951 (1996); http://dx.doi.org/10.1063/1.117632 (3 pages) | Cited 1 time

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Phase‐pure epitaxial (Sr1−xCax)CuO2 thin films having the infinite‐layer crystal structure were grown on SrTiO3 (100) substrates by low pressure metal‐organic chemical vapor deposition using fluorinated metal‐organic precursors. The substrate temperature and reactant gas (O2, H2O) partial pressure are crucial for stabilizing the tetragonal infinite‐layer structure. Films with compositions over the range x=0–0.3 can be stabilized. In‐plane epitaxy was confirmed by x‐ray diffraction ϕ scan. The films were semiconducting but exhibit resistivity anomalies. The orthorhombic phases of Sr2CuO3 and SrCuO2 were stabilized at 700 °C and 750 °C, respectively. © 1996 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Current capability of filaments depending on their position in (Bi,Pb)2Sr2Ca2Cu3O10+δ ‐multifilament tapes

Th. Schuster, H. Kuhn, A. Weißhardt, H. Kronmüller, B. Roas, O. Eibl, M. Leghissa, and H.‐W. Neumüller

Appl. Phys. Lett. 69, 1954 (1996); http://dx.doi.org/10.1063/1.117633 (3 pages) | Cited 36 times

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The microstructures of single filaments of silver‐sheathed (Bi,Pb)2Sr2Ca2Cu3O10+δ‐multifilament tapes are investigated by polarized light and scanning electron microscopy. Large differences in the microstructure of filaments depending on their position in the cross section of the tape are found. The influence of this microstructure on the critical current density is investigated by magneto‐optics. A drastic reduction of the critical current density by a factor of about 10 of the outer, compared to the filaments in the center of the tape is observed. © 1996 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
84.71.Mn Superconducting wires, fibers, and tapes

Influence of the microstructure of a SrTiO3 buffer layer on the microwave properties of Y1Ba2Cu3O7−x films on MgO

Muralidhar R. Rao

Appl. Phys. Lett. 69, 1957 (1996); http://dx.doi.org/10.1063/1.117634 (3 pages) | Cited 10 times

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YBa2Cu3O7−x (YBCO) films were grown on SrTiO3 buffered (100)‐MgO substrates by pulsed laser deposition. The microstructure of the SrTiO3 layers was varied by changing the growth parameters and thickness. The surface morphology of the layers was characterized by atomic force microscopy. Stripline microwave resonators were fabricated from the films, and the resonator characteristics were measured. The microwave loss in the YBCO was found to correlate to SrTiO3 grain size. © 1996 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.78.Fk Multilayers, superlattices, heterostructures
74.25.N- Response to electromagnetic fields
85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors

Mutual phase‐locking of ten YBa2Cu3O7 step‐edge Josephson junctions up to 45 K

G. Kunkel and R. H. Ono

Appl. Phys. Lett. 69, 1960 (1996); http://dx.doi.org/10.1063/1.117635 (3 pages) | Cited 7 times

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We have developed a microwave circuit using ten parallel‐biased high‐temperature superconductor Josephson junctions to demonstrate phase‐locking for applications such as oscillators, mixers, and detectors. The basic cell consists of two Josephson junctions enclosed in a microstrip resonator, which provides voltage‐locking and low dynamic resistance in the current–voltage characteristic. Partial synchronization of the ten junctions was observed up to 45 K and up to 1 THz. The implications of this design for power and radiation linewidth will be discussed. © 1996 American Institute of Physics.
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85.25.Cp Josephson devices

Quenching of giant magnetoresistance by interface roughening and alloying in annealed [(NixFe1−x)yAu1−y]/Au multilayers

R. F. C. Farrow, S. S. P. Parkin, R. F. Marks, Kannan M. Krishnan, and N. Thangaraj

Appl. Phys. Lett. 69, 1963 (1996); http://dx.doi.org/10.1063/1.117636 (3 pages) | Cited 7 times

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Antiferromagnetically coupled permalloy/Au multilayers display giant magnetoresistance (GMR) with large changes in resistance in very low fields. We show that thermal annealing of such structures, exhibiting GMR, leads to a quenching of the magnetoresistance. The detailed structure of the permalloy/Au interfaces has been probed using high‐resolution cross‐section transmission electron microscopy. On annealing, the Au layers interdiffuse into the permalloy layers, which leads both to rougher permalloy/Au interfaces and to ‘‘thinner’’ Au spacer layers. We infer that the latter results in ferromagnetic coupling of the permalloy layers, which accounts for the reduced GMR. © 1996 American Institute of Physics.
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75.47.De Giant magnetoresistance
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.Nq Composition and phase identification

Large magnetic‐field‐induced strains in Ni2MnGa single crystals

K. Ullakko, J. K. Huang, C. Kantner, R. C. O’Handley, and V. V. Kokorin

Appl. Phys. Lett. 69, 1966 (1996); http://dx.doi.org/10.1063/1.117637 (3 pages) | Cited 882 times

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Strains of nearly 0.2% have been induced along [001] in unstressed crystals of Ni2MnGa with magnetic fields of 8 kOe applied at 265 K. These stains are associated with the superelastic motion of twin boundaries in the martensitic phase that is stable below about 274 K. © 1996 American Institute of Physics.
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75.80.+q Magnetomechanical effects, magnetostriction
75.50.Cc Other ferromagnetic metals and alloys
81.30.Kf Martensitic transformations

A simple and robust electron beam source from carbon nanotubes

Philip G. Collins and A. Zettl

Appl. Phys. Lett. 69, 1969 (1996); http://dx.doi.org/10.1063/1.117638 (3 pages) | Cited 185 times

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A simple fabrication method is described to produce reliable and robust (self‐repairing) field emission sources from randomly aligned carbon nanotubes. The sources display stable and reproducible current–voltage characteristics with sharp turn on near 100 V and emission currents up to 400 mA/cm2 at 200 V. Two successful methods are described for patterning the emission source area into emitting and nonemitting regions. © 1996 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors
79.70.+q Field emission, ionization, evaporation, and desorption
81.05.ub Fullerenes and related materials
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