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2 Sep 1996

Volume 69, Issue 10, pp. 1343-1495

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

Observation of electrically resettable negative persistent photoconductivity in InAs/AlSb single quantum wells

Fu‐Cheng Wang, W. E. Zhang, C. H. Yang, M. J. Yang, and B. R. Bennett

Appl. Phys. Lett. 69, 1417 (1996); http://dx.doi.org/10.1063/1.117600 (3 pages) | Cited 20 times

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The mechanism of the negative persistent photoconductivity (NPPC) in InAs/AlSb single quantum wells is discussed. The molecular beam epitaxy grown single InAs quantum well sample is made into Hall bars with the substrate as the backgate. Using the newly designed buffer, the gate bias can deplete or enhance the two‐dimensional electrons in the InAs quantum well without substantial gate leakage current. Based on the 4.2 K magnetoresistance data, and the fact that the trapped electrons can be redistributed by gate bias, we conclude that the NPPC effect at low temperatures is a result of the capture of photoexcited electrons by ordinary, deep donors in AlSb. Numerical modeling using physical assumptions can quantitatively explain our experimental observation, and the calculated AlSb donor energy is 0.41±0.05 eV above the AlSb valence band maximum, with 4×1016/cm3 to 1017/cm3 in concentration. The previously discussed DX‐center‐like characteristic of deep levels in AlSb, i.e., lattice‐relaxation with a relatively high activation energy, is not evidenced in this work. © 1996 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Photoluminescence characterization of the quantum well structure and influence of optical illumination on the electrical performance of AlGaN/GaN modulation‐doped field‐effect transistors

S. N. Mohammad, Z.‐F. Fan, A. Salvador, O. Aktas, A. E. Botchkarev, W. Kim, and Hadis Morkoç

Appl. Phys. Lett. 69, 1420 (1996); http://dx.doi.org/10.1063/1.117601 (3 pages) | Cited 38 times

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Electrical characteristics of high performance GaN modulation‐doped field‐effect transistors (MODFETs) grown by reactive molecular beam epitaxy method are studied experimentally both in dark and under white light illumination. The maximum measured drain‐source current is 626 mA/mm in dark and 695 mA/mm under illumination, which saturates at a relatively low drain‐source voltage VDS. The transconductance increases with decreasing gate length reaching a value of 210 mS/mm in dark and 222 mS/mm under illumination for devices with a gate length of LG=1.5μm. Breakdown voltages of about 90 V have also been exhibited by devices with gate length LG=1.5 μm and drain‐gate distance LDG=1 μm. To our knowledge, these are the best values obtained so far from GaN MODFETs which we attribute to the suppression of leakage currents and improved materials structure of the devices. © 1996 American Institute of Physics.
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85.30.Tv Field effect devices
78.55.Cr III-V semiconductors

Dependence of threshold current density on the energy‐band offsets in Zn1−uCduSe/ZnSzSe1−z/Zn1−xMgxSySe1−y separate‐confinement heterostructures lasers

Khalid Shahzad and Maarten Buijs

Appl. Phys. Lett. 69, 1423 (1996); http://dx.doi.org/10.1063/1.117602 (3 pages) | Cited 1 time

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We use a theoretical model of semiconductor lasers to calculate threshold current density (Jth), optical gain (g), and spontaneous emission rate (rsp) as a function of the two heterojunction band offsets between Zn1−uCduSe(well)/ZnSzSe1−z(guiding) layers and ZnSzSe1−z (guiding)/ Zn1−xMgxSySe1−y(cladding) layers. We find that for the conduction‐band offset between the well and the guiding layers ranging from ∼0.55ΔEg to ∼0.75ΔEg (ΔEg being the energy band‐gap difference), there is very little change in Jth, g, rsp. Furthermore, these three quantities are very weakly dependent on the conduction‐band offset between the guiding and the cladding layers ranging from 0.2ΔEg to 0.5ΔEg. However, if the offset between the well and the guiding layers is increased from ∼0.75ΔEgto ∼0.8ΔEg, the calculations indicate a sharp drop in Jth, g, and rsp. We explain this behavior as due to the unbinding of the ground‐state light‐hole subband as the valence band offset is reduced. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

ICl/Ar electron cyclotron resonance plasma etching of III–V nitrides

C. B. Vartuli, S. J. Pearton, J. W. Lee, J. Hong, J. D. MacKenzie, C. R. Abernathy, and R. J. Shul

Appl. Phys. Lett. 69, 1426 (1996); http://dx.doi.org/10.1063/1.117603 (3 pages) | Cited 29 times

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Electron cyclotron resonance plasma etch rates for GaN, InN, InAlN, AlN, and InGaN were measured for a new plasma chemistry, ICl/Ar. The effects of gas chemistry, microwave and rf power on the etch rates for these materials were examined. InN proved to be the most sensitive to the plasma composition and ion density. The GaN, InN, and InGaN etch rates reached ∼13 000, 11 500, and ∼7000 Å/min, respectively, at 250 W rf (−275 V dc) and 1000 W microwave power. The etched surface of GaN was found to be smooth, with no significant preferential loss of N from the surface at low rf powers, and no significant residue on the surface after etching. © 1996 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors

Passivation of GaAs surface by sulfur glow discharge

Xiaoyuan Hou, Xiying Chen, Zheshen Li, Xunmin Ding, and Xun Wang

Appl. Phys. Lett. 69, 1429 (1996); http://dx.doi.org/10.1063/1.117604 (3 pages) | Cited 10 times

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A new sulfur passivation technique, the sulfur vapor glow discharge, has been developed to form a thick sulfide layer on GaAs surface. By using Auger electron spectroscopy and x‐ray photoelectron spectroscopy measurements, the main composition of the passivation layer is found to be gallium sulfide without the existence of unstable As–S bonds. The stability of the passivation effect is demonstrated by the nondecaying behavior of the photoluminescence intensity of the GaAs passivation surface under the illumination of the laser beam with very high intensity. © 1996 American Institute of Physics.
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81.65.Rv Passivation
79.60.Dp Adsorbed layers and thin films
78.55.Cr III-V semiconductors
79.20.Fv Electron impact: Auger emission

Colloidal chemical synthesis and characterization of InAs nanocrystal quantum dots

A. A. Guzelian, U. Banin, A. V. Kadavanich, X. Peng, and A. P. Alivisatos

Appl. Phys. Lett. 69, 1432 (1996); http://dx.doi.org/10.1063/1.117605 (3 pages) | Cited 161 times

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InAs nanocrystal quantum dots have been prepared via colloidal chemical synthesis using the reaction of InCl3 and As[Si(CH3)3]3. Sizes ranging from 25 to 60 Å in diameter are produced and isolated with size distributions of ±10%–15% in diameter. The nanocrystals are crystalline and generally spherical with surfaces passivated by trioctylphosphine giving them solubility in common organic solvents. The dots have been structurally characterized by transmission electron microscopy (TEM) and powder x‐ray diffraction (XRD) and the optical absorption and emission have been examined. Quantum confinement effects are evident with absorption onsets well to the blue of the bulk band gap and size dependent absorption and emission features. The emission is dominated by band edge luminescence. These quantum dots are particularly interesting as they provide an opportunity to make important comparisons with comparably sized InAs quantum dots synthesized by molecular beam epitaxy techniques. © 1996 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.05.Cy Elemental semiconductors
78.66.Fd III-V semiconductors

Negative differential conductance in three‐terminal silicon tunneling device

Junji Koga and Akira Toriumi

Appl. Phys. Lett. 69, 1435 (1996); http://dx.doi.org/10.1063/1.117606 (3 pages) | Cited 10 times

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Negative differential conductance based on lateral band‐to‐band tunneling is demonstrated in a three‐terminal silicon tunneling device. The device is fabricated with the current silicon ultra‐large scale integration (Si ULSI) process, taking care of the field isolation to reduce the excess tunneling current that flows over some intermediate states. It is observed that the forward biased band‐to‐band tunneling current is largely controlled by the gate bias which modulates the tunneling barrier width. The three‐terminal Si tunneling device is promising as the post complementary metal–oxide‐semiconductor device in future Si ULSI. © 1996 American Institute of Physics.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.30.Kk Junction diodes
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Very high breakdown voltage and large transconductance realized on GaN heterojunction field effect transistors

Y.‐F. Wu, B. P. Keller, S. Keller, D. Kapolnek, P. Kozodoy, S. P. Denbaars, and U. K. Mishra

Appl. Phys. Lett. 69, 1438 (1996); http://dx.doi.org/10.1063/1.117607 (3 pages) | Cited 178 times

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We report record high breakdown voltages up to 340 and 230 V realized on unintentionally doped (1.5 μm gate length) and Si doped (1 μm gate length) AlGaN/GaN modulation doped field effect transistors (MODFETs), respectively. The devices also have large transconductances up to 140 mS/mm and a full channel current of 150–400 mA/mm. The Si doped MODFET sample demonstrated a very high room temperature mobility of 1500 cm2/Vs. With these specifications, GaN field effect transistors as microwave power devices are practical. © 1996 American Institute of Physics.
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85.30.Tv Field effect devices

Arsenic precipitation from thin surface layers of low‐temperature grown GaAs

R. A. Kiehl, M. Yamaguchi, T. Ohshima, M. Saito, and N. Yokoyama

Appl. Phys. Lett. 69, 1441 (1996); http://dx.doi.org/10.1063/1.117608 (3 pages) | Cited 2 times

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Arsenic precipitation from a thin, 100‐nm surface layer of GaAs grown at low temperature (LT) by molecular beam epitaxy is investigated. The precipitate depth distribution is examined for different rapid thermal annealing cycles. It is found that the precipitate distribution can tail a long distance into the underlying stoichiometric GaAs layer, depending on the peak annealing temperature. The distribution for an 800 °C anneal is virtually unaffected by a prior low temperature ‘‘soak’’ at 600 °C, thus showing that the precipitation is insensitive to the initial point defect concentrations in this temperature range. The relevance of these results to the precipitation process and to the use of thin LT layers in device applications is discussed. © 1996 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.30.Mh Solid-phase precipitation

Photoluminescence study of initial interdiffusion of SiGe/Si quantum wells grown by ultrahigh vacuum‐chemical vapor deposition

H. Lafontaine, D. C. Houghton, N. L. Rowell, and G. C. Aers

Appl. Phys. Lett. 69, 1444 (1996); http://dx.doi.org/10.1063/1.117609 (3 pages) | Cited 6 times

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SiGe quantum wells were grown at 525 °C using a commercially available, ultrahigh vacuum–chemical vapor deposition system, in which the purity of the material and quality of interfaces have already been demonstrated. Changes in photoluminescence line energies are monitored and the extent of interdiffusion in the wells during annealing is calculated. A strong initial enhancement of the diffusivity is observed in as‐grown material. Material annealed using a two‐step process in which strain and Ge peak concentrations are unchanged after the first (low temperature) step, shows a much lower interdiffusion during the second step. It is argued that strain alone cannot explain the enhanced interdiffusion, which is, thus, attributed to grown‐in, nonequilibrium point defects. © 1996 American Institute of Physics.
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66.30.Ny Chemical interdiffusion; diffusion barriers
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.55.Ap Elemental semiconductors

Hydrogen ion motion in amorphous silicon solar cells at elevated temperatures

D. E. Carlson and K. Rajan

Appl. Phys. Lett. 69, 1447 (1996); http://dx.doi.org/10.1063/1.117610 (3 pages) | Cited 14 times

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Electric field‐enhanced degradation has been observed in amorphous silicon solar cells exposed to intense illumination (45–60 suns) at elevated temperatures (≳160 °C). The front tin oxide contacts of both p–i–n and n–i–p cells darken significantly when a strong reverse bias is applied at elevated temperatures and under intense illumination. Compositional profiles of the cells show that a strong reverse bias causes a depletion of hydrogen near the contacts. These results are interpreted in terms of proton motion near the p/i interface of p–i–n cells and negative hydrogen ion motion near the i/n interface. © 1996 American Institute of Physics.
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84.60.Jt Photoelectric conversion
66.30.Qa Electromigration

Monte Carlo calculations of hot‐carrier noise under degenerate conditions

P. Tadyszak, F. Danneville, A. Cappy, L. Reggiani, L. Varani, and L. Rota

Appl. Phys. Lett. 69, 1450 (1996); http://dx.doi.org/10.1063/1.117611 (3 pages) | Cited 9 times

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We present a Monte Carlo investigation of noise and velocity fluctuations in Si at 300 K under full degenerate conditions. The presence of the Pauli principle is found to strongly modify the shape of the correlation functions: at low electric fields, the time decay decreases due to the shortening of momentum relaxation time and the variance evidences nonparabolicity effects. At increasing electric fields, the correlation function exhibits a negative part that can be associated with ballistic carriers crossing the velocity space from negative to positive values of the Fermi velocity without scattering. A microscopic analysis in terms of diagonal and off‐diagonal contributions to the velocity correlation confirms this interpretation. © 1996 American Institute of Physics.
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72.70.+m Noise processes and phenomena
72.20.Ht High-field and nonlinear effects
72.80.Cw Elemental semiconductors

Charge trapping, isolated Ge defects, and photosensitivity in sputter deposited GeO2:SiO2 thin films

W. L. Warren, K. Simmons‐Potter, B. G. Potter, and J. A. Ruffner

Appl. Phys. Lett. 69, 1453 (1996); http://dx.doi.org/10.1063/1.117612 (3 pages) | Cited 7 times

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The nature of the defects in sputter‐deposited GeO2:SiO2 thin films and their relationship to charge trapping and enhanced photosensitivity have been studied using electron paramagnetic resonance, capacitance–voltage, and optical bleaching and absorption spectroscopies. We find a good qualitative agreement between the density of isolated Ge dangling bonds measured magnetically, the density of charge trapping sites measured electrically, and the density of absorbing centers measured optically. Collectively, all observations can be modeled by assuming that a change in spin state and charge state of isolated paramagnetic neutral Ge dangling bonds, to form either diamagnetic positively or negatively charged Ge sites, are largely responsible for the charge trapping and photosensitivity in these thin films. © 1996 American Institute of Physics.
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78.66.Nk Insulators
76.30.-v Electron paramagnetic resonance and relaxation
77.55.-g Dielectric thin films
61.43.Fs Glasses

High temperature chemical vapor deposition of SiC

O. Kordina, C. Hallin, A. Ellison, A. S. Bakin, I. G. Ivanov, A. Henry, R. Yakimova, M. Touminen, A. Vehanen, and E. Janzén

Appl. Phys. Lett. 69, 1456 (1996); http://dx.doi.org/10.1063/1.117613 (3 pages) | Cited 25 times

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A growth process has been investigated for the epitaxial growth of silicon carbide. The technique can simply be described as chemical vapor deposition (CVD) at high temperatures, hence the name high temperature CVD (HTCVD). The growth process however, differs greatly from that of the CVD process due to the significant sublimation and etch rates at the extreme growth temperatures (1800–2300°C). The grown rates obtained with the HTCVD are in the order of several tens of μm/h to 0.5 mm/h. The purity and crystallinity of the growth layers are outstanding showing strong free exciton related photoluminescence. © 1996 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
78.66.Li Other semiconductors

Etched‐surface roughness measurements from an in situ laser reflectometer

M. A. Parker, R. J. Michalak, J. S. Kimmet, A. R. Pirich, and D. B. Shire

Appl. Phys. Lett. 69, 1459 (1996); http://dx.doi.org/10.1063/1.116907 (3 pages) | Cited 2 times

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An in situ laser reflectometer is used to determine the surface roughness of III–V laser heterostructure as it etches in an electron cyclotron resonance etcher. A stochastic model links the reflectometer signals with the fluctuations of the surface height and slope, and with the size of the illuminated surface area. This technique is valuable for improving the quality of optical waveguides etched in III–V heterostructure, and the electrical contacts for optoelectronic devices. © 1996 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Cf Surface cleaning, etching, patterning
07.60.Hv Refractometers and reflectometers
78.66.Fd III-V semiconductors

17.1% efficient metal‐insulator‐semiconductor inversion layer silicon solar cells using truncated pyramids

Manfred Grauvogl, Armin G. Aberle, and Rudolf Hezel

Appl. Phys. Lett. 69, 1462 (1996); http://dx.doi.org/10.1063/1.116908 (3 pages) | Cited 14 times

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Metal‐insulator‐semiconductor inversion layer (MIS‐IL) silicon solar cells are of significant interest for terrestrial solar electricity production due to their simple, energy‐saving fabrication process. In this work we present experimental results for an improved MIS‐IL silicon solar cell design based on the truncated‐pyramid concept. The cells exhibit independently confirmed 1‐sun efficiencies above 17%, by a clear margin the highest values ever reported for this promising class of photovoltaic devices. © 1996 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.60.Jt Photoelectric conversion

The role of point defects and arsenic precipitates in carrier trapping and recombination in low‐temperature grown GaAs

A. J. Lochtefeld, M. R. Melloch, J. C. P. Chang, and E. S. Harmon

Appl. Phys. Lett. 69, 1465 (1996); http://dx.doi.org/10.1063/1.116909 (3 pages) | Cited 47 times

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GaAs epilayers were grown with a wide range of excess arsenic concentrations and subjected to various anneals to study the role of the point defects and arsenic precipitates in carrier trapping and recombination. Prior to anneal, the point defects rapidly trap photogenerated electrons and holes—usually on subpicosecond time scales. However, full electron‐hole recombination occurs on a significantly longer time scale. After anneal, the full electron‐hole recombination lifetime appears to be greatly reduced, indicating that the arsenic precipitates play a significant role. © 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
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing

Variation of surface morphology with substrate temperature for molecular beam epitaxially grown GaSb(100) on GaAs(100)

S. J. Brown, M. P. Grimshaw, D. A. Ritchie, and G. A. C. Jones

Appl. Phys. Lett. 69, 1468 (1996); http://dx.doi.org/10.1063/1.116910 (3 pages) | Cited 8 times

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Using molecular beam epitaxy (MBE) several layers of GaSb were grown on GaAs at substrate temperatures of 400, 475, and 550 °C, and the surface morphology was studied with an in situ ultra high vacuum scanning tunneling microscope (STM). We have observed spiral mound growth of different morphology originating from surface dislocations for the samples grown at 400 and 475 °C, however at 550 °C there is no spiral mound growth and neighboring dislocations are joined by a single step. The surfaces have different rms surface roughness and dislocation density which has important consequences with regard to heterointerface quality. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Noninvasive measurement of charging in plasmas using microelectromechanical charge sensing devices

Kiran Pangal, Samara L. Firebaugh, and James C. Sturm

Appl. Phys. Lett. 69, 1471 (1996); http://dx.doi.org/10.1063/1.116911 (3 pages) | Cited 1 time

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The plasma induced charging of surfaces in a plasma during semiconductor processing has been measured noninvasively using microelectromechanical devices. We have designed, modeled, and fabricated microcantilevers to act as charge sensing probes. The devices exhibit a mechanical deformation when charged, which is probed in situ by optical techniques, or measured by optical inspection after removal from plasma. Charging voltage measurements in a parallel‐plate reactive‐ion‐etching reactor show that more charging is evident at the electrode edge, and that the charging is a strong function of input rf power, chamber pressure, and flow rate of gases. © 1996 American Institute of Physics.
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07.10.Cm Micromechanical devices and systems
85.30.-z Semiconductor devices
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition

Nature of Mg impurities in GaN

J. Z. Li, J. Y. Lin, H. X. Jiang, A. Salvador, A. Botchkarev, and H. Morkoc

Appl. Phys. Lett. 69, 1474 (1996); http://dx.doi.org/10.1063/1.116912 (3 pages) | Cited 71 times

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Mg doped GaN epilayers grown by reactive molecular beam epitaxy (MBE) exhibit clear persistent photoconductivity (PPC) whose manifestation has been used to probe the nature of Mg impurities in GaN. PPC buildup and decay transients and the dependence of the PPC decay time constant on the PPC buildup time have been systematically measured and formulated in the context of lattice relaxed Mg impurities (or AX centers). Our results have demonstrated that there is an energy barrier of about 129 meV which prevents free hole capture by ionized Mg impurities and that there is a lattice relaxation associated with Mg impurities in GaN. We also present a detailed comparison for Mg impurities in p‐type GaN epilayers grown by MBE (hydrogen‐free) and metalorganic chemical deposition (hydrogen rich). © 1996 American Institute of Physics.
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71.55.Eq III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors

Ridge‐geometry InGaN multi‐quantum‐well‐structure laser diodes

Shuji Nakamura, Masayuki Senoh, Shin‐ichi Nagahama, Naruhito Iwasa, Takao Yamada, Toshio Matsushita, Yasunobu Sugimoto, and Hiroyuki Kiyoku

Appl. Phys. Lett. 69, 1477 (1996); http://dx.doi.org/10.1063/1.116913 (3 pages) | Cited 89 times

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Stripe‐ and ridge‐geometry in InGaN multi‐quantum‐well (MQW)‐structure laser diodes (LDs) were fabricated on sapphire substrates with (1120) orientation (A face). The ridge‐geometry InGaN MQW LDs showed strong stimulated emission at a wavelength of 411.3 nm under a pulsed current injection of 199 mA at room temperature. The differential quantum efficiency per facet and the threshold current of ridge‐geometry LDs were 30% and 180 mA, respectively. The laser threshold current density was 3 kA/cm2. These values were greatly improved in comparison to those of stripe‐geometry LDs. The characteristic temperature of the threshold current was around 185 K. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.66.Fd III-V semiconductors

Evidence of enhanced pinning properties in optimally doped Bi2Sr2Ca1−xYxCu2O8+δ  single crystals

G. Villard, D. Pelloquin, A. Maignan, and A. Wahl

Appl. Phys. Lett. 69, 1480 (1996); http://dx.doi.org/10.1063/1.116914 (3 pages) | Cited 8 times

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A comparative study of the magnetic properties of Bi2Sr2Ca1−xYxCu2O8+δ single crystals with different yttrium contents is presented. An optimum in the doping can be reached that corresponds to a high Tc (onset) value (91.5 K) and a high position of the irreversibility line. Moreover, the fishtail feature disappears for this optimally Y doped Bi‐2212 crystal due to the increase of the magnetic field dependence of the critical current density. This demonstrates the better pinning efficiency of the crystals with the highest Tc. © 1996 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.62.Dh Effects of crystal defects, doping and substitution
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)

Radio frequency‐SQUID effect in YNi2B2C due to natural grain boundary weak links

Neeraj Khare, A. K. Gupta, Sangeeta Khare, L. C. Gupta, R. Nagarajan, Z. Hossain, and R. Vijayaraghavan

Appl. Phys. Lett. 69, 1483 (1996); http://dx.doi.org/10.1063/1.116915 (3 pages) | Cited 9 times

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We report the observation of radio frequency‐superconducting quantum interference device (rf‐SQUID) effect due to natural grain boundary weak links in a bulk sample of a YNi2B2C superconductor at 4.2 K, confirming that the superconducting grains are coupled at the grain boundaries through Josephson effect. Periodic oscillations in voltage‐flux characteristic due to rf‐SQUID effect have been clearly observed at 4.2 K when the driving rf frequency was kept slightly away from the resonance frequency of the tank circuit. Phase reversal in the voltage‐flux characteristics on changing the rf frequency has been observed. Noise spectrum of the YNi2B2C bulk rf‐SQUID is also reported. © 1996 American Institute of Physics.
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74.50.+r Tunneling phenomena; Josephson effects
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.70.Dd Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.)
74.81.Bd Granular, melt-textured, amorphous, and composite superconductors

Manganese perovskites: Thick‐film based position sensors fabrication

Ll. Balcells, R. Enrich, J. Mora, A. Calleja, J. Fontcuberta, and X. Obradors

Appl. Phys. Lett. 69, 1486 (1996); http://dx.doi.org/10.1063/1.116916 (3 pages) | Cited 27 times

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In this letter we report on the growth of thick films of magnetoresistive La2/3Sr1/3MnO3 films using a spray printing technique. The as‐prepared films display a room‐temperature magnetoresistance of 0.0012%/Oe in the 1 kOe field region. We will show that this field sensitivity is high enough to fabricate devices which, operated under a bias magnetic field, can be used as a sensitive and low‐cost magnetic sensors. © 1996 American Institute of Physics.
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85.70.-w Magnetic devices
75.47.De Giant magnetoresistance
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Polarized neutron reflectometry study of an exchange biased Fe3O4/NiO multilayer

A. R. Ball, A. J. G. Leenaers, P. J. van der Zaag, K. A. Shaw, B. Singer, D. M. Lind, H. Fredrikze, and M.Th. Rekveldt

Appl. Phys. Lett. 69, 1489 (1996); http://dx.doi.org/10.1063/1.116917 (3 pages) | Cited 11 times

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Polarized neutron reflectometry was performed on a [Fe3O4/NiO]x15 multilayer, molecular beam epitaxy grown on a (001) MgO substrate, in both exchange biased and nonexchange biased states. The Fe3O4 layers exhibit a depth‐dependent magnetic profile characterized by a change in the magnetization near the Fe3O4/NiO interfaces. In the exchange biased state, measurements performed in the two saturated states of the magnetic hysteresis loop reveal magnetic differences in the Fe3O4, possibly due to the interfacial domain wall formation in the ferromagnetic layer. © 1996 American Institute of Physics.
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61.05.fj Neutron reflectometry
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
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