jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

1 Dec 1994

Volume 76, Issue 11, pp. 7175-7653

Page 2 of 4 Pages Previous Page Next Page | Jump to Page

Radiation‐induced shallow donors in Czochralski‐grown silicon crystals saturated with hydrogen

V. P. Markevich, M. Suezawa, K. Sumino, and L. I. Murin

J. Appl. Phys. 76, 7347 (1994); http://dx.doi.org/10.1063/1.357958 (4 pages) | Cited 16 times

Full Text: | Download PDF

Show Abstract
Far‐infrared absorption has been investigated in n‐type Czochralski‐grown silicon saturated with hydrogen and then irradiated with fast electrons. Two series of absorption bands in the range 200–330 cm−1 are observed upon postirradiation annealing of the crystals at 300–550 °C. These bands are associated with ground–to–excited‐state electronic transitions in two kinds of shallow donors with ionization energies of 37.0 and 42.6 meV, which are described well with the effective‐mass approximation. These donors are related to defects observed earlier in electrical measurements. © 1994 American Institute of Physics.
Show PACS
71.55.Cn Elemental semiconductors
78.30.Hv Other nonmetallic inorganics
61.80.Fe Electron and positron radiation effects

Thermogalvanomagnetic properties of Sn‐doped Bi95Sb5 and its application for solid state cooling

P. Jandl and U. Birkholz

J. Appl. Phys. 76, 7351 (1994); http://dx.doi.org/10.1063/1.357959 (16 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
Measurements of the complete set of thermogalvanomagnetic coefficients of Sn‐doped Bi95Sb5 have been carried out from liquid nitrogen up to room temperature as a function of magnetic field strength and crystallographic direction (parallel and perpendicular to the trigonal axes). The dependences of the transport coefficients on temperature, magnetic field strength, and impurity density as well as their complex mutual correlations are explained, qualitatively. These investigations were performed in order to establish the optimum tin concentration that will maximize the thermomagnetic and thermoelectric figures of merit at a given temperature and magnetic field. As calculated theoretically a 2.5‐fold enhancement of the thermomagnetic figure of merit was achieved. The crystals were grown by the horizontal zone‐leveling technique under a hydrogen atmosphere. To achieve high homogeneity and to avoid constitutional supercooling a traveling double‐ellipsoid mirror furnace was built up. This method enables us to produce a small liquid zone and a steep temperature gradient at the solid–liquid interface. © 1994 American Institute of Physics.  
Show PACS
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Pa Thermoelectric and thermomagnetic effects
72.15.Gd Galvanomagnetic and other magnetotransport effects

Polarization currents in zinc oxide varistors from 77 to 450 K

R. W. Major, A. E. Werner, C. B. Wilson, and F. A. Modine

J. Appl. Phys. 76, 7367 (1994); http://dx.doi.org/10.1063/1.357960 (5 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
The time and temperature dependencies of polarization currents are investigated to higher temperatures and with greater temperature resolution than has been reported previously for zinc oxide varistors. Arrhenius plots of these transient polarization currents yield two thermal activation energies near 140 and 8 meV, which are in reasonable agreement with values reported recently, as well as an additional thermally activated level at 0.66 eV, which becomes evident in the extension of the measurements to T≳300 K. Conductance data in this higher temperature range yield the nearly identical energy of 0.68 eV for the intergranular (Schottky) barrier height. The temperature dependence of the exponent m in the power‐law expression for the current‐time dependence I=I0t−m was carefully examined and found to change twice from 0.5 to 1.0. The nonmonotonic behavior of m(T) can be interpreted as due to resolution of polarization currents from two different traps, each of which evolves from diffusive to dispersive transport as temperature is lowered rather than, for example, a complicated distribution of relaxation times. © 1994 American Institute of Physics.
Show PACS
72.80.Sk Insulators
77.22.Ej Polarization and depolarization
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

1/f noise produced by the random motion of the carriers crossing potential barriers in semiconductors

Hiromichi Yoshida, Masanori Yoshida, Tsutomu Shinoda, and Ihoe Saito

J. Appl. Phys. 76, 7372 (1994); http://dx.doi.org/10.1063/1.357961 (5 pages)

Full Text: | Download PDF

Show Abstract
A new model for 1/f noise is discussed. When carriers in a semiconductor are separated by a potential barrier into two groups, some of the carriers climb over the barrier and move into the other group as a series of random events. If one group is in a trap, the number of the carriers in the trap varies with time. The probability of the occurrence of the first return to the initial state is in inverse proportion to the cube root value of the number of random events. The number of carriers is proportionate to the electric charge. The charge induces change in the resistance in the local area near the trap. The area is so small that the semiconductor shows the small resistance change of a square wave form. The distribution of the random square wave is represented by the Poisson distribution and its autocorrelation function has a Lorentzian spectrum. The characteristic of first return to the initial state shows that the probability of the Lorentzian spectrum is in inverse proportion to the wavelength. A 1/f spectrum is obtained by the superposition of the spectra. © 1994 American Institute of Physics.
Show PACS
72.70.+m Noise processes and phenomena
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion

Reduction of defects in laser‐induced crystallized and amorphized silicon films using plasma hydrogenation

T. Sameshima, M. Sekiya, M. Hara, N. Sano, and A. Kohno

J. Appl. Phys. 76, 7377 (1994); http://dx.doi.org/10.1063/1.357962 (7 pages)

Full Text: | Download PDF

Show Abstract
Plasma hydrogenation of laser‐crystallized and ‐amorphized films was investigated. The hydrogen concentration was determined to be 1.5 at. % using a method of laser‐induced hydrogen effusion for 20‐nm‐thick crystallized films which were hydrogenated at 250 °C for 30 s. The defect density was reduced from 1×1017 to 4×1016 cm−3. The hydrogen concentration was 2.5 at. % for amorphized films of 12 nm‐thickness. This low hydrogen concentration resulted in a low optical band‐gap energy of 1.7 eV for amorphized films, while the width of the Urbach tail was 0.06±0.005 eV, which is close to that of hydrogenated amorphous silicon (a‐Si:H) films fabricated using radio‐frequency glow discharge (rf GD). The defect density of the laser‐amorphized silicon films was reduced from 2×1020 to 4×1015 cm−3 eV−1 comparable to a‐Si:H films fabricated by rf GD. © 1994 American Institute of Physics.
Show PACS
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Jv Disordered structures; amorphous and glassy solids
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.66.Jg Amorphous semiconductors; glasses

Saturation of generation‐recombination current for very small recombination times

Lourdes Pelaz, J. L. Orantes, L. Enríquez, L. Bailón, and J. Barbolla

J. Appl. Phys. 76, 7384 (1994); http://dx.doi.org/10.1063/1.357963 (6 pages)

Full Text: | Download PDF

Show Abstract
Analysis of the generation‐recombination processes by numerical simulation allows consideration of a very small recombination time constant in order to study the behavior of p‐n junctions in this extreme situation. The generation‐recombination current does not increase indefinitely as the generation or recombination mechanism is more and more active. Instead, current saturation occurs as a result of the continuity equation along with the generation‐recombination expression. This generation‐recombination current saturation takes place in any semiconductor and establishes the maximum current limit that can be yielded by this mechanism. © 1994 American Institute of Physics.
Show PACS
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Kk Junction diodes

Hydrogen passivation effects in InGaAlP and InGaP

V. A. Gorbylev, A. A. Chelniy, A. Y. Polyakov, S. J. Pearton, N. B. Smirnov, R. G. Wilson, A. G. Milnes, A. A. Cnekalin, A. V. Govorkov, B. M. Leiferov, O. M. Borodina, and A. A. Balmashnov

J. Appl. Phys. 76, 7390 (1994); http://dx.doi.org/10.1063/1.357964 (9 pages) | Cited 12 times

Full Text: | Download PDF

Show Abstract
The effects of hydrogen treatment on electrical properties, luminescence spectra, and deep traps in InGaAlP and InGaP have been studied. It is shown that acceptors and donors (both shallow and deep) can be effectively passivated by hydrogen. The hydrogen is found not only to passivate the main electron and hole traps in our samples, but also to generate electron traps in n‐InGaAlP and hole traps in p‐InGaP. The influence of hydrogen treatment mode (direct plasma or a crossed‐beams source in which the low‐energy ion bombardment of the surface is effectively eliminated) on hydrogen concentration and hydrogen profiles in InGaAlP are discussed. © 1994 American Institute of Physics.
Show PACS
73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
71.55.Eq III-V semiconductors

The effects of strain on intrasubband scattering rates in InP‐based strained‐layer quantum‐well lasers

Shunji Seki, Kiyoyuki Yokoyama, and Paul Sotirelis

J. Appl. Phys. 76, 7399 (1994); http://dx.doi.org/10.1063/1.357965 (6 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
We analyze the strain effects (both compressive and tensile) on the intrasubband scattering rates for electrons and holes in InP‐based strained‐layer quantum‐well (SL‐QW) lasers. Carrier‐carrier and carrier‐LO‐phonon interactions are taken into account on an equal basis within the fully dynamic random phase approximation for multi‐subband structures at finite temperatures. The principal influences of the strain‐induced changes in the valence band structures on the scattering rates are discussed in terms of the changes in the valence‐band density of states and the phonon coupling with holes. We show that the hole‐hole interaction plays a dominant role in determining the hole scattering rates regardless of the carrier energy. On the other hand, for electron scattering rates, the dominant scattering mechanism switches from electron‐hole interaction to electron‐electron interaction as the initial energy of electron increases. We also demonstrate that it is essential to take into account the mutual interactions among the individual scattering processes, such as carrier‐carrier scattering and carrier‐LO‐phonon scattering, when evaluating the intrasubband scattering rates in SL‐QW lasers. © 1994 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Bk General theory, scattering mechanisms

Interface formation of Bi on ceramic ZnO: A simple model varistor grain boundary

K. O. Magnusson and S. Wiklund

J. Appl. Phys. 76, 7405 (1994); http://dx.doi.org/10.1063/1.357966 (5 pages) | Cited 10 times

Full Text: | Download PDF

Show Abstract
The Schottky barrier formation between Bi and polycrystalline, ceramic ZnO has been studied with photoelectron spectroscopy (PES) under ultrahigh‐vacuum conditions. This system is a simple model of a varistor compound. Evaporation of Bi on highly n‐doped (Al) sintered ZnO surfaces, fractured in situ and held at room temperature, results in considerable upward band bending. After evaporation of 10 Å of Bi (approximately 3 monolayer coverage), the Bi‐induced band bending amounts to 0.43 eV, as evident from the energy shift of the Bi 5d emission in PES. From valence‐band and band‐gap studies using ultraviolet PES, the states responsible for the observed band bending could be identified: Bi induces states in the ZnO band gap at 0.9 eV above the valence‐band maximum. The filling of this high density of band‐gap states results in a pinning of the surface Fermi level which makes the band bending proportional to the Bi coverage, with a rapid increase during the formation of the first monolayer and markedly slower thereafter. These results show the importance of Bi in the formation of the varistor Schottky barriers. © 1994 American Institute of Physics.  
Show PACS
73.30.+y Surface double layers, Schottky barriers, and work functions
79.60.Jv Interfaces; heterostructures; nanostructures
73.20.At Surface states, band structure, electron density of states

Deep center scattering potential in InGaP

Q. S. Zhu, K. Hiramatsu, N. Sawaki, I. Akasaki, and X. N. Liu

J. Appl. Phys. 76, 7410 (1994); http://dx.doi.org/10.1063/1.358524 (5 pages)

Full Text: | Download PDF

Show Abstract
Mobility limited by the scattering of a phosphorous vacancy‐induced deep center in In0.5Ga0.5P alloy grown by liquid‐phase epitaxy on a (100) GaAs substrate has been investigated by means of Hall mobility and deep‐level transient spectroscopy measurements. Two kinds of scattering potentials, Gaussian well type and square‐well type, were considered. It was found that the scattering potential can be better described by the Gaussian‐type potential than the square‐well one. The mobility limited by deep center scattering has been fully calculated and analyzed. As a result, the mobility is characterized by a temperature dependence of T−1/2 in the temperature range from 77 to 400 K. The point defect scattering severely reduces the total mobility as its concentration increases. In addition, the scattering case when there is an electron trapped in the Gaussian potential well was also quantitatively investigated. © 1994 American Institute of Physics.
Show PACS
71.55.Eq III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance

High electric‐field amorphous silicon p‐i‐n diodes: Effect of the p‐layer thickness

J. B. Chévrier and B. Equer

J. Appl. Phys. 76, 7415 (1994); http://dx.doi.org/10.1063/1.357967 (8 pages) | Cited 14 times

Full Text: | Download PDF

Show Abstract
We present amorphous silicon p‐i‐n diodes able to sustain a reverse bias corresponding to 106 V/cm with a reasonably low leakage current. The influence of the p‐layer thickness on the reverse bias current and the breakdown voltage is investigated. The high‐voltage reverse current at room temperature is attributed to two different mechanisms: field enhanced thermal generation in the p‐i interface region and, at the highest bias, electron injection through the p layer. Variable range hopping is also contributing to the low‐temperature reverse current. Charge collection measurements after pulsed photogeneration were also performed up to the maximum voltage. No evidence for signal amplification is found, which sets a lower limit of 106 V/cm for impact ionization and avalanche phenomena. © 1994 American Institute of Physics.
Show PACS
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Jc Amorphous semiconductors; glasses
85.30.Kk Junction diodes

Characterization of Pt‐Si interface by spectroscopic ellipsometry

Y. C. Liu, T. P. Chen, S. Fung, and C. D. Beling

J. Appl. Phys. 76, 7423 (1994); http://dx.doi.org/10.1063/1.357968 (5 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
Spectroscopic ellipsometric measurements for Pt/n‐Si samples with different thickness of Pt films have been performed. The thickness of the Pt films determined with the three‐phase model (air/Pt/Si) changes with the wavelength λ while that with the four‐phase model (air/Pt/interface layer/Si) remains unchanged, showing the existence of an interface layer. At the same time, the apparent optical dielectric constants of the interface layer as a function of λ are also obtained. A calculation based on the effective medium theory is carried out to simulate the optical dielectric data of the interface layer. Some structural information of the interface layer is obtained from the calculation. © 1994 American Institute of Physics.
Show PACS
73.30.+y Surface double layers, Schottky barriers, and work functions
07.60.Fs Polarimeters and ellipsometers
68.55.-a Thin film structure and morphology

Quantum state transfer in double‐quantum‐well devices

Jürgen Jakumeit, Marcel Tutt, and Dimitris Pavlidis

J. Appl. Phys. 76, 7428 (1994); http://dx.doi.org/10.1063/1.357969 (9 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
A Monte Carlo simulation of double‐quantum‐well (DQW) devices is presented in view of analyzing the quantum state transfer (QST) effect. Different structures, based on the AlGaAs/GaAs system, were simulated at 77 and 300 K and optimized in terms of electron transfer and device speed. The analysis revealed the dominant role of the impurity scattering for the QST. Different approaches were used for the optimization of QST devices and basic physical limitations were found in the electron transfer between the QWs. The maximum transfer of electrons from a high to a low mobility well was at best 20%. Negative differential resistance is hampered by the almost linear rather than threshold dependent relation of electron transfer on electric field. By optimizing the doping profile the operation frequency limit could be extended to 260 GHz. © 1994 American Institute of Physics.
Show PACS
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.De Semiconductor-device characterization, design, and modeling

Analyses of localized confinement potential in semiconductor strained wires and dots buried in lattice‐mismatched materials

Kenichi Nishi, A. Atsushi Yamaguchi, Jouni Ahopelto, Akira Usui, and Hiroyuki Sakaki

J. Appl. Phys. 76, 7437 (1994); http://dx.doi.org/10.1063/1.357970 (9 pages) | Cited 32 times

Full Text: | Download PDF

Show Abstract
Analytical and finite‐element‐method calculations have been conducted for obtaining strain distributions and consequent carrier confinement potential changes in semiconductor strained wires and dots made of lattice‐mismatched materials. The inhomogeneous strain distribution modifies the confinement potentials locally, which causes carrier wave function localization. First, to obtain a fundamental strain distribution and band‐structure change semiquantitatively, analytical calculations are performed in simple, symmetrical structures such as an InP cylinder and an InP ball buried in GaAs or InGaP matrices assuming isotropic valence bands and isotropic elastic characteristics. Here, strain is found to exist in the surrounding matrices as well as in the wires and dots. This effect is peculiar to the strained wire and dot because in pseudomorphic strained layers there is no strain in surrounding matrices. Thus, the band structures are found to be greatly modified in the surrounding matrix as well as in the wire or dot. Hole effective masses at the band edge are also calculated by diagonalizing a 4×4 orbital strain Hamiltonian. Furthermore, to calculate the effects in a realistic structure, finite‐element‐method calculations are performed for a triangle‐shaped InP wire along the 〈110〉 direction, including anisotropic elastic characteristics. Calculated nonuniform strain within the wire is found to modify the confinement potential, which localizes electrons near the base. Valence subbands are largely split near the vertices. From these results, the strained wires and dots are found to be applicable for quantum wires and dots, in which the quantum confinement effect will be enhanced by the modified confinement potential due to the inhomogeneous strain. © 1994 American Institute of Physics.
Show PACS
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.60.Bs Mechanical and acoustical properties

Scaling of the volume pinning force in superconducting wires and tapes based on Bi2Sr2CaCu2Ox

J. Löhle, K. Mattenberger, O. Vogt, and P. Wachter

J. Appl. Phys. 76, 7446 (1994); http://dx.doi.org/10.1063/1.357971 (6 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
Silver‐sheathed Bi2Sr2CaCu2Ox wires and tapes were fabricated by the powder‐in‐tube method. The wires show critical current densities of about 18 000 A/cm2 in zero magnetic field and 5300 A/cm2 in a field of 23 T at 4.2 K, respectively. A detailed study of the critical current density as a function of the temperature and the magnetic field resulted in a scaling behavior of the derived volume pinning force FV, which approximately obeys the formula FV≊H∗h0.75(1−h)2.75. Here H∗ represents the irreversible field and h=H/H∗ is the scaling field. Further, the critical current densities of our textured tapes were measured. In zero magnetic field they reach critical current densities of about 43 000 A/cm2. In a magnetic field applied perpendicularly to the current direction the critical current density shows an anisotropic behavior with respect to the direction of the magnetic field. For a magnetic field of 23 T applied parallel to the tape plane the tapes reached critical current densities of about 15 000 A/cm2 at 4.2 K. In the unfavorable direction, the magnetic field is applied perpendicularly to the tape plane, the current density was reduced to 10 000 A/cm2. The volume pinning force in the tapes was investigated versus the magnetic field at 4.2 K and a power‐law behavior FV≊Hp with p=0.75 for H parallel and p=0.55 for H perpendicular to the tape plane was found. © 1994 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
84.71.Mn Superconducting wires, fibers, and tapes

The magnetic properties of R2(Fe1−xSix)17 compounds (R=Dy, Y)

D. M. Zhang, Y. H. Gao, B. M. Yu, C. Q. Tang, N. Tang, X. P. Zhong, W. G. Lin, F. M. Yang, and F. R. de Boer

J. Appl. Phys. 76, 7452 (1994); http://dx.doi.org/10.1063/1.357972 (4 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
The structures and magnetic properties of R2(Fe1−xSix)17 compounds (R=Dy, Y) were investigated by x‐ray phase analysis and magnetic measurements. It is shown that Si substitution for Fe leads to a phase transition at x=0.2, and that the mean iron magnetic moment μFe of R2(Fe1−xSix)17 compounds (R=Dy, Y) decreases as Si concentration x increases; moreover, there is a maximum of dependence Tc(x) at about x=0.16. It is found that the exchange interaction constant AFeFe in R2(Fe1−xSix)17 compounds (R=Dy, Y) increases with x increasing by means of mean‐molecular‐field analysis of Tc. © 1994 American Institute of Physics.
Show PACS
75.50.Bb Fe and its alloys
75.30.Gw Magnetic anisotropy

Model for calculating Tc of pluralistic magnetic component compounds

Y. H. Gao, D. M. Zhang, C. Q. Tang, B. M. Yu, W. D. Qin, Z. H. Lu, and F. M. Yang

J. Appl. Phys. 76, 7456 (1994); http://dx.doi.org/10.1063/1.357973 (5 pages)

Full Text: | Download PDF

Show Abstract
A coupling model of the pluralistic magnetic component R‐T intermetallic compounds (R denotes rare earth, T denotes transition metal) has been proposed by means of the mean‐molecular‐field analysis. Using the model, the Curie temperature Tc of (Sm1−xPrx)2Fe17 compounds has been calculated and the calculated values have been compared with the experimental values. It is found that the former are consistent with the later. © 1994 American Institute of Physics.
Show PACS
75.50.Gg Ferrimagnetics
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)

Influence of Ni additions on the low‐temperature magnetic properties of a Cu–1% Mn alloy

M. D. Sumption and E. W. Collings

J. Appl. Phys. 76, 7461 (1994); http://dx.doi.org/10.1063/1.357974 (7 pages)

Full Text: | Download PDF

Show Abstract
dc susceptibility and magnetization measurements were made on three alloys with the nominal compositions Cu–1% Mn, Cu–15% Ni, and Cu–1% Mn–15% Ni. dc susceptibility [χdc=C/(T+θW)] measurements were made with a Curie‐type balance from room temperature down to 77.2 K. Magnetization measurements consisted of M‐H loops at 4.2 and 1.37 K, and initial magnetization runs from room temperature down to 1.37 K. The results were analyzed in terms of an addition of Ni to Cu‐Mn. High‐temperature χdc data were used to find θW, C, and μeff (from C and the concentration), and it is found that these properties are influenced only to a minor extent by the Ni addition. At low temperatures, however, a suppression of the freezing temperature and an enhancement in the superparamagnetic signal are noticed for Cu‐Mn‐Ni as compared to Cu‐Mn. Finally, hysteretic loss and magnetization for the ternary at 4.2 K were compared to that of the Cu‐Ni and Cu‐Mn alloys in order to determine its suitability for use as matrix material in multifilamentary superconductive wire. © 1994 American Institute of Physics.
Show PACS
75.50.Lk Spin glasses and other random magnets
75.30.Hx Magnetic impurity interactions

Susceptibility of ErBa2Cu3O6 single crystal: A dipolar antiferromagnet

Y. Abulafia, J. Barak, and J. L. Peng

J. Appl. Phys. 76, 7468 (1994); http://dx.doi.org/10.1063/1.357975 (5 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
The susceptibility of an ErBa2Cu3O6 single crystal was measured at 2 K<T<100 K. The low‐temperature (T<10 K) data yield g∥=5.39 and g⊥=7.45. The shapes of the susceptibility curves are well explained by the dipolar fields, calculated for the Er3+ ions in the layered structure of the sample, and by a small contribution of exchange fields. Extending the calculations to the antiferromagnetic state of ErBa2Cu3O6 shows that this material is well described as a two‐dimensional dipolar antiferromagnet. The dipolar field calculations are also applied to DyBa2Cu3O6 and GdBa2Cu3O6 and are shown to be compatible with the magnetic structure of these materials. © 1994 American Institute of Physics.
Show PACS
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
74.72.-h Cuprate superconductors
75.30.Gw Magnetic anisotropy

Magnetic anisotropy and magnetization processes in 3:29 and 1:12 Nd(FeTi)‐based compounds

L. Pareti, A. Paoluzi, F. Albertini, M. R. Ibarra, L. Morellon, and P. A. Algarabel

J. Appl. Phys. 76, 7473 (1994); http://dx.doi.org/10.1063/1.357976 (5 pages) | Cited 11 times

Full Text: | Download PDF

Show Abstract
The temperature behavior of the magnetic anisotropy and magnetization processes in the tetragonal Nd(FeTi)12 and monoclinic Nd3(FeTi)29 have been studied and compared. Both compounds are characterized by the occurrence of temperature‐induced spin reorientation transitions, as well as field‐induced magnetization processes of different types, which have been interpreted as first‐order magnetization process. In both systems the resultant anisotropy of Nd favors the occurrence of an easy magnetization direction out of the principal axes at low temperature. On the contrary the overall Fe sublattice anisotropy favors the tetragonal c‐axis in the 1:12 and seems to prefer the monoclinic a‐axis in the 3:29 compound. © 1994 American Institute of Physics.
Show PACS
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Electrical characteristics of (100), (111), and randomly aligned lead zirconate titanate thin films

Chang Jung Kim, Dae Sung Yoon, Joon Sung Lee, Chaun Gi Choi, Wong Jong Lee, and Kwangsoo No

J. Appl. Phys. 76, 7478 (1994); http://dx.doi.org/10.1063/1.358467 (5 pages) | Cited 25 times

Full Text: | Download PDF

Show Abstract
(100), (111), and randomly aligned lead zirconate titanate thin films on Pt/Ti/Corning 7059 glass substrates were prepared using a sol‐gel method. The thin films, having different alignments, were fabricated by different drying conditions for pyrolysis. The hysteresis loop and the capacitance‐voltage characteristics were investigated using a standardized ferroelectric test system. The dielectric constant and the current‐voltage characteristics of the films were investigated using an impedance analyzer and a pA meter, respectively. The microstructure was investigated using scanning electron microscopy. The (100) aligned film showed a relatively larger dielectric constant than the (111) and the randomly aligned films. The films aligned in particular directions showed higher hysteresis parameters than the randomly aligned film. The leakage current densities of the films aligned in particular directions were lower than that of the randomly aligned film. © 1994 American Institute of Physics.
Show PACS
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
73.61.Ng Insulators

Synchrotron radiation x‐ray absorption of ion bombardment induced defects on diamond (100)

L. J. Huang, I. Bello, W. M. Lau, S.‐T. Lee, P. A. Stevens, and B. D. DeVries

J. Appl. Phys. 76, 7483 (1994); http://dx.doi.org/10.1063/1.357977 (4 pages) | Cited 13 times

Full Text: | Download PDF

Show Abstract
The surface defect structures on diamond (100) surfaces induced by 500 eV neon ion bombardment and by subsequent annealing were studied in situ with x‐ray absorption near‐edge structure (XANES) spectroscopy using 250–800 eV synchrotron radiation and with low energy electron diffraction. Ex situ x‐ray photoemission spectroscopy (XPS) was also used to characterize the defective layer. Significant changes in the XANES spectra were identified for the defects induced by ion bombardment and subsequent annealing. The diamond discrete exciton absorption at 289.0 eV was clearly suppressed even at the lowest ion fluence used in this study, i.e., 3×1014/cm2, and no such exciton could be observed at 7×1014/cm2. However, the changes in the multi‐maxima shape‐resonance absorption structure in the range of 290–310 eV indicated that a loss of the diamond long range order required a fluence of 1×1015/cm2. The structural changes were also manifested by the transformation of gap state absorption typical of clean 2×1 surfaces to the π∗ absorption typical of amorphous carbon. XPS showed that the defective layer was about 2 nm thick. For all samples prepared with the bombardment conditions in the study, both the XANES and XPS data also indicated no phase transformation from defective layers to graphite even after annealing to a temperature of 1100 °C. © 1994 American Institute of Physics.
Show PACS
78.70.Dm X-ray absorption spectra
61.80.Jh Ion radiation effects
68.35.Dv Composition, segregation; defects and impurities

Investigation of the structure of barium titanate thin films by Raman spectroscopy

Lawrence H. Robins, Debra L. Kaiser, Lawrence D. Rotter, Peter K. Schenck, Gregory T. Stauf, and Daniel Rytz

J. Appl. Phys. 76, 7487 (1994); http://dx.doi.org/10.1063/1.357978 (12 pages) | Cited 52 times

Full Text: | Download PDF

Show Abstract
Raman spectroscopy was used to examine the structure of barium titanium oxide thin films grown by metal‐organic chemical vapor deposition (MOCVD) and laser‐assisted deposition. The spectra were compared with the spectra of a ceramic specimen and a single crystal. Raman peaks specific to the tetragonal ferroelectric phase of BaTiO3 were seen in the spectra of several films. Other Raman peaks were ascribed to impurity (non‐BaTiO3) phases in the films or to the substrates (fused quartz, MgO). Some of the Raman peaks showed a strong polarization dependence. The MOCVD films were also characterized by x‐ray diffraction, energy‐dispersive x‐ray spectroscopy, and transmission electron microscopy. The film‐to‐film variation of the strength of BaTiO3 features in the Raman spectrum, relative to impurity‐phase features, was qualitatively consistent with the x‐ray diffraction and electron microscopy results. Spatially resolved Raman measurements showed that the structure of the laser‐deposited film varies significantly over the deposited area. The temperature dependencies of the Raman spectra of two MOCVD films were examined in the 25–175 °C range. Raman peaks due to the tetragonal phase of BaTiO3 were observed at temperatures well above the Curie temperature of bulk single‐crystal BaTiO3 (132 °C). This observation suggests that the tetragonal ferroelectric phase is stabilized by an anisotropic film‐substrate interaction that gives rise to a two‐dimensional stress in the plane of the film. © 1994 American Institute of Physics.  
Show PACS
78.30.Hv Other nonmetallic inorganics
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Impurity optical absorption of Cd1−xHgxGa2Se4:Co2+ single crystals

Yang‐Lae Lee, Chang‐Dae Kim, and Wha‐Tek Kim

J. Appl. Phys. 76, 7499 (1994); http://dx.doi.org/10.1063/1.357980 (7 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
Structural and optical properties of Cd1−xHgxGa2Se4 and Cd1−xHgxGa2Se4:Co2+ single crystals grown by the chemical transport reaction method have been investigated. It has been found that these single crystals have a defect chalcopyrite structure and a direct optical energy gap. It has been seen that the optical energy gap decreases as a composition x increases and as a cobalt impurity is introduced. The temperature dependence of the optical energy gap is well presented by the Varshni equation. Impurity optical absorption peaks due to a cobalt atom were observed in the optical‐absorption measurements of Cd1−xHgxGa2Se4:Co2+ single crystals. It has been analyzed that the impurity optical‐absorption peaks are attributed to the electronic transition between the split energy levels of a Co2+ ion occupying a cubic Td symmetry site of the host lattice. © 1994 American Institute of Physics.
Show PACS
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors

Magneto‐optical properties of Ba‐ferrite particulate media

M. Kishimoto, Y. Sakurai, and T. Ajima

J. Appl. Phys. 76, 7506 (1994); http://dx.doi.org/10.1063/1.357981 (4 pages) | Cited 12 times

Full Text: | Download PDF

Show Abstract
Magneto‐optical properties of Ba‐ferrite particulate media were investigated. Faraday rotation and reflectivity were measured for different thicknesses of the magnetic layer, and compared with the predictions of a simple analytical model. The magneto‐optical output of the media measured using a laser showed a maximum at a particular thickness. The dependence of the magneto‐optical output on thickness is explained on the basis of equations approximating the Faraday rotation and the reflectivity. © 1994 American Institute of Physics.  
Show PACS
78.20.Ls Magneto-optical effects
75.50.Dd Nonmetallic ferromagnetic materials
Page 2 of 4 Pages Previous Page Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close