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1 Apr 1998

Volume 83, Issue 7, pp. 3453-3938

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Oxidation and roughening of silicon during annealing in a rapid thermal processing chamber

B. Mohadjeri, M. R. Baklanov, E. Kondoh, and K. Maex

J. Appl. Phys. 83, 3614 (1998); http://dx.doi.org/10.1063/1.366629 (6 pages) | Cited 7 times

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Silicon wafers were annealed at 1100 °C in nitrogen flowing ambient, using a conventional rapid thermal processing system operating at atmospheric pressure. Subsequently, silicon oxidation and the resulting surface morphology following chemical etching of the oxide film were studied. According to atomic force microscopy analysis, a significant amount of roughening occurs on the silicon surface after the high temperature anneal in nitrogen. However, by adding 10% oxygen to the nitrogen ambient, the average surface roughness was reduced by a factor of ∼ 3. Ellipsometry measurements were performed to study silicon oxidation following annealing. It was shown that the ellipsometric characteristics of the surface after removal of the oxide layers can be correlated to generation of surface roughness. A close agreement between the experimental results and theoretical calculations was obtained with respect to the oxidation induced surface roughening. © 1998 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Mq Oxidation
61.72.Cc Kinetics of defect formation and annealing
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

Step structure and ordering in GaInP

S. H. Lee and G. B. Stringfellow

J. Appl. Phys. 83, 3620 (1998); http://dx.doi.org/10.1063/1.366580 (6 pages) | Cited 17 times

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Steps are known to affect the ordering phenomenon in GaInP; [110] steps assist ordering and [110] steps retard ordering. However, the mechanism leading to this behavior has not been determined. In this paper, the step spacing is used as a semiquantitative indicator of the attachment of adatoms at the step edge for organometallic vapor phase epitaxial growth on singular (001) GaAs substrates. The step spacing and degree of order in the epitaxial layers have been studied as a function of temperature and the flow rate of the P precursor for both tertiarybutylphosphine (TBP) and phosphine. As the flow rate of the P precursor is lowered beyond a certain critical point, both the degree of order and the step spacing are seen to decrease together. The behavior is the same for TBP and for PH3. Similarly, as the growth temperature is increased above a certain value, the step spacing and order parameter decrease together. This suggests a relationship between adatom attachment at steps and the ordering mechanism. Possible explanations for these phenomena are explored. At low temperatures, the degree of order is reduced and the step spacing decreases exponentially. The data suggest that the reduction in the surface diffusion coefficient with decreasing temperature is the main factor acting to reduce both the step spacing and the degree of order. However, the increasing adatom sticking coefficient at both step edges expected at low temperatures will affect both phenomena as well. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.35.Fx Diffusion; interface formation

Stacking effects on dielectric properties of sol-gel derived Pb(Zr0.53Ti0.47)O3/PbTiO3 thin films

Ki Hyun Yoon, Ji Hwan Shin, Jeong Hwan Park, and Dong Heon Kang

J. Appl. Phys. 83, 3626 (1998); http://dx.doi.org/10.1063/1.366581 (4 pages) | Cited 17 times

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A thin film multilayer structure consisting of Pb(Zr0.53Ti0.47)O3(PZT) and PbTiO3(PT) were fabricated by a sol-gel process. The effects of the number of PZT/PT layers upon microstructure and dielectric characteristics were investigated. For a pure PZT thin layer annealed at 600 °C, the microstructure observed was a rosette type, whereas the insertion of PT interlayers yielded thin films with homogeneous grain distribution regardless of the number of PZT/PT layers. With increasing number of PZT/PT layers, the leakage current density and coercive field effectively decreased, while the dielectric constant increased. Loss tangent and fixed charge were found to be independent of the number of PZT/PT layers. These results are possibly explained by the enhanced crystallization resulting from the introduction of large number of nucleation sites in the multilayer film, and by the stacking of stable and dense PZT/PT layers. The thin film composed of three PZT/PT layers with a thickness of ∼ 450 nm exhibited dielectric constant of 1000, remnant polarization of 20 μC/cm2, coercive field of 40 kV/cm, and tan δ of 0.03. The relaxorlike ferroelectric behavior was observed with an increasing number of PZT/PT layers. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization
77.22.Gm Dielectric loss and relaxation
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

X-ray interference effect as a tool for the structural investigation of GaInAs/InP multiple quantum wells

T. Marschner, J. Brübach, C. A. Verschuren, M. R. Leys, and J. H. Wolter

J. Appl. Phys. 83, 3630 (1998); http://dx.doi.org/10.1063/1.366582 (8 pages) | Cited 6 times

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We present x-ray diffraction (XRD) investigations of the structure of nominally lattice-matched GaInAs/InP multiple quantum well (MQW) structures grown by chemical beam epitaxy (CBE). To obtain information about the individual MQW layers and the interface structure we make use of the x-ray interference effect between two layers of equal lattice constant but different layer thickness separated by ultrathin strained (interfacial) layers. This effect predicted by the dynamical diffraction theory provides a powerful tool to quantitatively investigate ultrathin single quantum well structures and monolayer thin interfaces as well as MQW structures. For a given switching sequence during CBE growth, we determine the interface structure of GaInAs/InP MQW structures within the limits given by XRD theory. Additionally we found that an As gradient from the GaInAs quantum well layers into the InP barrier layers is present. The influence of the substrate off-orientation, the growth rate, and the group V flux in the InP barriers on the total amount of strain incorporated into the InP layers is shown. The obtained results indicate that the mechanism of As incorporation into InP layers is similar to the mechanism observed for the As incorporation into (qua)ternary GaxIn1−xAsyP1−y layers. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.Ct Interface structure and roughness
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Scanning tunneling microscopy study on the surface and interface of Si(111)/SiO2 structures

Ken Fujita, Heiji Watanabe, and Masakazu Ichikawa

J. Appl. Phys. 83, 3638 (1998); http://dx.doi.org/10.1063/1.366579 (5 pages) | Cited 17 times

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Scanning tunneling microscopy was used to investigate the surface and interface of Si(111)/SiO2 structures. The oxide thickness ranged from 0.3 to 1.7 nm. The surface was observed using a sample bias larger than 4.0 V. Fourier transform spectra of the surface images showed clear seventh order spots originating from the Si(111)7×7 reconstruction, indicating that 2.7 nm periodicity of the reconstruction remains on the oxide surface. At a sample bias of less than 4.0 V, a Si(111)/SiO2 interface was observed when 0.3-nm-thick oxide was partially left on the Si surface. © 1998 American Institute of Physics.
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78.30.-j Infrared and Raman spectra
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Ct Interface structure and roughness
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Backscattering of slow positrons from semi-infinite aluminum

N. Bouarissa, A. B. Walker, and H. Aourag

J. Appl. Phys. 83, 3643 (1998); http://dx.doi.org/10.1063/1.366583 (6 pages) | Cited 10 times

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Monte Carlo simulation for 1–10 keV positron backscattering from semi-infinite aluminum with normal angle of incidence is reported. The elastic scattering cross sections have been obtained from the modified Rutherford differential cross section where the numerical coefficient in the atomic screening parameter is taken to be variable. To model inelastic scattering, we have investigated for the first time the effects of continuous slowing down through collisions with conduction electrons. Attention has also been paid to effects of changing the angle of incidence. Our simulated results and the available experimental data are found to be in reasonable agreement, and show that the energy dependence of the backscattered fractions can be fitted with a simple function: B(E) = 0.0187997 ln E+0.102644. This suggests that both the transport model and the scattering cross sections used in the present work are reliable. © 1998 American Institute of Physics.
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79.20.Kz Other electron-impact emission phenomena
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
61.80.Fe Electron and positron radiation effects
61.82.Bg Metals and alloys

Observation of near-surface electrically active defects in n-type 6H–SiC

J. P. Doyle, A. Schöner, N. Nordell, A. Galeckas, H. Bleichner, M. K. Linnarsson,, J. Linnros, and B. G. Svensson

J. Appl. Phys. 83, 3649 (1998); http://dx.doi.org/10.1063/1.367147 (3 pages)

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In n-type 6H–SiC epitaxial layers grown by vapor phase epitaxy, we find that in contrast to the majority of the epitaxial layer, where electrically active defects are observed with a concentration less than 1×10−13 cm−3, a region near the front surface contains defects with concentrations approaching 1014 cm−3. A relationship between the near-surface defects and metallic impurities is suggested by a Ti concentration of 1×1016 cm−3 in this region. The high concentration of near surface defects is found to significantly reduce the carrier lifetime. © 1998 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Le Other inorganic semiconductors
81.05.Hd Other semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.35.Dv Composition, segregation; defects and impurities
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Reduction of photoscission of σ bonds in polysilanes by fullerene doping

Shinsuke Ninomiya, Yoji Ashihara, Yoshikazu Nakayama, Kunio Oka, and Robert West

J. Appl. Phys. 83, 3652 (1998); http://dx.doi.org/10.1063/1.366584 (4 pages) | Cited 7 times

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We report here an effective reduction of photoscission of σ bonds in polysilanes by C60 doping. The temporal variation of photoluminescence in polysilanes has been measured as a function of a doping amount of C60. The results indicate that the photoscission of σ bonds is related to a photogenerated electron-hole pair rather than a hole or an electron. The energy released when the electron-hole pair recombines nonradiatively is more likely required in addition to the thermal energy to scissor σ bonds. The C60 doping does not affect the activation energy of the photoscission process but decreases the photoscission cross-section. It is also demonstrated that the photoluminescence quenching by the C60 doping is observed for polysilanes not only with aromatic side groups but also with saturated hydrocarbon side groups. © 1998 American Institute of Physics.
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78.55.Kz Solid organic materials
61.41.+e Polymers, elastomers, and plastics
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
71.55.Jv Disordered structures; amorphous and glassy solids
72.80.Rj Fullerenes and related materials
72.40.+w Photoconduction and photovoltaic effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Scattering of electrons at threading dislocations in GaN

Nils G. Weimann, Lester F. Eastman, Dharanipal Doppalapudi, Hock M. Ng, and Theodore D. Moustakas

J. Appl. Phys. 83, 3656 (1998); http://dx.doi.org/10.1063/1.366585 (4 pages) | Cited 253 times

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A model to explain the observed low transverse mobility in GaN by scattering of electrons at charged dislocation lines is proposed. Filled traps along threading dislocation lines act as Coulomb scattering centers. The statistics of trap occupancy at different doping levels are investigated. The theoretical transverse mobility from Coulomb scattering at charged traps is compared to experimental data. Due to the repulsive potential around the charged dislocation lines, electron transport parallel to the dislocations is unaffected by the scattering at charged dislocation lines. © 1998 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
73.23.-b Electronic transport in mesoscopic systems

1/f noise investigations in small channel length amorphous silicon thin film transistors

J. Rhayem, M. Valenza, D. Rigaud, N. Szydlo, and H. Lebrun

J. Appl. Phys. 83, 3660 (1998); http://dx.doi.org/10.1063/1.366586 (8 pages) | Cited 15 times

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Conduction and low-frequency noise are analyzed in hydrogenated amorphous thin film transistors with small channel length. From current–voltage characteristics a set of conduction parameters is extracted pointing out parasitic resistances in series with the active channel. The low-frequency noise behavior is studied by means of the small equivalent circuit of the device. Intrinsic channel noise is separated from access resistance noise. Channel noise variations versus device biases agree with Hooge’s theory (carrier mobility fluctuations) but the noise levels are greater than in crystalline metal-oxide-semiconductor transistors. For high drain current 1/f noise in access series resistances prevails and becomes the main noise source. So, the results show the important part taken by these resistances in conduction and noise. Some comments for the design of thin film transistors are given. © 1998 American Institute of Physics.
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85.30.Tv Field effect devices
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.50.Td Noise processes and phenomena
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Improvement in buried silicon nitride silicon-on-insulator structures by fluorine-ion implantation

C. M. S. Rauthan, G. S. Virdi, B. C. Pathak, and A. Karthigeyan

J. Appl. Phys. 83, 3668 (1998); http://dx.doi.org/10.1063/1.366587 (10 pages) | Cited 4 times

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As an effort to improve buried Si3N4–Si interfaces in silicon-on-insulator (SOI) structures, fluorine was implanted either before or after the synthesis of buried silicon nitride layers by high dose nitrogen ion implantation. In these synthesized SOI structures, the thickness of Si overlayer and the buried silicon nitride layer was found to be 2400±25 and 1725±25 Å, respectively. Auger electron spectroscopy depth profile analysis illustrates that the fluorine ion implantation in the SOI structures modifies the distribution of nitrogen that results in better stoichiometry of the buried silicon nitride layers and abrupt Si3N4–Si interfaces. Current–voltage and high frequency capacitance–voltage characteristics were measured, and electrical breakdown measurements were performed on metal-nitride-silicon (MNS) structures, fabricated after removing the Si overlayer in the SOI structures. In the fluorine-implanted SOI specimens, the buried Si3N4 layers show a higher breakdown field strength of 4.4–5.2 MV/cm as compared to 3.5–4.0 MV/cm in the nonfluorine-implanted one. The capacitance–voltage analysis of the MNS capacitors reveals that the buried Si3N4–Si substrate interface exhibits a better quality with reduced fixed insulator charge and interface state densities after the fluorine ion implantation. Midgap interface state density at the buried Si3N4–Si substrate interface was as low as 1.48×1011 cm−2 eV−1 after the fluorine implantation, which is comparable to that of silicon nitride films deposited on silicon by the conventional low pressure chemical vapor deposition technique. The role of fluorine in improving the basic electrical properties of these SOI structures has been discussed. © 1998 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.up Other materials
73.61.Ng Insulators
61.72.S- Impurities in crystals
77.22.Jp Dielectric breakdown and space-charge effects

Band gap energies of bulk, thin-film, and epitaxial layers of CuInSe2 and CuGaSe2

S. Chichibu, T. Mizutani, K. Murakami, T. Shioda, T. Kurafuji, H. Nakanishi, S. Niki, P. J. Fons, and A. Yamada

J. Appl. Phys. 83, 3678 (1998); http://dx.doi.org/10.1063/1.366588 (12 pages) | Cited 45 times

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Band gap and excitonic resonance energies of high-quality bulk single crystals, polycrystalline thin films, and epitaxial layers of CuInSe2 and CuGaSe2 were determined as a function of temperature by means of photoreflectance, optical absorption (OA), and photoluminescence measurements. OA spectra were fit including excitonic absorption from low temperature up to room temperature (RT). The band gap energy of 1.032 eV and free exciton (FE) resonance energy of 1.024 eV were obtained at RT for strain-free CuInSe2 giving an exciton binding energy of 7.5 meV. The band gap energy of both CuInSe2 and CuGaSe2 was found to be essentially independent of the molar ratio of Cu to group-III atom (Cu/III) for near-stoichiometric and Cu-rich samples. The disappearance of the FE absorption in the In-rich (Cu/In<0.88) CuInSe2 thin films was explained by plasma screening of Coulomb interactions. A slight decrease in the band gap energy of the In-rich films was attributed to a degradation of film quality such as high-density defects, grains, and structural disordering. The fundamental band gap energy in strained CuInSe2 and CuGaSe2 epilayers was shown to decrease due to in-plane biaxial tensile strain. © 1998 American Institute of Physics.
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78.66.Li Other semiconductors
78.20.-e Optical properties of bulk materials and thin films
78.55.Hx Other solid inorganic materials
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.40.Fy Semiconductors

Analysis of Fermi level pinning and surface state distribution in InAlAs heterostructures

W. Y. Chou, G. S. Chang, W. C. Hwang, and J. S. Hwang

J. Appl. Phys. 83, 3690 (1998); http://dx.doi.org/10.1063/1.366593 (6 pages) | Cited 6 times

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The band gaps, built-in electric field, and surface Fermi level of a series In1−xAlxAs surface-intrinsic-n+ (SIN+) structures have been studied by photoreflectance at room temperature. The samples were grown by molecular beam epitaxy with an undoped layer thickness of 1000 Å. Our study indicates that, in contrast to GaAs and AlGaAs, the surface Fermi level is not pinned at midgap over aluminum concentration of 0.42–0.57. The pinning position is composition dependent. The undoped layer was subsequently etched to 800, 600, 400, and 200 Å. Different chemical solutions were used in the etching process and the built-in electric field is found independent of the etching process. Although the surface Fermi level, in general, varies with the undoped layer thicknesses, there exists, for each Al concentration, a certain range of thicknesses within which the surface Fermi level is weakly pinned. From the dependence of electric field and surface Fermi level on the undoped layer thickness, we conclude that the surface states distribute over two separate regions within the energy band gap and the densities of surface states are as low as 1.36±0.05×1011 cm−2 eV−1 for the distribution near the conduction band and 4.38±0.05×1011 cm−2 eV−1 for the distribution near valence band. © 1998 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.20.At Surface states, band structure, electron density of states
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
78.20.-e Optical properties of bulk materials and thin films

Size and temperature dependence of electrical resistance and thermoelectric power of Bi2Te2Se1 thin films

V. Damodara Das and S. Selvaraj

J. Appl. Phys. 83, 3696 (1998); http://dx.doi.org/10.1063/1.366594 (7 pages) | Cited 6 times

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Thin films of Bi2Te2Se1 of various thicknesses have been deposited on clean glass plates using the flash evaporation technique. Electrical resistance and thermoelectric power measurements have been carried out on these films in the temperature range 300–485 K. The thickness dependences of electrical resistivity and thermoelectric power of the films have been analyzed using the effective mean-free path model. The thickness dependence of activation energy of the films is explained by Seto’s polycrystalline model. Various material parameters such as mean-free path and Fermi energy have been calculated from the analysis of experimental data. The thermoelectric power factor of the films has been calculated using the measured electrical resistivity and thermoelectric power values. © 1998 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
72.80.Jc Other crystalline inorganic semiconductors
73.50.Lw Thermoelectric effects
72.20.Pa Thermoelectric and thermomagnetic effects

A comparative study on the electrical conduction mechanisms of (Ba0.5Sr0.5)TiO3 thin films on Pt and IrO2 electrodes

Cheol Seong Hwang, Byoung Taek Lee, Chang Seok Kang, Jin Won Kim, Ki Hoon Lee, Hag-Ju Cho, Hideki Horii, Wan Don Kim, Sang In Lee, Young Bum Roh, and Moon Yong Lee

J. Appl. Phys. 83, 3703 (1998); http://dx.doi.org/10.1063/1.366595 (11 pages) | Cited 108 times

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Electrical conduction mechanisms for Pt/(Ba0.5Sr0.5)TiO3 (BST)/Pt, IrO2/BST/IrO2, and Pt/BST/IrO2 capacitors were studied. The Pt/BST/Pt capacitor shows a Schottky emission behavior with interface potential barrier heights of about 1.5–1.6 eV. The barrier height is largely determined by the surface electron trap states of the BST. The IrO2/BST interface shows an ohmic contact nature due to the elimination of the surface trap states as the result of the formation of strong chemical bonds between the IrO2 and BST which results in the Poole–Frenkel emission conduction mechanism. Pt/BST/IrO2 capacitor shows Schottky emission behavior and a positive temperature coefficient of resistivity (PTCR) effect depending on the bias polarity. The electron trap states at the Pt/BST interface and the positive space charges within the carrier depletion layer result in the PTCR effect. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
73.30.+y Surface double layers, Schottky barriers, and work functions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
77.22.Jp Dielectric breakdown and space-charge effects
73.50.Fq High-field and nonlinear effects
73.20.At Surface states, band structure, electron density of states

Observation of a geometrical barrier in YBa2Cu3O6.95 single crystals

M. W. Gardner, S. A. Govorkov, R. Liang, D. A. Bonn, J. F. Carolan, and W. N. Hardy

J. Appl. Phys. 83, 3714 (1998); http://dx.doi.org/10.1063/1.366596 (6 pages) | Cited 7 times

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The remnant and in-field magnetic field distributions of two crystals of YBa2Cu3O6.95, one with a single twin boundary and one completely untwinned, were observed using a nondestructive magneto-optic technique. Geometrical barrier effects on the flux penetration of both samples were found to be present. Two distinct penetrating field patterns were observed resulting from the different pinning characteristics of the samples. A concentration of penetrating vortices in the center of one sample indicated an extremely low degree of pinning. A comparison was made between experimental flux penetration profiles from both samples and those calculated using a theoretical model for a thin strip superconductor. A single twin boundary in the extremely low pinning crystal was also observed to be a barrier to transverse vortex motion. © 1998 American Institute of Physics.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
61.72.Mm Grain and twin boundaries
74.72.-h Cuprate superconductors
78.20.Ls Magneto-optical effects

Spin valves exchange biased by Co/Ru/Co synthetic antiferromagnets

J. L. Leal and M. H. Kryder

J. Appl. Phys. 83, 3720 (1998); http://dx.doi.org/10.1063/1.366597 (4 pages) | Cited 56 times

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Spin valves exchange biased by a Co/Ru/Co synthetic antiferromagnet were fabricated and characterized. Room temperature measurements show giant-magnetoresistance ratios above 5% and that fields in excess of 5000 Oe are needed to saturate the synthetic antiferromagnet. The saturation field of the synthetic antiferromagnet is higher than 3000 Oe at 250 °C, which yields the possibility of observing the spin valve effect at very high temperatures. The transfer curve of the patterned structure shows a much weaker magnetostatic coupling than that observed in standard spin valves of identical dimensions. This is a consequence of the particular magnetic configuration of the synthetic antiferromagnet, which promotes an almost vanishing magnetostatic field. © 1998 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.61.At Metal and metallic alloys
75.47.De Giant magnetoresistance
75.50.Ee Antiferromagnetics
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Microstructural modification in Co/Cu giant-magnetoresistance multilayers

C. Christides, S. Stavroyiannis, N. Boukos, A. Travlos, and D. Niarchos

J. Appl. Phys. 83, 3724 (1998); http://dx.doi.org/10.1063/1.366598 (7 pages) | Cited 14 times

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Three different classes of [Co/1.1 nm/Cu/2.1 nm]30 multilayers were grown by magnetron sputtering deposition. The effect of magnetostatic interactions on the giant-magnetoresistance (GMR) and magnetic properties are examined in relation to the induced changes in the film microstructure as it is varied by: (i) the substrate surface roughness and (ii) the effect of thermal isolation of the Si(100) substrate from the cooling plate during deposition. A remarkable variation in shape and magnitude of GMR, and in the magnetic (M-H) loops, is observed for the three classes of films. It is found that there are three characteristic features in every sample that vary systematically: (i) The (ΔR/R)max ratio. (ii) The magnetic field range where a GMR loop reaches its minimum value. (iii) The (M-H) loops that vary from the characteristic antiferromagnetic to a typical ferromagnetic loop shape. Two well-separated grain size distributions below and above 12 nm were found from transmission electron microscopy. The smaller grains are associated with the appearance of a considerable fraction of ferromagnetically coupled regions in the multilayer. © 1998 American Institute of Physics.
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75.47.De Giant magnetoresistance
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
75.50.Cc Other ferromagnetic metals and alloys
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.35.Ct Interface structure and roughness

Alternating current susceptibility study of a two-phase nanocomposite Fe88Nd6B6 alloy in the temperature range 77–990 K

J. S. Fang, M. S. Leu, and T. S. Chin

J. Appl. Phys. 83, 3731 (1998); http://dx.doi.org/10.1063/1.366599 (7 pages)

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Alternating current-initial susceptibility (χac) studies on as-spun amorphous and rapid-thermal-annealed two-phase nanocomposite Fe88Nd6B6 alloy ribbons are performed at 77–990 K. A novel means of quantitatively estimating the amount of the residual amorphous phase in heated ribbons is also derived from the χac measurement. Experimental results indicate that the amount of the residual amorphous phase decreases with an increasing heating temperature. The residual amount is 28.87 vol % after the amorphous ribbons are heated to 773 K, and then becomes undetectable when the temperature reaches heating to 923 K. The amount of the residual amorphous phase can be described as follows: R (in vol %) = 0.857T/(T–753)–4.392, where T denotes the heating temperature above 753 K. In addition, the full width at half-maximum of the χac peak corresponding to the Curie temperature of the Nd2Fe14B phase correlates well with the extent of exchange coupling interaction between the hard and soft nanophases. Furthermore, the spin reorientation transition temperature of the Nd2Fe14B nanophase in the two-phase nanocomposite Fe88Nd6B6 alloy shifts to 110 K, i.e., significantly lower than 135 K for the Nd2Fe14B single crystal. This shift is attributed to the exchange coupling effect between the nanophases. © 1998 American Institute of Physics.
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75.50.Ww Permanent magnets
75.30.Cr Saturation moments and magnetic susceptibilities
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
75.30.Et Exchange and superexchange interactions

Ferromagnetic resonance modes in coupled layers with cubic magnetocrystalline anisotropy

A. Layadi

J. Appl. Phys. 83, 3738 (1998); http://dx.doi.org/10.1063/1.366600 (6 pages) | Cited 4 times

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The ferromagnetic resonance (FMR) relations of an interfacially coupled two-layer magnetic system have been derived. In the case modeled here, the two films are assumed to be characterized by uniaxial and cubic magnetocrystalline anisotropies. Analytical expressions for the resonance condition have been found for a strong coupling case for both ferromagnetic and antiferromagnetic coupling. The FMR modes have also been studied as a function of the coupling strength. In the strong coupling cases, the system behaves as a single thin film with effective cubic and uniaxial anisotropy fields and effective magnetogyric ratios. When the coupling is antiferromagnetic a “spin-flop” can occur beyond a critical coupling value Kcrit. There will be a discontinuity in mode position. The critical coupling and field have been derived. This analysis could be used to study experimentally the nature and the strength of the magnetic coupling in systems with cubic and/or uniaxial magnetocrystalline anisotropies. © 1998 American Institute of Physics.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.30.Gw Magnetic anisotropy
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Theory of a high frequency magnetic tunable filter and phase shifter

R. J. Astalos and R. E. Camley

J. Appl. Phys. 83, 3744 (1998); http://dx.doi.org/10.1063/1.366601 (6 pages) | Cited 23 times

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Microwave propagation in a layered dielectric/ferromagnet were explored in the past. Previous studies, however, made use of an approximation to the full permeability tensor in the ferromagnet. This approximation fails in a frequency range where the structure can act as a band pass filter. Here we seek to verify the behavior in the predicted band pass region using the full permeability tensor. We also explore the use of the layered structure in two devices: a tunable band pass filter and an adjustable phase shifter. © 1998 American Institute of Physics.
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85.70.Ay Magnetic device characterization, design, and modeling
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
84.30.Vn Filters
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
84.40.-x Radiowave and microwave (including millimeter wave) technology
85.70.-w Magnetic devices

Spin reorientation transition due to thickness ratio variation in EuBi2Fe5O12/Y3Fe5O12 multilayer films—ferrimagnetic resonance studies

S. E. Lofland, S. M. Bhagat, V. V. Srinivasu, R. Ramesh, B. M. Simion, and G. Thomas

J. Appl. Phys. 83, 3750 (1998); http://dx.doi.org/10.1063/1.366602 (4 pages)

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We present the results of an investigation into ferrimagnetic resonance at room temperature in superlattice heterostructures with alternating layers of Y3Fe5O12 and EuBi2Fe5O12 grown by pulsed-laser deposition. We find that in the Y3Fe5O12 layer, the spins always prefer to lie in the plane. In the EuBi2Fe5O12 layer, on the other hand, the spin direction switches from normal to the film plane to in-plane as its thickness falls below that of the Y3Fe5O12 layer. © 1998 American Institute of Physics.
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75.50.Gg Ferrimagnetics
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
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Shear response of lead zirconate titanate piezoceramics

V. Mueller and Q. M. Zhang

J. Appl. Phys. 83, 3754 (1998); http://dx.doi.org/10.1063/1.366603 (8 pages) | Cited 34 times

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The piezoelectric shear strain S5 of several commercial lead zirconate titanate (PZT) piezoceramics was evaluated under the nonresonant condition in a sinusoidal ac-field E1(t) applied perpendicular to the poling direction. Results obtained on donor doped (soft PZT) and acceptor doped (hard PZT) ceramics are compared. At fields sufficiently below the limiting field Elim necessary to electrically depole the sample, we find a linear, nonhysteretic relationship between S5 and the polarization P1. In soft PZT ceramics, the effective piezoelectric shear coefficient d15 = S5/E1 shows a pronounced ac-field dependence which was fitted according to d15(E1) = dlin[1+(dnlE1)α] with α ≈ 1.2. The results indicate that irreversible motion of non-180° walls causes the nonlinearity of PZT and the contribution of 180° walls to the linear and nonlinear coefficients is negligible. The analysis of the relationship between linear and nonlinear coefficients obtained at different ceramic systems suggests that there exists another extrinsic contribution to the permittivity in PZT which may not be attributed to domain wall motion but may be responsible to the dielectric dispersion at microwave frequencies. © 1998 American Institute of Physics.
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77.65.Bn Piezoelectric and electrostrictive constants
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
77.22.Ej Polarization and depolarization
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis

Translational vibrations of domain structure in ferroelectrics

A. S. Sidorkin

J. Appl. Phys. 83, 3762 (1998); http://dx.doi.org/10.1063/1.366604 (7 pages) | Cited 6 times

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The collective vibrations of domain boundaries connected with a local change of a domain width in ferroelectrics with the 180° domain structure are investigated. It is shown that there exist two branches of such vibrations: of quasiacoustic and quasioptic type. The influence of the piezoelectric effect on the change of the dispersion law of these vibrations was investigated. The influence of the spectrum of translational vibrations of domain boundaries on the frequency dispersion of dielectric permeability of ferroelectrics was also determined. © 1998 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
63.20.-e Phonons in crystal lattices
77.65.-j Piezoelectricity and electromechanical effects

Effect of reflectivity at the interface of oxide layer on transverse mode control in oxide confined vertical-cavity surface-emitting lasers

Yong-Zhen Huang

J. Appl. Phys. 83, 3769 (1998); http://dx.doi.org/10.1063/1.366605 (4 pages) | Cited 4 times

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The transverse mode control in oxide confined vertical-cavity surface-emitting lasers is discussed by modeling the dielectric aperture as a uniform waveguide and an extra reflectivity at the oxide layer. The phase of the extra reflectivity and the refractive index step can be adjusted to change the mode threshold gain. We calculate the lateral refractive index step from the mode wavelength difference between aperture and perimeter modes, and compare it with that obtained from the weighted average index. The mode reflectivity in terms of the lateral optical confinement factor at the oxide layer is considered in calculating the threshold gain for transverse modes. The numerical results show that higher transverse modes can be suppressed by adjusting the position of a thin AlAs-oxide layer inside a three-quarter-wave layer in the distributed Bragg reflector. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Fd III-V semiconductors
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