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1

Digitale Medien

Applicability of effective medium theory to ferroelectric/ferrimagnetic composites with composition and frequency-dependent complex permittivities and permeabilities (1996)

Mantese, Joseph V. ; Micheli, Adolph L. ; Dungan, Dennis F. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 79 (1996), S. 1655-1660

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: High-frequency (1 MHz–1 GHz) transmission line measurements were used to determine the composition and frequency-dependent complex permittivities and complex permeabilities of ferroelectric/ferrimagnetic (barium titanate and a magnesium-copper-zinc ferrite) composites. The effective medium rules of Maxwell–Garnett give both lower and upper bounds for the effective permittivities and permeabilities and yield accurate estimates of the bulk electric and magnetic properties at low volume fill fraction of either component provided the proper host matrix is chosen. Bruggeman theory yielded the best predictive values for the permittivity and permeability over the entire composition range. In all cases these complex quantities were shown to be constrained by Bergman–Milton bounds. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.361010

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2

Digitale Medien

Surface modification during scanning tunneling microscope measurements on YBa2Cu3O7 thin films (1994)

Geyer, Ulrich ; von Minnigerode, Gunther ; Krebs, Hans-Ulrich

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 76 (1994), S. 7774-7777

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: During scanning tunneling microscopy measurements on YBa2Cu3O7 thin films with positive sample bias voltages, different kinds of surface modifications appear. While in the topography condition no surface modification occurs, the cleaning and etching conditions irreversibly change the surface topography. In the deformation condition a strong elastic deformation of the tip and/or the surface is observed. It is shown that field evaporation of material from the surface to the tip is responsible for the observed surface modification. In consequence, the tip is contaminated with different oxides. Localized states in the oxides make resonant tunneling of electrons through the oxide layer possible. The configuration of these localized states determines the kind of surface modification by the scanning tunneling microscope. © 1994 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.357955

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3

Digitale Medien

Optical deflection setup for stress measurements in thin films (1998)

Bicker, M. ; von Hülsen, U. ; Laudahn, U. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 69 (1998), S. 460-462

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ISSN: 1089-7623

Quelle: AIP Digital Archive

Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: We demonstrate an optical two-beam deflection setup for in situ stress measurements in thin films. By using improved position sensitive photodetectors we reach a resolution of better than 10−4 m−1 for substrate curvature measurement at a bandwidth of 1 kHz, with a relatively short optical path of 0.53 m and without employing a lock-in technique. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1148721

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4

Digitale Medien

Defect characterization in amorphous silicon based solar cells by subband-gap spectroscopy with constant photocurrent measurements (1991)

Frammelsberger, W. ; Rübel, H. ; Lechner, P. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 58 (1991), S. 2660-2662

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We used the constant photocurrent method to characterize a-Si:H based pin cells in order to discuss the correlation between the device characterizing quantity, the fill factor (FF), and the number of defects which is related to the quantity αD (subbandgap optical absorption constant). We show that the changes in the i layer due to the creation of metastable defects after light soaking or current injection−characterized by αD−directly correlate with the changes in solar cell performance (FF). We are able to show that other reasons than an increased defect density can lead to a reduction of the fill factor. Further we try to quantify αD in terms of a defect density of states.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.104799

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5

Digitale Medien

Spectra and structure of small ring compounds. XLVIII. Conformational stability of methylcyclobutane from low frequency Raman data of the gas (1987)

Durig, J. R. ; Geyer, T. J. ; Little, T. S. ; [weitere]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 86 (1987), S. 545-551

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: The low frequency (500–80 cm−1) Raman spectra of gaseous methylcyclobutane, c-C4H7CH3, and methyl-d3-cyclobutane have been recorded. A series of Q branches beginning at 161 cm−1 for the light molecule and 154 cm−1 for the d3 compound with successive transitions falling to lower frequencies have been assigned to the ring puckering vibrations of both the low energy equatorial and high energy axial conformers. These data have been fitted to an asymmetric potential function of the form: V(cm−1)=(4.78±0.10)×105X4−(3.08±0.04)×104X2 +(2.18±0.1)×104X3 with an assumed reduced mass of 160 amu for the light compound. Utilizing this potential the difference between the puckering angles for the two conformers was calculated to be 4.3° with the equatorial conformer having the larger value of 20.7°. A similar potential was obtained for the d3 molecule. The energy difference between the equatorial and axial forms was found to be 247±20 cm−1 (706 cal/mol) and a barrier of 641±20 cm−1 (1.83 kcal/mol) was found for the interconversion. Experimental values for the ΔH of both the liquid (354±179 cm−1) and gas (295±75 cm−1) from relative intensities of different Raman band pairs over 85 and 37 °C temperature ranges, respectively, were found to be consistent with the value obtained from the potential function. These results are compared to the corresponding quantities for similar molecules.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.452305

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6

Digitale Medien

The osp(1,2)-covariant Lagrangian quantization of irreducible massive gauge theories (1999)

Geyer, B.

College Park, Md. : American Institute of Physics (AIP)

Journal of Mathematical Physics 40 (1999), S. 674-698

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ISSN: 1089-7658

Quelle: AIP Digital Archive

Thema: Mathematik , Physik

Notizen: The osp(1,2)-covariant Lagrangian quantization of general gauge theories is formulated which applies also to massive fields. The formalism generalizes the Sp(2)-covariant Batalin–Lavrov–Tyutin (BLT) approach and guarantees symplectic invariance of the quantized action. The dependence of the generating functional of Green's functions on the choice of gauge in the massive case disappears in the limit m→0. Ward identities related to osp(1,2) symmetry are derived. Massive gauge theories with closed algebra are studied as an example. © 1999 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.532681

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7

Digitale Medien

The osp(1,2)-covariant Lagrangian quantization of reducible massive gauge theories (1999)

Geyer, B.

College Park, Md. : American Institute of Physics (AIP)

Journal of Mathematical Physics 40 (1999), S. 6189-6208

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ISSN: 1089-7658

Quelle: AIP Digital Archive

Thema: Mathematik , Physik

Notizen: The osp(1,2)-covariant Lagrangian quantization of irreducible gauge theories is generalized to L-stage reducible theories. The dependence of the generating functional of Green's functions on the choice of gauge in the massive case is discussed and Ward identities related to osp(1,2) symmetry are given. Massive first-stage theories with closed gauge algebra are studied in detail. The generalization of the Chapline–Manton model and topological Yang–Mills theory to the case of massive fields are considered as examples. © 1999 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.533086

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8

Digitale Medien

Internal interfaces and intrinsic stress in thin amorphous Cu-Ti and Co-Tb films (1998)

Geyer, U. ; von Hülsen, U. ; Kopf, H.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 83 (1998), S. 3065-3070

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A combined investigation of intrinsic stress formation by in situ substrate curvature measurements and of surface morphology evolution by scanning tunneling microscopy during the growth of amorphous Cu-Ti and Co-Tb films is reported. Intrinsic tensile stress and surface morphology are clearly correlated: all films that show intrinsic tensile stress formation in the late growth stages exhibit a cluster-like surface morphology and vice versa. Both the magnitude of the intrinsic tensile stress and the cluster size at the surface depend systematically on the reduced substrate temperature during film preparation. This dependence fits Hoffman's model for tensile stress formation in thin films. Thus, the observed surface clusters are probably the top domes of growth columns, and the atomic mismatch at the column boundaries gives rise to tensile stress formation. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.367061

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9

Digitale Medien

Spectral characteristics of plasma emission during ArF excimer laser ablation of YBa2Cu3O7 (1989)

Geyer, T. J. ; Weimer, W. A.

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 54 (1989), S. 469-471

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: In order to characterize the laser ablation process as it relates to the deposition of high Tc superconducting thin films, optical emission spectra produced during ArF excimer laser ablation of the high Tc superconductor YBa2Cu3O7 were studied. The population of excited states within the gas phase blow-off material depends strongly on excimer laser fluence at 193 nm. Ablation using relatively low excimer laser fluences produces a significant fraction of YO in the gas phase. The plasmas derived from ablation of targets made from the high Tc material are similar to plasmas observed from ablation of the individual components BaCO3, CuO, and Y2O3.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.101555

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10

Digitale Medien

Small atom diffusion and breakdown of the Stokes–Einstein relation in the supercooled liquid state of the Zr46.7Ti8.3Cu7.5Ni10Be27.5 alloy (1996)

Geyer, U. ; Johnson, W. L. ; Schneider, S. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 69 (1996), S. 2492-2494

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Be diffusivity data in the bulk metallic glass forming alloy Zr46.7Ti8.3Cu7.5Ni10Be27.5 are reported for temperatures between 530 and 710 K, extending 85 K into the supercooled liquid state of the alloy. At the glass transition temperature Tg, a change in temperature dependence of the data is observed, and above Tg the diffusivity increases more quickly with temperature than below. The data in the supercooled liquid can be described by a modified Arrhenius expression based on a diffusion mechanism suggested earlier. The comparison with viscosity data in the supercooled liquid state of Zr46.7Ti8.3Cu7.5Ni10Be27.5 reveals a breakdown of the Stokes–Einstein relation, indicating a cooperative diffusion mechanism in the supercooled liquid state of Zr46.7Ti8.3Cu7.5Ni10Be27.5. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.117716

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