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1

Digitale Medien

Microstructure and properties of giant magnetoresistive granular Au80Co20 alloys (2001)

Vrenken, H. ; Kooi, B. J. ; De Hosson, J. Th. M.

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

Journal of Applied Physics 89 (2001), S. 3381-3387

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The relationship between microstructure and giant magnetoresistance (GMR) of granular Au80Co20 was investigated. Two different processing routes were explored. With the melt spinning technique the microstructure appeared to be so coarse that it was not expected to exhibit any substantial GMR effect. On the other hand, with the procedure of solid-solution annealing and water quenching afterwards, a suitable nanostructure was prepared that showed a GMR of 29% at 10 K and 50 kOe. Subsequent annealing causes coarsening of Co particles. In additional spinodal decomposition occurred for a certain temperature range and a loss of coherency of the Co particles with respect to the Au was observed with high-resolution transmission energy microscopy. At magnetic fields above ∼20 kOe, all annealed alloys showed a saturating magnetization, whereas the resistance is still steadily decreasing, challenging the presumed mathematical relationship between GMR and overall magnetization. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1325381

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2

Digitale Medien

Mechanism of the structural phase transformations in epitaxial YHx switchable mirrors (2002)

Kooi, B. J. ; Zoestbergen, E. ; De Hosson, J. Th. M.

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

Journal of Applied Physics 91 (2002), S. 1901-1909

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The detailed mechanisms of the structural phase transformations that occur in epitaxial Y–hydride switchable mirrors are revealed with high resolution transmission electron microscopy (both cross sectional and plan view). The triangular ridge network that develops in Y prior to the α–β transformation is a result of {101¯2} deformation twinning. The basal plane that is originally parallel to the film/substrate interface is rotated by twinning over 5.6° and transformed into a prismatic plane and similarly the prismatic plane is transformed into a basal plane giving a final crystal reorientation for the ridge of 95.6°. After transformation to β, nearly vertical Σ3{111} twin boundaries arise in the ridges. In contrast, horizontal twin boundaries develop in the β domains to prevent macroscopic shape changes. Inbetween the two twin variants within the domains, Shockley partial dislocations are persistently present, which enable efficient reversible β–γ switching of the mirror. © 2002 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1431427

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3

Digitale Medien

Mound surface roughness effects on the thermal capacitance of thin films (2001)

Palasantzas, G. ; De Hosson, J. Th. M.

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

Journal of Applied Physics 89 (2001), S. 6130-6134

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We investigate the influence of roughness at a nanometer scale on the thermal properties of thin films. It is shown that the roughness causes an increase of the thermal capacitance. For mound rough surfaces the increase of the thermal capacitance depends strongly on the relative magnitude of the average mound separation λ and the system correlation length ζ. Indeed, a rather complex behavior develops for ζ〉λ, while for ζ〈λ a smooth decrease of the capacitance as a function of the average mound separation λ takes place. Finally, the roughness strongly affects the thermal capacitance as a function of the film thickness as long as ζ〈λ, while a precise determination of the actual effect requires a more-detailed knowledge of the thickness dependence of the involved roughness parameters during film growth. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1368390

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4

Digitale Medien

Growth front roughening of room-temperature deposited copper nanocluster films (2002)

Palasantzas, G. ; Koch, S. A. ; De Hosson, J. Th. M.

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 81 (2002), S. 1089-1091

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Growth front aspects of copper nanocluster films deposited with low energy onto silicon substrates at room temperature are investigated by atomic force microscopy. Analyses of the height-difference correlation function yield a roughness exponent H of 0.45±0.05. The root-mean-sqaure roughness amplitude w evolves with deposition time as a power law, w∝tβ (β=0.62±0.07), leading also to a power-law increase of the local surface slope ρ, ρ∝tc (c=0.73±0.09). These scaling exponents, in combination with an asymmetrical height distribution, point at a complex nonlinear roughening mechanism dominated by the formation of voids resulting in a highly porous film. © 2002 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1497200

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5

Digitale Medien

Linear growth of thin films under the influence of stress (2001)

Palasantzas, G. ; De Hosson, J. Th. M.

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 78 (2001), S. 3044-3046

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We have studied the growth of thin films in the presence of stress instability that enhances the roughness and roughening induced by conservative as well as nonconservative noise. It is clearly illustrated that nonconservative noise effects may enhance stress induced roughness. Nevertheless, the incorporation of conservative noise appears to also be substantial in growth processes driven by diffusion. For growth on a rough substrate the dependence of the amplitude of the surface roughness on the film thickness differs from that of a film growing on a flat substrate. The amplitude shows a minimum at a particular substrate thickness, which indicates that the growth up to this thickness is enforced by undulations of the substrate. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1372209

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6

Digitale Medien

Rectangular nanovoids in helium-implanted and thermally annealed MgO(100) (2000)

Kooi, B. J. ; van Veen, A. ; De Hosson, J. Th. M.

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 76 (2000), S. 1110-1112

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Cleaved MgO(100) single crystals were implanted with 30 keV 3He ions with doses varying from 1×1019 to 1×1020 m−2 and subsequently thermally annealed from 100 to 1100 °C. Transmission electron microscopy observations revealed the existence of sharply rectangular nanosize voids at a depth slightly shallower than the helium-implantation range. Monitoring of the defect depth profile and the retained amount of helium was performed by positron-beam analysis and neutron depth profiling, respectively. © 2000 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.125954

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