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X-ray diffraction analysis of Si1−xGex/Si superlattices (1992)

Mai, Z. H. ; Ouyang, J. T. ; Cui, S. F. ; [et al.]

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

Journal of Applied Physics 72 (1992), S. 3474-3479

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: Si1−xGex/Si strained-layer superlattices grown by molecular-beam epitaxy on Si substrates were investigated by x-ray double-crystal diffraction and x-ray grazing incidence diffraction. Both coherent and incoherent interfaces between the two components of the superlattices were observed. By fitting computer-simulated double-crystal x-ray-diffraction rocking curves to the experimental data, it is determined that there exist graded variations in both the component thickness ratio t1/t2 (t1 and t2 are the thickness of the Si1−xGex and the Si layers, respectively) and the fraction x in one sample. The x-ray grazing incidence diffraction experiments reveal a lattice strain relaxation of about 27% in another sample. The lattice relaxation and the influence of variations of x and t1/t2 on the rocking curves are discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.351423

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Physical phenomena in a coplanar macroscopic plasma display cell. II. Comparisons between experiments and models (2002)

Ganter, R. ; Ouyang, J. ; Callegari, Th. ; [et al.]

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

Journal of Applied Physics 91 (2002), S. 1000-1007

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: Measurements of infrared and visible emission in a macroscopic discharge cell similar to a plasma display panel (PDP) cell are analyzed using a two-dimensional fluid model of the discharge. The comparisons between experiments and models show a good qualitative agreement but the plasma spreading velocity above the cathode surface is much faster in the experiments. We find that including photoemission (in a simplified way) in the model considerably increases the agreement between experiments and models. With a well-chosen photoemission coefficient, the model reproduces the trends observed in the experiments when the gas mixture (between 2% and 10% of xenon in neon) or the applied voltage is changed. The influence of photoemission on the current rise time and on the velocity of plasma spreading above the dielectric surfaces is more important in the macrocell than in a similar (same dimension × pressure) PDP cell because resonant photon transport does not follow the similarity laws. © 2002 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1425426

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Physical phenomena in a coplanar macroscopic plasma display cell I. Infrared and visible emission (2002)

Ganter, R. ; Ouyang, J. ; Callegari, Th. ; [et al.]

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

Journal of Applied Physics 91 (2002), S. 992-999

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: The space and time variations of the light emission in a macroscopic plasma display panel (PDP) discharge cell have been studied with an image-intensified charge-coupled device. The discharge cell is similar to a real PDP cell with a coplanar electrode configuration. The cell dimensions are on the order of 100 times larger than those of a real PDP cell and the operating pressure is about 100 times smaller. Different xenon–neon gas mixtures have been investigated. Optical filters have been used to measure infrared emission from xenon excited states 823.1 and 828.0 nm, and visible emission from neon at 640.2 nm. The measurements show that the neon visible emission occurs only above the cathode while xenon infrared emission occurs above both cathode and anode. Standing striations can be observed above the anode. The strong xenon emission above anode indicates that this region is more efficient than the cathode region in terms of ultraviolet production. The measurements are in excellent qualitative agreement with similar measurements performed in real PDP cells. However the velocity of plasma spreading above the cathode in the macrocell is significantly larger than in a real PDP cell. The interpretation of this discrepancy is given in a companion paper (part II) [J. Appl. Phys. 91, 1000 (2002)] where the experimental results are compared with results from a fluid model of the plasma. © 2002 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1425425

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Examination of the magnetism dynamics from intermixing effects in γ-Fe2O3/MnO core-shell nanoparticles (2015)

E. Skoropata, T. T. Su, H. Ouyang, J. W. Freeland and J. van Lierop

American Institute of Physics (AIP)

In: Journal of Applied Physics

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Publication Date: 2015-03-25

Description: We have examined the effects of core-shell intermixing on the dynamical magnetism of γ -Fe 2 O 3 /MnO nanoparticles. The core and shell phases were identified using x-ray diffraction, and x-ray absorption spectroscopy identified Mn ions in both octahedral and tetrahedral sites, consistent with a significant amount of substitution at the core-shell interface to form an Fe/Mn-ferrite. The dynamical response was probed by Mössbauer spectroscopy, which decouples surface and core spins, and suggested a change in the relaxation behaviour among the spin populations within γ -Fe 2 O 3 /MnO relative to the γ -Fe 2 O 3 seed particles. Interestingly, the magnetic relaxation effects at the atomic scale, measured via Mössbauer spectroscopy, were enhanced, indicating that the addition of an MnO shell and intermixing affected the dynamical freezing process which altered the surface magnetism of the γ -Fe 2 O 3 core. Our results show that both the MnO shell and the interfacial intermixed layer are important in determining the core-shell nanoparticle magnetism.

Print ISSN: 0021-8979

Electronic ISSN: 1089-7550

Topics: Physics

Published by American Institute of Physics (AIP)

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