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Digitale Medien

Polymer/metal interfaces studied by carbon near-edge x-ray absorption fine structure spectroscopy (1988)

Jordan-Sweet, J. L. ; Kovac, C. A. ; Goldberg, M. J. ; [weitere]

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

The Journal of Chemical Physics 89 (1988), S. 2482-2489

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: Interaction of polyimide and two simple organic polymers with an evaporated chromium metal overlayer was studied by surface-sensitive carbon 1s near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. The technique was used to measure unoccupied electronic states in the polymers. Assignments of C1s→π* transitions in poly(pyromellitimido oxydianiline) (PMDA-ODA polyimide) were based upon transitions measured for model polymers which contained structural subunits of the polyimide. Changes in the NEXAFS spectrum of each polymer were observed after sequential depositions of chromium. Abrupt changes in the carbonyl C1s→π* transition peaks show that the carbonyl groups on these polymers are sites for initial interaction with chromium. No evidence was seen for the formation of Cr–arene complexes on any of the polymer surfaces.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.455042

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2

Digitale Medien

Unique x-ray diffraction pattern at grazing incidence from misfit dislocations in SiGe thin films (1996)

Jordan-Sweet, J. L. ; Mooney, P. M. ; Lutz, M. A. ; [weitere]

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

Journal of Applied Physics 80 (1996), S. 89-96

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Grazing-incidence x-ray diffraction (GIXD) permits the direct measurement of in-plane lattice parameters of SiGe films that are too thin to yield good results from normal-geometry triple-axis techniques. A unique "X''-shaped pattern has been seen in H–K reciprocal space maps of diffracted x-ray intensity from SiGe films that have relaxed via a modified Frank–Read mechanism. Contours of intensity are seen along the 〈110〉 directions from the (4¯00) reciprocal lattice peak with the introduction of the first dislocations. For higher dislocation densities the X-shaped contours are anisotropically distorted and a satellite peak, corresponding to the lattice parameter for a partially relaxed film, becomes identifiable at lower H. In contrast, H–K reciprocal-space contours from thin SiGe films that have relaxed by roughening and subsequent random nucleation of dislocations display broad, oval-shaped contours centered at the (4¯00) reciprocal lattice point for the film. Numeric simulations of GIXD from a variety of dislocation arrangements were performed in order to understand the origin of the X pattern. We show that this pattern arises from an array of long misfit dislocations running in the 〈110〉 directions. The anisotropic distortion of the X pattern arises at higher dislocation densities from orthogonal intersections of dislocations with equal Burgers vector, which are characteristic of dislocation networks generated by the modified Frank–Read mechanism. We also verify that the measured values of the in-plane lattice parameter, together with the out-of-plane lattice parameter determined from the symmetric (004) reflection, lead to accurate calculation of the composition and strain in these SiGe layers. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.362776

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3

Digitale Medien

Instrumentation for millisecond-resolution scattering studies (invited) : INTERNATIONAL CONFERENCE ON SYNCHROTRON RADIATION INSTRUMENTATION (1989)

Stephenson, G. B. ; Ludwig, K. F. ; Jordan-Sweet, J. L. ; [weitere]

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

Review of Scientific Instruments 60 (1989), S. 1537-1540

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ISSN: 1089-7623

Quelle: AIP Digital Archive

Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: Time-resolved x-ray scattering studies of phase transition kinetics have been carried out using the wide-bandpass monochromator and fast linear position-sensitive detector system at the IBM/MIT beamline X-20C at the National Synchrotron Light Source (NSLS). We report here on the instrumentation that has been developed for these studies, and in particular on the methods used to measure, change, and control sample temperature with millisecond resolution.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1141031

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4

Digitale Medien

Dislocation nucleation barrier in SiGe/Si structures graded to pure Ge (1994)

Mooney, P. M. ; LeGoues, F. K. ; Jordan-Sweet, J. L.

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 65 (1994), S. 2845-2847

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: High-resolution triple-axis x-ray diffraction measurements were used to study strain relaxation in the individual layers of a SiGe/Si structure step-graded to pure Ge. The tilt of each layer is explained by extending the model previously proposed for obtaining the nucleation activation energy of dislocations to account for the reduced miscut of the growth surface as the sample relaxes and the variation in the materials properties with alloy composition. © 1994 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.112511

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5

Digitale Medien

Relaxed Si0.7Ge0.3 buffer layers for high-mobility devices (1995)

Mooney, P. M. ; Jordan-Sweet, J. L. ; Ismail, K. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 67 (1995), S. 2373-2375

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The minimum epitaxial layer thickness required to produce relaxed, thermally stable, Si0.7Ge0.3 buffer layer structures for high electron- and hole-mobility devices has been determined, using high resolution x-ray diffraction. A 1.4-μm-thick layer, step graded to x=0.35, is sufficiently thick so that the residual strain in a uniform composition Si0.33Ge0.67 layer grown on top of it is essentially independent of thickness or growth temperature of the layer. Such structures are stable when annealed at 750 °C. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.114349

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6

Digitale Medien

Evolution of strain relaxation in step-graded SiGe/Si structures (1995)

Mooney, P. M. ; Jordan-Sweet, J. L. ; Chu, J. O. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 66 (1995), S. 3642-3644

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Strain relaxation in a series of step-graded SiGe/Si structures has been quantitatively investigated by high-resolution x-ray diffraction measurements. We show that beyond a critical thickness, dislocations nucleate continuously as layers with higher Ge mole fraction are added to the structure and that the mismatch strain at which nucleation occurs is therefore essentially constant. It had been found empirically that a lower growth temperature is required to suppress roughening of layers with higher Ge mole fraction, even in graded structures. We prove that this is not because the strain increases, but rather because of the lower melting temperature of layers with higher Ge content. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.114126

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7

Digitale Medien

Observation of local tilted regions in strain-relaxed SiGe/Si buffer layers using x-ray microdiffraction (1999)

Mooney, P. M. ; Jordan-Sweet, J. L. ; Noyan, I. C. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 74 (1999), S. 726-728

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The microstructure of strain-relaxed Si1−xGex/Si films that relaxed by different dislocation nucleation mechanisms has been investigated using x-ray microdiffraction with a diffracted beam footprint of 1 μm×5μm. Intensity variations in the x-ray microtopographs of samples having step-graded intermediate layers, which relaxed by dislocation multiplication, are due to the presence of local tilted regions which are larger in area than the diffracted x-ray beam. In contrast, microtopographs of uniform composition layers, which relaxed by surface roughening and subsequent random dislocation nucleation, show little intensity contrast as the local tilted regions in these samples are much smaller than the diffracted x-ray beam. The difference in microstructure arises from the different distributions of 60 ° misfit dislocations in these two types of samples. © 1999 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.123104

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8

Digitale Medien

X-ray diffraction analysis of SiGe/Si heterostructures on sapphire substrates (1998)

Mooney, P. M. ; Ott, J. A. ; Chu, J. O. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 73 (1998), S. 924-926

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Si/Si1−xGex heterostructures on improved silicon-on-sapphire substrates were grown epitaxially by ultrahigh vacuum chemical vapor deposition for application as p-channel field effect transistors. High-resolution triple-axis x-ray diffraction was used to analyze these structures quantitatively and to evaluate their thermal stability. Outdiffusion of Ge from the strained Si1−xGex quantum well was observed after annealing at 850 °C. The amount of outdiffusion was comparable to that observed in Si1−xGex structures on bulk Si wafers. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.122039

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Digitale Medien

Scanning x-ray microtopographs of misfit dislocations at SiGe/Si interfaces (2001)

Mooney, P. M. ; Jordan-Sweet, J. L. ; Christiansen, S. H.

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 79 (2001), S. 2363-2365

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Misfit dislocations at Si1−xGex/Si interfaces have been imaged by x-ray microdiffraction using the 004 diffraction peak of both the Si1−xGex layer and the Si(001) substrate. At the Si1−xGex layer peak, a decrease in the diffracted intensity is found at dislocations, with features as narrow as 4 μm. Similar features are seen using the Si peak; however, the diffracted intensity increases at the dislocations. We discuss the intensity contrast mechanisms and demonstrate that the distortion of the crystal lattice from the dislocations extends throughout the entire epitaxial layer structure. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1408601

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