ZIB

1

Digitale Medien

Structural analysis of imperfect GeSi superlattices grown on Ge(001) substrates (1995)

Tweet, D. J. ; Tatsumi, T. ; Miyanaga, K. ; [weitere]

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

Journal of Applied Physics 78 (1995), S. 117-121

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: By combining the complementary techniques of x-ray diffraction and transmission electron microscopy we have been able to accurately determine the structure of imperfect GeSi superlattices (SL's). The samples were epitaxially grown on Ge(001) substrates using Si2H6 and GeH4 source gases. In this report, details of the x-ray experiment and analysis are emphasized. In particular, a model is presented for calculating the diffracted intensity from a SL containing gradients in composition and thickness. Applying this model to the data it is found that between the first and last layers of each SL there exists a roughly 10% increase in the growth rate, without a corresponding change in the alloy composition. This is attributed to a slow increase in the substrate temperature, Tsub, of just a few degrees. A sample grown with a corresponding gradual decrease in the control temperature, TC, was found to be much more uniform. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.360660

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2

Digitale Medien

Determination of the composition of strained tetragonal epilayers (1996)

Fons, P. ; Bottomley, D. J. ; Tweet, D. J. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 69 (1996), S. 761-763

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Elasticity theory is applied to calculate the total strain present in a tetragonal symmetry epilayer due to heteroepitaxial misfit. By relating pseudobinary alloy composition to the lattice constants of the epilayer, it is shown that the composition of a pseudobinary epilayer can be determined from measurement of the strained epilayer lattice constants. This is accomplished by expressing the misfit strain in terms of the composition and the individual lattice constants of the components of the epilayer and using Vegard's rule. As a result, determination of the composition of two chalcopyrite symmetry epilayers from x-ray diffraction measurements is demonstrated. The approach presented here is general and can be applied to any substrate-epilayer combination in the elastic limit. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.117883

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3

Digitale Medien

Factors determining the composition of strained GeSi layers grown with disilane and germane (1994)

Tweet, D. J. ; Tatsumi, T. ; Hirayama, H. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 65 (1994), S. 2579-2581

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Growth rates and compositions are reported for GeSi alloy films and superlattices epitaxially grown on both Ge(100) and Si(100) substrates using disilane and germane source gases in an ultrahigh vacuum chemical vapor deposition chamber. Although the growth rate changes rapidly with temperature the composition is nearly independent of it. Specifically, we find that the order of the adsorption reaction for disilane and germane is the same, resulting in the composition being determined by the partial pressures and by the ratio of the adsorption reaction rate constants. This ratio depends very weakly on temperature, if at all, and appears to vary slightly with the layer composition. © 1994 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.112644

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4

Digitale Medien

Effect of strain and temperature on anomalously large interdiffusion in InAsP/InP heterostructures (1997)

Tweet, D. J. ; Matsuhata, H. ; Fons, P. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 70 (1997), S. 3410-3412

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We present evidence for anomalously large, strain-dependent interdiffusion in InAs1−xPx layers grown on InP(001) substrates by organometallic vapor phase epitaxy at 620 °C. Specifically, there are strong indications for the existence of a "critical strain:" if the strain is ∼1.9% or more, much P–As mixing occurs, but for smaller strain the mixing is greatly decreased. The interdiffusion is also highly sensitive to temperature. A set of samples grown at 580 °C exhibits a factor of ∼2 decrease in P–As mixing compared to a set grown at 620 °C. © 1997 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.119187

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5

Digitale Medien

Island growth, strain, and interdiffusion in InAs1−xPx/InP heterostructures (1995)

Tweet, D. J. ; Matsuhata, H. ; Shioda, R. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 67 (1995), S. 1286-1288

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Using x-ray diffraction and transmission electron microscopy we have found that InAs1−xPx films deposited on InP(001) substrates with organometallic vapor phase epitaxy grow in an unusual island growth mode characterized by large strain-dependent interdiffusion. Initially, strong intermixing occurs, producing pseudomorphic islands of intermediate composition. These grow only until some point in the relaxation process, possibly a critical value of the strain, after which islands of the intended composition begin to appear. Furthermore, both types of islands are found to penetrate deeply into the substrate. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.114399

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6

Digitale Medien

Development of a compact six-circle goniometer (1998)

Tweet, D. J. ; Oyanagi, H.

Chester : International Union of Crystallography (IUCr)

Journal of synchrotron radiation 5 (1998), S. 905-907

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ISSN: 1600-5775

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: A compact versatile six-axis goniometer has been built which can be used with the scattering plane vertical or horizontal for anomalous X-ray diffraction and diffraction X-ray absorption fine structure using a tunable X-ray undulator at SPring-8. The diffractometer consists of a four-circle goniometer for the standard ω, 2θ, φ and χ motions and a two-circle goniometer on the 2θ arm for mounting the detector and analyser crystal. The goniometer is controlled via Ethernet, and standard data-acquisition software with a graphical user interface has been developed. A closed-cycle helium cryostat is mounted on the ω axis for temperature-dependent experiments from 330 K to 14 K. Preliminary experiments on a Bi2Sr2CaCu2O8 single crystal demonstrate the performance. Superstructure peaks due to the one-dimensional spatial modulations in the b axis were recorded as a function of temperature above 20 K using an image plate.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0909049597018098

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