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Time-of-flight scattering and recoiling spectrometer (TOF-SARS) for surface analysis (1990)

Grizzi, O. ; Shi, M. ; Bu, H. ; [et al.]

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

Review of Scientific Instruments 61 (1990), S. 740-752

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ISSN: 1089-7623

Source: AIP Digital Archive

Topics: Physics , Electrical Engineering, Measurement and Control Technology

Notes: A UHV spectrometer system has been designed and constructed for time-of-flight scattering and recoiling spectrometry (TOF-SARS). The technique uses a pulsed primary ion beam and TOF methods for analysis of both scattered and recoiled neutrals (N) and ions (I) simultaneously with continuous scattering angle variation over a flight path of ≈1 m. The pulsed ion beam line uses an electron impact ionization source with acceleration up to 5 keV; pulse widths down to 20 ns with average current densities of 0.05–5.0 nA/mm2 have been obtained. Typical current densities used herein are ≈0.1 nA/mm2 and TOF spectra can be collected with a total ion dose of 〈10−3 ions/surface atom. A channel electron multiplier detector, which is sensitive to both ions and fast neutrals, is mounted on a long tube connected to a precision rotary motion feedthru, allowing continuous rotation over a scattering angular range 0°〈θ〈165°. The sample is mounted on a precision manipulator, allowing azimuthal δ and incident α angle rotation, as well as translation along three orthogonal axes. The system also accommodates standard surface analysis instrumentation for LEED, AES, XPS, and UPS. The capabilities of the system are demonstrated by the following examples: (A) TOF spectra versus scattering angle θ; (B) comparison to LEED and AES; (C) surface and adsorbate structure determinations; (D) monitoring surface roughness; (E) surface semichanneling measurements; (F) measurements of scattered ion fractions; and (G) ion induced Auger electron emission.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1141488

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On finite deformation plasticity with directional softening Part I: One-component model (1990)

Shi, M. F. ; Gerdeen, J. C. ; Aifantis, E. C.

Springer

Acta mechanica 83 (1990), S. 103-117

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ISSN: 1619-6937

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Summary A physically based continuum model of finite deformation plasticity with anisotropic hardening is developed and used to evaluate the differences of stress responses in tension, compression and torsion (directional softening) for various materials at large deformations. The coupling effects of back stress and plastic spin are incorporated into the model according to the scale invariance method recently suggested by Aifantis. Moreover, the effects of nonlinear dislocation hardening and recovery softening are included. It is shown that the theoretically obtained stress responses in tension, compression and torsion are in good agreement with available experimental data for Copper, Brass and Silver.