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The main purpose of the present paper is to provide practical and numerical implementations of the method of fundamental solutions for three-dimensional exterior Stokes problems with quiet far-field condition and discuss the issues therein. The solutions of the steady Stokes problems are obtained by utilizing the boundary collocation method as well as the expansion of Stokeslets, which are the fundamental solutions of the steady Stokes equations. To validate the proposed model, numerical results of a lid-driven cavity flow, uniform flow passing a sphere, and a rotating dumbbell-shaped body show good agreement with the numerical and analytical solutions available in the literature. Also, a hypothetical problem with both vorticity and velocity boundary conditions is solved and compared with the analytical solution. The proposed model is then properly exploited to obtain the flow results of uniform flow passing a pair of vertical spheres in tandem and uniform flow passing a pair of horizontal spheres in tandem. Furthermore, the accuracy of the present numerical scheme is addressed and the detail flow characteristics, such as pressure distribution, streamline contour, velocity field, and vorticity fields are sketched. DOI: 10.1061/(ASCE)0733-9399(2006)132:3(317) CE Database subject headings: Numerical models: Hydrodynamics: Particles; Boundaries; Uniform flow; Velocity.

Microstructure, surface roughness, morphology, defect spectrum, and low-temperature photoluminescence of thin (10–125 nm) strained Si1-xGex layers (0.1<=x<=0.3), deposited by chemical vapor deposition (CVD) at 650 °C on silicon wafers have been studied. Nominally undoped layers with crystalline orientations of <100> and <111> have been investigated. Local strain within the layers was estimated from x-ray diffraction data. It decreases with the layer thickness in the <100>-oriented samples, but rises in the <111>-oriented ones. Nanoscale (∼10–30 nm) and microscale (∼0.2–1 μm) morphologies have been found on the surface of the Si1-xGex layers by atomic-force microscopy. The lateral sizes of the morphologies and surface roughness depend on the thickness, germanium concentration x, and crystalline orientation of the layers. The spectrum of defect states N(E) in the band gap of these samples has been experimentally studied by the deep-level-transient-spectroscopy (DLTS) technique. The standard D1(P1), D2, P3, and P4 defect peaks were observed. The N(E) spectrum is strongly influenced by germanium concentration, crystalline orientation, and surface roughness of the films (especially at Ec-E<0.4 eV). Photoluminescence (PL) was excited with argon ion (Ar+) laser at a sample temperature of about 5 K. Both “no-phonon” and phonon-assisted PL peaks around 1.1 eV, as well as a strong peak at 0.80 eV were observed. These peaks originated, respectively, from the no-phonon line from the Si substrate, transverse optical/acoustical phonon replica and dislocation-related Si1-xGex band, D1. Intensities of these PL peaks are influenced by the layer thickness, internal strain, surface roughness, and germanium concentration x. Possible mechanisms of relationship between the local strain, film roughness, the defect spectrum N(E), and the D1 line strength are discussed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Results of structural characterization by Fourier transform infrared spectroscopy, x-ray diffraction, and specular x-ray reflectivity measurements are employed for the interpretation of electrical measurement data and the deconvoluted distribution of electron states, N(E) of carbon doped hydrogenated silicon oxide (SiOCH) low-k dielectric films. Atomic structure of the films is identified as a mixture of a dominant and totally amorphous SiO[SUB2]-like phase with a partially polycrystalline SiC phase. The n-type dc conductivity that dominates in this material points to the principal role of the SiC-like phase in the dc transport of the SiOCH material. The deep level transient spectroscopy technique is applied for the N(E) shape studies in the energy range up to 0.7 eV below the conduction band bottom. Typical N(E) values lie in the 10[SUP10]-10[SUP14] eV[SUP-1] cm[SUP-3] range for films deposited at different ratios of tri-methyl-silane to oxygen flow rate. No correlation between the N(E) shape and the film deposition conditions have been found in this case. The Fermi level position usually lies at 0.18-0.4 eV below conduction band bottom. For the SiOCH films prepared at different levels of rf power densities, the N(E) in the whole studied range increases nearly monotonically with increasing rf power, which is attributed to the SiC-like phase fraction increment. An N(E) peak at 0.25-0.35 eV below conduction band bottom has been found in the films. The possible origin of the peak appearance is discussed. [ABSTRACT FROM AUTHOR]

Presents a study which characterized amorphous germanium-copper alloy films at temperatures down to 3.9 Kelvin. Theoretical background; Methodology; Findings.