[en] A new internal configuration bias (ICB) scheme for Monte Carlo (MC) sampling of any number of internal degrees of freedom in chain molecules with arbitrary fixed bond lengths and angles is proposed, extending recent methods restricted to lattice chains, freely jointed chains or short segments. The move is described pictorially for the case of a linear chain; the method may also be readily generalised to branched chains or networks. Its application to a 'phantom' hexadecane backbone with no interatomic potential confirms that it satisfies detail balance. Its application in a strategy for atomistic simulation of bulk polymeric systems is depicted. Unlike previous polymer MC schemes ICB is not dependent on the presence of chain ends, making it potentially highly suitable for the kinds of dense, entangled, high molecular weight and crosslinked systems relevant to applications in the polymer industry

No abstract available

[en] In the present note, we report on the presence of fullerenes in the laser produced carbon plasma in vacuum. The carbon clusters were characterised using infrared (IR) and UVIS absorption spectroscopic techniques. (orig.)

[en] Ellipsometry is a traditional technique for the thickness and the optical constants of CVD films determination, and if in situ film control is impossible, the best way is to use spectroellipsometry. The novel method for quick estimation of the film parameters in the case of weakly absorbing thick film (80 - 600 nm) on nonabsorbing substrate, using spectroellipsometry is presented. The experimental results for electronbeam assisted CVD ZrO₂ films on quartz, PECVD diamond and a-B/C:H films on Si (100) are reported and the influence of substrate absorption and intermediate layers presence is discussed. Both the thickness and the wave dependence of the film optical constants were calculated from the azimuth of polarization spectra in the range of 360-660nm. (orig.)

[en] Full text: In usual growth techniques, dopants are introduced at random locations in a semiconductor crystal. An ordered array of dopants would be an extremely interesting system in which to study 2D band structure and commensurability effects in a 2D periodic system in an applied perpendicular magnetic field. Dopant arrays are also of interest as computational cells in cellular automata and in electron and nuclear spin quantum computers. We propose a technique for creating dopant arrays using superfluid He films on a semiconductor surface. Dopant ions are introduced into the He, confined <100 Angstroms below the He surface by an applied electric field. At T≅1K for ion separations <1000 Angstroms, the ions will condense into a Wigner crystal suspended in the He film. Rapidly switching off the applied electric field should result in the transfer of the crystal onto the semiconductor surface. Growth of covering layers of the semiconductor will produce an embedded dopant array. Modeling of the He film-ion system indicates that dopant atom separations of ≥300 Angstroms are achievable, and short range fluctuations in the dopant spacing can in principle be comparable to the lattice spacing of the semiconductor crystal

[en] Full text: One of the major factors limiting the use of adhesive bonding is the problem associated with the production of adhesive joints that can maintain their initial strength over long periods of time in hostile environments. It is well known that the adherent surface preparation method is critical to the formation of a durable adhesive bond. Work presented in this paper focuses on the critical aspects of the surface preparation of aluminium employed for the manufacture of aluminium-epoxy joints. The surface preparation procedure examined is currently employed by the RAAF for repairs requiring metal to adhesive bonding. The influence of each step in the surface preparation on the ultimate bond durability performance of the adhesive joint is examined by a combination of methods. Double cantilever wedge style adhesive joints are loaded in mode 1 opening and then exposed to a humid environment. X-ray photoelectron spectroscopy (XPS) and contact angle measurements of the aluminium adherent before bonding provides information about the adherent surface chemistry. XPS is also employed to analyse the surfaces of the bonded specimens post failure to establish the locus of fracture. This approach provides important information regarding the properties influencing bond durability as well as the bond failure mechanisms. A two step bond degradation model was developed to qualitatively describe the observed bond durability performance and fracture data. The first step involves controlled moisture ingress by stress induced microporosity of the adhesive in the interfacial region. The second step determines the locus of fracture through the relative dominance of one of three competitive processes, viz: oxide degradation, polymer desorption, or polymer degradation. A key element of the model is the control exercised over the interfacial microporosity by the combined interaction of stress and the relative densities of strong and weak linkages at the metal to adhesive interface. Copyright (1999) Australian X-ray Analytical Association Inc

[en] Thin films of W-N alloys have been prepared by reactive rf sputtering from a W target. Alloy compositions up to about 65at.%N can be achieved by this method. The structure and stability of these films have been studied using x-ray diffraction analysis. Between 18 and 38at.%N, amorphous phases are formed with crystallization temperatures up to above 600⁰C. All the films gradually release N upon vacuum annealing and decompose into αW between 700 and and 800⁰C in vacuo. Application of W-N alloys as diffusion barriers in a Si metallization scheme is discussed

No abstract available

[en] Evaporated thin films of indium, deposited at room temperature onto n-GaAs, forms a Schottky barrier which, upon annealing above In's melting point, turns into an ohmic contact. Such a behavior has been interpreted as the result of the formation, at least locally, of a graded Ga/sub 1-x/ In/sub x/ A s heterojunction, the conductivity of which (in the 10/sup -6//10/sup -7/ Ω . cm/sup 2/ range) had been previously checked by Molecular Beam Epitaxy (MBE). During the time this work was in preparation, other authors have supported the idea that the junction was probably not graded but abrupt, suggestion which has also been confirmed by (MBE) recent results. Whatever the Ga/In profile within these non-alloyed structures is, it appears to us that their fabrication might be facilitated by a previous arsenic enrichment of the GaAs surface before in deposition, It can be noted that SPICER's group has recently shown that the obtention of large values for x(x>0.3) does in fact require an As-rich surface. The aim of the present work is to check such assessment by using two means of endogenic As enrichment of (100) Si doped GaAs samples. 1. a photoelectrochemical (PEC) technique, previously proposed by WOODALL et al., which consists in the illumination of GaAs substrates immersed in a 1:1 HCl : H/sub 2/O solution (HCl 6M) by photons of energy higher than the band-gap of this material; and 2. a combined anodic/thermal/etching process which involves first the growth of an anodic oxide layer on GaAs in an AGW medium, followed by an annealing of the structure and a final post-etching of the oxide in a 1:11 MeOH : HCl etchant

[en] The homogeneity of the composition of solid Cd /SUB x/ Hg /SUB 1-x/ Te solutions is one of the most important characteristics governing the quality of multielement photodetectors fabricated from these semiconductors. This dependence is the result of the change in forbidden bandwidth with change in composition of the semiconductor. At high temperatures, the forbidden bandwidths of a solid solution determines the magnitude of the free carrier concentration in the semiconductor which can be measured by the contact-free method of magnetooptical rotation (MOR) of the plane of polarization in the IR spectrum range. This was the stimulus for the investigation in this article for the application of the MOR method for contact-free determination of the composition of solid Cd /SUB x/ Hg /SUB 1-x/ Te solutions