Frozen CH4 and CH4/Ar were irradiated by protons and 3He2+ ions at 15 and 77K in order to simulate the interaction between the solar wind and the surface of comets. After irradiation, polymerised organic matter is left over as solid residues, whenwarming up the remainingCH4. The carbon isotopic composition of these residueswas determined. Isotopic fractionation between organic residues and meth...

The damage created in SiO2 layers by low-energy Ar ions ~130 keV! and the reconstruction of the structure after various annealing steps have been characterized as a function of the implantation dose. Quantitative determinations of the damage produced have been performed from infrared spectroscopy. We show that two dose thresholds for damage are encountered: At 10 cm damage saturates and for dos...

We study the morphological evolution of surfaces during ion sputtering and we compare their dynamical corrugation with aeolian ripple formation in sandy deserts. We show that, although the two phenomena are physically different, they must obey similar geometrical constraints and therefore they can be described within the same theoretical framework. The present theory distinguishes between atoms...

A d.c. reactive magnetron sputtering technique was used to deposit (Ti, Si, Al)N films. The ion current density in the substrate was varied by the superimposition of an axially symmetric external magnetic field between the substrate and target. It was found that the variation of the magnetic field strength induced changes in the ion current density in the substrate with a consequent change in f...

The interaction of plasmas with surfaces is dominated by synergistic effects between incident ions and radicals. Film growth is accelerated by the ions, providing adsorption sites for incoming radicals. Chemical etching is accelerated by incident ions when chemical etching products are removed from the surface by ion sputtering. The latter is the essence of anisotropic etching in microelectroni...

The evolution of the microstructure during irradiation is now widely recognized due to: (1) radiation altered kinetic phenomena; (2) collisional processes by energetic cascades. In this paper, we investigate the specific nature of the collisionai interaction between energetic cascades and precipitates. A new Monte Carlo-based computer program, TRIPOS, has been developed for the TRansport of Ion...

Low-energy ~1–1.5 kV! nitrogen-ion bombardment of sharply pointed Fe-3 at. % Mo tips is performed, at room temperature and 473 K, by applying a negative voltage to the tip in the presence of nitrogen gas ~10–10 Torr! in an ultrahigh vacuum atom-probe field-ion microscope ~APFIM!. Tip sharpening, as a consequence of sputtering, is observed directly in situ via APFIM. This sharpening phenomenon c...

The microstructure of the redeposited surface in tokamaks may affect sputtering and reflection properties and subsequent particle transport. This subject has been studied numerically using coupled models/codes for near-surface plasma particle kinetic transport (WBC code) and rough surface sputtering (fractal-TRIM). The coupled codes provide an overall Monte Carlo calculation of the sputtering c...

The electronic structures of nitrogen species incorporated into highly oriented pyrolytic graphite (HOPG), prepared by low energy (200 eV) nitrogen ion sputtering and subsequent annealing at 1000 K, were investigated by X-ray photoelectron spectroscopy (XPS), angle-dependent X-ray absorption spectroscopy (XAS), and Raman spectroscopy. An additional peak was observed at higher binding energy of ...

We review the use of elemental depletions in determining the composition of interstellar dust and present a new interpretation of the elemental depletion patterns for the dust forming elements in a range of diffuse cloud types. We discuss this within the context of dust processing in the ISM and show that Si and Mg are selectively eroded from dust, with respect to Fe, as expected for a sputteri...