[en] The channeling effect technique was applied to investigate dechanneling by dislocations in Al-implanted crystals and by stacking faults in heteroepitaxially grown silicon layers. For these defects direct backscattering has been found negligible with respect to dechanneling. Analysis of ion backscattering data for several analyzing beam energies shows that dislocation dechanneling increases with the square root of the beam energy. Stacking-fault defects are characterized by an energy-independent dechanneling cross-section. Comparison with transmission electron microscopy allows the quantitative determination of the cross-sections which compare well with existing calculated values. Large densities of dislocations and stacking-faults are necessary for channeling analysis

[en] The keV-MeV ion irradiation of polymers produces deep changes in their physical and chemical properties associated with the breaking and rearrangement of original bonds. The modification of chain structure occurs within a well defined ion fluence range which depends on the ion linear energy transfer as well as on the target parameters. At low ion fluences (≅ 10¹⁴ ions/cm²) crosslinks between chains and chain-scissions are detected with a chemical yield in the range 0.05-0.3, depending on the ion mass. With increasing ion fluence (10¹⁵ ions/cm²) the original polymer structure is heavily modified and the irradiated films exhibit properties close to those of hydrogenated amorphous carbon. At very high fluences (≅ 10¹⁶ ions/cm²) graphitization of the material occurs. (orig.)

[en] In general ion implantation leads to irreversible changes in organic films and hence it is important to understand the damage mechanisms in these solids. Most of the technology based on irradiation effects in organics must somehow make use of the fact that the chemistry of the organic films is easily changed. This chapter is organized to explore the various ion induced chemical changes in the organic films followed by a description of the optical and electrical property changes produced in the films due to the ion irradiation

No abstract available

[en] The in situ measurement of thin film thickness between 50 and 100 KeV is described. The method used seems to be flexible enough and can be applied to any type of material. The only parameter intervening in the thickness measurement is the specific energy loss of the proton beams. Film of Al, Cu and Ag have been considered. When the primary beam energy increases the perception in depth of the method grows, reaching 10 μm with 1 MeV beam. In this case the autoabsorption takes place

[en] Thin films of hydroxyapatite bioceramic, 5-50 A in thickness, have been deposited on ion cleaned titanium surfaces to study the chemical-physical adhesion of metal-ceramic interfaces of biomedical devices (orthopaedic and dentistry prosthesis). Film deposition was performed in ultrahigh vacuum condition (10^-10 mbar) using 5 keV argon sputtering of hydroxyapatite matrix; the film thickness was measured in situ with Auger electron spectroscopy. The hydroxyapatite-titanium interface was irradiated with an electron beam of 0.5-5 keV energy and 0.2-2 A/cm² current density. During electron irradiation, Auger spectra show chemical shifts of phosphorus, titanium and oxygen peaks. The released electron energy induces modifications in the tetraedric phosphorus-oxygen groups with production of new chemical bonds between phosphorus, oxygen and titanium. Oxygen, for example, diffuses into the titanium interface forming titanium oxide. Chemical reactions induced by electron irradiation are driven by the metal-ceramic interface. Near the interface a strong and fast effect is observed while far from the interface a weak and slow effect occurs. Chemical reactions depend on the electron irradiation dose showing an inhibition threshold at about 10¹⁹ e/cm² and, near the interface, a saturation condition at about 5x10²⁰ e/cm². Titanium-ceramic chemical reactions are inhibited if the substrate titanium surface is rich in oxide. (orig.)

[en] We present an overview of the irradiation effects induced by keV-MeV ion implantation on polymeric materials what is concerned in particular in the modifications of the physical and chemical properties of polymers are the change of density, hydrogen content, hydrogen outgassing, solubility and electrical conductivity after ion irradiation

[en] The existence of pure ice grains in the first evolutive stage of a T tau star has been proposed in recent years on the basis of IR spectrophotometric observations. In the present paper we assume that ice grains are destroyed in later phases of T tau evolution. We then suggest that the mechanism responsible for their destruction is the erosion by energetic particles produced by flare activity. By using experimental results we show that such a destruction occurs on a time scale shorter than the estimated duration of the T tau phase and that a noticeable number of molecules (H₂, O₂, H₂O) are restored to the gas phase

[en] Ion channeling and backscattering measurements along the (110) axis of implantation disorder in Al single crystal are reported as a function of the He analyzing beam energy (0.5-2.0 MeV). For 100-keV N⁺ implants (8 x 10¹⁶ ions/cm²), appreciable dechanneling is observed near the end of the projected ion range (2400 A) and the minimum yield increases with decreasing analyzing beam energy. A different behavior was observed for 150-keV Zn⁺ implantation into Al with fluences of 6 x 10¹⁵ and 1.2 x 10¹⁶ ions/cm², respectively. The minimum yield in the Zn-implanted region (790 A) shows a √E dependence on the energy E of the analysis beam. These channeling measurements show that the nature of the disorder for light and heavy mass implants in Al is different. The energy dependence of the minimum yield points out that the defects for the N implant are consistent with random scattering centers while for Zn implants extended defects with associated strains, like dislocations, are produced. The energy dependence of the critical angle can also be related to the defect structure

[en] The atomic and electronic structure of polymer films undergoes deep modifications during high energy (keV-MeV) ion irradiation, from molecular solid to amorphous material. At low energy density (10²²-10²⁴ eV/cm³) typical effects include chain scissions, crosslinks, molecular emission and double bonds formation. In hydrocarbon polymer (polystyrene, polyethylene) the main effect of irradiation is the formation of new bonds as detected by molecular weight distribution, solubility and optical measurements. Moreover the concentration of trigonal carbon (sp²) in the polymer changes with ion fluence (10¹¹-10¹⁴ ions/cm²) and stabilizes to a value of 20% independently on the initial chemical structure of the irradiated sample. Photoemission spectroscopy shows an evolution of valence band states from localized to extended states. At high energy density (10²⁴-10²⁶ eV/cm³) the irradiated polymer continues to evolve showing spectroscopic characteristics close to those of hydrogenated amorphous carbon. Trigonal carbon concentration changes with ion fluence (10¹⁴-10¹⁶ ions/cm²) reaching the steady state value of 60% and the hydrogen concentration decreases to 20%. Moreover the values of the optical gap (2.5-0.5 eV) suggest the presence of medium range order in the obtained hydrogenated amorphous carbon. These values are consistent with the formation of graphitic clusters, whose size goes from 5 A to 20 A by changing the ion fluence (or energy density). (orig.)