Interaction of Energetic Heavy Ions with Polymers

The effects of electronic excitations due to irradiation of electrons or energetic heavy ion (\u3e1 MeV/amu) irradiations on Linear polymers of general formula -(CR1R2-CR3R4)n- are reviewed and compared with previous results obtained with γ and electron irradiation. The polymer modification are discussed accounting for the nature and the position of the R1, R2, R3 and R4 substituents on the main chain. It is suggested that Linear polymers evolve according to the R can nature (R=R1, R2, R3, R4). This paper includes the physical and chemical processes of electronic excitation and the mechanisms which Lead to modification of the macromolecules. An attempt is made to relate the macromolecular structure of polymers and their structural modifications under irradiation

Electrical Surface Breakdown: Secondary Electron Emission and Electron Spectroscopy of Insulators

These results question the usual scheme of flashover. They lead to a different interpretation based on classical concepts in solid state physics which can be verified at every step. An ionizing cascade in the bands, rather than a cascade of electron multiplication on the insulating surface, could explain the flashover, the conditioning and the deconditioning of high voltage generators through the building of a surface charge. As in the usual model the positive charge is responsible for the flashover, in this new model the building of this charge is the basis of the conditioning. The ionizing cascade in the bands is initiated by a tunnel injection into the insulator from the soldering metal-insulator junction or by electronic excitation. This interpretation is supported by the analysis of charging phenomena in insulators, the study of localization sites of carriers and by the neutralization mechanisms, charge diffusion or defect annealling. These studies are achieved by scanning electron microscopy and electron spectroscopy

Physical Basis for Spectrometer Calibration

Progress in quantitative surface analysis is hampered by the lack of experimental procedure including spectrometer calibration, sample preparation, and general experimental setting-up. Two methods for spectrometer alignment are compared: the linearization method and the elastic peak test. Experimental spectra are presented, which can be considered as stringent reference data to check the instrument response and the analyser transmission at low energies

Influence of Ion Implantation and Gas Exposure on the Charge in Silicon Oxide Created by Electronic Excitation

Low energy electron bombardment of amorphous SiO2 induces point defects such as oxygen vacancy by electronic excitation. The defects build a macroscopic negative charge by trapping of electrons on the localized levels in the band gap; this phenomenon was previously described as the mirror effect. In the present paper, we investigate, by mirror effect, the behavior of the charge after an argon, nitrogen and oxygen implantation at 1 and 4 keV, and after exposure to the same gases at various low pressures. We observe a difference of behavior between Ar (or N2) and O2, The results reinforce the outstanding role of oxygen in the defect production in SiO2 by electronic excitation

Oxidation of Aluminum Studied by Ion Scattering Spectroscopy (I.S.S) in a Scanning Auger Microscope

The set up of an ion gun, producing a focused beam in the analysis chamber of a Scanning Auger Microscope permits ion scattering experiments: surface studies performed by electron spectroscopies can then be enlarged by Ion Scattering Spectroscopy (I.S.S.) to get additional information. I.S.S. appears to be very sensitive to the cleanliness of the surface: comparison between Electron Energy Loss Spectroscopy (E.E.L.S.) and I.S.S. studies on clean samples show that I.S.S. can still detect oxygen even when it is not detectable by E.E.L.S. Preliminary results on oxidation of Al (111) and Al (100) give oxidation curves in good agreement with those obtained by Auger Electron Spectroscopy (A.E.S.) and X Ray Photoemission Spectroscopy (X.P.S.)

Study by Scanning Electron Microscopy and Electron Spectroscopy of the Cascade of Electron Multiplication in an Insulator Submitted to an Electric Field

An original method for revealing the dielectric heterogeneities on an insulating surface has been developed on creation of an electron multiplication cascade inside the insulator placed in an electric field. The steps of the physical process are: (i) excitation of electrons into the conduction band, (ii) electric field acceleration of the conduction electrons, (iii) ionization of the valence levels, (iv) creation of many more new defects in the vicinity of dielectric heterogeneities, (v) charge localization on defects and appearance of a local residual potential. The potential map is observable by scanning electron microscopy after propagation of the ionizing cascade, but only during the first scan which smoothes the surface potential. By electron spectroscopy the energy of the secondary negative particles emitted during the cascade can be analysed

Intensity of Valence Auger Transitions (L23VV) of Al and Si in Metal, Oxide and Nitride

L23VV Auger transition has been studied in Si, SiO2, Al, AlN, Al2O3 by electron spectroscopy excited either by electron beam or X Rays. A strong difference is observed in intensity between pure solid and oxide or nitride under electron bombardment. Auger intensity is very sensitive to changes in the backscattering coefficient or inelastic mean free path. However transient local trapping of electrons seems to be responsible for the large change observed

Glow Discharge Effects on Polytetrafluoroethylene Polymers Investigated by Secondary Electron Microscopy and X-Ray Photoelectron Spectroscopy

A glow discharge treatment of Polytetrafluoroethylene avoids charging effects and permits observation of the sample in Scanning Electron Spectroscopy; x-ray Photoelectron Spectroscopy has been used to study changes in the surface chemical composition and electronic structure of the polymer produced by this treatment

Formation of metal-ceramic interfaces : a surface science approach

Metal-ceramic interfaces are involved in a great number of technologies, where specific electrical, optical, magnetic or mechanical properties are required. These properties often depend on the characteristics of the interfaces, such as their atomic structure and composition, as well as the nature of the interfacial bonds. Such relevant characteristics can be obtained by studying the initial stages of the metal-ceramic interface formation, the metallic deposit being condensed from a vapor phase, onto the in situ prepared and well characterized ceramic surface. The usual surface science methods relying on the detection of the electrons emitted under an electron or photon beam can then be used in situ, and information on the interface can be obtained, while it is being formed, provided that the deposited metallic layer is thinner than the escape depth of the detected electrons. Through some examples, we show how it is possible to follow, when the interface is being formed : the growth mode of the metallic film onto the ceramic surface, the atomic structure at the interface (long range and short range order), the chemical bond formation, the composition of the interface, and the possible formation of an interfacial new compound.Les interfaces métal-céramique interviennent dans de nombreuses technologies, où l'on recherche des propriétés électriques, optiques, magnétiques ou mécaniques particulières. Ces propriétés dépendent des caractéristiques des interfaces, comme leur structure atomique et leur composition, ainsi que la nature des liaisons interfaciales. L'étude des étapes initiales de la formation de l'interface métal-céramique, par condensation de la vapeur métallique sur la surface céramique préparée et caractérisée in-situ, permet d'accéder à ces caractéristiques. Les méthodes d'étude des surfaces qui reposent sur la détection des électrons émis sous un faisceau de photons ou d'électrons, peuvent alors être utilisées pour obtenir des informations sur l'interface, à condition que la couche métallique déposée ait une épaisseur inférieure au libre parcours moyen des électrons détectés. Au moyen de quelques exemples, nous montrons comment il est possible de suivre, au fur et à mesure que l'interface se forme : le mode de croissance du film métallique sur la surface céramique, la structure atomique de l'interface (ordre à longue et courte distance), l'établissement des liaisons chimiques, la composition de l'interface, et la formation éventuelle d'un composé d'interface