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

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

Deconvolution in Auger Electron Spectroscopy

Deconvolution calculations have been applied in Auger Electron Spectroscopy to increase resolution and/or to eliminate loss features. We present: i) A short review of the methodology; ii) Recent results obtained in our laboratory in spectroscopy of Al, Ni, Cu, Ag and Te; iii) A discussion on the conditions for the appearance of artefacts originating either in the calculation or the physical processes (emission anisotropy, distribution of electron path lengths, and intrinsic losses)

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

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

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.)

A Metal-Polymer Interface Study using Electropolymerized Acrylonitrile on Nickel Surfaces

Studies of the interface between mineral and organic materials have been realized for a couple formed between pure transition metal and a polar and polarizable molecule (acrylonitrile). The results presented show the effects of a local electric field on the activation processes associated with adsorption sites and the molecule, interaction mechanisms and the resulting types of chemical bond. The structural, electronic and chemical properties of a nickel-polyacrylonitrile interface are described. Molecular and energetic qualitative models for the interaction mechanisms are proposed

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

MICROSCOPIC STUDY OF SURFACES BY AUGER TYPE EMISSION

L'effet Auger se prête à l'étude microscopique des surfaces au travers de la spectroscopie des raies caractéristiques des atomes émetteurs, des spectroscopies de seuils ou des spectroscopies d'électrons secondaires accompagnant la relaxation d'ions et la dé-excitation d'atomes métastables. Les informations obtenues se rapportent à la composition élémentaire, à la liaison chimique, à la distribution des états électroniques du solide, et aux distances entre proches voisins. Les retombées de telles analyses en sciences des matériaux sont déjà considérables.The Auger effect lends itself well to the microscopic examination of surfaces through the spectroscopy of the characteristic lines of the emitter atoms, threshold spectroscopies, and spectroscopies of secondary electrons accompanying the relaxation of ions and the de-excitation of metastable atoms. The data obtained pertain to the elemental composition, the chemical bond, the distribution of electron states of the solid, and the distances between close neighbors. These analyses have already had considerable repercussions on the materials sciences