Francois Girard

Scanning secondary ion analytical microscopy with parallel detection

The secondary ion microscope described here allows to obtain the simultaneous registration of chemical and isotopic distribution maps of several elements composing the sample. The instrument has been specially designed to optimize both sensitivity and selectivity: bombardment with primary Cs+ ions to increase the ionization yields of negative secondary ions, efficient collection of secondary ions at the target surface, matching of the secondary ion beam etendue with the acceptance of the mass spectrometer working at high mass resolution, spectrometer with parallel detection capabilities. The probe diameter can be made as low as 30 nm and ion induced electron images registered at the same time as ion images. Presently, four ion micrographs are obtained simultaneously over a field of view up to 20 × 20 μm2 containing up to 512 × 512 pixels. Examples are shown with an ion probe diameter of 0.1 μm.

Texture poreuse et reactivite d'un carbone vitreux et d'un coke de saccharose—I. Examen de l'oxyreactivite et de la carboxyreactivite

Abstract Vitreous carbon (in shape of plates and balls) and a saccharose coke, both heat-treated at 1000°C were examined. The variations of the oxyreactivity and of carboxy-reactivity were determined against burn-off for various granulometric portions at different temperatures. Though the average reactivity of the carbons is comparable, differences in structure were detected. In particular, for vitreous carbon balls, the carbon reactivity is greater for the core of the particles than for their periphery. This is most likely due to the treatment undergone by this material at the very last stage of its preparation to mold it to the desired shape. Experimental data are presented which suggest that texture of vitreous carbon balls and of saccharose coke present some similarities.