par Medvedev, Valentyn;Suchorski, Yuri;Visart de Bocarmé, Thierry 
;Bar, Thomas ;Kruse, Norbert
Référence Ultramicroscopy, 79, page (239-244)
Publication Publié, 1999-01-24
;Bar, Thomas ;Kruse, Norbert Référence Ultramicroscopy, 79, page (239-244)
Publication Publié, 1999-01-24
Article révisé par les pairs
| Résumé : | Selected areas of a clean or Li-doped Rh field emitter IIp were studied by low-temperature 02+ -FIM and Li +-FDM order 10 reveal (he promoting influence of Li on the early stages of the oxidation process. The experiments were conducted by graphitizing a Rh tip specimen 111 a first step and reacting old subsequently the surface carbon to create two single "windows" with a clean Rh surface in the region of(l00) and (123). Both windows were imaged by Li+ -FOM. At high field strenglhs Li + formation was restneted to the border bel ween the clean surface areas of the windows and the graphite-like overlayer. i.e. ring-like ion Images appeared on an otherwise dark background. Since the Li source was originally present on the shank of the Rh tip it must be concluded that Li atoms penetrate the graphite-like layer in order to form an intercalation structure ensurmg high mobility to sustain steady supply for image formation in Li+ -FOM. Field strengths and temperatures could also be adjusted so that the Initially clean Rh windows were preeovered by Li without desorption occurring. This enabled us 10 study the influence of Li on the rate of surface oxidation while imaging in 0+ -FIM at 78 K We found an enhancement of this rate (as compared to the clean surface) and explain this observation by an increase of the sticking probability of O2 on the Li-covcred surface. In another experiment. we found that 0+ -FIM of Rh surfaces covered by COad yield higher brightness than those covered by Oads. |
