Étude de l'adsorption du palladium sur les faces vicinales de Si(111) par diffraction d'électrons rapides, diffraction d'électrons lents et spectroscopie Auger

Abstract

The structural properties of palladium deposited onto clean silicon surfaces inclined at small angles to a (111) plane were studied by low energy electron diffraction, reflection high energy electron diffraction and Auger electron spectroscopy techniques. For all palladium deposits (the maximum mean thickness of palladium condensed is about 20 Å) on steps with edges towards [ 2 11], annealing at high temperatures (600–1000°C) produces (122) facets with 2×2 reconstruction. Also at low coverage (1 monolayer), only a (3×1) structure in a single orientation is observed after an annealing at 200°C. For higher coverage (5 to 10 Å), annealing produces epitaxial Pd 2Si islands. In the case of steps with edges towards [2 1 1 ] annealing of palladium deposits smaller than 10 Å at temperatures between 200 and 400°C gives flat smooth Pd 2Si islands epitaxially grown on the substrate. The surface structure of these islands is Si(111)√3×√3R(30°). Between these islands, the silicon surface presents the structure Si(111)3×1 Pd. For higher coverage (10–20 Å) annealing at 400°C gives a Si(111)3√3×3√3R(30°) structure. These results are the same as those we have observed on cleaved (111) surfaces.