Structure fine de l'intensité du faisceau électronique réfléchi par le W(110) et l'influence de la chimisorption de l'hydrogène

Abstract

Measurements with high resolution in energy and angle of the intensity of the electron beam reflected from W(110) in the [10] azimuth are presented. For high values of the reflected angles (θi ≥ 65°) intensity profiles present narrow fluctuations related to the emergence of the [Formula: see text] diffracted beam. This LEED fine structure is caused by the interference of the wave directly reflected from the crystal with a wave temporarily trapped between the substrate and its surface potential barrier. The shape of these singularities is studied in detail for a clean target and for the same target submitted to various hydrogen exposures. In the latter case, a gradual modification of the lineshape as a function of the hydrogen coverage is observed. This phenomenon is explained by the modification of the substrate scattering properties rather than by a transformation of its surface barrier. The LEED fine structure accentuation induced by hydrogen adsorption could be the indication of the ordered chemisorption of this gas in interstitial sites on W(110).