HYDROGEN ANALYSIS OF SILICON SURFACES BY LOW-ENERGY ION-BEAMS

For the analysis of hydrogen adsorption on silicon surfaces, low-energ y recoil ion spectroscopy (LE-RIS) is one of the most powerful methods because it directly provides information over 'real-space' interatomi c distance and the adsorbed coordinates. Observing both the surface re coils and the direct recoils which are created by He ion beams, we inv estigate the structure of Si(100)-1 X 1:2H dihydride and Si(100)-2 X 1 :H monohydride surfaces. Comparing our experimental results with compu ter simulations, we conclude that the H-Si bond angle in the Si(100)-2 X 1:H monohydride surface is 65-70 degrees and that in the Si(100)-1 X 1:2H dihydride surface is 55-60 degrees. For this dihydride surface, a canted dihydride structure is suggested rather than a symmetric dih ydride structure. (C) 1997 Elsevier Science B.V.