SURFACE-STRUCTURE OF HYDROGEN-TERMINATED (100) SI BY MEDIUM-ENERGY ION-SCATTERING

(1 0 0) Si surfaces were terminated with hydrogen atoms by hydrogen fl uoride (HF) treatment. X-ray photoelectron spectroscopy (XPS) and bloc king measurements with medium energy ion scattering (MEIS) using 100 k eV He+ were performed to investigate the relaxation of the hydrogen ad sorbed Si layers. XPS measurements after HF treatments suggested that hydrogen atoms were directly bonded with top surface Si atoms. Blockin g measurements along [1 1 0] and [1 1 1] axes resulted in the shifts i n blocking dip position by about 1.17 +/- 0.3 degrees and 1.7 +/- 0.3 degrees, respectively, indicating the Si layer spacing of about 1.28 /- 0.02 Angstrom between the top and second layers after hydrogen term ination. These results indicated that the top Si layer had a relaxatio n of about 6%, provided that the bulk Si lattice spacing is 1.358 Angs trom. (C) 1998 Elsevier Science B.V.