Quantitative determination of hydrogen adsorption site on the Pt(111)-(1 x1) surface by low energy ion channeling

Ion channeling using low keV energies is introduced as a sensitive probe fo r determining the adsorption site of hydrogen on surfaces. The technique is shown to be capable of quantitatively probing the positions of light eleme nts on heavy substrates with analysis by simple geometrical constructs. Qua ntitative analysis of the Pt(111)-(1x1)-H surface using 5 keV Ne+ ions show s that the hydrogen atoms preferentially populate the fcc site with a heigh t of 0.9 +/- 0.1 Angstrom above the first-layer Pt atoms and a correspondin g Pt-H bond length of 1.9 +/- 0.1 Angstrom. (C) 1999 American Institute of Physics. [S0003-6951(99)01030-X].