Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 56: Metal substrates: Epitaxy, growth and adsorbates

O 56.17: Talk

Thursday, March 26, 2009, 19:00–19:15, SCH A316

The Interaction of Hydrogen with the Cobalt(0001) Surface — Zita Hüsges and •Klaus Christmann — Institut für Chemie und Biochemie der FU Berlin, 14195 Berlin

We report latest data on the interaction of hydrogen with the hexagonal Co(0001) surface in the temperature range between 90 K and 600 K as obtained by means of LEED, thermal desorption spectroscopy (TDS) and work function change measurements. Expectedly, hydrogen adsorbs spontaneously and dissociatively with an initial sticking probability around 0,1. The H atoms form two binding states having desorption energies between 80 and 100 kJ/mole. Interestingly, H adsorption causes only a slight decrease of the work function between 10 and 17 meV near saturation (~ 0.7 ML). Most notably, a H-induced c(2x2) LEED phase forms around half a monolayer coverage, similar to the H/Ni(111) system. T and coverage dependent LEED intensity measurements suggest a critical temperature of the ordered H phase of about 240 K and a strongly asymmetric phase diagram that points to a H honeycomb structure. Our data will be discussed and compared with previous work on Co(0001)/H and on Ni(111)/H.